Daniel Dinu
email: daniel.dinu@insep.fr.

Radu Bidiugan

Françoise Natta

Nicolas Houel

Preliminary study of accuracy and reliability of high-speed human-motion tracking using miniature inertial sensors

Keywords: Inertial navigation system, shot put, 3D kinematic studies

published or not. The documents may come

Preliminary study of accuracy and reliability of high-speed human-motion tracking using miniature inertial sensors

Introduction

The evaluation of athlete's performance is one of the main issues in coaching, as well as in sports biomechanical analysis. In this aim, the analysis of the complex motions like shot put, without influencing or constraining athletes' activity and with a quick feedback is now becoming mandatory [START_REF] Bergamini | Biomechanics of sprint running: a methodological contribution[END_REF]. Shot put is a complex movement that associates translation and rotation [START_REF] Ariel | Computerized biomechanical analysis of the world's best shot-putters[END_REF][START_REF] Zatsiorsky | Biomechanical analysis of shot putting technique[END_REF][START_REF] Mccoy | Kinematic analysis of elite shot-putters[END_REF][START_REF] Hubbard | The throwing events in track and field[END_REF][START_REF] Lanka | Shot putting[END_REF]. The goal is to release the shot with maximum forward velocity at an angle of approximately forty degrees [2-5, 7, 8, 9, 10, 11]. Nowadays, most of the high level competitors use the spin style whose main purposes are to reach a high rotational speed of the body and to transfer the energy into the shot put [START_REF] Linthorne | Optimum release angle in the shot put[END_REF].

Among the new wearable and lightweight technologies allowing for such assessment, miniature inertial centrals appear to be a good compromise between accuracy and using easily. The Moven system includes this original technology. The Moven system is composed of 17 miniature inertial centrals attached to the body. These sensors combine three-axial accelerometers, gyroscopes, and, magnetometer used for the measurement of a global reference frame. They allow data collection during unconstrained continuous movement over prolonged periods of time, potentially even during training and competition. The advantage of this kind of system seems to be fast reconstruction of the motion patterns and feedback.

Nevertheless, the extraction of the movement related to information from the signal derived from inertial technologies can be exposed to the offset errors and the drifts accumulated over time [START_REF] Winter | Biomechnics and motor control of human movement[END_REF][START_REF] Woodman | Introduction to Inertial Navigation[END_REF].

It can also be exposed to sensors oscillations caused by the inertia of soft tissues [START_REF] Bergamini | Biomechanics of sprint running: a methodological contribution[END_REF][START_REF] Winter | Biomechnics and motor control of human movement[END_REF]. The purpose of this study was to compare a new motion analysis system that used the technology of inertial sensors with the kinematic data given by an optoelectronic system in sport training conditions. The results of this preliminary study only concern the velocity norm of the right hand during the shot put.

Methods

The experiment took place in an indoor hall at the National Institute for Sport, Expertise and Performance. Three male subjects voluntarily participated to this study. All subjects were high level shot putters of the French national team. All subjects were asked to perform three shot puts with standard (7.2 kg) shots. For each subject, only the best shot put (longest distance) was studied.

Kinematic data were collected simultaneously with a Moven (Xsens Technologies BV, Enschede, Holland) and Vicon (Vicon Motion systems, Oxford, UK) systems. The Moven system is composed of straps. Each nIMU contains three gyroscopes, three accelerometers, three magnetometers in a 35-g box about the size of a match box. Each nIMU captures in real time the full 6 degrees of freedom of the body where it is fixed. The subjects wore the Moven capture suit which also included a wireless data link. The sampling frequency was equal to 60 Hz. Kinematic analysis was performed with a modified version of the software provided by Moven. In order to determine the velocity motion, numerical integration of the kinetic data was performed using trapezoid rule. The optoelectronic system (Vicon) consisted of 6 infrared Vicon 612 camcorders. A static calibration around the throwing area was done. A dynamic calibration was performed using a 390 mm stick with two markers moving in the throwing area. The sampling frequency of the Vicon system was 200 Hz. For this experiment, reflective markers were attached on the nIMU sensors of the Moven System. 3D Kinematic data were computed with the software provided with the optoelectronic Vicon system. In order to determine velocity of the reflective markers, numerical derivation of the kinematics data was performed using moving average rule. In the aim to compare velocity data of both systems (Moven versus Vicon), the kinetic data of the Vicon system have been re-sampled at 60 Hz. Data of both systems were synchronised when the shot left the athlete's hand. The validation procedure consisted in comparing the velocity patterns of the middle of the second metacarpal on the right hand computed by the Moven system with those given by an optoelectronic system (Vicon) composed of 6 infrared camcorders.

Paired t-test was used to compare the significant difference between the velocities' data measured with the systems (Vicon, Moven). Correlation coefficient (r) was used to estimate the relation between the velocities' data measured with both systems. A Bland and Altman test [START_REF] Bland | Comparing methods measurement: why plotting difference against standard method is misleading[END_REF] was used to define the accuracy and reliability between the kinematic variables of both devices. The results of this preliminary study only concern the velocity module of shot put.

Results

The statistical results showed that velocity data computed with both systems were not agreed sufficiently well to be used interchangeably. However the results showed that the velocity data of the two systems presented similar patterns during the whole movement. Results showed no significant difference on velocity data between both system (p = 0.066). Correlations between the systems for velocity data was r > 0.46 (p = 6×10-6). Bland & Altman test showed a very low under estimation (mean bias < 0.5 m.s-1) of the velocity data using the Moven system and a high reliability (mean reliability < 0.92 m.s-1) compared with the Vicon system (figure 1). Similar same pattern of shot put velocity curve during the whole movement were obtained with both systems (figure 2).

Discussion and conclusion

This study has compared velocity data computed with Moven and Vicon systems and has shown that data presented similar patterns and kinematics relations but can not be used interchangeably. The main limit of this study is the difference of computational algorithms employed by the Moven and Vicon systems.

In our study, the result of the paired t-test showed that both systems could be used to estimate velocity data with no significant difference. But the correlation result and the Bland & Altman test showed that some precautions should be taken into account before interchanging both systems. First, correlation between both systems stays very low during the full movement. Second, the Bland & Altman test have showed that i) the Moven system tended to underestimate velocities lower than 2 m.s-1 during the first phase of the shot put; ii) velocity computed with both systems seemed similar with decreasing reliability, when it ranked between 2 to 3 m.s-1; iii) the Moven system tended to underestimate velocities upper than 3 m.s-1 during the last phases of the shot put. Different assumptions could explain these results. The low sampling frequency used in the Moven system and the numerical integration used to compute the velocity data may influence the results and improve the drift [START_REF] Pfau T Witte | A method for deriving displacement data during cyclical movement using an inertial sensor[END_REF][START_REF] Winter | Biomechnics and motor control of human movement[END_REF][START_REF] Baumgart | Sampling rate influences on vertical jump height in force plate analysis[END_REF]. The integration process used to compute the velocity data with the Moven system could be sensitive to sensor drifts [START_REF] Baumgart | Sampling rate influences on vertical jump height in force plate analysis[END_REF]. In the case of the Vicon system, errors in the velocity data depend of the accuracy positioning of the marker during the recording process. The derivation computing process improved the noise added to the kinematics data and could have influenced the velocity [START_REF] Winter | Biomechnics and motor control of human movement[END_REF]. In our study, the differences in velocity curves obtained with both systems could be explained by the magnetic field sensors that have been altered by the metallic put. The proximity of a metallic mass added by the shot put could disturb the Moven data acquisition process. Indeed, the magnetic field sensors, which contribute to the process of orientation estimation, are sensitive to alteration of the earth magnetic field. In recent studies using inertial sensor system in skiing and sprint running, the inaccuracy of the motion capture system was assumed to be mostly due to geomagnetic variations [START_REF] Supej | 3D measurements of alpine skiing with an inertial sensor motion capture suit and GNSS RTK system[END_REF][START_REF] Bergamini | Biomechanics of sprint running: a methodological contribution[END_REF]. However, velocity data computed by both systems presents similar velocity patterns. It can be assumed that the Moven system could be also used even during training without laboratory constraint. The asset of the Moven system is that it could be used to evaluate sport motion in outside sports without restriction of area recording, light conditions, tracking and markers recognition.

FIGURESFig. 1 .Fig. 2 .

 12 FIGURES


Yassine Banouar

Clovis Anicet Ouedraogo

Christophe Chassot
email: chassot@laas.fr

Abdellah Zyane
email: a.zyane@uca.ma

QoS Management Mechanisms for Enhanced Living Environments in IoT

Keywords: Internet of Things, Enhanced Living Environments, Middleware, Quality of Service mechanisms, Autonomic Computing I

The Internet of Things (IoT) paradigm is expected to bring ubiquitous intelligence through new applications in order to enhance living and other environments. Several research and standardization studies are now focused on the Middleware level of the underlying communication system. For this level, several challenges need to be considered, among them the Quality of Service (QoS) issue. The Autonomic Computing paradigm is now recognized as a promising approach to help communication and other systems to self-adapt when the context is changing. With the aim to promote the vision of an autonomic Middlewarelevel QoS management for IoT-based systems, this paper proposes a set of QoS-oriented mechanisms that can be dynamically executed at the Middleware level to correct QoS degradation. The benefits of the proposed mechanisms are also illustrated for a concrete case of Enhanced Living Environment.

INTRODUCTION

The Internet of Things (IoT) is expected to bring a large and promising spectrum of ubiquitous intelligence through new applications in various domains such as health, transport, industry, energy, environment, retail or logistics. Living environments should strongly benefit from those new communication capabilities that will make possible the execution of dynamic and autonomous actions going from, for instance in healthcare context, accurate supervision of patients to intervention in case of emergency. To make possible the deployment of such Enhanced Living Environments (ELE), network-level communication capabilities (such as Bluetooth, Zigbee, Wi-Fi, or wired technologies) are not sufficient. Indeed, Middleware-level platforms are required to allow hiding complexity of heterogeneous devices (sensors, effectors, tags, etc.) and communication technologies. Without such an intermediate abstraction layer between the IoT applications and the underlying communication technologies, the implementation of each application would be dependent on the devices technologies, leading to a vertical fragmentation between IoT applications and an impossible extensibility when new devices/capabilities appear.

In 2012, the ETSI standardization effort resulted in the proposition of the Machine-to-Machine (M2M) architectural framework [START_REF]Machine-to-Machine communications (M2M); Functional architecture[END_REF] enabling the management of IoT applications, the abstraction of networks and devices heterogeneity, etc. This specification has been extended recently under the oneM2M architectural framework [START_REF] Zyane | [END_REF] which is now recognized as the de facto standard for the IoT paradigm.

Basically, both ETSI M2M and oneM2M frameworks are built on 4 levels: [START_REF]Machine-to-Machine communications (M2M); Functional architecture[END_REF] Application level where business applications (home automation, smart metering, smart grid, etc.) offering final solutions are defined; (2) Middleware level that aims at hiding the details of various underlying networks and technologies to facilitate interoperability; (3) Network level that includes different types of networks to interconnect equipment; and (4) Device level that includes IoT sensor / actuators devices. An instantiation of this framework (Fig. 1) is composed of Business applications, Server and Gateways acting as Middleware entities, and finally Devices interconnected to their Gateways through specific network technologies (Bluetooth, Zigbee, etc.). ELE are expected to be driven by several kinds of applications. In healthcare context, IoT can bring remote supervision of patients' health (heartbeat rate, glycaemia, etc.) and intervention when critical situation occurs. Each activity may be supported thanks to several devices held by the patients themselves, but also by all the entities involved in the global process (pharmacy, doctor, hospitals, etc.). All the exchanges have different priorities depending on the context: for instance, an alarm indicating a heart attack of a "riskycondition" patient is more important than supervision information of a young jogger. In terms of communication, such differences have to be translated into quality of service (QoS) requirements: the transmission delay of an alarm is expected to be as fast as possible, while a great delay of a nonsensitive supervision data could be acceptable.

Providing IoT platforms with QoS-oriented capabilities becomes a necessity that remains under research study [START_REF] Banouar | Monitoring solution for autonomic Middleware-level qos management within iot systems[END_REF][START_REF] Khanouche | Energy-centered and qos-aware services selection for internet of things[END_REF]. QoS issue in such environments is more considered at the network and device levels by the proposition of packet scheduling algorithms [5], service differentiation techniques [START_REF] Abdullah | A qos aware message scheduling algorithm in internet of things environment[END_REF], routing protocols [START_REF] Shih | Distributed qos aware meta-routing for iot/cps[END_REF] and adaptive architectures for devices [START_REF] Ezdiani | An iot environment for wsn adaptive qos[END_REF]. The work presented in this paper focuses on the Middleware level and aims at promoting the vision of a dynamic and autonomic management of QoS-oriented adaptive actions, following the autonomic computing paradigm (AC) [START_REF] Kephart | The vision of autonomic computing[END_REF]. As depicted in Fig. 2, this paradigm is based on the monitoring, analysis, planning and execution steps, which are aimed at applying adaptation actions on the managed system according to its state thanks to a shared knowledge base. In our case, the considered system is an ETSI-M2M compliant Middleware platform, the open-source OM2M platform [START_REF] Ben Alaya | OM2M: extensible ETSI-compliant M2M service platform with selfconfiguration capability[END_REF]. The contributions of this paper are foccussed on the adaptation actions that may be performed to go toward the respect of the required QoS. Two kinds of adaptation actions are considered: "request-oriented" adaptation deals with the differentiation actions that can be done in the processing of requests having different QoS requirements; "resourceoriented" actions deals with the adaptation of the deployment resources, for instance at the virtual machine level for Middleware-level entities that are deployed in a cloud environment (typically IoT Servers).

The rest of this paper is structured as follows. Section II describes the QoS-oriented mechanisms that we propose at the Middleware level for an ETSI M2M compliant IoT platform. Section III illustrates how some of those mechanisms can be implemented within a typical example of ELE scenario. Performance measurements allow showing the benefits that can be induced with the application of those mechanisms. Finally, section V provides conclusion and future work.

II. QOS-MANAGEMENT MECHANISMS AT THE MIDDLEWARE LEVEL

In order to satisfy the requirements of critical IoT applications, Middleware-level functionalities need to be extended to include QoS management mechanisms. In this section, we propose two levels of mechanisms: (1) requestoriented mechanisms that intervene on incoming HTTP requests; and (2) resource-oriented mechanisms that reconfigure Middleware resources. Those mechanisms are supposed to be configured by an autonomic manager (AM), and more specifically by its planning component, according to the QoS constraints of critical IoT applications but also to the type of the managed entity (Server or Gateway) and its current performance state.

A. Request-oriented Mechanisms

Request-oriented mechanisms are inspired by the mechanisms used in the Internet, specifically at the Transport and Network layers of the TCP/IP architecture. The approach follows the main principles of the DiffServ model [START_REF] Blake | An architecture for differentiated services[END_REF], which is based on packet marking at the network entry and differentiation of the packet processing in each core routers depending on their mark. To implement a similar approach at the Middleware level, we add a field to the HTTP request specifying its priority; this priority allows guiding the request processing through the mechanisms components.

Two successive steps are then carried out (Fig. 3). The first one is the classification and priority marking based on a number of criteria defined by the AM; this step is done by the Classification and Marking Component (CMC). The second step is the processing of the request based on its priority by the Performance Enhancing-Proxy (PEP), and then its possible redirection to the Middleware entity (i.e. server or gateway)

1) Classification and Marking Component

The Classification and Marking Component (CMC) adds a TOS_HTTP header (Type Of Service for HTTP) that contains the priority assigned to the HTTP request. The CMC interacts with two main actors:

• Source: sender of the HTTP request towards the system. We consider two types of sources: QoSunaware sources that are not able to express their QoS requirements, and QoS-aware sources that are able to express them through the adding of the TOS_HTTP field with an appropriate priority ;

• Autonomic Manager: responsible of the configuration of the underlying components (CMC, PEP and Middleware). For the CMC, the AM intervenes for the classification (requests classes) and the marking (priority of each class) policies.

As described in Fig. 4, the CMC contains the following components:

• CMC Manager: acts as a communication interface with the AM; it allows activation/deactivation of the CMC as well as management of classification and marking policies;

• CMC Receiver: receives requests from sources. When activated, it directs the traffic either to the "Request Classifier" if the TOS_HTTP header does not exist, or directly to the "HTTP Forwarder" if it exists or if the component is deactivated;

• Request Classifier: classifies the incoming requests according to the classification policy. It first analyses the HTTP request (without TOS_HTTP header) according to the criteria specified in the policy (source IP address, destination IP address, resource URL, etc.), and then redirects it to the "Request Marker";

• Request Marker: assigns a priority to each request based on its membership class. It is based on the marking policy and adds the TOS_HTTP header to the HTTP request with the corresponding priority. For instance, the TOS_HTTP can get as a value PRIORITY_HIGH, PRIORITY_MEDIUM or PRIORITY_LOW;

• CMC Forwarder: redirects the request containing the TOS_HTTP header to the PEP component if the QoS management is activated, otherwise to the OM2M platform.

2) Performance Enhancing Proxy

The Performance Enhancing Proxy (PEP) is responsible for processing requests according to their priorities (TOS_HTTP). This component can make either request rejection, request delaying, request scheduling, or a combination of these mechanisms depending on the policy communicated by the AM. As illustrated in Fig. 5, the PEP contains the following components:

• PEP Manager: applies the policy coming from the AM. It includes the mechanism(s) to be triggered (rejection, delaying or scheduling) as well as the configuration to be applied (percentage of rejection, delaying duration, scheduling policy to be applied and weight of each priority, etc.);

• PEP Receiver: receives requests containing the TOS_HTTP header and sends them to the "PEP Controller";

• PEP Controller: analyses the TOS_HTTP header of the requests and sends them to one of the internal components according to the management policy;

• PEP Rejecter: is responsible for rejecting requests based on their priorities. Each priority corresponds to a percentage of rejection;

• PEP Delayer: delays requests according to their priorities. Each priority corresponds to a delaying duration;

• PEP Scheduler: schedules the incoming requests according to their priorities. This component offers two scheduling policies: priority-first and weighted far queuing;

• PEP Forwarder: redirects requests to the OM2M platform for processing. The diagram presented by Fig. 6 describes the algorithm implemented by the PEP. M1, M2, and M3 respectively represent the rejecter, delayer and scheduler algorithms. In addition to request-oriented mechanisms, here after we propose resource-oriented mechanisms in order to manage the resources of M2M platforms deployed in dynamic environments such as cloud computing.

B. Resource-oriented Mechanisms

These mechanisms are inspired by those used in virtualisation deployment environments such as cloud computing. They target the adaptation of the underlying computing resources available in order to improve performances of the Middleware entities. This type of mechanism is more suitable for the server entity that can be run on a cloud platform.

1) Horizontal Scalability oriented Mechanisms

Horizontal scalability consists in adding new instances of the server entity (or part of its components). "Federation" and "Clustering" are two deployment approaches that allow exploitation of the distribution properties of the OM2M platform. Several mechanisms can be used in each approach.

The federation-oriented management that is proposed here consists in the subdivision of the OM2M platform into several components and the dynamic distribution of some of them onto independent virtual machines (VMs). This action can involve, for instance, the Database (DB) by deploying it in another VM (Fig. 7) in order to allow the platform to manage several concurrent accesses and thus reduce the consequent losses. Clustering-oriented management mechanisms consist in the creation of several instances of OM2M and the use of a load balancer (Fig. 8) to distribute the HTTP requests. The distribution policy can be guided by several techniques, among them:

• Round Robin: fair distribution of the load among all OM2M instances;

• Weighted Round Robin: distribution according to weights attributed to each OM2M instance;

• Load-oriented: forwarding of the requests to the OM2M instances depending on their load.

2) Vertical Scalability oriented Mechanisms

Vertical scalability allows adaptation (increasing or decreasing) of the OM2M platform resources in order to support the traffic load. Given that the implementation of the platform is based on the JAVA programming language, three adaptation levels are considered (Fig. 9):

• dynamic adaptation of the VM resources: the adapter allows dynamic adjustment (addition or deletion) of VM resources, based on the use of physical resources (processors, memory, physical disk, etc.);

• dynamic adaptation of JVM resources: by dynamically taking into account the new resources allocated to the VM;

• dynamic adaptation of OM2M resources: OM2M has a number of internal resources (such as threads).

The adapter allows dynamic configuration of these resources to improve the performance of OM2M. For example: dynamic configuration of maxThreads to process new requests according to the load. In the next section, we give a scenario of application of a request-oriented mechanism in order to demonstrate the benefits in the case of a critical IoT application. Due to space limits, we do not provide a similar scenario demonstrating the benefits of a resource-oriented mechanism.

III. VALIDATION SCENARIO

This section shows the benefits of the previous mechanisms for a critical application (i.e. having some QoS requirements) through a proof-of-concept. Due to space limits, we only focus on request-oriented mechanisms through the implementation of a rejection policy. Validation is done through performance measurements performed upon an emulation platform allowing generating HTTP requests from different sources towards a real M2M Middleware platform (in our case, the open source OM2M platform).

A. Considered ELE and its applications

Let us consider an ELE consisting in a connected nursing home in which the residents are submitted to different kinds of monitoring according to their individual health situation. These monitoring can range from the simple location of patients or their daily diet to potentially very fine supervision, for example during a convalescence period after medical treatment or surgical procedure. Numerous sensors have to be used in the context of multiple applications. In this scenario, we consider three kinds of monitoring applications having characteristics and QoS requirements exposed in Table I. Let now study how those features and requirements may be taken into account thanks to the proposed QoS oriented mechanism.

B. The validation platform

As shown in Fig. 10, the validation platform is composed of the following entities:

• Traffic Emulator: allows generating http traffic from different IoT sources in order to implement the application scenario. This emulator is based on a controller for injectors configuration. Each injector is able to simulate the traffic of a given application independently of the other injectors. The traffic can be stochastic, periodic or burst;

• Request-oriented QoS Manager: consists in the CMC and PEP components. The CMC relies on the IP source address to assign priority and the PEP uses the rejection mechanism;

• GSCL: OM2M platform following the SmartM2M standard deployed on a Gateway. The different components have the physical resources described in Table II. The frequency of each processor is 1.6GHz.

CPU (core) 1 1 2 1
In this scenario, the collected metrics are: RTT (round trip delay), CPU and RAM consumption.

C. Implementation of the rejection-oriented policy

In this scenario, we consider the monitoring applications introduced in section A. The traffic generated by each application is emulated by a traffic injector. The injectors send HTTP traffic (POST requests) to the Gateway environing the patients. We focus on the injector representing the Postoperative monitoring (PostOp_Inj) for which the system has to respect strong QoS constraints in presence of the other monitoring application flows (Loc_Inj and Food_Inj).

Given those constraints, the CMC assigns a priority to each request coming from a given injector, with respect to its loss tolerance (CMC is guided by the injector ID). It assigns priority HIGH to PostOp_Inj, MEDIUM to Loc_Inj and LOW to Food_Inj. The PEP implements the actions described in Table III For adaptation actions, when the PostOp_Inj RTT approaches the required RTT threshold, an alarm is set up in order to anticipate the degradation of the response time.

D. Results and analysis

Fig. 11 represents the RTT evolution of PostOp_Inj requests in presence of traffic from Loc_Inj and Food_Inj, without QoS mechanisms. We note that the RTT threshold is fast exceeded at the 36 th request (RTT = 536 ms) and evolves quickly to reach huge RTT values (RTT > 6000 ms). We can then conclude that by default, without QoS mechanisms integration, the system is not able to guarantee a systematic respect of QoS constraints for critical applications. By integrating QoS management through CMC and PEP, and applying the rules and actions described above, the RTT of PostOp_Inj evolves as described by Fig. 12. In this rejection scenario, the RTT of initial requests is less than the "Warning" threshold. After saturation of the gateway, the RTT increases to exceed a threshold of 400ms, which generates a "Critical" state (41 th request). The generation of this symptom leads to activate the critical policy allowing the PEP to reject 40% of the Loc_Inj (MEDIUM priority) traffic and 80% of the Food_Inj (LOW priority) traffic. This action reduces the load of the Gateway and allows again having a RTT in a normal state (less than 300ms) from the 57 th request.

When this state lasts a certain time (after 12 events), it leads to the generation of a state "Normal" which disables the blocking of requests from other injectors. By applying this policy, the system returns to the initial conditions at the beginning of the scenario (197 th request). In terms of benefices, the average PostOp_Inj RTT for the entire scenario is 222 ms and therefore remains under the threshold (350 ms). Regarding the integration cost of this management, the additional average processing time induced by the CMC and PEP components is 7,992 ms. In terms of resources consumption, the consumed CPU (Fig. 13) of the two mechanisms remains low with an average consumption of 30%. In the same time, the RAM consumption (Fig. 14) of the CMC and the PEP increases gradually until becoming insufficient; this is due to the Garbage Collector default configuration.

Based on this validation scenario, the integration of a rejection mechanism provides response times that match the requirements of the Postoperative monitoring application, leading to the improvement of the patient health monitoring and intervention in case of emergency. We can therefore conclude that an IoT system "alone" may not be sufficient, and that it is necessary to integrate a QoS management taking into account constraints of the different applications, in order to enhance the living environments of people (here the patients).

IV. CONCLUSIONS ET PERSPECTIVES

The IoT paradigm is expected to bring ubiquitous intelligence through new applications in order to enhance living and other environments. IoT applications present different features and QoS requirements. Both Network and Middleware underlying levels have to be considered to tackle those QoS requirement. This paper focused on the Middleware level which QoS-oriented mechanisms are proposed, specified and implemented. Those mechanisms are evaluated through an emulation platform combining applicative traffic emulation and real ETSI M2M compliant Middleware platform. The obtained results allows showing both the need in QoS management and the benefits that can be performed within an instance of ELE thanks to the application of simple QoS-oriented mechanisms.

Our vision is to propose an autonomic QoS-oriented Middleware for the IoT. The current work presents a set of QoS-oriented mechanisms that can be used by the autonomic manager to manage the Middleware platform. The next step will be to integrate the required intelligence to guide the planning component of the Autonomic Manager and propose the most efficient plan. This intelligence can be based on artificial intelligence paradigm in order to choose the adequate mechanism(s) to activate and compute their settings (policies) depending on the characteristics (entity type, deployment context) and the state of the managed entity.

Fig. 1 .

 1 Fig. 1. Instantiation of the oneM2M framework for IoT.

Fig. 2 .

 2 Fig. 2. Deployment context of the proposed autonomic computing-based approach for Middleware-level QoS management.

Fig. 3 .

 3 Fig. 3. Architectural composition of request-oriented mechanisms.

Fig. 4 .

 4 Fig. 4. Internal composition of the CMC.

Fig. 5 .

 5 Fig. 5. Internal composition of the PEP.

Fig. 6 .

 6 Fig. 6. PEP algorithm flow chart.

Fig. 7 .

 7 Fig. 7. Distribution mechanism.

Fig. 8 .

 8 Fig. 8. Load balancing-based adaptation mechanism.

Fig. 9 .

 9 Fig. 9. Multi-level resources adaptation.

Fig. 10 .

 10 Fig. 10. Validation platform based emulation.

Fig. 11 .

 11 Fig. 11. RTT evolution without QoS management.

Fig. 12 .

 12 Fig. 12. RTT evolution with rejection mechanism.

Fig. 13 .

 13 Fig. 13. CPU usage by the CMC and PEP.

Fig. 14 .

 14 Fig. 14. RAM usage by the CMC and PEP.

TABLE I

 I

	.	FEATURES AND QOS REQUIREMENTS OF THE CONSIDERED
			MONITORING APPLICATIONS
	Application	Average	Acceptable	Acceptable
			requests	RTT	Loss rate
			rate
	Postoperative monitoring	6 req/s	< 350 ms	0%
	Location monitoring	2 req/s	~10s	50%
	Calories monitoring	2 req/s	No constraint	No constraint

TABLE II .

 II PHYSICAL RESOURCES ALLOCATION

	Resource	Emulator CMC	PEP	GSCL
	RAM (MB)	1024	1024	2048	512

  depending on the priorities (medium and low priorities (MED_PR & LOW_PR)) in order to meet RTT required by PostOp_Inj. The RTT state is supposed to be triggered when five successive RTT values satisfy the state condition.

TABLE III

 III

	.	ADAPTATION ACTIONS BASED ON THE RTT STATE
	RTT (ms)	State	MED_PR	LOW_PR
			Rejection	Rejection
	RTT < 300	Normal	0	0
	300 ≤ RTT < 400	Warning	30	70
	RTT ≥ 400	Critical	40	80


Mohamed Gharbi
email: gharbim.mohamed@gmail.com

Amara Masrouhi

Nicolas Espurt

Olivier Bellier

Amjed El

Mohamed Ben Amari

Mohamed Ben Youssef

Ghanmi

El Amjed Amari

Mohamed Ghanmi

New tectono-sedimentary evidences for Aptian to Santonian extension of the Cretaceous rifting in the Northern Chotts range (Southern Tunisia)

Keywords: South Tethyan margin, Rifting, Aptian-Santonian, Southern Atlassic domain, Tunisia, Chotts range, Zemlet el Beidha anticline

Based on new structural, sedimentary, stratigraphic and seismic reflection data from Cretaceous sequences of the Zemlet el Beidha anticline of the northern Chotts range (South Tunisia), this study yields fresh insights into the geodynamic evolution of the South Tethyan margin. The rifting of the margin started in the Triassic-Jurassic and continued during the Aptian-Albian. In this last period N to NE trending extension was associated with WNW and NW trending normal faults, bounding the developing horsts and grabens structures. This tectonic framework is highlighted by strong thickness and facies changes in the Aptian-Albian series associated with slumps and syntectonic conglomerates. During the Coniacian to Santonian times, the study area was characterized by continued subsidence. Consequently, the Coniacian-Santonian series are represented by sedimentary infilling consisting of post-rift marl-rich sequences followed by limestone and marl sequences. 2 Folds geometry and associated faults system and tectonics analysis, confirm the role of the Aptian-Albian rifting inheritance faulting in the structuring and the development of the folds and thrusts belts of the southern Tunisian Atlas during the Cenozoic inversion, in particular in the development of the ENE striking structures such as the Zemlet el Beidha anticline.

Introduction

The geodynamic evolution of the northern margin of Africa has been studied by many authors [START_REF] Dercourt | Geological evolution of the Tethys belt from the atlantic to the pamirs since the LIAS[END_REF][START_REF] Philip | Evolution tectonique moi-plio-quaternaire du fossée de Kasserine (Tunisie centrale): implications sur l'évolution géodynamique récente de la Tunisie[END_REF][START_REF] Dewey | Shortening of continental lithosphere: The neotectonics of eastern Anatolia[END_REF][START_REF] Soyer | La crise aptienne en Tunisie centrale : approche paléostructurale aux confins de l'Atlas et l'Axe Nord-Sud[END_REF][START_REF] Guiraud | Le rifting en Afrique au Crétacé inférieur: synthèse structurale, mise en évidence de deux étapes dans la genèse des bassins, relations avec les ouvertures océaniques périafricaines[END_REF][START_REF] Guiraud | Early Cretaceous Rifts of Western and Central Africa. An overview[END_REF][START_REF] Martinez | Le contexte géodynamique de la distension albo-aptienne en Tunisie septentrionale et centrale: structuration éocrétacée de l'Atlas tunisien[END_REF][START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF]Burnet and Cloetingh, 2003), observing, that this margin was characterized by (1) the extension, crustal stretching and thinning, as well as subsidence during the Mesozoic Tethyan rifting [START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Bumby | The geodynamic setting of the Phanerozoic basins of Africa[END_REF], and (2) the occurrence of subsequent inversion during Late Cretaceous-Cenozoic subduction and collision [START_REF] Guiraud | Le rifting en Afrique au Crétacé inférieur: synthèse structurale, mise en évidence de deux étapes dans la genèse des bassins, relations avec les ouvertures océaniques périafricaines[END_REF][START_REF] Guiraud | Senonian basin inversion and rejuvenation of rifting in Africa and Arabia: synthesis and implications to plate-scale tectonics[END_REF][START_REF] Guiraud | Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview[END_REF][START_REF] Laville | A restatement of the Mesozoic Atlasic Rifting (Morocco)[END_REF][START_REF] Abrajevitch | Neotethys and the India-Asia collision: insights from a palaeomagnetic study of the Dazhuqu ophiolite, southern Tibet[END_REF][START_REF] Bumby | The geodynamic setting of the Phanerozoic basins of Africa[END_REF]Dhari and Boukadi, 2010).

Along the northern margin of Africa, the rifting began during the Late Permian-Middle Triassic period [START_REF] Raulin | Late Triassic-early Jurassic block tilting along E-W faults, in southern Tunisia: New interpretation of the Tebaga of Medenine[END_REF], and culminated at the transition between the Triassic and Jurassic. The Early Mesozoic transgressions are characterized by a heterogeneous sedimentary cover [START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Courel | Mid-Triassic to Early Liassic clastic/evaporitic deposits over the Maghreb Platform[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF]. During this sedimentation cycle an extensional tectonic context predominated, as indicated by numerous synsedimentary normal faults systems. During the Jurassic time, a regional extensional tectonic regime produced the dislocation of the existing continental platform, which is related to the opening of the Central Atlantic and led to the development of "en échelon" normal faults, tilted blocks and volcanic activity [START_REF] Laridhi-Ouazaa | Les migrations tectono-magmatiques du Trias au Miocène sur la marge orientale de la Tunisie[END_REF]. The distribution of the sedimentary facies has taken place along the WSW trending Atlassic range from Morocco to northern Tunisia during the Late Liassic-Early Cretaceous period [START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF].

In southern Tunisia, the rifting has been associated with the development of WNW to NW trending half grabens related to high rate subsidence, especially during Neocomian and Barremian [START_REF] Piqué | Evolution structurale des domaines atlasiques du Maghreb au Méso-Cénozoïque; le rôle des structures héritées dans la déformation du domaine atlasique de l'Afrique du Nord[END_REF][START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF][START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF].

The rifting led to presence of unconformities within many basins in the Early Aptian [START_REF] Guiraud | Le rifting en Afrique au Crétacé inférieur: synthèse structurale, mise en évidence de deux étapes dans la genèse des bassins, relations avec les ouvertures océaniques périafricaines[END_REF][START_REF] Guiraud | Early Cretaceous Rifts of Western and Central Africa. An overview[END_REF]Zouaghi et al., 2005b;[START_REF] Bodin | Timing of early to mid-cretaceous tectonic phases along North Africa: New insights from the Jeffara escarpment (Libya-Tunisia)[END_REF] and continued during the Aptian-Albian creating N to NE trending regional extension [START_REF] Zghal | Syn-sedimentary tectonics in central Tunisia (Jebel Mrhila area) during the Aptian-Albian[END_REF][START_REF] Rigane | The "Aptian Crisis" of the South-Tethyan margin: New tectonic data in Tunisia[END_REF]. The Early Aptian unconformities mentioned above are associated with the lower Cretaceous rifting stage. On the contrary, these later are related by some authors to the compressional regime (Austrian Event;Ben Ayed, 1993;Bedir et al., 2001;[START_REF] Zouaghi | ,775,657 Echinoderme, Cytherella sp, Cythereis sp, Brachycythere Coniacian-Santonian EH 153 585000 3,775,593 Radiole, Cytherella sp, Bairdia sp Coniacian-Santonian EH 155 584483 3,775,204 Rotallia, Gavelinella sp, Lenticulina sp. Coniacian-Santonian EH 156 582497 3,775,659 Rotallia, Gavelinella sp Coniacian-Santonian EH 220 584,262 3,774,591 Brachycythere, Globotruncana fornicata, Bairdia sp. Coniacian-Santonian Jebel Romana-Gouada plain EH 221[END_REF]Lazez et al., 2008) and/or halokinetic movements [START_REF] Rigane | The "Aptian Crisis" of the South-Tethyan margin: New tectonic data in Tunisia[END_REF]Zouaghi, al., 2011).

Along the southern margin of Tunisia, the rifting has been associated with volcanism in the Pelagian block (Fig. 1A; [START_REF] Laridhi-Ouazaa | Les migrations tectono-magmatiques du Trias au Miocène sur la marge orientale de la Tunisie[END_REF]. Extensional structures have been recognized by surface and subsurface data in the Northern African margin [START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Bumby | The geodynamic setting of the Phanerozoic basins of Africa[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF]. The Cretaceous evolution of this margin was associated with thickness and facies variations of the sedimentary sequences (Ben [START_REF] Ben Youssef | La Formation Orbata (Aptien) en Tunisie méridionale précisions biostratigraphiques nouvelles[END_REF][START_REF] Ben Ferjani | Petroleum geology of Tunisia[END_REF]Delteil et al., 1991;[START_REF] Abdallah | Le Crétacé supérieur de la chaîne Nord des Chotts (Tunisie du centre-sud): Biostratigraphie et comparaison avec les régions voisines[END_REF][START_REF] Souquet | Séquences et cycles d'ordre 2 en régime extensif et transtensif: exemple du Crétacé inférieur de l'Atlas tunisien[END_REF][START_REF] Bédir | Subsurface Mesozoic basins in the central Atlas of Tunisia, tectonics, sequence deposit distribution and hydrocarbon potential[END_REF][START_REF] Patriat | The Hammamet, Gabes and Chotts basins (Tunisia) a review of the subsidence history[END_REF][START_REF] Zouaghi | ,775,657 Echinoderme, Cytherella sp, Cythereis sp, Brachycythere Coniacian-Santonian EH 153 585000 3,775,593 Radiole, Cytherella sp, Bairdia sp Coniacian-Santonian EH 155 584483 3,775,204 Rotallia, Gavelinella sp, Lenticulina sp. Coniacian-Santonian EH 156 582497 3,775,659 Rotallia, Gavelinella sp Coniacian-Santonian EH 220 584,262 3,774,591 Brachycythere, Globotruncana fornicata, Bairdia sp. Coniacian-Santonian Jebel Romana-Gouada plain EH 221[END_REF]. This tectonic regime involved the reactivation of pre-existing (Early Cretaceous) passive margin structures, with a maximum extension occurring during Albian times. Early Cretaceous extensional structures have been sealed by Senonian post-rift series with reefal buildings along uplifted ridges [START_REF] Negra | Sedimentation, diagenesis and syntectonic erosion of Upper Cretaceous rudist mounds in central Tunisia. Carbonate mud-mounds: their origin and evolution[END_REF]. Thereafter, during Late Cretaceous and Cenozoic times, tectonic inversion occurred as a result of convergence between Africa and Eurasian plate. The North African margin was characterized by the reactivation of pre-existing extensional faults systems which controlled fault-related folds [START_REF] Zargouni | Tectonique de l'Atlas méridional de Tunisie, évolution géométrique et cinématique des structures en zone de cisaillement[END_REF][START_REF] Ben Ayed | Evolution tectonique de l'avant-pays de la chaîne alpine de la Tunisie du début du Mésozo à l'Actuel[END_REF][START_REF] Catalano | Paleogeography and structure of the central Mediterranean: sicily and its offshore area[END_REF][START_REF] Doglioni | On the interference between the early Apennines-Maghrebides back arc extension and the Alps-betics orogen in the Neogene geodynamics of the Western Mediterranean[END_REF]Vergés and Sabat, 1999;[START_REF] Frizon De Lamotte | Some recent developments on the geodynamics of the Maghreb[END_REF][START_REF] Masrouhi | Mise en évidence d'une nappe de charriage à deux unités paléogènes au plateau de Lansarine (Tunisie du Nord): Définition d'un nouvel élément structural de l'Atlas Tunisien et réévaluation du calendrier des serrages tertiaires[END_REF][START_REF] Dhahri | The evolution of pre-existing structures during the tectonic inversion process of the Atlas chain of Tunisia[END_REF].

This study focuses on the structure of the Zemlet el Beidha anticline in the eastern part of the northern Chotts range, which belongs to the southern Atlassic front of Tunisia. In this area, the tectono-sedimentary framework displays evidence for the southernmost Cretaceous rifting. Our study provides new structural elements, new detailed geologic mapping, sedimentologic, palaeontologic and new interpretation of geophysical data to understand the Cretaceous passive margin evolution.

Geological setting

Structural features of the study area

The Atlas orogen forms a part of the present-day North African margin and is the result of the collision between the African and the European plates. The development of the southern Tunisian Atlas fold-and-thrust belt is related to this tectonic convergence occurred during Tertiary times. This domain is characterized by E-W to NE-SW and NW-SE anticlines separated by synclines filled with Neogene and Quaternary series (Fig. 1B; [START_REF] Zargouni | Tectonique de l'Atlas méridional de Tunisie, évolution géométrique et cinématique des structures en zone de cisaillement[END_REF]Abdeljaoued and Zargouni, 1981;[START_REF] Burollet | Structures and tectonics of Tunisia[END_REF][START_REF] Bédir | Subsurface Mesozoic basins in the central Atlas of Tunisia, tectonics, sequence deposit distribution and hydrocarbon potential[END_REF][START_REF] Bédir | Subsurface Mesozoic basins in the central Atlas of Tunisia, tectonics, sequence deposit distribution and hydrocarbon potential[END_REF][START_REF] Hlaiem | Halokinisis and structural evolution of the major features in eastern and southern Tunisian Atlas[END_REF][START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF].

The southern Tunisian Atlas fold-and-thrust belt is limited westward by major NW trending strike-slip fault systems (Gafsa and Negrine-Tozeur fault systems; Fig. 1A,B). The Gafsa fault system [START_REF] Zargouni | Style et chronologie des déformations des structures de l'Atlas tunisien méridional. Évolution récente de l'accident Sud-atlasique[END_REF][START_REF] Burollet | Structures and tectonics of Tunisia[END_REF]Haleim, 1999) is a N120° E trending dextral strike-slip system [START_REF] Zargouni | Rôle des couloirs de cisaillement de Gafsa et de Négrine-Tozeur dans la structuration du faisceau des plis des Chotts, éléments de l'accident sud-atlasique[END_REF][START_REF] Abbès | Anatomie d'un couloir de décrochements: le couloir de Hadifa (Chaîne Nord des Chotts-Tunisie)[END_REF]Abbès et al., 1994;Boutib and Zargouni, 1998) and cuts the Bou Ramli, Ben Younes and Orbata anticlines in the north and the Zemlet el Beidha and Koudiat Hammamet anticlines in the south (Fig. 1B,C). Another prominent northwest striking strike-slip fault is the Negrine-Tozeur fault (Fig. 1B), which borders the west of the Gafsa-Metlaoui basin and parallel to the Gafsa fault.

It extends from the Negrine (Algeria) through the Tunisian Atlas Mountains [START_REF] Zargouni | Style et chronologie des déformations des structures de l'Atlas tunisien méridional. Évolution récente de l'accident Sud-atlasique[END_REF][START_REF] Zargouni | Rôle des couloirs de cisaillement de Gafsa et de Négrine-Tozeur dans la structuration du faisceau des plis des Chotts, éléments de l'accident sud-atlasique[END_REF]. The Sehib, Berda, Chemsi and Belkheir folds separate the wide Gafsa-Metlaoui basin to the northern Chotts range towards the south.

The Chotts depression corresponds to foredeep depozone (according to the nomenclature of [START_REF] Decelles | Foreland basin systems[END_REF]. This foredeep depozone is formed by two connected depression: the Chott El-Jérid to the west and the Chott El-Fejej to the east (Fig. 1B,C). The Chott El-Fejej occupies the core of a mega-anticline called "Fejej dome" whose southern limb corresponds to Jebel Tebaga and northern limb is formed by the northern Chotts range (Fig. 1B,C).

The eastern part of the northern Chotts range fold belt is affected by several faults that's the most significant is the Bir Oum Ali and Fejej faults system (Fig. 1B). The northern Chotts range (E-W trend) changes direction to a NE-SW in its eastern part that corresponds to the Zemlet el Beidha anticline. The Zemlet el Beidha anticline limits the Sidi Mansour basin in the north and the Chotts Fejej basin in the south (Fig. 1C). The Zemlet el Beidha anticline (Fig. 2) belongs to the southern Atlassic front of Tunisia in the eastern part of the northern Chotts range (Fig. 1B). It is located between an intensely deformed domain, the southern Atlassic fold-and-thrust belt, in the north, and a less deformed domain, the Saharan Platform, in the south (Fig. 1A,B), [START_REF] Zargouni | Style et chronologie des déformations des structures de l'Atlas tunisien méridional. Évolution récente de l'accident Sud-atlasique[END_REF][START_REF] Ben Ferjani | Petroleum geology of Tunisia[END_REF][START_REF] Burollet | Structures and tectonics of Tunisia[END_REF]Haleim, 1999;[START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF].

General stratigraphy

The stratigraphy (Fig. 3) of the Zemlet el Beidha region is derived from micropaleontology analysis (Table. 1) and from boreholes which were drilled close to the anticline (wells 1, 2, 3 and 4, Fig. 1 C). The sedimentary series outcropping in the study area are Cretaceous to Quaternary in age (Fig. 1C, 2 and 3). The core of the Zemlet el Beidha anticline (Fig. 2) is formed by Hauterivian-Barremian marls, alternating with anhydrites, limestones and claystones of the Bouhedma Formation (Abdejaouad and [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF]Lazez and Ben Youssef, 2008). The Bouhedma Formation is overlain by shale-rich sands and ferruginous sandstones of the Sidi Aïch Formation, for which a Barremian (pro parte) age is deduced from its stratigraphic position. The Sidi Aich Formation is overlain by the dolomitic bank of the Lower Aptian Orbata Formation (Ben [START_REF] Youssef | Données micropaléontologiques et biostratigraphiques nouvelles sur le Crétacé inférieur marin du Sud tunisien[END_REF][START_REF] Chaabani | Aptian sedimentation: an example of interaction between tectonics and eustatics in Central Tunisia[END_REF], which is topped by a rich-Orbitolinidae hardground, showing some Ammonites [START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF]. This massive dolomitic bank is a common feature all over the area and forms the flanks of folded structures. The Upper Albian deposits correspond to the lower member of the Zebbag Formation. This formation, which rarely outcrops in the study area, is dominated by dolomitic sandstones, marls, limestones and argillaceous limestones.

The upper member of Zebbag Formation (Upper Cenomanian-Turonian) is characterized by the flint dolomitic bank of the Guettar member. This sequence is only deposited at Jebel Jerouala (Fig. 2). The Coniacian-Santonian series of the Aleg Formation unconformably overlie the previous series. They are defined by thick sequences of dolomitic sandstones at the base and interbedded green marls and bioclastic limestones at the top. The fauna of this formation is distinguished (Fig. 3 andTable. 1) by the ammonites in the Khanguet Aïcha River, planktonic foraminiferas in the Gouada plain and the Rudistes in the Khanguet Telmem [START_REF] Abbès | Tectonique précoce et sédimentation de la série Crétacée dans le bassin des Chotts (Tunisie du sud) Géologie Méditerranéenne[END_REF][START_REF] Louhaïchi | Tectonique synsédimentaire des séries post-Barrémiennes au Nord-Est de la chaîne Nord des Chotts (Tunisie méridionale)[END_REF][START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF]. The Abiod Formation conformably overlies the Aleg Formation and consists of limestone banks with intercalations of thin clay layers. These intercalations are enriched by phosphatic debris and glauconite grains. The associated fauna suggests a deep marine environment, similar to the central and northern Tunisian domain [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF]. According to facies [START_REF] Louhaïchi | Tectonique synsédimentaire des séries post-Barrémiennes au Nord-Est de la chaîne Nord des Chotts (Tunisie méridionale)[END_REF] and microfauna data [START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF], the Abiod Formation is Upper Campanian to Maastrichtian in age (Fig. 3 andTable. 1 [START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF]. The Bouloufa Formation is dated to the Middle Eocene by [START_REF] Abdeljaouad | Sur l'âge Paléocène supérieur-Miocène des dépôts continentaux à calcrètes ou dolocrètes de la Formation Bouloufa en Tunisie méridionale. Conséquences paléogéographiques[END_REF] and overlies unconformably (U1) the clays of the El Haria Formation. It is formed by red gypsum clay and encrusted limestone with Bulimes fauna. At the end of Eocene period, south and central Tunisia emerged and compressional deformations took place [START_REF] Masrouhi | New tectono-sedimentary evidence constraining the timing of the positive tectonic inversion and the Eocene Atlasic phase in northern Tunisia: Implication for the North African paleo-margin evolution[END_REF][START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF]. As a result, intense erosion in the Atlassic fold-andthrust belt zone caused the deposition of thick syntectonic series of silt and molasse basins during the Neogene and Quaternary. Miocene sands of the Beglia Formation unconformably overlie (U2) the Bouloufa Formation. Finally, the Segui Formation, which crops out on the southern flank of the Zemlet el Beidha anticline, consists of coarse alluvial conglomerate deposits. The Segui Formation unconformably overlies (U3) the Beglia Formation and record the growth of the Zemlet el Beidha anticline.

Zemlet el Beidha Cretaceous structures

Structures

The Zemlet el Beidha structure corresponds to a south-verging asymmetric thrustrelated anticline with a curved axis that changes from an E strike to NE strike from west to east (Fig. 2). The Zemlet el Beidha anticline has a single periclinal closure in the east. As shown in geologic map of Figure 2, the core of the Zemlet el Beidha consists of Coniacian-Santonian outcrops in the Jebel Romana and Gouada plain (NE part of Zemlet el Beidha).

Westward, the anticline of Jebel Haidoudi is occupied by the Coniacian-Santonian deposits.

In the central part, the core of the anticline is formed by the Hauterivian-Barremian series.

The geometry of the Zemlet el Beidha anticline is illustrated by the two cross sections of Figure 4. The section A-A' crosses the eastern part of the anticline (Fig. 2 and4). In the Tebaga Fatnassa region, the fold corresponds to a gently deformed anticline of Cretaceous strata unconformably overlain by Late Miocene (U2) and Late Pliocene to Quaternary series (U3). The northern backlimb is formed by ~10° N-dipping thin layers of marls (Fig. 4A), alternating with anhydrites, limestones and claystones of the Bouhedma Formation. The series are also deformed by the N-dipping normal faults. The southern forelimb is formed by Coniacian-Santonian series of the Aleg Formation and dips ~20°southeastward. The central part, the Khanguet Aïcha and Khanguet Amor region, exposes a forelimb formed by ~ almost 45° S-dipping layer (Fig. 2 and5). The southern flank of the Zemlet el Beidha anticline also shows subvertical faults, previously interpreted by several authors as strike-slip faults [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF][START_REF] Zargouni | Rôle des couloirs de cisaillement de Gafsa et de Négrine-Tozeur dans la structuration du faisceau des plis des Chotts, éléments de l'accident sud-atlasique[END_REF][START_REF] Abbès | Anatomie d'un couloir de décrochements: le couloir de Hadifa (Chaîne Nord des Chotts-Tunisie)[END_REF]Abbès et al., 1986).

Along the cross section B-B' (Fig. 4), the northern limb of the anticline exhibits 5-10° N-dipping Hauterivian-Barremian series. The cross section B-B' shows a Cretaceous series from the Hauterivian to Late Maastrichtian unconformably overlain by Middle Eocene, Late Miocene and Late Pliocene to Quaternary (U1, 2, 3) series on the Jebel Jerouala and Jebel Haidoudi (Figs. 2 and4).The western part of the Zemlet el Beidha anticline is characterized by a 70°-80° S-dipping forelimb intensively deformed by the S-vergent faults acting now as right-lateral oblique-slip of the Fejej coridor (Fig. 2).

Fault kinematics analysis

The Zemlet el Beidha area has undergone a complex tectonic evolution related to its geometric position in relation to the whole northern Chotts range. To support our structural interpretation we measured and analyzed striated fault planes within Aptian-Albian series.

Such a fault kinematics analysis of mesoscale faults permits a quantitative reconstruction of paleostresses that can be related to the chronological sequence and orientations of larger-scale structures. These paleostresses thus provide useful information not only on the compressional, extensional or strike-slip origin of larger structures, but also on their kinematics and orientation relative to the stress field (oblique or normal).

The western part of the Zemlet El Beidha anticline (Jebel Haidoudi, Jebel Fejej and Jebel Jerouala) is characterized by a major NW to WNW-trending fault Fejej system [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF][START_REF] Zargouni | Rôle des couloirs de cisaillement de Gafsa et de Négrine-Tozeur dans la structuration du faisceau des plis des Chotts, éléments de l'accident sud-atlasique[END_REF][START_REF] Abbès | Tectonique précoce et sédimentation de la série Crétacée dans le bassin des Chotts (Tunisie du sud) Géologie Méditerranéenne[END_REF][START_REF] Louhaïchi | Tectonique synsédimentaire des séries post-Barrémiennes au Nord-Est de la chaîne Nord des Chotts (Tunisie méridionale)[END_REF]). This fault system, acting now with a right-strike-slip component, may correspond to inherited Cretaceous normal faults [START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF]. The detailed geologic mapping (1:25 000) of the Khanguet Aïcha area (central part of Zemlet el Beidha, Fig. 2) combined with the SPOT images (Fig. 5A,B) also show numerous N100-110° E apparent trending strike-slip faults. These faults are well expressed in the southern flank of the Zemlet el Beidha anticline. The Khanguet Aïcha and the Khanguet Amor faults appear on map as strike-slip faults. They affect the Hauterivian to Albian series and are sealed by Coniacian-Santonian deposits (Fig. 5B,C) with no evidence of recent displacement (Fig. 5 and6). Fault kinematics analysis performed along the Khanguet Aïcha and Khanguet Amor faults (Fig. 5D) shows oblique strike-slip faulting component. The normal faulting generates the sedimentary reworking of the Aptian dolomitic bank in the Khanguet Aïcha and Khanguet Amor. The syntectonic Aptian conglomerates (Fig. 7 A, B, C andD) observed in the downdropping normal fault of Khanguet Aïcha and Khanguet Amor (Fig. 6) indicated tilted block geometry. In addition, the eastern part of Tebaga Fatnassa (Fig. 2) exposes growth strata in the hanging-wall of the ancient normal fault testifying the Albian extensional regime (Fig. 8).

Using the fault diagram, we rotated the fault data to restore the bedding plane to its horizontal orientation. The resulting back-tilted fault diagram shows that these faults were normal faults before Cenozoic tilting (Fig. 5D). This pre-tilting normal faulting shows a ~NE trending extension (Fig. 5D). The reactivation of this normal fault is attested by reverse sense of movement (Fig. 8) and shows thrust reactivation and the shortcut geometry affecting the Bouhedma Formation in the core of the Zemlet el Beidha anticline (Fig. 9).

Tectono-sedimentary data

Along-strike correlation of the sedimentary sequences of the Zemlet el Beidha region allows us to characterize at least four periods of tectono-sedimentary evolution related to the Cretaceous rifting (Fig. 10A) i.e. Neocomian, Aptian-Albian, Coniacian-Santonian and Campanian-Maastrichtian tectono-sedimentary sequences.

During the Neocomian, a sporadic clastic sedimentation testifies two periods of marine regression. The sequences correspond essentially to continental sediment including sands, clays, silts, lacustrine dolomites and gypsum deposits. The Early Albian tectonic extensional episode is recorded by N100-110° E trending faults related to a regional N to NE trending extension. This tectonic episode may be associated with the general uplift and erosion (ds1) of the Zemlet el Beidha zone (Fig. 10A) and continued to Early Albian times. The subsidence in the northern Chotts range area began during the Hauterivian-Barremian. Sedimentary features such as small slumps (Fig. 11 A), turbidites, mudflows (Fig. 11 B), and several meter scale olistoliths (included within the Barremian anhydrites, limestones and claystones) indicate basin instabilities. The Early Aptian dolomitic series include rare orbitolines and ammonites (Fig. 11 C; [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF]Ben Youssef and Peybernès, 1986;[START_REF] Chaabani | Aptian sedimentation: an example of interaction between tectonics and eustatics in Central Tunisia[END_REF]Lazez et al., 2008;[START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF] give evidence for a hard ground surface. In the Khanguet Aïcha, this dolomitic bank is also affected by the N110°E trending faults. This faulting is associated with thickness and facies variations of the Barremian series (Fig. 5C) as well as the occurrence of Aptian conglomerates within the hanging-walls of the Kanguet Aïcha and Kanguet Amor faults (Figs. 5 and6). These conglomerates probably attest to syntectonic sedimentation during normal faulting. Moreover, the stratigraphic correlation of Fig. 10A shows usually lateral thickness changes from the Khanguet Amor (log 7) to the Kanguet Aïcha (log 8) areas that appear to be correlated with the normal faults. The Early Aptian tectonic extensional episode is well known in the northern Chotts range and south Atlassic domain. It is characterized by a tilted block system associated with horsts and grabens. In fact, this structural frame is responsible for the distribution of the Albian sequences in the northern Chotts range and the regional unconformity deposits which are defined by the absence of the deposits of Late Aptian and of the Early and Middle Albian age [START_REF] Abdeljaouad | Mise en évidence d'une tectonique intracrétacé dans le secteur de J. Zemlet El Beïda[END_REF]Ben Youssef et al., 1984;Lazez et al., 2008).

In this area, the irregular distribution of these series is also expressed within deposits around the uplifted zone of the present-day Zemlet el Beidha fold (Fig. 10B). In this region, the series distribution is related to a tilted bloc geometry, which has been dated to the Neocomian-Early Albian. Faulting produced differential uplift and high subsidence rates in the northeastern Chotts range (Fig. 10B).

The transgressive Cenomanian and Turonian period is well known across the northern African plate. Despite this transgression [START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF], the tectonic activity induced differential subsidence; the Zemlet el Beidha formed an uplift zone during this period of high sea level. The Jebel Jerouala is the unique locality (log 3 in Fig. 10A) where Turonian sediments were deposited. In this zone we note the presence of red flint dolomite limited by the Fejej normal fault systems. The thickness variations and the main tectonic elements suggest that the Turonian sedimentation was controlled by WNW to NW trending faults.

The Coniacian-Santonian sedimentation is characterized by a subtle onlap pattern and facies changes. These sediments consist of marl-rich limestones and clays enriched by benthic and pelagic foraminifera and ostrea, indicating a deepening basin. On the northern side and southern flank of the Zemlet el Beidha anticline, the strong thickness of the Coniacian-Santonian series is related to the reactivation of NW trending faults that delimited the Zemlet el Beidha horst (Fig. 2 and10A). Eastward, the region of Gouada plain (Fig. 2) is characterized by pelagic facies (Fig. 10A) while westward, at Jebel Haidoudi, the deposits are characterized by benthic facies. In the Khanguet Telmem (Fig. 2 and log 5 and 6 in Fig. 10A), a lens of reef-building rudist colonies (Fig. 11D) has been observed, which recorded and developed due to the Zemlet el Beidha uplift. The rudist coral limestones preferentially developed on the horst of Zemlet el Beidha. During the Coniacian-Santonian stage, the paleostructure of the Zemlet el Beidha limits SW and NE marginal zones with basin sedimentation. In particular, the eastern Tebaga Fatnassa-Gouada plain and the western Jebel Fejej-Haidoudi area are characterized by strong subsidence during the Coniacian-Santonian (log 1, 2, 9, 10 in Fig. 10A). This subsidence is consistent with the previous tectonic context described above.

During the Campanian, the western part of the Zemlet el Beidha domain is characterized by marine transgression, recorded by the occurrence of deepwater limestones and clays, and pelagic facies in the Late Campanian. West of the Zemlet el Beidha area, just at the south of Jebel Fejej (Fig. 2 and Fig. 10 log 1, 2 and 3) and on the Jebel Haidoudi, these series are transgressive, and a significant increase in thickness subsidence rate is recorded by the Late Maastrichtian series. In the Fejej graben, the structural evolution during the Campanian and Late Maastrichtian led to a significant subsidence increase as a consequence of the transtensional [START_REF] Guiraud | Senonian basin inversion and rejuvenation of rifting in Africa and Arabia: synthesis and implications to plate-scale tectonics[END_REF]Zouari et al., 1999) displacement of the Fejej fault.

Discussion: Geodynamic evolution of the southern Atlassic margin

1. Cretaceous rifting inheritances

Aptian-Albian syn-rift

The northern Chotts range was dominated by regional normal faulting. The WNW and NW trending faults were mainly inherited from the Jurassic and reactivated during the Early Cretaceous-Albian times [START_REF] Gharbi | Etude Tectonique de la région de Zemlet El Beidha (Chaîne Nord des Chotts) : Structuration Crétacée et Evolution Tertiaire[END_REF]. Seismic reflection profiles of Figure 12 illustrate the structural architecture of the southern Tethyan margin in the northern Chotts range. Analysis of the seismic profiles EL05 and EL07 crossing the Sidi Mansour Basin (Fig. 1C) permits to identify faults with normal components bounding the subsiding domains (Fig. 12). These faults are associated with other synthetic faults that have contributed to the formation of a major graben systems. The study area is marked by thick Hauterivian-Barremian and Albian deposits, which are progressively thickening, associated with listric faults (Fig. 12). The geometry and the thickness variations are interpreted to be related to the regional extensional strain during the Aptian-Albian. The evolution proposed in Fig. 13 shows a possible tectonic scenario for the Zemlet el Beidha zone during Aptian-Albian faulting. The reactivation of the Khanguet Aïcha fault is associated with syntectonic conglomerates and leads to produce an unconformity at the base of the Upper Aptian series (Fig. 3, log 5, 8 in Fig. 10A andB, Fig. 13). Our observations suggest that this unconformity is associated with normal faults and an extensional tectonic regime. Such as the Jebel Chemsi, Jebel Bir Oum Ali at west of Zemlet el Beidha, Jebel Tebaga of Kebili (Fig. 14 a, b andc), the fault kinematics deduced from the study of striated fault planes display evidence for the tectonic regime which is extensional during the Aptian-Albian period. Geologic and geophysic data were integrated to confirm that the syn-rift tectonic in the northern Chotts range is still related to the Early Albian. This rifting has been accompanied by an episode of volcanism which is testified by basalt flows observed in the pelagian blocks of eastern Tunisia (Fig. 1B; [START_REF] Ellouz | From rifting to Alpine inversion: Mesozoic and Cenozoic subsidence history of some Moroccan basins[END_REF][START_REF] Laridhi-Ouazaa | Les migrations tectono-magmatiques du Trias au Miocène sur la marge orientale de la Tunisie[END_REF].

Many interpretations have been proposed to explain the Upper Aptian-Lower Albian regional unconformity. Several authors interpret this unconformity as the result of a major compressional event during the Aptian-Albian time (the Austrian Phase, Ben Ayed, 1993; Bédir et al., 2000;[START_REF] Piqué | The Mesozoic-Cenozoic Atlas belt (North Africa): an overview[END_REF][START_REF] Zouaghi | ,775,657 Echinoderme, Cytherella sp, Cythereis sp, Brachycythere Coniacian-Santonian EH 153 585000 3,775,593 Radiole, Cytherella sp, Bairdia sp Coniacian-Santonian EH 155 584483 3,775,204 Rotallia, Gavelinella sp, Lenticulina sp. Coniacian-Santonian EH 156 582497 3,775,659 Rotallia, Gavelinella sp Coniacian-Santonian EH 220 584,262 3,774,591 Brachycythere, Globotruncana fornicata, Bairdia sp. Coniacian-Santonian Jebel Romana-Gouada plain EH 221[END_REF]. Other authors plead for an extensional event (normal faulting regime) [START_REF] Martinez | Le contexte géodynamique de la distension albo-aptienne en Tunisie septentrionale et centrale: structuration éocrétacée de l'Atlas tunisien[END_REF][START_REF] Guiraud | Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview[END_REF][START_REF] Zghal | Syn-sedimentary tectonics in central Tunisia (Jebel Mrhila area) during the Aptian-Albian[END_REF]Zouari et al., 1999;[START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF][START_REF] Bodin | Timing of early to mid-cretaceous tectonic phases along North Africa: New insights from the Jeffara escarpment (Libya-Tunisia)[END_REF][START_REF] Rigane | The "Aptian Crisis" of the South-Tethyan margin: New tectonic data in Tunisia[END_REF]. Our observations yield fresh data to support an Aptian-Albian extensional deformation of the south Tethyan margin. This rifting episode ended with a regional unconformity identified by a hard ground surface, and halokinetic movements [START_REF] Bédir | Subsurface Mesozoic basins in the central Atlas of Tunisia, tectonics, sequence deposit distribution and hydrocarbon potential[END_REF][START_REF] Rigane | The "Aptian Crisis" of the South-Tethyan margin: New tectonic data in Tunisia[END_REF]Zouaghi et al., 2011). Thus, the Upper Aptian-Lower Albian unconformity can be related to intraplate extensional deformation linked to the opening of the central segment of the South Atlantic while the northward movement of part of the African Plate was accompanied by N trending extension registered in the central African basins [START_REF] Martinez | Le contexte géodynamique de la distension albo-aptienne en Tunisie septentrionale et centrale: structuration éocrétacée de l'Atlas tunisien[END_REF][START_REF] Guiraud | Le rifting en Afrique au Crétacé inférieur: synthèse structurale, mise en évidence de deux étapes dans la genèse des bassins, relations avec les ouvertures océaniques périafricaines[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF] and northeastward movement of the Arabian-Nubian block during the Aptian-Albian transition [START_REF] Bodin | Timing of early to mid-cretaceous tectonic phases along North Africa: New insights from the Jeffara escarpment (Libya-Tunisia)[END_REF].

Coniacian-Santonian post-rift

The Coniacian-Santonian stage is attested by thick deposits of pelagic and benthic facies (Fig. 10A). These deposits are characterized by thickness and facies variations and by reefal carbonates on horst structures (log; 5, Fig. 10A). In Sidi Mansour Basin, the Coniacian-Santonian sequence observed in seismic profile (EL-05, Fig. 12) shows along-strike changed in term of thickness which does not follow the usual hierarchies of the Early Cretaceous sequences. The ancient normal fault systems controlled the distribution of the Coniacian-Santonian deposits that are marked by a significant thickness and facies variations from northwest to southeast (Fig. 12). The Coniacian-Santonian distribution of the sedimentary deposits testifies for a post rift stage with major transgression [START_REF] Abdallah | Le rôle de la faille de Gafsa dans le jeu transgressif et régressif au Crétacé supérieur de la chaîne nord des Chotts (Tunisie)[END_REF][START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF].

During the Coniacian-Santonian, the Maghreb area was covered by an important transgression leading to a very extensive marine incursion covering the northern platforms of the Sahara domain corresponding to shallow sea characterized by the deposition of a homogeneous carbonate platform [START_REF] Zouaghi | ,775,657 Echinoderme, Cytherella sp, Cythereis sp, Brachycythere Coniacian-Santonian EH 153 585000 3,775,593 Radiole, Cytherella sp, Bairdia sp Coniacian-Santonian EH 155 584483 3,775,204 Rotallia, Gavelinella sp, Lenticulina sp. Coniacian-Santonian EH 156 582497 3,775,659 Rotallia, Gavelinella sp Coniacian-Santonian EH 220 584,262 3,774,591 Brachycythere, Globotruncana fornicata, Bairdia sp. Coniacian-Santonian Jebel Romana-Gouada plain EH 221[END_REF][START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF][START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF]. A subsiding deep-marine basin has been developed in the Aurès [START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF]) that allows the deposition of black deep-marine shales in the Tunisian Atlas, which is one of the most important hydrocarbon-source rocks of the Atlas system [START_REF] Bédir | Subsurface Mesozoic basins in the central Atlas of Tunisia, tectonics, sequence deposit distribution and hydrocarbon potential[END_REF]Zouaghi el al., 2005;[START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF].

Campanian-Maastrichian tectonic reactivation

Several authors have suggested tectonic inversion in the Tunisia Atlas since the Campanian [START_REF] Guiraud | Senonian basin inversion and rejuvenation of rifting in Africa and Arabia: synthesis and implications to plate-scale tectonics[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF][START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF][START_REF] Masrouhi | New tectono-sedimentary evidence constraining the timing of the positive tectonic inversion and the Eocene Atlasic phase in northern Tunisia: Implication for the North African paleo-margin evolution[END_REF]Frizon de Lamote et al., 2009;[START_REF] Masrouhi | Submarine "salt glacier" kinematics of Northern Tunisia, a case of Triassic salt mobility in North African Cretaceous passive margin[END_REF]. Zouari et al.

(1999) defined that the inversion occurred between middle Turonian and the Late Maastrichtian. In our study area, Late Campanian to Paleocene series are absent in the eastern Zemlet el Beidha region. However, these series develops westward in the Fejej corridor (Fig. 2 and Fig. 10A). We propose that fault reactivation occurred during Late Campanian to Paleocene, producing the westward migration of the subsidence from the Gouada plain to the Fejej corridor (Fig. 10A). This tectonic event may be related to N trending compression which reactivated the major inherited fault. This stage corresponds to southwestward migration of the subsidence in the southern Atlasic domain, especially in the Gafsa Basin (Zouari et al., 1999).

Implications for Cenozoic tectonic evolution

In this study, field data show evidences for unconformities and syntectonic deposits recording several periods of shortening during the Cenozoic. We present here the sedimentary signatures of the different pulses of shortening associated with the development of the Zemlet el Beidha fold.

According to the cross section A-A' (Fig. 4), the unconformity angle between the Coniacian-Santonian and the erosional Late Miocene surface is 10° while between Coniacian-Santonian and Late Pliocene-Quaternary is about 20°. Locally south of the Jebel Jerouala, we observed that the Late Middle Eocene unconformably overlie the Late Maastrichtian-Palaeocene series (cross section B-B', Fig. 4). This unconformity confirms that the Zemlet el Beidha Cretaceous basin was inverted during the Cenozoic. During the compressional deformations, some extensional structures were not reactivated (Fig. 2 andFig 4) while others were reactivated and evolved to strike-slip faults, such as the apparent Khanguet Aïcha and Khanguet Amor strike-slip faults (Fig. 5 and Fig. 6) and reverse faults (Fig. 8).

In addition, some Atlassic folds are related to the early halokinesis during Jurassic and Early Cretaceous associated with the synsedimentary activity of some normal faults [START_REF] Rigane | The "Aptian Crisis" of the South-Tethyan margin: New tectonic data in Tunisia[END_REF]. The seismic lines interpreted by several authors (e.g., [START_REF] Hlaiem | Halokinisis and structural evolution of the major features in eastern and southern Tunisian Atlas[END_REF]Frizon de Lamotte et al., 2000;[START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF] show that the fold structures are associated with reverse deepseated faults rooting at depth within the Triassic levels. The position and orientation of preexisting structures would be related to the position of ancient normal faults which may be probably linked to structural inheritance due to the Triassic-Jurassic to Aptian-Albian rift [START_REF] Guiraud | Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview[END_REF][START_REF] Guiraud | Phanerozoic geological evolution of Northern and Central Africa: An overview[END_REF]. In our study area, the Upper Aptian-Albian normal faulting also played a major role during Cenozoic compressions in controlling the structural architecture of the Zemlet el Beidha anticline and probably, of others structures of the Chott range.

Conclusion

The structural and tectono-sedimentary study of Jebel Zemlet el Beidha underlines the predominant role of inherited structures acquired during the evolution of the southern Tethyan margin, and their influence of the present-day geometry of the Atlassic fold belt. The geodynamic history of the Tethyan margin during the Cretaceous in the northern Chotts range can be divided into three different tectonic events. The first syn-rift Aptian-Albian period shows a general episode of variable depositional thickness and facies variations. It is dominated by an extensional stress regime. The onset of the tilted blocks along the N100-110°E trending normal fault was associated with Upper Aptian syn-depositional conglomerates. This extensional tectonics was also accompanied, in several regions of the Atlas, by volcanic activity and halokinetic movement. The second Coniacian-Santonian period corresponds to a post-rift stage with major marine transgression. The Coniacian-Santonian extensional faulting is recognized in the southern Tunisian Atlassic domain. In contrats, in Algeria and Morocco, the Coniacian-Santonian is characterized by the first period of inversion tectonics [START_REF] Herkat | The relationships between tectonics and sedimentation in the Late Cretaceous series of the Eastern Atlasic Domain (Algeria)[END_REF][START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF]. In our study area, we propose that fault reactivation occurred during Late Campanian to Paleocene, producing the westward migration of the subsidence. This tectonic event can be correlated with the onset of the Africa-Eurasia convergence [START_REF] Guiraud | Senonian basin inversion and rejuvenation of rifting in Africa and Arabia: synthesis and implications to plate-scale tectonics[END_REF][START_REF] Zouaghi | ,775,657 Echinoderme, Cytherella sp, Cythereis sp, Brachycythere Coniacian-Santonian EH 153 585000 3,775,593 Radiole, Cytherella sp, Bairdia sp Coniacian-Santonian EH 155 584483 3,775,204 Rotallia, Gavelinella sp, Lenticulina sp. Coniacian-Santonian EH 156 582497 3,775,659 Rotallia, Gavelinella sp Coniacian-Santonian EH 220 584,262 3,774,591 Brachycythere, Globotruncana fornicata, Bairdia sp. Coniacian-Santonian Jebel Romana-Gouada plain EH 221[END_REF][START_REF] Frizon De Lamotte | Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria,Morocco, Tunisia): an overview[END_REF]. Major structural inversion of the Upper Aptian-Albian normal faults occurred during successive Cenozoic compressions. This Cretaceous inheritance controlled the structural architecture of the Zemlet el Beidha anticline and probably of others structures of the Chott range. Zouaghi, T.;Ferhi, I.;Bédir, M.;Ben Youssef, M.;Gasmi, M. and Inoubli, M.H., 2011. Analysis of Cretaceous (Aptian) strata in central Tunisia, using 2D seismic data and well logs.

. Afr. Earth Sci. Vol. 61, pp. 38-61. Zouari, H., Turki, M.M., Delteil, J., et Stephan, J.-F., 1999. Tectonique transtensive de la paléomarge tunisienne au cours de l'Aptien-Campanien. Bull. Soc. Géol. France 170 (3), pp. 295-301.

Figure captions

  ). The Cenozoic series of the study area are composed by thin Paleocene marine marls covered by Paleogene and Neogene continental sediments. The Early Tertiary comprises green clays of the El Haria Formation. The clays show a Maastrichtian to Paleocene marine fauna

Figure 1 :

 1 Figure 1: Structural map of the northern African margin. B. Tectonic background of the

Figure 2 :

 2 Figure 2: Detailed geologic map of the Zemlet el Beidha anticline. Location of Fig. 5 is

Figure 3 :

 3 Figure 3: Stratigraphic column of the Mesozoic and Cenozoic series in the Zemlet el Beidha

Figure 4 :

 4 Figure 4: Surface cross sections (For location, see Fig. 2) across the Zemlet El Beidha

Figure 5 :

 5 Figure 5: A: The SPOT image of the Khanguet Aïcha area; B: Interpretative geological and

Figure 6 :

 6 Figure 6: A: Panoramic view of the tilted synsedimentary Khanguet Aicha normal fault. This

Figure 7 :

 7 Figure 7: Details of the Aptian syn-tectonic conglomerates of the Orbata Formation.

Figure 8 :

 8 Figure 8: Panoramic view, looking ENE, of a preserved Early Cretaceous normal fault. For

Figure 9 :

 9 Figure 9: Shortcut inverted normal fault with hangingwall shortcut deformation in the

Figure 10 :

 10 Figure 10: A: NE-SW correlations of Cretaceous sedimentary log in the Zemlet el Beidha

Figure 11 :

 11 Figure 11: Photographs showing the principal features of the extensional Cretaceous along

Figure 12 :

 12 Figure 12: Seismic reflexion profiles EL05 and EL07 across the Sidi Mansour Basin,

Figure 13 :

 13 Figure 13: Interpretative model of Khanguet Aicha fault: genetic mechanism explaining the

Figure 14 :

 14 Figure 14: Similar Aptian-Albian extensional structures observed in the southern Atlas of

Table 1 :

 1 Biostratigraphic data from the Zemlet el Beidha. Location of sample are in meter (UTM system). Microfauna and corresponding age of samples are also shown.

Acknowledgments

This work is based on M. Gharbi's Masters at "Faculté des Sciences de Tunis" (Tunisia) and PhD research at "University of Sfax", "Unité de Recherche Hydrosciences Appliquées à Gabés (06/UR/10-03)" (Tunisia) and at CEREGE (Université Paul Cézanne Aix-Marseille (UPCAM), France). M. Gharbi benefits of a Foreign Affair Ministry (Ministère des Affaires Etrangères) grant through French Embassy in Tunisia and a complement support through the "Cotutelle de thèse" program (F2IR program -UPCAM ). Field has benefited from financial support under UPCAM RFQ's International Relations. SPOT images were provided thanks to the ISIS program (©CNES, distribution SPOT images S.A.). The Tunisian Enterprise for Petroleum Activities (ETAP) and particularly A. Amri and Y. Bouazizi are thanked for providing access to the seismic lines. We are indebted to Nick Marriner and Rita Katharina Kraus for comments and English language corrections. We are grateful to Dr. W.

Bosworth and the anonymous reviewer for providing constructive reviews that significantly improved this article.

Locality

Nb X Y Fauna Age

Highlights:

►We used new data to examine inheritance Cretaceous structure pattern of Atlassic front.

►Most faults were active during Aptian Albian times of rifting stage.

►Lower Cretaceous rifting structure are sealed by Coniacian Santonian post-rift deposits.