Maëlle Kabir-Querrec

Stéphane Mocanu

Jean- Marc Thiriet

Eric Savary

A Test bed dedicated to the Study of Vulnerabilities in IEC 61850 Power Utility Automation Networks

Keywords: cybersecurity, IDS, smart-grid, test bed, hardwarein-the-loop, IEC 61850, electrical protection, false data injection

Industrial control systems rely more and more on digital technologies. Although the cyber risk such technologies induce is widely judged as serious, especially for critical infrastructures, these systems have generally not been designed to serve cybersecurity purposes. Instead they were thought first for serving operational efficiency. It thus becomes critical to study cyber threats in industrial environments and experimental test beds are needed to evaluate risks, physical consequences of cyber incidents, and performance of countermeasures. The test bed we present here focuses on studying cyber risks and their mitigation in IEC 61850 power utility automation systems. The operational part is composed of engineering computers, supervision software, off-the-shelf intelligent relays (Intelligent Electronic Device -IED), a hardware-in-the-loop process simulation, and the cybersecurity tools include an attack generation station and a network analyzer. In this paper, we present the operational part, giving details on the power grid hardware-in-the-loop simulation and its importance in the understanding of cyber consequences on the global system. The article concludes giving preliminary experimental results showing consequences of a false data injection attack on a simple electrical architecture.

I. INTRODUCTION

The two last decades have given examples of blackouts caused by both informatics bugs [START_REF] Andersson | Causes of the 2003 major grid blackouts in North America and Europe, and recommended means to improve system dynamic performance[END_REF] and cyber-attacks [START_REF]Cyber-Attack Against Ukrainian Critical Infrastructure[END_REF]. They make it plain that there is an urgent need of developing and deploying cybersecurity means to secure the smart-grid. There exist a wide range of them: some to be included at design time of products (e.g. secure boot of devices) and others to be set up when conceiving automation systems (e.g. Network-based Intrusion Detection System -NIDS). As available today, automation system technologies (relays, communication protocols, supervision software…) offer very few cybersecurity mechanisms for two main reasons: first because the threat is rather recent and Industrial Control Systems (ICS) often have a many-decade lifetime, and second because transposing security technologies from business field to industrial field is widely considered as difficult and not always relevant. Research is a necessity to develop cybersecurity methods and tools for ICS, and particularly for smart-grid control environments. Such research cannot be run in real facilities and dedicated test beds help to discover cyber vulnerabilities in industrial control applications, to understand their possible impacts on the facilities, to develop cybersecurity solutions, to test and validate them. The test bed we are setting up specifically concerns Substation Automation System (SAS), which is responsible for electrical protection, i.e. the mechanisms ensuring infrastructure resiliency to electrical faults. Its components use Ethernet-based communication protocols, such as Modbus/TCP or more recently IEC 61850. Using such standard technologies introduces vulnerabilities in SAS, which if exploited may lead to consequences out SAS boundaries, as critical as a blackout for instance. The objective of this test bench is thus the study of cybersecurity in IEC 61850 communication networks and systems for power utility automation.

Section II of this article explains the basics of IEC 61850 electrical protection. Section III presents similar initiatives. Section IV describes the proposed test bed. A concrete example of an attack scenario is given in section V with experimental results. To conclude the paper, section VI gives an insight of the global research project this test bed is part of.

II. ELECTRICAL PROTECTION

Electrical protection role is to stem breakdown, to contain it and prevent it from spreading and causing a cascading failure. Protection is realized by SAS whose protection relays continuously monitor the state of the supervised electrical components and isolate them when they are subjected to serious disturbances such as short circuits. Protection mechanisms cannot prevent disturbances from occurring, they aim at limiting their impact instead. Their main purpose is to protect people from electrical accidents and power assets from damages (a three-phase short-circuit on medium-voltage bus bars can melt up to 50 kg of copper in one second), and to provide service continuity [START_REF] Schneider | Protection guide[END_REF].

A. Selectivity

Selectivity is key to electrical protection, it is essential for maintaining service continuity. It consists in localizing and disconnecting the fault part of the power grid, and no more, while maintaining under power the greatest part of the architecture [START_REF] Alstom | Network Protection and Automation Guide[END_REF]. This is done by opening the circuit breaker (CB) immediately upstream to the fault and that CB alone. There are many selectivity methods, among which the two main are time-based and logical or communication-based selectivity. In Figure 1 In conventional protection systems, such logical selectivity blocking commands are transmitted from relay to relay through copper wires. In IEC 61850 design, these hard wired command signal exchange is replaced by a high speed inter-relay communication, thus reducing cost. In Figure 1, IED stands for Intelligent Electronic Device and denotes intelligent relay, that is a relay with digital capacities, especially an IEC 61850 relay.

B. IEC 61850 high speed inter-relay communication

Among the three IEC 61850 protocols, one is devoted to inter-IED high-speed information exchange: GOOSE (Generic Object Oriented Substation Event). To meet IEC 61850 standard requirements its end-to-end transfer time must be less than 4ms. This time-critical specification explains GOOSE implementation as an Ethernet Link layer-based protocol (mapped on ISO/IEC 8802-3): GOOSE messages are broadcasted over the Ethernet network, IEDs that need a specific-GOOSE message content must have been subscribed to it at configuration time of the substation. To ensure reliability of such communications, message publication follows a periodical mechanism: in stable conditions, the same information is published with a T0 period. When a data item changes, its new value is sent at a higher frequency, then publication rhythm progressively slows down back to stable conditions. Details about GOOSE protocol are given in the standard [START_REF]Communication networks and systems for power utility automation[END_REF] and in [START_REF] Kabir-Querrec | Corrupted GOOSE Detectors: Anomaly Detection in Power Utility Real-Time Ethernet Communications[END_REF].

III. RELATED WORKS

Literature is full of examples of test beds developed for cybersecurity of the smart-grid. Power grid simulation software with hardware-in-the-loop often serves the purpose of evaluating the performance of a developed tool. This is the objective of the experimental framework depicted in [START_REF] Parvania | Hybrid control network intrusion detection systems for automated power distribution systems[END_REF]- [START_REF] Koutsandria | A hybrid network IDS for protective digital relays in the power transmission grid[END_REF]: its end is to test the presented IDS (Intrusion Detection System). Simulink is used to run the virtual physical model of a transmission line. A communication module then manages Modbus communication with a PLC (Programmable Logic Controller) emulating a protection relay and performing the overcurrent protection algorithm. Similarly, the test bed set up for testing the IDS of [START_REF] Pan | Developing a hybrid intrusion detection system using data mining for power systems[END_REF] uses a Real-Time Digital Simulator (RTS), that is a commercial software for power grid simulation running on-the-fly to ensure a behavior as close to a real network as possible. Such real-time capabilities may be useful when evaluating time performance of the designed IDS. RTS simulation is hardwired to real relays and measurement units to avoid time delay induced by communication between process simulation and real devices. This solution is costly, though. Communication protocol in control network is Modbus/TCP too.

This second test bench is actually part of a platform developed at Mississippi State University (MSU) [START_REF] Morris | A testbed for SCADA control system cybersecurity research and pedagogy[END_REF], which is very comparable to Idaho National Laboratory initiative [START_REF]Common Cyber Security Vulnerabilities Observed in Control System Assessments by the INL NSTB Program[END_REF] or the G-ICS lab (see next section) with its double objective, teaching and research in cybersecurity of many critical industries.

Test beds dedicated to cybersecurity in IEC 61850 systems exist but are not well documented. We can mention two initiatives from British Columbia Institute of Technology [START_REF] Farhangi | W4: Smart Grid Cyber Security[END_REF] and Freiburg Intelligent and Secured Systems Institute iSIS [13].

IV. TEST BED Ense3 Grenoble Institute of Technology, together with GIPSA-lab (Grenoble Images Speech Signal and Control laboratory), has developed an experimental platform dedicated to ICS interoperability and cybersecurity, G-ICS (GreEn-ER 1Industrial Control Systems Sandbox) [START_REF] Available | [END_REF]. The presented test bed comes as a part of G-ICS. Its objective is the study of cybersecurity in IEC 61850 communication networks and systems for power utility automation. It includes all typical components of a SAS:

• Ethernet network for supervision-to-IEDs and inter-IEDs communications.

• Off-the-shelf IEDs from diverse vendors: Current experiments use a bay controller, an overcurrent protection relay, a transformer protection relay and a feeder protection relay from two vendors. Other IEDs are available but have not been operated yet.

• Engineering workstations with configuration tools.

• Supervision applications (such as PCVue) and Human-Machine Interfaces (HMI).

Regarding the process, that is the power grid, we do not have access to any real infrastructure (neither real-world one nor small-size laboratory one). But the process must be part of such a test bench dedicated to cybersecurity of the automation systems controlling it to comprehend possible impacts of cyber risks on the physical infrastructure. We thus made the choice of a feasible and affordable solution: hardware-in-the-loop simulation where electrical architectures are simulated by a software platform but still controlled and monitored by real offthe-shelf IEDs. Of course, such a solution helps understanding the system behavior but cannot give a complete representation of components interactions. A STM32-based I/O (Input/Output) card was developed by GIPSA-lab to ensure signal conversion between simulation and IEDs. Simulation software communicates with the I/O card over UDP for sending and receiving both analog and binary values to and from the IED physical connections. The card is wired to the IED binary I/O and to its measurement modules.

Regarding cybersecurity tools, an attacking computer is connected to the high-speed real-time network and launches false data injection and spoofing GOOSE attacks, and another computer runs our anomaly detection tool.

V. ATTACK SCENARIO EXAMPLE

A. Protection scenario

Let us consider a simple distribution substation from the typical substation topologies used as reference in the IEC 61850 standard [START_REF]Communication networks and systems for power utility automation[END_REF]. These are classified by types (transformation or distribution) and size (small, medium, large) to be representative of worldwide substations. Figure 3 shows the considered distribution single-line diagram with an overcurrent protection and a backup protection. Logical selectivity as explained in section II is implemented here.

When an overload or a phase-to-phase short-circuit occurs downstream line 1, the associated protection relay IED 1 measures an overcurrent. It simultaneously sends a trip signal to CB 1, the CB directly upstream to the fault, and publishes a GOOSE message with the faulty current value and a Boolean variable to prevent CB 2 from opening. When CB 1 operating time has elapsed and fault is still present, meaning CB 1 has failed to open, or if CB 1 has an internal failure, IED 1 changes blocking Boolean variable to false. When IED 2 receives the corresponding GOOSE message, it sends a trip signal to CB 2.

B. Risk analysis

The IEC 62351 [START_REF]Power systems management and associated information exchange -Data and communications security[END_REF] standard provides requirements about data and communication security in power systems. It points out the importance of risk assessment in the process of understanding cybersecurity risk and deploying countermeasures to target only pertinent assets and to the right level of security. No risk assessment methods or threat modeling has been developed specifically for substation communication, though. Attempts of assessing cyber risk in the smart-grid can be found in literature [START_REF] Langer | Smart grid cybersecurity risk assessment[END_REF] and help to run such an analysis at the scale of a substation, first step of a global cyber risk analysis covering the distribution grid.

Cyber threats in IEC 61850 power utility automation systems include: malware insertion to modify IED programs or erase them, theft of credentials and passwords to launch malicious operations from work and supervision stations, communication integrity violation such as spoofing and false data injection…

Considering the simple distribution substation described in previous paragraph, we focus our risk analysis onto false data injection in the high-speed Ethernet network. Such an attack can cause CB 2 to trip inappropriately or conversely to not trip when it should. In case of an inappropriate trip, the whole substation is de-energized since CB 2 protects the incoming feeder line. If there is an electrical fault on line 1 and neither CB 1 nor CB 2 trips, fault is not isolated and possible consequences are physical damages to substation components (worst possible case being destruction) and/or substation breakdown.

Of course, we consider a single protection mechanism in this case study but a single IED may implement many and a substation has multiple layers of protection like concentric barriers so if an inner barrier fails next one takes over. All the electrical protection layers should be examined when assessing cyber risk with both success and failure outcomes of protection mechanisms.

C. Attack model

A fictive attacker wants to disturb the production of a factory. His/her target is then the substation responsible for powering the factory facilities, which topology is shown in Figure 3. We assume that the attacker can connect to the substation Ethernet network and sniff or send packets. We also assume he/she knows the substation GOOSE messages configuration. The attacker is thus able to read GOOSE messages, forge new ones and inject them on the network for targeted IEDs to read them and use their malicious content. Attacker's objective is to de-energize the facility. He/she sniffs GOOSE packets of the substation until the situation of an overcurrent on line 1. He/she then injects GOOSE messages with the genuine current value (greater than configured overcurrent threshold) and Boolean variable "CB 1 Failure" as TRUE while its genuine value is FALSE. Attack timeline is depicted in Figure 4. Once IED 2 has read an attack GOOSE message it denies following genuine GOOSE flow because of mismatching message counters [START_REF]Communication networks and systems for power utility automation[END_REF]- [START_REF] Kabir-Querrec | Corrupted GOOSE Detectors: Anomaly Detection in Power Utility Real-Time Ethernet Communications[END_REF].

D. Preliminary experimental results

Our protection scenario is simulated on Matlab, current values and CBs states are sent to IEDs over UDP initially and then when changing. IED commands to CBs are also transferred to the simulation in UDP packets. The described protection and attack scenarios are run. Figure 5 shows the resulting GOOSE communication captured with Wireshark protocol analyzer. First column is capture time. Source column gives the MAC address of publisher IED: the "1c" address is IED 1's and "1a" is IED 2's. Green messages from IED 1 corresponds to stable conditions with no fault and pale blue messages from IED 2 asserts CB 2 state is closed. Orange messages from t=7.938807s to t=8.589623s evidences an overcurrent with operating delay for CB 1 still going on. Attack message is highlighted by the red rectangle. It consequences is that IED 2 opens CB 2 and sends this new CB 2 state in the blue GOOSE messages. The orange message with capture time t=9.231743s is the next genuine message from IED 1. But it is too late, CB 2 has already been open and the substation is not powered any longer.

VI. CONCLUSION

Test beds are clearly needed for supporting research on cybersecurity in industrial environments such as power utility automation systems. The test bed presented here includes real IEDs for a hardware-in-the-loop simulation. It is part of a research project on intrusion detection in IEC 61850 networks. An experimental set up was required to validate tools and methods we developed (main one being an IEC 61850 NIDS) but further use is also possible for research and industrial purpose: penetration testing, vulnerabilities discovery, risk assessment, Factory Acceptance Testing, etc. Further development of the test bed includes more protection and attack scenarios with other protection functions and more complex systems, development of attacks exploiting the other IEC 61850 protocols, use of the other vendor IEDs available on G-ICS platform.

  , the fault on transmission line A is observed by both protecting relays A and B. The relay the closest to the fault, A, is supposed to open its associated CB A if the fault is persistent. If relay B still observes the fault after a configured time-delay, it means that CB A has failed to trip and relay B opens CB B. In a wider application there could be C and D relays/CBs with longer time delays. Logical selectivity ensures a quicker isolation of the affected power assets because it does not rely on programmed time-delays: relay A sends a command to its upstream relay B to prevent it from tripping CB B. If the CB A fails to open and the fault still exists, relay A stops sending its blocking command to relay B that opens CB B.

Fig. 1 .

 1 Fig. 1. Protection and selectivity systems.

Fig. 2 .

 2 Fig. 2. IEC cybersecurity test bed.

Fig. 3 .

 3 Fig. 3. Example of a distribution substation with overcurrent protection.

Fig

  Fig. 5. GOOSE traffic during attack scenario.

Fig. 4 .

 4 Fig. 4.Protection scenario, its associated genuine GOOSE communication published by IED 1 and GOOSE messages injected by the attacker.

Grenoble Energy -Enseignement Recherche (Grenoble Energy -Teaching Research): a center of innovation for Energy field


Joseph Martinod

Vincent Regard

Rodrigo Riquelme

German Aguilar

Benjamin Guillaume

Sébastien Carretier

Joaquin Cortes

Laetitia Leanni

Gérard Hérail

ÔØ Å ÒÙ× Ö ÔØ Pleistocene uplift, climate and morphological segmentation of the northern Chile coasts (24S-32S): Insights from cosmogenic 10 Be dating of paleoshorelines

Keywords: Andes, Uplift, cosmogenic nuclide, Paleoshores, Tectonics, Climate

We present new cosmogenic ( 10 Be) exposure ages obtained on Pleistocene marine abrasion shore terraces of Northern Chile between 24°S and 32°S in order to evaluate the temporal and spatial variability of uplift rates along the coastal forearc. Both the dispersion of cosmogenic concentrations in samples from the same terrace and data obtained in vertical profiles show that onshore erosion rates, following emergence of paleoshorelines, approached 1m/Myr. Therefore, minimum ages calculated without considering onshore erosion may be largely underestimated for Middle Pleistocene terraces. The elevation of the last interglacial (MIS-5) paleoshoreline is generally between 25 and 45 m amsl, suggesting that the entire coast of the study area has been uplifting during the Upper Pleistocene at rates approaching 0.3 mm/yr. Available ages for Middle Pleistocene terraces suggest similar uplift rates, except in the Altos de Talinay area where uplift may have been accelerated by the activity of the Puerto Aldea Fault. The maximum elevation of Pleistocene paleoshorelines is generally close to 250 m and there is no higher older Neogene marine sediment, which implies that uplift accelerated during the Pleistocene following a period of coastal stability or subsidence. We observe that the coastal morphology largely depends on the latitudinal climatic

A C C E P T E D

M A N U S C R I P T

Introduction

Many authors, following [START_REF] Darwin | Voyage of a naturalist, or journal of researches into the natural history and geology of the countries visited during the voyage of H. M. S. Beagle round the world[END_REF], noted that most of the Pacific coasts of South America are uplifting. [START_REF] Brüggen | Fundamentos de la geología de Chile[END_REF] and [START_REF] Fuenzalida | High Stands of Quaternary Sea Level Along the Chilean Coast[END_REF] reported the presence of several marine terraces, partly cut in bedrock and partly filled or veneered with clastic materials along most of the Chilean coasts, particularly between 26°S and 40°S. They observed that the elevation of the highest terraces generally exceeds 150 m above mean sea level (m amsl).

The analysis of the Norte Chico coastal morphology and associated continental and marine deposits evidences periods of coastal uplift alternating with periods of subsidence during Tertiary times (Le [START_REF] Roux | Determining the Neogene behavior of the Nazca plate by geohistory analysis[END_REF]. In the Tongoy area (~30°S), for instance, [START_REF] Paskoff | Recherches géomorphologiques dans le Chili semi-aride[END_REF] describes a period of subsidence marked by the deposit of the Neogene Coquimbo marine formation. He shows that this episode of subsidence followed a period of coastal uplift during which the paleo Limari River had excavated a deep valley, today preserved 500 m below sea level. Although the particular geological evolution of this area has been affected by fault activity, the same succession of periods of uplift interrupted by episodes of subsidence is registered by geological markers in many places of the Norte Chico coastal area. For instance, in the Caldera region (27°S), continental deposits overlain by Miocene marine sediment fill valleys carved in the Paleozoic and Mesozoic basement [START_REF] Marquardt | Neotectónica de la franja costera y aportes a la geología regional entre Caldera y Caleta Pajonal (27° -27°45'S), tercera región de Atacama[END_REF][START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF]).

An active margin coastal area being subject to tectonic uplift or subsidence is not surprising. The question of how subduction drives forearc vertical motions, however, is not clear, and several processes may act together to change the dynamics of the coastal area (e.g., [START_REF] Regalla | Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin[END_REF][START_REF] Henry | Upper Pleistocene uplifted shorelines as tracers of (local rather than global) subduction dynamics[END_REF][START_REF] Martinod | How do subduction processes contribute to forearc Andean uplift? Insights from numerical models[END_REF]. In order to constrain the causes of observed motions, it is important to quantify and date the coastal morphological evolution. Scientific questions relative to this issue are listed as follows. When did the present-day coastal uplift begin? Did it occur at constant speed or during short pulses? How does its speed vary laterally? Do periods of uplift and subsidence Central Andes during the Middle Pleistocene. In many sites however, the uplift velocity is only constrained by a single age, and there is no information on its temporal variability. Moreover, the constant uplift velocity hypothesis adopted by [START_REF] Regard | Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary[END_REF] conflicts with results obtained by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] in the Altos de Talinay area (~30.5°S). Indeed, data presented by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] suggest that Altos de Talinay have been affected by a pulse of very rapid uplift culminating at 1.2 mm/yr between MIS-9 and MIS-7, preceding a severe decrease of the vertical velocity close to 0.2 mm/yr since MIS-5. It implies that the Pleistocene history of coastal uplift may have been much more complex than supposed by [START_REF] Regard | Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary[END_REF] and, in turn, raises the question of how the geodynamic processes operating in the area may explain highly variable uplift rates.

The spatial variability of coastal uplift in the study area is also disputed. Between 32°S and 26°S

('Norte Chico' region) raised shoreline markers are almost continuously preserved above the presentday coastline (e.g., [START_REF] Brüggen | Fundamentos de la geología de Chile[END_REF][START_REF] Paskoff | Recherches géomorphologiques dans le Chili semi-aride[END_REF], whereas between 24°S and 26 °S ('Norte Grande') the coast is marked by the presence of a high scarp whose elevation approaches 1000 m, and below which terraces or other structures marking the position of ancient seashores are generally absent (see below). In some places north of Tal-Tal (25.4°S), the ocean is actively eroding the scarp. Does the scarp mark a different tectonic evolution and a different uplift velocity north of 26°S?

In the following, we present new cosmogenic data ( 10 Be) to date Pleistocene shorelines in Chile between 24°S and 32°S. We dated terraces in places where no ages where available, in order to look

A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

at the spatial variability of uplift rates. On the other hand, we also dated new paleoshorelines in sites where some terraces had already been dated, in order to evaluate the Pleistocene temporal variability of uplift rates. We confirm that uplift has been active everywhere in the study area during the Middle and Upper Pleistocene. Finally, we show that the morphological signature of coastal uplift in the study area, and particularly the preservation of paleoshorelines, largely depends on climate. Paradoxically, we observe that paleoshorelines are better preserved in the semi-arid Norte

Chico than in the hyper-arid Atacama Desert because the coastal cliff, whose preservation is permitted by the hyper-arid climate of Atacama, restrains the formation of wide shore platforms.

Coastal morphology of the Norte Chico region, between 24° and 32°S

Both erosional and depositional paleoshores are present in the study area. Erosional paleoshores often consist in staircase marine terraces directly cut in bedrock (abrasion shore platforms). Their formation is related to sea-level highstands associated to the Quaternary glacial/interglacial cycles (e.g., Chapell, 1974;[START_REF] Lajoie | Costal tectonics[END_REF][START_REF] Pedoja | Coastal staircase sequences reflecting sea-level oscillations and tectonic uplift during the Quaternary and Neogene[END_REF]. During sea-level highstands that correlate to odd-numbered Marine Isotopic Stages (MIS), wave action erodes rocky coasts. It results in the appearance of a cliff located above a planar shore platform gently inclined towards the sea. The shoreline angle at the base of the cliff marks the maximum elevation of the ocean during the highstand (e.g., [START_REF] Lajoie | Costal tectonics[END_REF][START_REF] Jara-Munoz | TerraceM: A MATLAB (R) tool to analyze marine and lacustrine terraces using high-resolution topography[END_REF]. This erosional surface is abandoned when the sea level falls. If the coast is uplifting, the shore platform is not reoccupied by the ocean, and the bedrock surface morphology is only weakly modified by continental erosion in the semi-arid to hyper-arid environment of Northern Chile. In many places of Northern Chile, the coastal fringe eroded by the ocean corresponds to a 'Rasa', i.e. a polygenic surface in which intermediate shoreline angles marking different highstand levels are difficult to observe [START_REF] Guilcher | Les « rasas » : Un problème de morphologie littorale générale[END_REF][START_REF] Regard | Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary[END_REF].

A C C E P T E D M A N U S C R I P T

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Depositional paleoshores result in terraces where marine deposits accumulated. They are generally covered by beach-ridges, and their presence in Northern Chile is generally restricted to bays where the energy of waves is lower [START_REF] Saillard | Beach ridges U-Th dating in Tongoy bay and tectonic implications for a peninsula-bay system, Chile[END_REF].

The morphology of the coast varies significantly depending on the bedrock lithology, the continental slope close to the present-day shoreline, and the considered latitude. We describe below, from north to south, the morphology of this segment of the Chilean Coast. See Fig. 1 for the geographical location of sites cited in the text.

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The coast of the northern part of the study area between Caleta El Cobre (24°S) and Caleta Obispito (26.75°S) is particularly steep (Fig. 1). In many segments, it is marked by the presence of a scarp built in Mesozoic volcanic and plutonic rocks whose elevation approaches 1000 m. The distance between the scarp and the present-day coastline is generally ~1 km. Most of the fringe between the coast and the scarp is composed by a single rasa, whose inner edge elevation is often lower than 100 m amsl, and no remnants of Pleistocene marine erosion are preserved at higher elevations. In some places, especially north of Tal-Tal (25.4°S), the coastal rasa totally disappears and the ocean is actively eroding the scarp. In this northern segment (24°S-25.4°S), the rasa at the base of the coastal scarp corresponds to a rough surface in which many ancient seastacks have been preserved, often covered by thick caps of debris fallen from the scarp. In many places, the bedrock is not visible beneath the scarp and the ocean is actively eroding the cap of fallen debris. Very few flat terraces containing marine deposits between sea stacks are preserved north of Tal-Tal. The larger ones are located close to Planta Paposo (25.1°S) and above Punta Piedras (24.75°S) (Fig. 2). The marine terrace located above Punta Piedras is only ~150 m wide per ~300 m long.

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The coastal segment located south of Caleta Obispito (26.75°S), in contrast, presents a gentle topography. Between Caleta Obispito and Caleta Sal (27.9°S), Pleistocene paleoshorelines often lie above Neogene marine sediment pertaining to the Bahia Inglesa Formation. Numerous paleoshorelines marked by the occurrence of beach ridges are visible between the present-day coastline and ~220 m amsl [START_REF] Marquardt | Neotectónica de la franja costera y aportes a la geología regional entre Caldera y Caleta Pajonal (27° -27°45'S), tercera región de Atacama[END_REF][START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF].

Between 27.9°S and 28.8°S (Caleta Sarco), Neogene deposits disappear and Pleistocene terraces are generally built above Paleozoic metamorphic series and Mesozoic intrusives. Large parts of the coastal fringe affected by marine erosion are covered by aeolian deposits, masking the morphology inherited from marine erosion. The width of the coastal fringe affected by Pleistocene marine erosion is roughly 2 km. In Huasco (28.5°S), [START_REF] Cooke | Les niveaux marins des baies de La Serena et de l'Huasco dans le nord du Chili[END_REF] and [START_REF] Fuenzalida | High Stands of Quaternary Sea Level Along the Chilean Coast[END_REF] note the presence of several narrow lower terraces. Above lower terraces, the coastal fringe consists of a large upper rasa, whose inner limit is between 130 and 220 m amsl.

The coastal area located between 28.8°S (Caleta Sarco) and 29.35°S (Choros Bajo) corresponds to a wide low elevation area. The basement consists in Paleozoic metamorphic series, Jurassic plutons, covered in some places by Neogene deposits of the Coquimbo Formation. Pleistocene marine paleoshorelines are preserved as far as 15 km onshore. Paleoshores consist either of abrasion terraces, or of beach ridges deposited above surfaces gently inclined toward the ocean. Lower terraces are narrow, they contain many preserved seastacks, and in many places their shoreline angle and the transition with the upper terrace is difficult to observe. In Caleta Agua de la Zorra, 15 km north of Caleta Chañaral, narrow marine terraces whose inner edge elevations are located 34, 54

and 74 m amsl are preserved. Shoreline angles of two higher terraces 92 and 110 m amsl are clearly visible 10 km to the south, close to Punta Tetillas. All these narrow terraces contain many preserved seastacks, and their morphology contrasts markedly with that of the upper marine terrace. The upper terrace, indeed, is several km-wide, flat and polished, and few seastacks have been preserved

by marine erosion on this level (Fig. 3).

Between 29.35°S and 29.8°S, Neogene deposits disappear and marine terraces are again built in Mesozoic volcanic and plutonic rocks, except in Quebrada Honda (29.6°S) where the Neogene Coquimbo Formation locally outcrops. Within Mesozoic rocks, marine erosion resulted in the appearance of a ~2 km-wide rasa. The inner edge of the rasa is generally 200 m amsl. Its surface is generally rough, including many ancient seastacks between 1 and 100 m long, and it is difficult to distinguish terraces in this geomorphological unit. Between 29.8°S and 30.3°S, the coastline is composed of several bays that are, from north to south, the Coquimbo, Herradura, Guanaqueros and Tongoy bays (Fig. 1). These bays are marked by depositional paleoshores whose morphology is dominated by numerous beach ridges deposited above Neogene marine sediments pertaining to the Coquimbo Formation [START_REF] Brüggen | Texto de geología[END_REF]. In Tongoy Bay, three levels of marine terraces are preserved [START_REF] Paskoff | Recherches géomorphologiques dans le Chili semi-aride[END_REF], while four major terrace levels had already been recognized in the Coquimbo Bay by 19 th century geologists [START_REF] Darwin | Voyage of a naturalist, or journal of researches into the natural history and geology of the countries visited during the voyage of H. M. S. Beagle round the world[END_REF][START_REF] Domeyko | Mémoire sur le terrain tertiaire et les lignes d'ancien niveau de l'Océan du sud, aux environs de Coquimbo (Chili)[END_REF]. The maximum elevation of Quaternary marine deposits is approximately 160 m amsl.

The SE boundary of Tongoy Bay corresponds to the Puerto Aldea Fault (Fig. 1), whose Pleistocene activity has been noted by [START_REF] Paskoff | Recherches géomorphologiques dans le Chili semi-aride[END_REF], [START_REF] Ota | Plioquaternary Marine Terraces and Their Deformation Along the Altos De Talinay, North-Central Chile[END_REF] and [START_REF] Saillard | Beach ridges U-Th dating in Tongoy bay and tectonic implications for a peninsula-bay system, Chile[END_REF]. The fault azimuth is approximately N-S, and it accommodates the uplift of the western block (Punta Lengua de Vaca). The morphology of the coastal segment located between Punta Lengua de Vaca and Los Vilos (32°S) is fully described in [START_REF] Paskoff | Recherches géomorphologiques dans le Chili semi-aride[END_REF], [START_REF] Ota | Plioquaternary Marine Terraces and Their Deformation Along the Altos De Talinay, North-Central Chile[END_REF] and [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. Abrasion surfaces built by oceanic erosion are particularly well preserved along this 150 km-long coastal segment, and authors distinguish four main marine terraces. The two highest platforms (denominated TI and TII in Ota et al. (1995)) are much larger than underlying terraces. TI and TII consist in large surfaces gently inclined towards the ocean. Their width is generally greater than 5 km, and their maximum elevation is approximately 500 m and 200 m, respectively. Lower terraces, in contrast, (TIII and TIV following [START_REF] Ota | Plioquaternary Marine Terraces and Their Deformation Along the Altos De Talinay, North-Central Chile[END_REF]) correspond to rough terraces in which many sea stacks are preserved, and their width is always less than 1 km. The maximum elevation of TIII is approximately 50 to 60 m, and that of TIV is ~25 m amsl. In the coastal segment between Punta Lengua de Vaca and Los Vilos, highest surfaces (TI and TII) are cut by faults whose azimuth is generally close to N165°, and that accommodate the uplift of the western block without any significant strike-slip motion [START_REF] Ota | Plioquaternary Marine Terraces and Their Deformation Along the Altos De Talinay, North-Central Chile[END_REF][START_REF] Saillard | Reply to a Comment on "Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. The largest of these faults crosses

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the Quebrada del Teniente valley, 17 km north of Caleta Maiten. [START_REF] Ota | Plioquaternary Marine Terraces and Their Deformation Along the Altos De Talinay, North-Central Chile[END_REF] report that the El Teniente Fault vertical offset through the high surface is approximately 50 m. They also note that the El Teniente Fault and other similar structures are apparently inactive, since lower marine terraces below 50 m amsl are not deformed.

To sum up, there is a sharp contrast in the coastal morphology north and south 26.75°S. In the northern part of the study area, the coastal fringe is narrower than ~1 km, its inner edge often corresponds to a very high scarp whose elevation approaches 1000 m, and paleoshorelines marking coastal uplift are poorly preserved. In contrast, paleoshorelines have a continuous longitudinal expression south of 26.75°S. This different morphology is not explained by lithology, since similar magmatic series constitute the larger proportion of coastal segments both north and south of 26.75°S (Fig. 1b). Finally, we also observe that higher preserved Pleistocene terraces are generally smoother and wider than lower terraces. [START_REF] Fuenzalida | High Stands of Quaternary Sea Level Along the Chilean Coast[END_REF] noted that paleontological data do not help in accurately dating shoreline changes. They show, however, that the highest raised shorelines are not older than the Pleistocene or Pliocene. Between Caleta Sal and Caldera, [START_REF] Marquardt | Neotectónica de la franja costera y aportes a la geología regional entre Caldera y Caleta Pajonal (27° -27°45'S), tercera región de Atacama[END_REF]), Ortlieb et al. (2003) and [START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF] describe a terrace whose elevation varies between 135 and 160 m amsl, containing warm water mollusks that live today north of 6°S along South American coasts. Ortlieb et al. (2003) proposed that this warm water fauna, also called TAMA (Thermally Anomalous Molluscan Assemblage), expanded southward when the intensity of the cold Humboldt current diminished, during MIS-11 (400 kyrs ago). However, U-Th data obtained by [START_REF] Leonard | Coral Uranium-series ages and mollusc amino-acid ratios from uplifted marine terrace deposits, Morro de Copiapo, northcentral Chile[END_REF] in Morro

Previously published ages and sampling strategy

Copiapo (27.2°S) in a terrace containing TAMA fauna suggest that warm water mollusks deposited during an older interglacial period (MIS-13 or MIS-15, [START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF]. Moreover, north of the study area, in the Mejillones Peninsula (23°S), [START_REF] Cortes | Upper-plate fault activity in the Coastal Forearc of nothern Chile (~23°30'S): Paleoseismology, neotectonic implications and relation with the subduction cycle[END_REF] shows that at least two levels

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contain warm water assemblages. Thus we consider that although TAMA deposits may help in correlating terraces, their age is not constrained enough to give precise information on the coastal uplift.

Paleoshorelines in the study area have been dated using different techniques. The U/Th method has been employed on marine shells by Radtke (1987a;1987b;[START_REF] Radtke | Marine Terrassen und Korallenriffe. Das problem der Quartären Meerespiegelschwankungen erlänter an Fallstudien aus Chile, Argentinien und Barbados[END_REF], [START_REF] Leonard | Coral Uranium-series ages and mollusc amino-acid ratios from uplifted marine terrace deposits, Morro de Copiapo, northcentral Chile[END_REF] and [START_REF] Saillard | Beach ridges U-Th dating in Tongoy bay and tectonic implications for a peninsula-bay system, Chile[END_REF]. Other methods applied on shells consist in mollusk aminostratigraphy and Electron Spin Resonance (ESR) ages [START_REF] Leonard | Low Uplift Rates and Terrace Reoccupation Inferred from Mollusk Aminostratigraphy, Coquimbo Bay Area, Chile[END_REF]. All these methods are appropriate to date shores from the more recent interglacial periods. In contrast, they do not permit accurate dating of shores older than ~400 kyr (MIS-11). In fact, most of the ages obtained using these techniques correspond to the lower paleoshorelines that mark the last or penultimate interglacial period (MIS-5 or MIS-7), and little information is available concerning older seashores.

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More recently, cosmogenic isotopes have also been used to date Quaternary paleoshorelines in Northern Chile [START_REF] Quezada | Pleistocene littoral uplift of northern Chile: Ne-21 age of the upper marine terrace of Caldera-Bahia Inglesa area[END_REF][START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF][START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF]. Quezada et al.

(2007) measured 21 Ne concentrations in pebbles collected in a terrace above Caldera (27°S).

However, they note that concentrations differ significantly between pebbles collected in the same paleoshoreline, suggesting that some of them contain large amounts of inherited cosmogenic isotopes. The problem of inherited concentration is avoided if directly sampling bedrock outcrops. In many terraces in Northern Chile, the ocean removed most of the eroded material, and the bedrock either directly outcrops or is covered by a very thin (<1 m) layer containing rounded pebbles, sand and shells. Measuring cosmogenic isotopes concentrations in bedrock samples from these terraces should indicate the timing of emersion of the terrace, or a minimum age in case the erosion that followed emersion cannot be neglected. [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] measured 10 Be concentrations as large as 2.9x10 6 atoms/g in quartz samples collected 240 m amsl in Altos de Talinay (30.9°S), evidencing that the erosion posterior to the formation of this paleoshoreline has been slower than 1 m/Myr there. These authors remark that samples collected on the same terrace have comparable 10 Be concentrations. They also observe that ages estimated from cosmogenic isotope concentrations and supposing that the erosion has been negligible following the emersion of the terrace (minimum ages)

correspond to sea-level highstand periods. Thus, they conclude that post-emergence erosion did not affect the cosmogenic isotope concentrations in the samples they collected, and that minimum ages calculated neglecting erosion processes give a good estimation of the real seashore age even for terraces that date from the beginning of the Middle Pleistocene (MIS-19, ~690 kyr). Indeed, they note that in the Central Depression and Precordillera of Northern Chile, [START_REF] Nishiizumi | Remnants of a fossil alluvial fan landscape of Miocene age in the Atacama Desert of northern Chile using cosmogenic nuclide exposure age dating[END_REF] and [START_REF] Kober | Denudation rates and a topography-driven rainfall threshold in northern Chile: Multiple cosmogenic nuclide data and sediment yield budgets[END_REF] report erosion velocities generally smaller than 1 m/Myr, and often as small as 0.1 m/Myr. Nevertheless, [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] acknowledge that samples they analyzed were collected in small areas (within a radius of ~6 m) within each terrace, which may also explain the small variability

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of measured concentrations. Moreover, we note that erosion rates as small as 1 m/Myr significantly decrease cosmogenic isotope concentrations in Middle Pleistocene surfaces.

Except in Bahia Inglesa (~27°S) and Tongoy-Altos de Talinay (30.5°S -31°S), only one terrace has been dated per site, which does not permit evaluating the temporal variability of uplift. In Bahia Inglesa, [START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF] propose that the uplift velocity remained close to 0.32 mm/yr since MIS-11. [START_REF] Quezada | Pleistocene littoral uplift of northern Chile: Ne-21 age of the upper marine terrace of Caldera-Bahia Inglesa area[END_REF] Our sampling strategy considered evaluating both the spatial and temporal variability of uplift rates during the Middle and Upper Pleistocene in the study region. We sampled preferentially basement in abrasion shore terraces, considering that post-emergence erosion rates are small enough to permit a precise dating of surfaces whose age may be as old as the beginning of Middle Pleistocene, which was suggested by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. We did not sample terraces covered by post-emergence deposits such as colluviums coming from the overlying cliff, or aeolian deposit that are frequent in some sectors of the coast. We also avoided sampling terraces whose inner edge elevation is not easy to determine. We estimated samples and the corresponding shoreline angle elevations using an altimeter calibrated at sea level whose precision is + 5 m. When possible, we dated high elevation paleoshorelines in areas where low terraces had already been dated by previous authors, to obtain information on the temporal variability of uplift. We also sampled areas of the study region where no data were available such as Caleta Chañaral (29°S) and the coast north of Pan de Azucar (26.1°S).

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In the following, we present and discuss measured cosmogenic isotope concentrations. We observe that erosion rates are not as small as assumed by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. Indeed, the variability of values measured in bedrock samples for a same paleoshoreline shows that the erosion rate may largely influence 10 Be concentrations, particularly when looking at several hundred kyr-old markers.

We also present 10 Be concentrations in two vertical profiles confirming that post-emergence erosion of marine terraces cannot be neglected.

Results: Cosmogenic 10 Be concentrations, erosion rates and age of paleoshorelines

Vertical profiles

Bedrock samples have been collected in two vertical profiles. Cosmogenic isotope production attenuates rapidly with depth in the basement and becomes negligible 10 m beneath the surface [START_REF] Braucher | In situ produced Be-10 measurements at great depths: implications for production rates by fast muons[END_REF]2011;[START_REF] Nishiizumi | A Longer-Lasting and Warmer lnterglacial Episode During Isotopic Stage 11: Marine Terrace Evidence in Tropical Western Americas[END_REF]. With preserved paleocliffs being generally higher than 10 m, we assume that bedrock samples did not accumulate cosmogenic isotopes prior to terraces formation. In Chigualoco (31.7°S), the highest paleocliff is located onshore, ~3 km from the present-day coastline, and the elevation of the shoreline angle at the base of the cliff is approximately 180 m amsl. The profile is drilled 146 m amsl in an altered granitoid, in the widest and highest terrace. The basement is covered by a ~30 cm-thick soil. 10 Be concentrations are given in Table 1 and presented in Fig. 5. The shape of concentration profiles in cosmogenic isotopes depends on the ratio between the isotopic production by spallation and that resulting from muons (e.g., [START_REF] Braucher | In situ produced Be-10 measurements at great depths: implications for production rates by fast muons[END_REF]. Production by muons is minor close to the surface, but becomes predominant at depth since muons penetrate deeper. This production, however, is poorly known (see discussion in [START_REF] Braucher | Production of cosmogenic radionuclides at great depth: A multi element approach[END_REF]. Considering production values proposed by the Cronus-Earth web calculator [START_REF] Balco | A complete and easily accessible means of calculating surface exposure ages or erosion rates from (10)Be and (26)Al measurements[END_REF], 10 Be concentrations vs. depth in Chigualoco suggest that the surface is older than 2 Myrs and at steady-state, with an erosion rate between 1.5 and 2.0 m/Myr. It is not possible to explain the observed profile considering the production rates proposed by [START_REF] Braucher | Production of cosmogenic radionuclides at great depth: A multi element approach[END_REF],

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except if we assume that rocks at depth contained some inherited cosmogenic isotopes, which is unlikely in basement rocks. The best fit of the profile using [START_REF] Braucher | Production of cosmogenic radionuclides at great depth: A multi element approach[END_REF] production rates is shown in Fig. 5. This fit also suggests the surface to be at steady-state, but proposes a smaller erosion rate (close to 1.1 m/Myr).

Figure 5: 10 Be concentrations along vertical profiles sampled in marine terraces in Chigualoco and

Huasco. The solid and dashed lines in the Chigualoco profile represent the best fit obtained using the cosmogenic production rates proposed by [START_REF] Balco | A complete and easily accessible means of calculating surface exposure ages or erosion rates from (10)Be and (26)Al measurements[END_REF] and by [START_REF] Braucher | Production of cosmogenic radionuclides at great depth: A multi element approach[END_REF], respectively.

Another vertical profile has been sampled close to Huasco, 110 m amsl, in the higher and wider terrace whose shoreline elevation is 155 m amsl. Depending on the adopted 10 Be muonic production rate, the profile fits with a terrace that was carved between 0.5 and 2.5 Myr ago, and has been eroding between 0 and 1 m/Myr (Fig. 5).

Surface samples, erosion rates and ages

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Be concentrations have been measured in 26 new surface samples, collected in 8 terraces from 5 sites between 24°S and 32°S (Table 1). Cosmogenic concentrations in bedrock samples depend on both the age of the surface and erosion rate. We generally sampled bedrock directly outcropping on marine terraces, and sometimes quartz clasts and rounded pebbles or gravels collected within a thin regolith covering the surfaces. Rounded gravels and pebbles cannot have been produced onshore in these environments. They were shaped by marine erosion and are often found in a thin and discontinuous sedimentary layer covering terraces, mixed with sand and marine shells. Thus, they may contain inherited cosmogenic isotopes acquired before the formation of the terrace on which they lie. Quartz clasts are collected close to eroding seastacks or on very flat surfaces, and we assume they either come from bedrock erosion close to the sampling location, or from rounded pebbles that have been fragmented by physical weathering (insolation weathering). Different samples from the same terrace were generally collected at several tens of meters of distance between each other, in order to analyze the variation in superficial cosmogenic isotope concentrations within terraces.

10

Be concentrations in samples from the same terrace often present significant variations, as for instance in the highest terrace in Caleta Chañaral (Table 1). This result differs from that obtained by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. 10 Be concentrations in bedrock samples are often larger than those measured in clasts and rounded gravels, despite clasts and rounded gravels may contain inherited cosmogenic isotopes. We conclude that in these surfaces, the erosion rate significantly affects the concentration in cosmogenic isotopes. Erosion is more intense where soft sediment covers the surface than in bedrock, which may explain larger cosmogenic concentrations in bedrock samples. In Caleta Chañaral, the minimum 10 Be concentration measured on the highest surface (1.44x10 6 at/g) shows that the erosion rate remained smaller than 1.4 m/Myr. However, this value is far from negligible when considering terraces whose formation is several hundreds of kyrs old, and minimum ages calculated assuming no erosion may be much smaller than the real age of formation of the terrace. In Table 2, we present ages calculated for different erosion rates between 0 and 1.5 m/Myr for the

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surface samples we collected, using the Cronus-Earth web calculator [START_REF] Balco | A complete and easily accessible means of calculating surface exposure ages or erosion rates from (10)Be and (26)Al measurements[END_REF].

Discussion:

Assignment of paleoshorelines to sea-level highstands using 10 Be data

We observe that terraces whose elevation is between 100 and 200 m amsl are older than 400 kyr (MIS-11), meaning that the uplift rate has everywhere been smaller than 0.5 mm/yr. Most authors that calculated uplift velocities in the study area based on other dating techniques also concluded that uplift velocities since MIS-5 and during the Middle Pleistocene remained lower than 0.5 mm/yr (e.g., [START_REF] Leonard | Low Uplift Rates and Terrace Reoccupation Inferred from Mollusk Aminostratigraphy, Coquimbo Bay Area, Chile[END_REF][START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF][START_REF] Quezada | Pleistocene littoral uplift of northern Chile: Ne-21 age of the upper marine terrace of Caldera-Bahia Inglesa area[END_REF]. Worldwide preserved paleoshoreline sequences generally contain shores built during MIS-5, 7, 9 and 11 that are 124 kyr, 210 kyr, 320 kyr and 400 kyr-old, respectively [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF][START_REF] Pedoja | Coastal staircase sequences reflecting sea-level oscillations and tectonic uplift during the Quaternary and Neogene[END_REF].

Indeed, sea level during these interglacial periods was close to the present-day one, and related paleoshorelines are now emerged even if the coastal uplift rate has been small. Shore terraces may also form during sea-level lowstands (e.g., MIS-2). They correspond to drowned terraces, and their morphology is modified during later interstadial oscillations or highstands if the coast is slowly uplifting. Thus, shores forming during sea-level lowstands are generally destroyed by marine erosion

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except if the coastal uplift has been larger than the subsequent sea-level rise, which requires uplift rates greater than several mm/yr [START_REF] Caputo | Sea-level curves: Perplexities of an end-user in morphotectonic applications[END_REF]. Shores formed during interstadial oscillations (e.g., MIS-3) when sea level was several tens of meters lower than today are only preserved onshore if the uplift rate has been rapid. For instance, uplift rates larger than 1.2 mm/yr or 1.5 mm/yr are necessary to preserve shores related to MIS-3 [START_REF] Pedoja | Coastal staircase sequences reflecting sea-level oscillations and tectonic uplift during the Quaternary and Neogene[END_REF][START_REF] Jara-Munoz | Unraveling sea-level variations and tectonic uplift in wave-built marine terraces, Santa Maria Island, Chile[END_REF]. Then, the moderate uplift rates observed in the study area suggest that preserved paleoshorelines in Northern

Chile were formed during sea-level highstands, as discussed in [START_REF] Saillard | Reply to a Comment on "Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF].

Table 2 shows that cosmogenic isotope concentrations do not permit precise assigning of paleoshorelines to sea-level highstands for terraces higher than 100 m amsl. Indeed, we do not constrain onshore erosion whose effect becomes predominant for old surfaces. Sea-level highstand assignments are easier for lower and younger terraces, as explained above. We discuss below the cosmogenic concentrations measured in paleoshore samples, from north to south. We propose, when possible, the assigning of terraces to sea-level highstand periods (see Table 3).

Punta Piedras (24.76°S): We analysed four samples, three of them collected in bedrock and one corresponding to quartz clasts collected between ancient sea-stacks on the terrace. Cosmogenic concentrations in the four samples give coherent 10 Be concentrations between 4.8x10 5 and 6.1x10 5 at/g. These concentrations suggest that the Punta Piedras terrace formed during MIS-5e, ~124 kyrs ago (Table 2). and 404 (+/-41) kyrs (Table 2). Concentration in cosmogenic isotopes in quartz clasts and rounded pebbles are close or slightly smaller than in quartz veins, suggesting that a very thin cap of sediment has been removed from the surface by continental erosion following the formation of the terrace. We also measured 10 Be concentrations in four bedrock samples collected at lower elevation, in poorly preserved terraces containing many seastacks. The two samples collected on the terrace whose shoreline angle is ~34 m amsl indicate that this level is 138 +15 kyrs-old and corresponds to

Esmeralda (25.9°S):

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the last interglacial period (MIS-5) (Table 2). We do not explain the relatively low 10 Be concentrations measured in the two samples collected 90 m amsl. They suggest that the terrace whose shoreline angle is 92 m amsl may have formed during MIS-5 or MIS-7. These ages would require a very rapid uplift rate following MIS-7, contrasting with a much smaller uplift rate that may have prevailed between the formation of the large upper terrace and MIS-7. Alternatively, these small concentrations in cosmogenic isotopes may result from sediment that temporarily covered the sampled area. Indeed, aeolian deposits are present only 500 m east of the two samples collected 90 m amsl (Fig. 6d). Then, dunes may have covered them in the past, explaining their low concentration in cosmogenic isotopes, and minimum ages deduced from these concentrations may differ significantly from the age of the terrace.

Another method to estimate the coastal uplift rate is to suppose that the lower terraces observed in Caleta Agua de la Zorra and Punta Tetillas formed during successive Pleistocene highstand periods.

If we assume that the 34 m amsl terrace formed during MIS-5e, the following one during MIS-7 and so on, the calculated uplift rate is remarkably constant (~0.25 m/kyr, see Fig. 6 and Table 3). Now, assuming that this uplift rate maintained constant since the final emersion of the uppermost rasa, the upper terrace would be ~700 kyrs-old, which is compatible with cosmogenic data.

Chigualoco -Altos de

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respectively. As discussed above, onshore erosion may limit cosmogenic concentrations and result in underestimated ages, particularly for ancient terraces. Cosmogenic concentrations published in [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] for terrace TII may result from a terrace formed during MIS-9 in the absence of erosion. Alternatively, it may also correspond to a terrace that formed during MIS-11 and that suffered moderate (1 m/Myr, see Table 2) onshore erosion comparable to that observed in our profiles (e.g., in Chigualoco, see above). Moreover, assigning this terrace to MIS-9 implies that the uplift rate decreased from an exceptionally high value (1.2 mm/yr) between MIS-9 and MIS-7 to much lower values (~0.2 mm/yr) following MIS-7. [START_REF] Saillard | Andean coastal uplift and active tectonics in southern Peru: Be-10 surface exposure dating of differentially uplifted marine terrace sequences (San Juan de Marcona, ~15.4°S)[END_REF] propose that this velocity decrease marked the end of the Quaternary activity of the Puerto Aldea Fault. Assigning terrace TII to MIS-11 would also require a diminution of the Altos de Talinay uplift velocity following MIS-7, but the corresponding uplift rate between MIS-11 and MIS-7 (0.6 mm/yr) would have been in the range of vertical velocities observed elsewhere in Northern Chile.

For the same reasons, we argue it is difficult to assign the Caleta Maiten terrace sampled by [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF] to a precise highstand period, and the cosmogenic data only give a minimum age for this terrace.

Pleistocene uplift rates in Northern Chile between 24°S and 32°S

Assigning paleoshorelines to sea-level highstands gives information on the uplift that occurred following the emersion of the marker. Apparent uplift rates presented in Table 3 correspond to paleoshoreline elevations divided by their age. Paleoshorelines formed during sea-level highstands when the level of the ocean was close to the present-day sea level [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF]. Hence, the apparent uplift rate is a good first order estimation of the tectonic uplift velocity. Calculating absolute uplift rates requires knowing the precise sea-level elevation during highstands, which is a controversial issue (e.g., [START_REF] Simms | Marine terraces and rates of vertical tectonic motion: The importance of glacio-isostatic adjustment along the Pacific coast of central North America[END_REF]. Table 4 summarizes the age of Middle and Upper Pleistocene highstands and the corresponding sea-level elevations according to [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF].

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Table 3 and Fig. 7 shows minimum and maximum possible absolute uplift rates, calculated considering eustatic variations presented in Table 4. 2006) (see Table 3)

The maximum elevation of terraces formed during the last interglacial period (MIS-5) generally varies between 25 m amsl (Tongoy and Coquimbo) and 45 m amsl (Esmeralda and Caldera) (Table 3).

Only one higher terrace located 60 m amsl, in Punta Piedras, has been assigned to MIS-5. These data show that the entire coast of Norte Chico has been uplifting during the upper Pleistocene, with apparent uplift rates generally between 0.18+0.08 and 0.35+0.08 mm/yr (Table 3), with a maximum of 0.48+0.09 mm/yr in Punta Piedras. Data do not show major changes in uplift rate between neighbor points, confirming that no superficial crustal fault deformed the coastal zone during the Upper Pleistocene. In particular, the Puerto Aldea Fault that accommodates the uplift of the Altos de Talinay with respect to Tongoy Bay does not displace MIS-5 paleoshorelines. It shows that this fault remained apparently inactive during the Upper Pleistocene, as already noted by [START_REF] Saillard | Andean coastal uplift and active tectonics in southern Peru: Be-10 surface exposure dating of differentially uplifted marine terrace sequences (San Juan de Marcona, ~15.4°S)[END_REF].

We also highlight that this range of uplift rates is a compilation of various methods applied in different geomorphologic features (erosional vs. depositional coasts), and that data obtained using different methods in neighbor points generally indicate comparable uplift rates.

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When available, uplift rates calculated considering older paleoshorelines (MIS-7 and MIS-9) are close to those calculated for the Upper Pleistocene (since MIS-5) (Fig. 7). In fact, absolute uplift rates calculated since the penultimate highstand (MIS-7) are generally slightly larger than those calculated considering MIS-5 and MIS-9 paleoshorelines. In Pan de Azucar, Bahia Inglesa, Caleta Chañaral and Altos de Talinay the average absolute uplift rate since MIS-7 is between 0.05 and 0.13 mm/yr higher than that calculated considering MIS-5. In Caleta Chañaral, the average absolute uplift rate since MIS-7 is also 0.08 mm/yr higher than that calculated since MIS-9 and MIS-11. Following [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF], we assumed that the maximum sea level was -10+5 m amsl during MIS-7. These authors note, however, that this value is debated, some data suggesting that the sea may have risen above the present-day sea level. Then, the systematic bias towards larger MIS-7 absolute uplift rates may simply result from an underestimated elevation of sea level during this highstand.

In many places, the new cosmogenic data obtained in high terraces do not constrain precisely the age of terraces because post-emergence erosion rates cannot be quantified. Only minimum ages, and hence maximum uplift rates, can be calculated. These uplift rates are generally close to those obtained considering lower paleoshorelines, suggesting that uplift rates remained approximately constant during the Middle and Upper Pleistocene, as already proposed for the Bahia Inglesa area by [START_REF] Quezada | Pleistocene littoral uplift of northern Chile: Ne-21 age of the upper marine terrace of Caldera-Bahia Inglesa area[END_REF]. The only area in which uplift rates significantly varied since MIS-11 is the Altos de Talinay area, SW of the Puerto Aldea Fault. This has been evidenced by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF], even if changes in uplift rates may have been much smoother than proposed by these authors (see discussion above, section 5.1). This change in uplift rates may mark the activity of the Puerto Aldea Fault that may have accommodated the accelerated uplift of the Altos de Talinay area before MIS-7 [START_REF] Saillard | Andean coastal uplift and active tectonics in southern Peru: Be-10 surface exposure dating of differentially uplifted marine terrace sequences (San Juan de Marcona, ~15.4°S)[END_REF]. Fig. 8 presents the elevation of dated paleoshorelines between 24°S and 32°S. Despite most segments of the Norte Chico coasts have been uplifting at rates approaching 0.3 mm/yr since MIS-11, the higher elevation of Pleistocene paleoshorelines generally does not exceed 250 m amsl (Fig. 8), except in the Altos de Talinay area where terraces higher than 400 m amsl are observed. Older Neogene marine deposits, although locally present along the coast (Fig. 1), generally outcrop at smaller elevations than the higher Pleistocene paleoshorelines. It means that coastal uplift in the study area is recent, possibly younger than 1 Myr, or at least that it accelerated significantly during the Pleistocene [START_REF] Regard | Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary[END_REF]. The morphology of marine terraces also suggests that the Middle and Upper Pleistocene uplift followed a period of stability of the continent, the higher terrace

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being generally much wider and smoother than lower ones (Fig. 3). The same conclusion has been proposed by [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF]. These authors studied the morphology of the Choapa River valley that flows to the Pacific Ocean close to Chigualoco (31.6°S), and its connection with the coastal morphology. They observe that this valley is marked by a large upper fluvial terrace that penetrates more than 25 km inland, incised by a narrow valley in which the river flows to the ocean. The large fluvial terrace connects with the upper marine surface, suggesting that both formed during a period of relative stability of the coastal area with respect to sea level.

Along the coasts of Northern Chile, stability and/or subsidence prevailed during the Miocene, which contrasts with the present-day uplift [START_REF] Fuenzalida | High Stands of Quaternary Sea Level Along the Chilean Coast[END_REF][START_REF] Paskoff | Sur l'évolution géomorphologique du grand escarpement côtier du désert chilien[END_REF][START_REF] Roux | Determining the Neogene behavior of the Nazca plate by geohistory analysis[END_REF][START_REF] Clift | Slow rates of subduction erosion and coastal underplating along the Andean margin of Chile and Peru[END_REF]. Thus, external forearc vertical motions in Northern Chile obey a temporal scenario completely distinct from that prevailing in the high Cordillera, where a major uplift episode is believed to have occurred in the Miocene (e.g., [START_REF] Gregory-Wodzicki | Uplift history of the Central and Northern Andes: A review[END_REF][START_REF] Farias | Late Cenozoic deformation and uplift of the western flank of the Altiplano: Evidence from the depositional, tectonic, and geomorphologic evolution and shallow seismic activity (northern Chile, 19°30[END_REF][START_REF] Garzione | Rapid late Miocene rise of the Bolivian Altiplano: Evidence for removal of mantle lithosphere[END_REF][START_REF] Aguilar | Variability in erosion rates related to the state of landscape transience in the semi-arid Chilean Andes[END_REF]. The possible causes of the Pleistocene accelerated coastal uplift are beyond the scope of this paper, but since it affects a coastal segment whose length is almost 1000 km, local causes such as seamount subduction or local tectonics cannot explain its onset. In fact, models show that several parameters related to plate dynamics, such as the convergence velocity or the interplate stresses, may result in forearc uplift or subsidence [START_REF] Pedoja | Relative sea-level fall since the last interglacial stage: Are coasts uplifting worldwide?[END_REF][START_REF] Martinod | How do subduction processes contribute to forearc Andean uplift? Insights from numerical models[END_REF]. Higher Pleistocene paleoshorelines observed between 30.3°S and 31.3°S (Altos de Talinay area), in contrast, correspond to a local anomaly resulting from the activity of the Puerto Aldea Fault and other N-S oriented faults that accommodated the relative uplift of their western (coastal) block.

Different coastal morphology north and south 26.75°S: role of climate and marine erosion

Elsewhere than in the Altos de Talinay area, the elevation of the higher paleoshoreline is generally approximately 200 m amsl between 32°S and 27°S. North of 26.75°S, the width of the coastal fringe

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narrows, the higher preserved paleoshorelines are generally below 100 m amsl (Fig. 8), and in few places, they are totally absent. This contrast is not explained by the present-day uplift rates, since most of the coasts have been uplifting at similar velocities during the Upper Pleistocene (and northern segments apparently somewhat quicker than southern segments of the coast). of the coast [START_REF] Paskoff | Sur l'évolution géomorphologique du grand escarpement côtier du désert chilien[END_REF][START_REF] Quezada | Tectonic and climatic effects in the morphologic configuration of the coastal relief of northern Chile[END_REF]. Continental erosion prevailing south of 26.75°S

does not allow the preservation of such a high scarp and results in a lower continent close to the coast.

The widening of marine terraces by marine erosion during sea-level highstands requires the attack of the base of the scarp by the mechanical action of waves, and the collapse of the cliff. Debris fallen at the base of the cliff protect it from further erosion until they are evacuated by the ocean.

Therefore, higher scarps should retreat more slowly, as observed in analogue experiments by [START_REF] Damgaard | Soft cliff recession under oblique waves: Physical model tests[END_REF] or [START_REF] Caplain | Cliff retreat and sea bed morphology under monochromatic wave forcing: Experimental study[END_REF]. In the coastal segment located north of Tal-Tal

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(25.4°S), the fringe located between the base of the coastal scarp and the ocean, is often covered by thick caps of fallen debris. In many places, the bedrock is not visible at the scarp toe and the ocean is actively eroding the cap of fallen debris. It suggests that the process limiting the widening of the terrace may not be erosion of the bedrock by waves but the time necessary to evacuate fallen debris, because the volume of debris is much larger for a similar coastal retreat when the scarp is higher (Fig. 9). This may explain why, despite comparable uplift rates, marine terraces are particularly narrow and poorly preserved in the northern part of the study area. Narrow terraces are easily erased by marine erosion during the following highstand period. The same result is obtained by [START_REF] Melnick | Rise of the central Andean coast by earthquakes straddling the Moho[END_REF] in numerical models reproducing the appearance of coastal staircase sequences in uplifting continents. Models show that for comparable uplift rates, high terraces are preserved if the initial continental slope is small, whereas they are eroded and disappear beneath the coastal scarp when the continental slope is large.

Then, the presence of the high coastal scarp and the absence of widely preserved paleoshorelines may not necessarily imply that the coast has not been uplifting during the Pleistocene. We propose instead that the present-day morphological segmentation of the coast at 26.75°S marks the transition from the semi-arid Norte Chico to the hyper-arid Norte Grande climate, rather than latitudinal changes in the Pleistocene uplift velocities.

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Conclusions

Cosmogenic ( 10 Be) concentrations were measured in Pleistocene marine terraces of northern Chile between 24°S and 32°S show that onshore erosion rates following the emergence of paleoshorelines approached 1 m/Myr. Then, minimum ages calculated without erosion may be largely underestimated for Middle Pleistocene terraces, and it is not possible to assign paleoshorelines to particular sea-level highstands for these terraces. The analysis of both new cosmogenic data and

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previously published ages shows that the Upper Pleistocene uplift rate has been 0.28 +/-0.15 mm/yr in the study area. Data do not show major changes in uplift rate between neighboring points, suggesting that this uplift is a regional phenomenon related to the dynamics of the entire forearc area. Active faulting does not seem to affect coastal uplift, except in the Altos de Talinay area during the Middle Pleistocene. Since the maximum elevation of Pleistocene paleoshorelines in Northern

Chile is generally close to 250 m amsl, measured rates imply that coastal uplift accelerated during the Pleistocene following a period of stability of the forearc, as already proposed by [START_REF] Regard | Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary[END_REF] and [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF]. Data confirm, however, that the coastal uplift rate has been rather constant during the Middle and Upper Pleistocene in most of the study area (Fig. 7), as already observed in Bahia Inglesa by [START_REF] Quezada | Tectonic and climatic effects in the morphologic configuration of the coastal relief of northern Chile[END_REF]. Within this period, brief pulses of very rapid uplift are not apparent, except possibly in Altos de Talinay where an episode of rapid uplift may have occurred during the Middle Pleistocene when crustal faulting was active. However, considering dating uncertainties resulting from post-emergence erosion implies that maximum uplift rates may have been lower than proposed by [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]. Although Pleistocene uplift rates are comparable everywhere in the study area, we observe that the morphology of the coast largely depends on the onshore continental slope. North of 26.75°S, the presence of a coastal scarp (whose preservation is encouraged by the hyper-arid climate of the Atacama Desert) inhibits the growth of marine terraces. This particular morphology of the coast may explain why paleoshorelines are poorly preserved between 26.75°S and 24°S despite Upper Pleistocene uplift rates being comparable with those prevailing in the southern part of the study area. 3) Table 1: 10 Be concentrations in samples collected along the coasts of Chile between 24°S and 32°S.

[1] new data; [2] data published in [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]; [3] data published in [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF].

Table 2: 10 Be concentrations measured in surface samples, and corresponding ages calculated considering different erosion rates between 0 and 1.5 m/Myr using the Cronus-Earth web calculator [START_REF] Balco | A complete and easily accessible means of calculating surface exposure ages or erosion rates from (10)Be and (26)Al measurements[END_REF] Table 3: Correlation of dated terraces to MIS, corresponding apparent and absolute uplift rates.

Minimum and maximum absolute uplift rates have been calculated considering uncertainties on sea-level highstand elevations and ages proposed by [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF] (Table 4), and an uncertainty of + 5 m in the elevation of shoreline angles. [START_REF] Leonard | Low Uplift Rates and Terrace Reoccupation Inferred from Mollusk Aminostratigraphy, Coquimbo Bay Area, Chile[END_REF] ; [9] [START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF][10] A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT [START_REF] Quezada | Pleistocene littoral uplift of northern Chile: Ne-21 age of the upper marine terrace of Caldera-Bahia Inglesa area[END_REF]. MIS correlations proposed by [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF] and [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] are discussed in section 5. [START_REF] Siddall | Eustatic sea level during past interglacials[END_REF], adopted to estimate the absolute uplift rates presented in Table 3.

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Highlights:

 We date paleoshorelines in Chile between 24°S and 32°S using 10 Be concentrations data  Post-emergence erosion of abrasion shore terraces approaches 1 m/Myr  The coast has been uplifting at ~0.3 mm/yr during the Upper Pleistocene  Uplift velocity increased during the Pleistocene following a period of stability  Paleoshorelines are poorly preserved beneath the northern coastal scarp

  the Chilean coasts, or are they instead controlled by local tectonic settings? Answers to the aforementioned questions require dating the beginning of the present-day episode of coastal uplift in Northern Chile. Considering published data, Regard et al. (2010) estimate the onset of coastal uplift in Northern Chile and Southern Peru, looking at the elevation of the highest preserved shoreline and supposing that the vertical velocity remained constant since the beginning of uplift. They propose that coastal uplift started in most sectors of Pacific coasts of the

Figure 1 :

 1 Figure 1: (a) Location of dated marine paleoshorelines and other sites cited in the text. Empty triangles: 10 Be data on surface samples; filled triangles: 10 Be data in vertical profiles; diamonds:

Figure 2 :

 2 Figure 2: View from the South of the Punta Piedras terrace beneath the coastal scarp (24.75°S).

Figure 3 :

 3 Figure 3: Contrasted morphology of the upper and lower terraces in Punta Tetillas (29°S). (a) The

Figure 4 :

 4 Figure 4: Latitude vs. elevation of dated paleoshorelines. Circles correspond to paleoshorelines dated

Figure 6 :

 6 Figure 6: Map and inner edge elevation of coastal terraces located close to Caleta Chañaral. The location of detailed maps (c) and (d) is given in (a). (b) Assigning terraces to successive oddnumbered isotopic stages (triangles) implies a remarkably constant uplift rate close to 0.25 mm/yr. Minimum ages deduced from 10 Be concentrations in samples from Punta Tetillas (empty diamonds) confirm that T1 corresponds to MIS-5, and that the higher 160 m amsl terrace is older than 600 kyrs. See the text for the discussion of 10 Be concentrations.

  Talinay coastal segment (31.5°S -30.2°S) Saillard et al. (2009) measured 10 Be concentrations on the four main platforms. Samples were collected 241 m amsl, 102 m amsl, 30 m amsl and 18 m amsl for TI, TII, TIII and TIV terraces, respectively, and gave minimum exposure ages of 679, 318, 225 and 149 kyrs. Considering that postemersion erosion has been negligible and does not affect cosmogenic isotope concentrations, Saillard et al. (2009) assigned terraces TI, TII, TIII and TIV to MIS 17, 9, 7, and 5, respectively. These authors also considered that the maximum position reached by the ocean during each of these highstand levels corresponded to the shoreline angle preserved above each sampling point, i.e. that MIS-17, 9, 7 and 5 marine transgressions reached elevations of 425, 170, 55 and 25 m amsl, A C C E P T E D M A N U S C R I P T

Figure 7 :

 7 Figure 7: Absolute uplift rates calculated considering Pleistocene eustatic variations proposed by

Figure 8 :

 8 Figure 8: Elevation of dated terraces along the coasts of Norte Chico. We also report the elevation of

  A younger initiation of coastal uplift north of 26.75°S may explain the absence of high Pleistocene paleoshorelines in the northern part of the study area. Nevertheless, this does not explain why MIS-5 terraces in the north are much more discreet and narrow than in the south. Everywhere in the study area, the coastal lithology is dominated by Mesozoic igneous rocks (Fig. 1). Hence, lithology does not explain the different morphology north of 26.75°S. In fact, 26.75°S marks a major change in the morphology of both the coastal area and Coastal Cordillera. South of 26.75°S, the climate of northern Chile is semi-arid (Fig. 1), and rivers flow from the Western Cordillera through the Coastal Cordillera to the ocean. 26.75°S corresponds to the southern boundary of the hyper-arid Atacama Desert. In Chile, it is known as the boundary between the semi-arid Norte Chico, and the hyper-arid Norte Grande area, in which Quaternary erosion of the Coastal Cordillera by rivers has been particularly small. North of 26.75°S, the elevation of the coastal scarp suddenly increases. The coastal scarp is a major morphological feature of Northern Chile whose average elevation approaches 1000 m. Its occurrence is related to the hyper-arid climate of that part

Figure 9 :

 9 Figure 9: Simple sketch of marine erosion, supposing that the evacuation of debris fallen at the base

Figure 1 :

 1 Figure Captions

Figure 2 :

 2 Figure 2: View from the South of the Punta Piedras terrace beneath the coastal scarp (24.75°S).

Figure 3 :

 3 Figure 3: Contrasted morphology of the upper and lower terraces in Punta Tetillas (29°S). (a) The

Figure 4 :

 4 Figure 4: Latitude vs. elevation of dated paleoshorelines. Circles correspond to paleoshorelines dated

Figure 5 :

 5 Figure 5: 10 Be concentrations along vertical profiles sampled in marine terraces in Chigualoco and

Figure 6 :

 6 Figure 6: Map and inner edge elevation of coastal terraces located close to Caleta Chañaral. The

Figure 7 :

 7 Figure 7: Absolute uplift rates calculated considering Pleistocene eustatic variations proposed by

Figure 8 :

 8 Figure 8: Elevation of dated terraces along the coasts of Norte Chico. We also report the elevation of

Figure 9 :

 9 Figure 9: Simple sketch of marine erosion, supposing that the evacuation of debris fallen at the base

  [1] new data published in this paper; Data after [2] Rodriguez et al. (2013); [3] Saillard et al. (2009); [4] Radtke (1987b); [5] Radtke (1987a); [6] Radtke (1989); [7] Saillard et al. (2012); [8] Leonard & Wehmiller (1992) ; [9] Marquardt et al. (2004) ; [10] Quezada et al. (2007). MIS correlations proposed by Rodriguez et al. (2013) and Saillard et al. (2009) are discussed in section 5.1.

  dated older (860 kyr-old) paleoshorelines in the same sector. The average uplift velocity they calculate is slightly smaller than that proposed by[START_REF] Marquardt | Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)[END_REF], and they note that this difference may evidence a moderate acceleration of the vertical coastal velocity during the second half of the Middle Pleistocene. In contrast, in the Altos de Talinay

area (~30.5°S), data presented by

[START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]

suggest highly variable uplift rates during the Middle and Upper Pleistocene (see Introduction).

  Table 2 also indicates ages calculated from 10 Be concentrations published in[START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] and in[START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF], for different possible erosion rates. It shows that taking into account erosion rates largely modifies calculated ages for ancient terraces. For instance, surface sample 10 Be concentrations in 400 kyr-old (MIS-11) terraces without onshore erosion are similar to concentrations in 670 kyr-old (MIS-17) terraces whose erosion rate is 1 m/Myr. For younger terraces that formed during the last or penultimate interglacial period (MIS-5 or MIS-7), the dependence of calculated ages on erosion rates is much smaller. For instance, 10 Be concentrations in MIS-5e (124 kyr-old) terraces only differ by less than 10% when the erosion velocity changes from 0 to 1 m/Myr, whereas the corresponding difference is 34% and 60% in MIS-11 and MIS-17 terraces, respectively.

  10 Be concentrations measured in the bedrock 45 m amsl show that marine erosion has been active at this elevation during the last interglacial period. The inner edge of the Table2). This value is coherent both with the age obtained by Quezada in Bahia Inglesa, 80 km north of Caleta Sal, on the highest 224 m amsl terrace (~860 kyrs), and with the profile presented above sampled close to Huasco, 50 km to the south. These three data suggest that the highest preserved Pleistocene paleoshoreline in this segment of the coast formed between 500 kyrs and 1 Myr.

	ACCEPTED MANUSCRIPT
	Pan de Azucar (26.15°S): We sampled ancient sea-stacks between 53 and 64 m amsl.
	Concentrations in cosmogenic isotopes correspond to minimum ages close to 200 kyrs (except one
	sample at 282 (+/-32) kyrs), suggesting that sampled seastacks formed during the penultimate glacial
	period (MIS-7). Coastal segment between Caleta Obispito (26.75°S) and Huasco (28.4°S): In Caleta Sal, we measured 10 Be cosmogenic concentrations both in bedrock and rounded pebbles from the highest terrace, 170 m amsl. Concentrations reach 1.9x10 6 at/g, indicating a minimum age of 460 kyr for the M A N U S C R I P T formation of this terrace (
	A C C E P T E D
	coastal rasa is generally below 100 m amsl. Above the main rasa, a small terrace located ~115 m
	amsl, covered by a thin cap of pebbles has been locally preserved. Concentrations in cosmogenic
	isotopes indicate a minimum age for this latter terrace of 424+/-44 kyrs (Table 2), i.e. that it formed
	during or before MIS-11.

Caleta Chañaral (29°S): Close to Punta Tetillas, in two sites 500 m apart, we sampled quartz veins, quartz clasts and rounded quartz pebbles on the surface of the upper terrace, at an elevation of 160 m amsl. Minimum ages deduced from cosmogenic concentrations in bedrock samples are 591 (+/-63)

Table 4 :

 4 Age of Middle and Upper Pleistocene highstands and corresponding sea-level elevations (after[START_REF] Siddall | Eustatic sea level during past interglacials[END_REF], adopted to estimate the absolute uplift rates presented in Table3.

	M A N U S C R I P T
	A C C E P T E D

Table 2 :

 2 10 Be concentrations measured in surface samples, and corresponding ages calculated considering different erosion rates between 0 and 1.5 m/Myr using the Cronus-Earth web calculator[START_REF] Balco | A complete and easily accessible means of calculating surface exposure ages or erosion rates from (10)Be and (26)Al measurements[END_REF]

		ACCEPTED MANUSCRIPT
			Terrace		Apparent	Minimum	Maximum
		Latitude	shoreline angle		uplift rate	absolute	absolute
	Site	(°S)	Elevation (m)	MIS	(mm/yr)	uplift rate	uplift rate	ref.
	Punta Piedras	24.76	61	5	0.48	0.38	0.57	[1]
	Esmeralda	25.91	115	> 11	< 0.27	-	0.27	[1]
	Esmeralda Pan de Azucar Pan de Azucar Caleta Obispito Caldera Caldera Bahia Inglesa Bahia Inglesa Bahia Inglesa Caleta Sal Huasco Huasco Caleta Chañaral Caleta Chañaral Caleta Chañaral Caleta Chañaral Caleta Chañaral Caleta Chañaral Quebrada Honda Teatinos Coquimbo Coquimbo Tongoy Tongoy Altos de Talinay Altos de Talinay Altos de Talinay A C C E P T E D 25.91 45 26.14 33 26.14 64 26.75 43 27.05 23 27.05 44 27.15 40 27.15 78 27.15 224 27.93 185 28.39 155 28.40 30 29.02 34 29.02 54 29.03 92 M A N U S C R I P T 5 0.35 0.26 5 0.25 0.17 7 0.35 0.27 5 0.33 0.24 5 0.17 0.09 5 0.34 0.25 5 0.31 0.22 7 0.42 0.33 > 13 < 0.43 -> 9 < 0.36 -> 13 < 0.30 -5 0.23 0.15 5 0.26 0.18 7 0.30 0.23 11 0.22 0.19 29.03 74 9 0.23 0.19 29.03 110 13 0.23 0.19 29.03 164 > 13 < 0.32 -29.60 33 5 0.25 0.17 29.82 58 > 7 < 0.17 -29.98 25 5 0.18 0.11 29.98 41 > 7 < 0.20 -30.20 25 5 0.18 0.11 30.20 114 11 0.29 0.24 30.48 25 5 0.18 0.11 30.84 170 9-11 0.52-0.42 0.37 30.87 55 7 0.31 0.23 Altos de Talinay 30.90 425 > 15 < 0.67 -	0.43 0.33 0.44 0.41 0.24 0.42 0.39 0.52 0.43 0.36 0.30 0.30 0.34 0.39 0.26 0.27 0.26 0.32 0.33 0.17 0.26 0.12 0.26 0.33 0.26 0.57 0.39 0.67	[1] [4] [1] [4] [4] [9] [5] [9] [4] [10] [1] [1] [4] [1] [1] [1] [1] [1] [1] [5] [8] [6] [8] [4] [7] [7] [3] [3] [3] [3]
	Caleta Maiten	31.15	185	> 13	< 0.36	-	0.36	[2]
	Chigualoco	31.70	180	> 11	< 0.41	-	0.41	[1]

Table 3 :

 3 Correlation of dated terraces to MIS, corresponding apparent and absolute uplift rates.Minimum and maximum absolute uplift rates have been calculated considering uncertainties on sealevel highstand elevations and ages proposed by[START_REF] Siddall | Eustatic sea level during past interglacials[END_REF] (Table 4) , and an uncertainty of + 5 m in the elevation of shoreline angles.[1] new data published in this paper; Data after[2]

[START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF] [3]

[START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF] [4]

Radtke (1987b); [5]

Radtke (1987a); [6]

[START_REF] Radtke | Marine Terrassen und Korallenriffe. Das problem der Quartären Meerespiegelschwankungen erlänter an Fallstudien aus Chile, Argentinien und Barbados[END_REF] [7]

[START_REF] Saillard | Beach ridges U-Th dating in Tongoy bay and tectonic implications for a peninsula-bay system, Chile[END_REF] [8]

Table 4 :

 4 1. Age of Middle and Upper Pleistocene highstands and corresponding sea-level elevations (after

	highstand	Sea level (m amsl)	Age (kyr)
	MIS 5e	3 ± 3	116 -131
	MIS 7	-10 ± 5	190 -235
	MIS 9	2 ± 5	315 -334
	MIS 11	0 ± 10	395 -415
	MIS 13	0 ± 10	472 -502
	MIS 15	0 ± 10	558 -620
	MIS 17	-15 ± 15	685 -695

Acknowledgments: This work has been financed by the Institut National des Sciences de l'Univers, France (Syster program), by the International Mixt Laboratory "Copedim", and by the ECOS-Conicyt program (project C11U02). Authors thank editor (A.J. Plater), D. Melnick and an anonymous reviewer for their detailed and constructive comments which helped us to largely improve the manuscript.

ACCEPTED MANUSCRIPT Table 1: 10 Be concentrations in samples collected along the coasts of Chile between 24°S and 32°S. [1] new data; [2] data published in

 [START_REF] A C C E P T E D M A N U S C R I P T Accepted Manuscript | Non-steady long-term uplift rates and Pleistocene marine terrace development along the Andean margin of Chile (31°S) inferred from Be-10 dating[END_REF]data published in [START_REF] Rodriguez | Geochronology of pediments and marine terraces in north-central Chile and their implications for Quaternary uplift in the Western Andes[END_REF].