Shengli Wang

Yan Chen

Julien Charreau

Yongxiang Li

Zhuxin Chen

Guangyou Zhu

Huaizhi Xu

Chao Li

Liangshu Wang
email: wangsl@nju.edu.cn

Underthrusting of the Tarim lithosphere beneath the western Kunlun range, insights from seismic profiling evidence

Underthrusting of the Tarim lithosphere beneath the western Kunlun range at ~8.18 mm/yr persisted since ~30 Ma.

• Growth of the western Kunlun range slightly predated ~40 Ma

Introduction

Continental underthrusting is one of mechanisms of growth of the Tibetan Plateau (Meyer et al., 1998;[START_REF] Tapponnier | Oblique stepwise rise and growth of the Tibet plateau[END_REF]. Quantifying it over the tens-of-millions-year time scale remains challenging. For the Indian subcontinent that is currently connecting with the active Indian Ocean mid-ridge, its underthrusting rates can be estimated by sea floor magnetic lineations [START_REF] Molnar | Cenozoic tectonics of Asia: effects of a continental collision[END_REF]). Yet, for parts of the Asian continent which passively underthrusted southwards beneath the Tibetan Plateau in the context of the India-Asia collision (Meyer et al., 1998;[START_REF] Gao | Deep seismic reflection profile across juncture zone between Tarim Basin and west Kunlun Mountain[END_REF][START_REF] Kao | Seismic image of the Tarim basin and its collision with Tibet[END_REF][START_REF] Tapponnier | Oblique stepwise rise and growth of the Tibet plateau[END_REF], this method is inapplicable since a continental underthrusting generally causes a synchronous forelandward migration of the foreland basin system overlying the underthrusted lithosphere [START_REF] Beaumont | Foreland basins[END_REF][START_REF] Jordan | Thrust loads and foreland basin evolution, Cretaceous, western United States[END_REF][START_REF] Karner | Gravity anomalies and flexure of the lithosphere at mountain ranges[END_REF]. The sedimentary sequences deposited within the foreland basin system, especially within the distal part of the foredeep depozone, gradually lap on the forebulge [START_REF] Decelles | Foreland basin systems[END_REF][START_REF] Decelles | Rates of shortening, propagation, underthrusting, and flexural wave migration in continental orogenic systems[END_REF][START_REF] Naylor | Pro-vs. retro-foreland basins[END_REF][START_REF] Decelles | Foreland basin systems revisited: variations in response to tectonic setting[END_REF]Sinclair and Naylor, 2012). Thus, the infilling sequences of the basin offer a complete, decipherable record of migration of a foreland basin system. Besides understanding continental underthrusting, foreland basin infilling sequences could also provide a means to estimate the uplift of the coupled collisional orogen (Wang et al., 2013).

Here, we present a prime example in Central Asia (Figure 1a) where the Tarim lithosphere is underthrusting beneath western Kunlun, and the underthrusting history is archived

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This article is protected by copyright. All rights reserved. et al., 2015). These strata are underlain by Paleozoic and Mesozoic strata (Xinjiang BGMR, 1993;[START_REF] Zhang | Phanerozoic stratigraphy in covered area of Tarim basin, petroleum Industry Press[END_REF][START_REF] Lu | Regional geology of People's Republic of China: Ayitkardinsayi (J43C002002)[END_REF][START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF].

To the north of the Tarim Basin is Tian Shan. Tian Shan is a Paleozoic orogen [START_REF] Charvet | Paleozoic tectonic evolution of the Tianshan belt, NW China[END_REF], and reactivated in the Mesozoic [START_REF] Chen | The Mesozoic paleo-relief of the Northern Tianshan (China)[END_REF]Wang et al., 2013) and Cenozoic [START_REF] Tapponnier | Active faulting and Cenozoic tectonics of the Tien Shan, Mongolia and Baykal regions[END_REF]Avouac et al., 1993;[START_REF] Yin | Late Cenozoic tectonic evolution of the southern Chinese Tian Shan[END_REF][START_REF] Yin | Cenozoic tectonic evolution of Asia: A preliminary synthesis[END_REF]Wang et al., 2013). Western Tian Shan collided with Pamir at the western corner of the Tarim Basin that caused the ponding of the Tarim Basin.

Our study focused on the middle segment of the western Kunlun foreland through the Bauchu uplift, covered by the Taklimakan sand sea (Figure 1b). In the range front, four rows of fold anticlines have been recognized [START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF]. The Bachu uplift, also named the central Tarim uplift, is a Cenozoic structural high [START_REF] Jia | Tectonic characteristic and Petroleum: Tarim Basin, China[END_REF][START_REF] Jia | Stratigraphy of the Tarim Basin and adjacent area, volume II, stratigraphic charts of sub-areas[END_REF]. Morphological analysis of nine levels of incised fluvial terraces and alluvial fans crossing a fold in conjunction with their age constraints produces a long-term slip rate of 2 to 2.5 mm/yr on its underlying blind ramp [START_REF] Guilbaud | Kinematics of active deformation across the Western Kunlun mountain range (Xinjiang, China) and potential seismic hazards within the southern Tarim Basin[END_REF]. A seismic profile approximately perpendicularly crossing the middle segment of the western Kunlun foreland images structures and the architecture of the infilling sequences (Figures 3,4 and S1), which is the target of this study.

Materials and methods

Materials

We present a seismic profile (Figures 3,4 and S1), and a borehole stratigraphic column in the western Kunlun foreland area. The seismic investigations were carried out and processed by Tarim Oilfield of PetroChina. These data were provided to Nanjing University for scientific purposes under a scientific agreement by Tarim Oilfield. The seismic profile is pre-stacked migration seismic one that has undergone static and dynamic corrections. The seismic profile image well; and some geologic features imaged in it have been confirmed by the exploration and development of Tarim Oilfield. Therefore, it is a high-quality, credible petroleum industry seismic profile. The seismic profile, trending northeast, begins from the Fusha-Keliyang (F-K) anticline in the southwest, crosses the east of the Yecheng city, the Jade anticline and the Qiaokatage homocline, and ends at the central Tarim Basin in the northeast (Figures 1b, 3 and4). The profile is ~323.2 km in length, and 7.5 sec of two-way travel time in depth.

Borehole K is located at the crest of the F-K anticline, and ~1 km east of the seismic profile (Figure 1b). This borehole was drilled through the Xiyu and the Artux formations, the Wuqia, and Kashi groups, and ended in the Mesozoic at the depth of 6580.0 m. Figure 5 shows the stratigraphy of this borehole column. VSP logging data and synthetic seismograms were used to correlate formation boundaries to seismic reflectors. And boundaries of Paleozoic strata were calibrated with well-logging data from the Bachu uplift.

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Methods

We employed contractional fault-related folding theories [START_REF] Shaw | Seismic Interpretation of Contractional Fault-Related Folds: An AAPG Seismic Atlas[END_REF], and the kink method to interpret the geometries of folds imaged in the seismic profile (Figs 3 and S1). The subsidence space of the western Kunlun foreland basin is recorded by infilling sedimentary sequences. Well-imaged seismic profiles (Figs 3 and S1) can reveal the sedimentary sequences. Seismic reflectors among Mesozoic and Cenozoic strata imaged in the profile were traced (Figures 3,4 and S1) to identify their terminations. The seismic profile images Paleozoic marine strata well (Figures 3 andS1), and therefore reflectors among them can be traced unambiguously. Mesozoic and Cenozoic strata are mainly of terrestrial sequences, and the continuity of an individual reflector among them is relatively poor. However, an assemblage of several reflectors is unique, and extends continuously. Thus, we simultaneously delineated a unique assemblage consisting of several reflectors in Mesozoic and Cenozoic strata. We traced a total of 211 reflectors (Figures 4 andS1; Table S1) in the entire profile.

The stratigraphic column (Figure 5) was correlated with the Kekeya magnetostratigraphic section [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF], and the Aeratshi section [START_REF] Bosboom | Linking Tarim Basin sea retreat (west China) and Asian aridification in the late Eocene[END_REF], based on the consistent lithology transitions, a growth unconformity, and a marker bed to constrain the ages of the foreland basin sequences.

Results

Structures imaged by the seismic profile

The southwestern segment of the profile images the F-K, Kekeya, and Guman anticlines (Figures 3a 4a andS1). The F-K anticline is made up of three thrust sheets. The upper sheet includes Permian, Mesozoic, and Cenozoic strata. The middle sheet comprises Permian and Mesozoic strata. Its roof thrust is located between Mesozoic and Cenozoic strata, and its bottom thrust occurs in Permian mudstone. The lower sheet is composed of Paleozoic rocks. Its bottom fault dips southwestwards, and thrusts northeastwards. The Kekeya anticline is a duplex structure including three thrust sheets. Their roof thrust was formed between Mesozoic and Cenozoic beds, and their floor thrust was produced along Permian mudstone. At the front limb, the floor thrusts cut upwards into Permian and Mesozoic strata, and merge with the roof thrust. The Guman anticline is a wedge structure. At its southwestern limb, the Mesozoic strata pinch out, and the roof thrust occurs in the lower part of the Paleocene evaporite bed. Its floor fault thrusts upwards, cuts Permian strata, and merges with the roof thrust at its northeastern limb to form a decollement fault, termed the Yecheng-Hetian decollement fault (YHD).

The YHD occurs along the gypsum-rich layer at the base of Paleocene strata, and extends northeastwards to the Qiaokatage homocline, and steps upwards to the ground surface to form the Qiaokatage-Mazatage thrust ramp (QMT). The slip along the YHD causes buckling of the hanging wall to form the Jade anticline (Figures 3b,4band S1). The slip along the bend between the YDH and the QMT produces folding of the hanging wall to form the Qiaokatage homocline.

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The high-angle fault below the QMT is the Qiaoka fault. Paleozoic strata of the hanging wall of the Qiaoka fault are slightly thicker than its footwall (Figures 3b,3c,and S1), suggesting that the Qiaoka fault was a normal fault in the Paleozoic, and inverted to a reverse fault in the Cenozoic (SI text).

The Selibuya fault is ~15 km northeast of the Qiaoka fault and the QMT. It cuts upwards in the middle part of the Artux Formation, and penetrates downwards through the profile. The vertical separation of the Permian base is ~1.1 sec of two-way travel time (~2750 m; the average interval speed of Paleozoic strata is ~5000 m/sec). Reflectors of the lower part of the Artux Formation near the Selibuya fault in the southwestern wall are steeply tilted southwestwards. The middle part of the Artux Formation overlies the Selibuya fault and the tilted lower part of the Artux Formation. The thickness of the Permian and Cambrian strata at the hanging wall of the Selibuya fault is ~1.68 sec (~4200 m), and its thickness at the footwall is ~1.63 sec (~4075 m), indicating that this fault was also normal in the Paleozoic and inverted in the Cenozoic (SI text). The Bachu uplift controlled by the Selibuya fault is a basement-involved structure (Figures 3c,4c and S1).

A small-scale normal fault is located at ~12 km northeast of the Selibuya fault, and another two antithetic normal faults at ~20 km north of the Selibuya fault. Reflectors between them form a pop-up structure (Figures 3c,4c and S1), the top of which was eroded and unconformably covered by the middle part of the Artux Formation.

The middle Eocene-Quaternary foreland unit

Based on thickness variation, unconformities, and their associated structures, the sedimentary strata imaged in the seismic profile (Figures 3,4 This unit accounts for the most thickness of the southwestern segment of the profile, and gradually decreases northeastwards (Figures 3, 4 andS1). The southwestern part of the unit constructs the western Kunlun fold-and-thrust belt. To the northeast of the Kekeya anticline, this unit is well imaged, and reflectors among it can be unambiguously identified. However, to the southwest of the Kekeya anticline, the Cenozoic strata dip at high angles, and are poorly imaged (Figures 3a, andS1). We have traced 157 reflectors in this unit (Figure S1 and Table S1 in SI), containing the Wulagen, Bashibulak, Keziluoyi, Anjuan, Pakabulak, Artux, and Xiyu Formations from bottom up, and identified 135 terminations due to the sedimentary pinch-out, and examined them in detail to decipher the architecture of this unit. For each formation, we delineate seismic reflectors according to their termination orders from southwest to northeast (SI Text). This middle Eocene-Quaternary foreland tectonostratigraphic unit consists of all the reflectors above R23' (Figures 4 andS1; Table S1). The seismic profile explicitly demonstrates that almost all the reflectors terminate to the foreland (northeastwards), and to the hinterland (southeastwards).

Reflector terminations to the foreland

According to basin-scale thickness and extent variations of the Eocene-Quaternary foreland tectonostratigraphic unit revealed by seismic reflectors (Figures 3,4 and S1; Table S1), the foreland sequences can be divided into four layers. Layer 1 ranges from R24 to R46, Layer 2 from R47 to T55, Layer 3 from R56 to R137; and Layer 4 consists of all reflectors above R138 (Figure S1 and Table S1).

Layer 1, from bottom up, is composed of reflectors R24 to R46 (Figure S1). The lowermost reflector R24 laps on the top reflector R23' of the pre-foreland unit (Figure 6). The thickness of this layer stays constant from the F-K anticline, via the Kekeya syncline, to the Kekeya anticline. And it gradually thins from the northeastern limb of the Kekeya anticline to the northeastern limb of the Guman anticline (Figures 3, 4 andS1). From the northeastern limb of the Guman anticline, this layer thins rapidly, and tapers out at the middle between the Jade anticline and the Qiaokatage homocline. These observations clearly demonstrate that deposition of Layer 1 was not directly disturbed by folding. The surface geology [START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF][START_REF] Lu | Regional geology of People's Republic of China: Ayitkardinsayi (J43C002002)[END_REF]Bosboom et al., 2014a;[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF] and borehole K stratigraphic column in the Kekeya anticline (Figure 5) reveal that Layer 1 is mainly composed of fine sandstone, siltstone, and mudstone. The thickness variation shown on the profile and fine sedimentary rocks indicate that Layer 1 was deposited in the middle and distal part of the foredeep depozone.

The termination of R47 is at ~283 km northeast of that of R46, indicating that the extent of R47 abruptly and significantly exceeded that of R46. Hence, R47 marks the lower boundary of Layer 2. Layer 2 includes R47 through R55. Its total thickness maintains relatively invariant from the outcrop at the northeastern limb of the F-K anticline, through the Kekeya syncline, and the Kekeya anticline, until to the Guman anticline (Figures 4 andS1). Its thickness decreases from the Guman anticline to the Jade anticline, and reaches its minimum between the Jade anticline and the Qiaokatage homocline (Figures 4 andS1). This layer maintains the minimum thickness from the Qiaokatage homocline, through the QMT, until to be cut by the Selibuya fault (Figures 4 andS1). These phenomena suggest that deposition of Layer 2 was not straightforwardly perturbed by growth of folds and thrusts involving this layer. Its thickness and lithology [START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF][START_REF] Lu | Regional geology of People's Republic of China: Ayitkardinsayi (J43C002002)[END_REF][START_REF] Jia | Stratigraphy of the Tarim Basin and adjacent area, volume II, stratigraphic charts of sub-areas[END_REF][START_REF] Zhang | Phanerozoic stratigraphy in covered area of Tarim basin, petroleum Industry Press[END_REF]) variations indicate that it was deposited beyond the foredeep depozone. We regarded the extent of the minimum thickness of this layer as forebulge and backbulge depozones.

Layer 3, the thickest one of this unit, ranges from R56 to R137 (Figure 4 and S1), and maintains a constant thickness from the core of the Kekeya syncline to the Guman anticline. From the Guman anticline to the Jade anticline, this layer slightly thins northwards. From the Jade anticline to the Selibuya fault, it considerably thins northwards (Figures 4 andS1). In the

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northeast of the Selibuya fault, this layer thins to its minimum thickness and only includes few reflectors extending beyond the profile. These observations indicate that deposition of the part of Layer 3 north of the Kekeya anticline was not disturbed by growth of the Kekeya anticline. This layer is mainly composed of gritstone and conglomerate at the outcrop of the northeastern limb of the F-K anticline [START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF], sandstone drilled at the Kekeya anticline (Figure 5; [START_REF] Jia | Stratigraphy of the Tarim Basin and adjacent area, volume II, stratigraphic charts of sub-areas[END_REF][START_REF] Zhang | Phanerozoic stratigraphy in covered area of Tarim basin, petroleum Industry Press[END_REF], fine sandstone and siltstone at the Mazatage hills (Sun et al., 2011). The thickness and lithology variations suggest that the wedge top depozone extends from the northeastern limb of the F-K anticline to the Guman anticline, the foredeep depozone spread from the Guman anticline to the Selibuya fault. The Selibuya fault, the southern boundary of the Bachu uplift, was inverted to a reverse fault, and caused the upper part of this formation to be eroded during deposition of the middle part of the Artux Formation of Layer 3. We suppose that the Selibuya fault was not a part of the western Kunlun orogenic belt, but an isolated reverse fault in the stable Tarim Block.

Layer 4 comprises only the Xiyu Formation ranging from R138 to the top most reflector R158. This layer occurs in the northeast of the Kekeya anticline, but absent on the crest of the Jade anticline (Figures 4 andS1). Layer 4 is mainly of conglomerate at the northeastern limb of the F-K anticline [START_REF] Wang | Regional geology of People's Republic of China: Yecheng County[END_REF], sandstone, and siltstone at the Mazatage (J. Sun et al., 2009;D. Sun et al., 2011). Deposition of the part of Layer 4 south of the Jade anticline was explicitly disturbed by the growth of the Kekeya, the Guman and the Jade anticlines. In other words, this part was the wedge-top depozone. And deposition of the part north of the Jade anticline was not perturbed by the growth of folds, and this part is interpreted to be the foredeep depozone.

Overall, Layer 1 of the foreland unit accumulated in the proximal foredeep, and the extent of Layer 2 exceeded sharply significantly the foredeep. And Layers 3 and 4 deposited in the entire foreland basin system, but the southern boundary of the wedge top depozone of Layer 4 migrated northeastwards by an anticline zone (the Kekeya anticline) with respect to Layer 3 (Figures 4 andS1). These observations indicate that the western Kunlun foreland basin progressively migrated northeastwards.

Reflector terminations to the hinterland

Some seismic reflectors terminate to the southwest (to the hinterland) in the profile due to tilting, and subsequent erosion (Figures 4a andS1); this type of reflector ends is termed erosion termination. Other reflectors buttress on the northeast limb of anticlines to terminate, which is termed sedimentary pinch-out. The reflectors beneath R55 terminate southwestwards due to erosion at the northeastern limb of the F-K anticline. The reflectors from R56 to R78 buttress on R55 southwestwards (Figure S1 in SI). At the crest of the Kekeya anticline, R79 and its overlaying reflectors very likely terminate southwestwards due to sedimentary pinch-out. Based on the relatively constant thickness and consistent strata dips, we speculate that R88 is the uppermost reflector at the Kekeya anticline. The thickness of the strata from R80 to R88 maintains constant in the Kekeya anticline area, so, we deduce that these reflectors were eroded to terminate at the northeast limb of this anticline. Hence, we infer that the reflectors from R88 to R137 terminate southwestwards due to the sedimentary pinch-out. The reflectors above R137 distinctly lap on the northeastern limb of the Kekeya anticline (Figure S1). The reflectors above R126 are folded to uplift, and subsequently eroded at the crest of the Jade anticline (Figure S1). Overall, the hinterland sedimentary pinch-out sites of seismic reflector gradually migrate to the foreland.

Chronological control of seismic reflectors

Ages of the western Kunlun foreland sequences have been well constrained by magnetostratigraphic (Sun and Liu, 2006;Sun et al., 2009;Sun et al., 2011;[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF], biostratigraphic (Bosboom et al., 2014a), and radioisotope dating [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF] studies. Zheng et al.'s (2015) magnetostratigraphic section at the northern limb of the F-K anticline is ~5 km west of the southwestern segment of the seismic profile (Figure 1b); and Bosboom et al.'s (2014a) section at the northern limb of the western extension of the F-K anticline (Figure 1b) is ~35 km west of the seismic profile. The ~6850-meter-deep borehole K is near our seismic profile, and at the crest of the Kekeya anticline (Figure 1b). Given that the Kekeya [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF], and the Aertashi (Bosboom et al., 2014a) sections are closest to the seismic profile as well as borehole K, and have several reliable anchoring points, we correlated these age constraints with the stratigraphic column of borehole K, and then with the traced reflectors based on borehole logging data, and synthetic seismograms of borehole K. Five matching boundaries between the stratigraphic column of borehole K, and the sections were correlated (Figure 5).

The first correlating boundary concerns the transition from the carbonate rocks to the mudstone. At the depth of ~6316.5 m in borehole K stratigraphic column, the lithology changes from the carbonate rocks of the Kalataer Formation to the mudstone (Figure 5); and in the Aertashi section, the lithology has identical change at ~0 meter (Figure 5). These two transitions match well. This matching transition corresponds to an age of ~41.16 Ma according to Bosboom et al.'s (2014a) study. At the depth of ~5449 m in borehole K column (Figure 5), the lithology changes from mudstone intercalated with sandstone to sandstone intercalated with mudstone. These identical transitions occur at ~736.9 m of the Aeratshi section, and at ~470.5 m of the Kekeya section. This is the second correlative boundary. This lithological transition was dated at ~33.01 Ma according to the magnetostratigraphic studies [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF]Bosboom et al., 2014a). The third correlative boundary is the transition from silty mudstone to sandstone at the depth of ~4238.3 m of borehole K column (Figure 5), which matches the identical transition at ~1694 meter of the Kekeya section (Figure 5) dated at ~27.00 Ma according to Zheng et al.'s (2015) study.

The lithology transition from sandstone to conglomerate of the Kekeya section was explained as a disconformity with a hiatus of ~6.84 Myr from ~22.00 Ma to ~15.16 Ma [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF]. The seismic image reveals that reflectors from R56 through R77 very likely buttress on R55 (Figures 3a,4a and S1) at the northeastern limb of the F-K anticline. Moreover, the Wuluwusitang section (Figure 7) also displays this contact relationship [START_REF] Zhou | Some problems concerning correlation of the Pliocene and Miocene series in southwest Tarim basin[END_REF]. The segment of the anticline from the Kekeya section to the Wuluwusitaing section trends steady south-southeast (Figure 1b), and thus can be regarded as a cylindrical fold. We assume that this segment grew synchronously by the same mechanism. Therefore, we infer that these 3 unconformities or disconformities can be taken as the same growth unconformity occurring during the same time. Based on the assumption and this deduction, we correlated the disconformity at Kekeya section with the unconformity at the Wulususitang section, and the growth unconformity in the seismic profile. The growth unconformity ranges from R55 to R78 (Fig S1). VSP (vertical speed profiling) logging data and synthetic seismograms of borehole K reveal that the bottom (R55), and the top (R78) boundaries of the unconformity correspond to the depths of ~2462.0 m and ~466.0 m of borehole K stratigraphic column, respectively (Figure 5). Therefore, we correlated the ~2462.0 m depth of the stratigraphic column of borehole K with the bottom boundary of the hiatus, corresponding to an age of ~20.00 Ma according to Zheng et al.'s (2015) results. This presents the fourth correlative boundary.

Moreover, the natural gamma ray logging curve of borehole K displays a ~2-meter-thick mudstone bed from the depth of ~371.5 m to ~373.5 m with a significantly high natural gamma ray value of ~167 API contrasting the overlying and underlying strata (Figure 8). It is also the highest natural gamma ray value bed above the Bashibulak Formation. Considering that the volcanic tuff generally has a high natural gamma ray value, we inferred that this mudstone bed corresponds to the volcanic ash bed exposed at the Kekeya section, and dated at ~11 Ma [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF]. Therefore, we obtained five matching age boundaries correlated with the stratigraphic column of borehole K.

Using these correlating results, we plotted ages versus depths of the strata drilled at borehole K to obtain a sedimentation curve (Figure 9). The curve shows five sedimentation rate values. From old to new, they are (1) ~100.99 m/Myr before ~33 Ma, (2) ~203.11 m/Myr from ~33 Ma to ~27 Ma, (3) ~355.26 m/Myr from ~27 Ma to ~22 Ma, (4) ~189.95 m/Myr from ~22 Ma to ~11 Ma, and (5) ~33.86 m/Myr after ~11 Ma. The sedimentation curve of borehole K (Figure 9) mimics a lazy "S", and is comparable to that of the classic foreland basin [START_REF] Decelles | Foreland basin systems[END_REF], suggesting that borehole K site has gone through each depozone of the western Kunlun foreland basin.

Afterwards, according to the VSP logging data and the synthetic seismograms of borehole K, these five boundaries were correlated to R23, R29′, R43, R55 and R82 (Figure 5). Ages of the reflectors are ~41.16 Ma, ~33.01 Ma, ~27.00 Ma, ~20.00 Ma, and ~11 Ma, respectively. For strata between them, we interpolated their ages. And for strata above the volcanic ash bed, we extrapolated their ages by assuming that the age of the top most bed in the present foredeep depozone with active sedimentation is zero. Accordingly, each traced reflector is correlated to a stratum age (Table S1). As such, reflectors R24, R47, R127, and R137 correspond to ~40 Ma, ~25.39 Ma, ~5.24 Ma, and ~4.07 Ma, respectively (Table S1).

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Discussion

Active thrusting and folding of the western Kunlun foreland fold-and-thrust belt (e.g., [START_REF] He | Source model of the 2015 Mw 6.4 Pishan earthquake constrained by interferometric synthetic aperture radar and GPS: Insight into blind rupture in the western Kunlun Shan[END_REF][START_REF] Lu | Coseismic and blind fault of the 2015 Pishan Mw 6.5 earthquake: Implications for the sedimentary-tectonic framework of the western Kunlun Mountains, northern Tibetan Plateau[END_REF][START_REF] Guilbaud | Kinematics of active deformation across the Western Kunlun mountain range (Xinjiang, China) and potential seismic hazards within the southern Tarim Basin[END_REF], GPS measurements [START_REF] Gan | Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[END_REF][START_REF] Liang | Threedimensional velocity field of present-day crustal motion of the Tibetan Plateau derived from GPS measurements[END_REF][START_REF] Wang | Present-day velocity field and block kinematics of Tibetan Plateau from GPS measurements[END_REF][START_REF] Wang | Present-day crustal deformation of continental China derived from GPS and its tectonic implications[END_REF], and the south-dipping Tarim lithosphere [START_REF] Gao | Deep seismic reflection profile across juncture zone between Tarim Basin and west Kunlun Mountain[END_REF][START_REF] Kao | Seismic image of the Tarim basin and its collision with Tibet[END_REF] indicate that the Tarim lithosphere underthrusts beneath the western Kunlun range. In addition, the continuous northern migration of the western Kunlun foreland basin offers an opportunity to quantify the underthrusting. The seismic reflection profile is nearly perpendicular to the main segment of western Kunlun (Figure 1b). Hence, we suppose that the migration of the foreland basin derived from the profile can reflect the evolution of the foreland basin along with western Kunlun. With underthrusting of the underlying plate, each point of it successively goes through a foreland basin system from the backbuldge through forebuldge, foredeep, and the wedge-top depozones. The sedimentation rates above this point changes with its position relative to the foreland basin system, with the highest one in the foredeep, the lower one in the forebuldege, and the wedge-top. The sedimentation curve of the point mimics a lazy "S" overall [START_REF] Decelles | Foreland basin systems[END_REF]. The sedimentation curve at borehole K (Figure 9) is consistent with that of a classic foreland basin [START_REF] Decelles | Foreland basin systems[END_REF]. This suggests that our correlating ages of the foreland sequences (Table S1) are admissible and viable. Consequently, the ages of the foreland sequences were correlated to seismic reflectors (Table S1 and Figure S1). Therefore, based on the architecture of the infilling sequences and their ages, we can retrieve the migration of the foreland basin with the underthrusting of the Tarim lithosphere, the initiation of the foreland basin, the initiation time of its coupling with the orogenic belt as well as the ponding time of the Tarim Basin.

5.1 Migration of the foreland basin due to the underthrusting of the Tarim lithosphere All reflectors terminate towards the foreland except that R127, R129, R137-2, R142, and R147 extend northeastwards beyond the profile (Figure S1). Reflector terminations to the foreland are classified as fault-cut termination, erosion termination and pinch-out types. Reflectors R47, R55, R62, R65, R68, R72, R75, and R76 are cut by the Selibuya fault to terminations (Figure S1). Reflectors R78, R80, R82, R83, R84, R85, R88, R91, R92, R95, R99, and R101 are tilted by the underlying Selibuya fault, and eroded to termination (Figure S1). The fault-cut, and erosion terminations are attributed to the growth of the local structures, e.g., the Selibuya fault. The other 135 reflectors above R23' pinch out forelandwards (Figure S1 and SI text).

Although terminations of seismic reflectors go back and forth with time (Figures 3,4, 10 and S1), they migrate to the foreland overall. The termination of a seismic reflector to the foreland represents the distal end of deposition at that time. Generally, the thinnest sedimentary sequences or no sediments occur in the forebuldege of a foreland basin system, and thicken to the foredeep [START_REF] Decelles | Foreland basin systems[END_REF]. Accordingly, the envelope of the distribution area of forelandward reflector terminations denotes the boundary between the foredeep and the forebulge. Thus, the migration of the boundary relative to the underlying plate can reflect that of

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a foreland basin (Figures10b and 10c). To quantify the migration of the western Kunlun foreland basin, we plotted the ages of strata represented by reflectors vs. the distances between reflector terminations and western Kunlun (the core of the Kekeya anticline). Although the distribution areas of lower boundaries of reflector terminations are not distinct, those of the upper boundaries are unambiguous as the upper envelop of the distribution area of reflector terminations apparently retreats toward the orogen by about 100 km from ~40 Ma to ~30 Ma (Figure 10a). Similarly, the pinch-out of the Keziluoyi Formation is at ~31 km southwest of the Wulagen and Bashibulak Formations (Figures 4 andS1). The upper envelope of the distribution area of reflector terminations after ~30 Ma demonstrates that the sedimentary boundary gradually migrated toward the foreland with time (Figure 10a). To further quantify the migration, we selected the most-distal reflector terminations within every one million years to fit an equation to quantify the migration of the western Kunlun foreland basin. The selected terminations are linked by the dashed fold line in Figure 10a. The linear fitting of the upper envelop gives an equation of y=8.18x+276.12, with a correlation coefficient of R 2 =0.75. From the deposition time of R24, the lowermost, oldest reflector of this unit, to that of R149, the farthest one away from the range, the foredeep has migrated forelandwards by ~119 km over a ~40 Myr time interval (Figures 4, S1 and 10a). The linear fitting equation of the upper envelop since ~30 Ma provides an average northeastward migration rate of ~8.18 mm/yr of the foreland basin.

In an orogen-foreland basin system, buildup of the orogenic wedge can cause flexure of the underlying plate to form a foreland basin, and migration of the forebuldge to the foreland (Figure10b) [START_REF] Decelles | Foreland basin systems[END_REF]. Furthermore, underthrusting of the underlying plate beneath the orogen may lead to migration of the foreland basin to the foreland. Thus, the migration of the foreland basin consists of the propagation of an orogenic wedge, and the underthrusting of an underlying lithosphere (Figure 10b; [START_REF] Decelles | Foreland basin systems[END_REF][START_REF] Decelles | Rates of shortening, propagation, underthrusting, and flexural wave migration in continental orogenic systems[END_REF][START_REF] Decelles | Foreland basin systems revisited: variations in response to tectonic setting[END_REF]. In other words, the migration of the foreland basin is indicative of the underthrusting of the underlying lithosphere. The upper envelop of the reflector terminations is an agent of the migration of the foreland basin.

Our analysis of the profile demonstrates that the forebuldge of the western Kunlun foreland basin system gradually retreated to the hinterland from ~40 Ma to ~30 Ma. The corresponding change in formations is the southwestward migration of the pinch-out of the Keziluoyi Formation relative to the underlying Wulagen and Bashibulak Formations. The width of a foreland basin depends on the flexural rigidity of the elastic underthrusting lithosphere [START_REF] Beaumont | Foreland basins[END_REF]. In contrast, a foreland basin over a viscoelastic lithosphere narrows through time during the early stage of the buildup of an orogen-basin system [START_REF] Quinlan | Appalachian thrusting, lithospheric flexure, and the Paleozoic stratigraphy of the Eastern Interior of North America[END_REF]; correspondingly, the forebuldge migrates to the hinterland. Alternatively, changes in the effective elastic thickness of the underlying lithosphere, and the tectonic load of the associated orogenic wedge can also cause migration of the forebuldge (Turcotte and Schubert, 2002). However, significant changes in the effective elastic thickness of the underthrusting Tarim lithosphere, and tectonic load of western Kunlun were not documented, and the northern movement of the Indian plate is relatively constant during this time-span (Molnar and

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This article is protected by copyright. All rights reserved. [START_REF] Molnar | Cenozoic tectonics of Asia: effects of a continental collision[END_REF]. Additionally, the pre-foreland basin substratum was not eroded during the northward migration of the western Kunlun foreland (Figures 3 andS1), suggesting that the forebuldge was weak in amplitude with the high viscoelasticity of the lithosphere [START_REF] Quinlan | Appalachian thrusting, lithospheric flexure, and the Paleozoic stratigraphy of the Eastern Interior of North America[END_REF]. Hence, we infer that the most likely reason for the retreat of the western Kunlun foreland basin is that the Tarim lithosphere is viscoelastic.

The upper envelop of the distribution area reveals that the foreland basin migrated forelandwards at ~8.18 mm/yr since ~30 Ma. This is also the rate of the Tarim lithosphere underthrusting beneath western Kunlun. This stable underthrusting rate indicates that the current orogenic belt, and basin configuration has been established, as also supported by stratigraphy, detrital zircon, and whole-rock geochemistry studies [START_REF] Cao | Neogene Source-to-Sink Relations between the Pamir and Tarim Basin: Insights from Stratigraphy, Detrital Zircon Geochronology, and Whole-Rock Geochemistry[END_REF], and a steady exhumation rate of ~0.9 km/Myr from the Late Oligocene to the Early Miocene [START_REF] Cao | Exhumation history of the West Kunlun Mountains, northwestern Tibet: Evidence for a long-lived, rejuvenated orogen[END_REF].

During activity of the Selibya fault from ~12.72 Ma (the correlated age of R78, the uppermost reflector cut by the fault; Table S1) to ~8.73 Ma (the correlating age of R103, the lowermost reflector overlying reflectors tiled by the fault; Table S1), the upper envelop of the termination distribution area does not change significantly (Fig 10a). Therefore, the effect of activity of the Selibuya fault on the migration of the forebulge of the western Kunlun foreland basin is negligible.

The active tectonics [START_REF] Lu | Coseismic and blind fault of the 2015 Pishan Mw 6.5 earthquake: Implications for the sedimentary-tectonic framework of the western Kunlun Mountains, northern Tibetan Plateau[END_REF][START_REF] Guilbaud | Kinematics of active deformation across the Western Kunlun mountain range (Xinjiang, China) and potential seismic hazards within the southern Tarim Basin[END_REF] reveals that the underthrusting of the Tarim lithosphere is still ongoing. GPS measurements reveal that the western Kunlun front and the northern Tarim Basin (Keping, Xinhe and Kuche area) moves northeastwards with respect to the stable Eurasia plate at ~20 mm/yr, and ~14.3-~16.2 mm/yr, respectively [START_REF] Gan | Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[END_REF][START_REF] Liang | Threedimensional velocity field of present-day crustal motion of the Tibetan Plateau derived from GPS measurements[END_REF][START_REF] Wang | Present-day velocity field and block kinematics of Tibetan Plateau from GPS measurements[END_REF][START_REF] Wang | Present-day crustal deformation of continental China derived from GPS and its tectonic implications[END_REF]. The velocity difference between them is ~3.8-~5.7 mm/yr, which can be treated as the present-day crustal shortening rate in the western Kunlun foreland fold-and-thrust belt. If this inference of GPS measurements represents the long-term shortening, the difference of ~4.4-~2.5 mm/yr between this shortening rate and the Tarim lithosphere underthrusting rate of ~8.18 mm/yr would suggest the latitudinal propagation rate of western Kunlun, i.e., a lateral growth rate of the northwestern Tibetan Plateau.

Initiation of the western Kunlun range

The base of this middle Eocene-Quaternary foreland unit is the lower limit of the Wulagen Formation, which corresponds to R24 lapping northeastward on R23' (Figures 6 andS1), correlated with ~40 Ma (the middle Eocene; Table S1). As the foreland basin moves forelandwards with the underthrusting of the underlying lithosphere at the same rate, the foreland basin filling sequences can be incorporated into the orogenic wedge, and eroded [START_REF] Decelles | Foreland basin systems[END_REF][START_REF] Naylor | Pro-vs. retro-foreland basins[END_REF]Sinclair and Naylor, 2012;[START_REF] Decelles | Foreland basin systems revisited: variations in response to tectonic setting[END_REF]. The surviving oldest strata may be younger than the initial sedimentary records. The basal part of the Wulagen Formation is the oldest infilling sequence identified in the western Kunlun foreland basin. We cannot exclude the possibility that some strata older than it could have ever occurred. Accordingly, we speculate that the initiation of the middle segment of the western Kunlun range

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This article is protected by copyright. All rights reserved. probably slightly predated the deposition time of the surviving bottom boundary of the Wulagen Formation, i.e., ~40 Ma (the middle Eocene). This result is based on the basin-scale analysis of the lowermost of the foreland basin sequences. It is worth noting that local outcrops exposed in the western Kunlun front may be not the lowermost part. Studies based on these local outcrops may find younger initiation of western Kunlun (e.g., [START_REF] Jin | Cenozoic depositional sequences in the piedmont of the west Kunlun and their paleogeographic and tectonic implications[END_REF][START_REF] Cao | Exhumation history of the West Kunlun Mountains, northwestern Tibet: Evidence for a long-lived, rejuvenated orogen[END_REF]. Alternatively, along the ~700-km-long western Kunlun range, it is unknown whether initiations of each segment of the range are synchronous or diachronous. More investigations are needed to constrain its initiation.

Ponding of the Tarim Basin

Layer 1 of the foreland unit deposited in the foredeep, and lapped on its underlying Kalataer Formation, and all the reflectors within this layer end up northeastwards due to sedimentary tapering out (Figures 3, 4 andS1). The bottom reflector R24 laps on the top reflector R23' of the pre-foreland basin substratum, which extends to the Selibya fault, and is not eroded (Figures 3, 4 andS1). If the foredeep was underfilled, the pre-foreland basin substratum should be eroded. These observations suggest that the foreland basin was in equilibrium of subsidence-filling. At this moment, the Pamir and ancient Tian Shan was not yet in contact [START_REF] Bosboom | Late Eocene sea retreat from the Tarim Basin (west China) and concomitant Asian, paleoenvironmental change[END_REF]2014a;[START_REF] Bosboom | Timing, cause and impact of the late Eocene stepwise sea retreat from the Tarim Basin (west China)[END_REF] and sediments sourced from western Kunlun can be transported away from the Tarim Basin. However, the extent of Layer 2 exceeded Layer 1 abruptly and significantly (Figures 4 andS1), indicating that the filling state of the western Kunlun foreland basin changed from a subsidence-infilling equilibrium to an overfilled state. This may be explained by a scenario where the sediments supply rate increased, and/or sediments beyond the subsidence space were not transported away from the Tarim Basin anymore. During the deposition of Layer 2, the sedimentation rate did not change (Figures 9 and10a). However, no evidence supports the increase in the sediments rate during this period. Nevertheless, the underthrusting of the Tarim lithosphere beneath western Kunlun may lead to progressively narrowing the corridor between western Kunlun and ancient Tian Shan [START_REF] Charvet | Paleozoic tectonic evolution of the Tianshan belt, NW China[END_REF][START_REF] Chen | The Mesozoic paleo-relief of the Northern Tianshan (China)[END_REF], until they collided to close the corridor. Its closure caused all the sediments sourced from the ranges surrounding the Tarim Basin to be trapped, and accumulate within it. Consequently, we interpret the abrupt, significant increase in the extent of Layer 2 relative to that of Layer 1 as the initial collision of western Kunlun with ancient Tian Shan. This interpretation implies that the modern geomorphology of the Tarim Basin, ponded by surrounding ranges, took shape since the deposition of Layer 2 (Figure 11). The bottom reflector R47 of Layer 2 (Figures 4a andS1) is correlated to ~25 Ma (the late Oligocene; Table S1), corresponding to the initial ponding time of the Tarim Basin.

Aeolian sediments appeared continuously since ~26.7 Ma [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF], which is interpreted as the desertification in the Tarim Basin (e.g., Sun and Liu, 2006;Sun et al., 2011;[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF]. This desertification was almost contemporaneous with ponding of the Tarim Basin, and the reactivation of ancient Tian Shan (Wang et al., 2013;[START_REF] Li | Tectonostratigraphic history of the southern Tian Shan, western China, from seismic reflection profiling[END_REF], suggesting that the closure of the corridor between western Kunlun and ancient Tian Shan may be one of the reasons for the desertification of the Tarim Basin due to the blockage of the wind carrying

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This article is protected by copyright. All rights reserved. moisture from the Atlantic [START_REF] Zhang | Late Miocene-Pleistocene aridification of Asian inland revealed by geochemical records of lacustrine-fan delta sediments from the western Tarim Basin, NW China[END_REF], and the retreat of the Para-Tethys sea [START_REF] Bosboom | Late Eocene sea retreat from the Tarim Basin (west China) and concomitant Asian, paleoenvironmental change[END_REF][START_REF] Bosboom | Timing, cause and impact of the late Eocene stepwise sea retreat from the Tarim Basin (west China)[END_REF].

Changes in sedimentation rates in the foredeep

Since the deposition time of R24, i.e. ~40 Ma, the rates of reflector formation in the Eocene-Quaternary foreland unit display a stepwise change, (1) 1 reflector per million years from ~40 Ma to ~33 Ma, (2) 2-3 reflectors per million years from ~33 Ma to ~12 Ma, (3) 4 reflector per million years from ~12 Ma to ~11 Ma, and (4) 7-9 reflectors per million years since ~11 Ma (Figure 10a). Considering that the Cenozoic strata in northwestern Tarim exhibit similar velocities as shown by well logging data, we assume that each seismic reflector represents the same strata thickness. The resulting sedimentation rates in the whole western Kunlun foreland basin increased in a stepwise fashion. The effective elevation of western Kunlun, representing the tectonic load, should also show stepwise increase in synchronization with subsidence and infilling of the foreland basins due to their coupling relationship [START_REF] Jordan | Thrust loads and foreland basin evolution, Cretaceous, western United States[END_REF]. The stepwise increases in sedimentation rates possibly imply that western Kunlun experienced four episodes of uplift. Studies in eastern segment of the western Kunlun foreland [START_REF] Jiang | Seismic reflection data support episodic and simultaneous growth of the Tibetan Plateau since 25 Myr[END_REF]) also indicate that episodic uplifts of western Kunlun. Accordingly, the constant sedimentation rate since ~11 Ma suggests that the tectonic load of western Kunlun reached its maximum. In other words, western Kunlun reached its currently effective elevation at ~11 Ma. The timing of the abrupt, significant increase in sedimentation rates of the western Kunlun foreland basin agrees with that of the uplift acceleration of Tian Shan [START_REF] Charreau | Magnetostratigraphy of the Yaha section, Tarim Basin (China): 11 Ma acceleration in erosion and uplift of the Tian Shan mountains[END_REF][START_REF] Li | Tectonostratigraphic history of the southern Tian Shan, western China, from seismic reflection profiling[END_REF][START_REF] Li | Evolution of the Cenozoic Tarim Basin by flexural subsidence and sediment ponding: Insights from quantitative basin modelling[END_REF], suggesting that the high elevation of the northwestern Tibetan Plateau facilitated the northward propagation of deformation.

Conclusions

The ~323.2-km-long seismic reflection profile crossing the middle segment of western Kunlun images well the infilling sequences of the foreland basin. Tracing, and analyzing of 157 seismic reflectors reveal that the infilling sequences consist of four major layers. Magnetostratigraphic results from the range front were correlated with reflectors to constrain their ages. Layer 1, from bottom up, accumulated in the foredeep, and its basal unit recorded the initiation of the western Kunlun range slightly prior to ~40 Ma. The extent of Layer 2 greatly exceeded that of Layer 1 toward the north, implying that the filling of the foreland basin changed from equilibrium to overfilling. The overfilling can be explained by the collision of western Kunlun with ancient Tian Shan that closed the corridor between them, and the Tarim Basin began to take its modern geomorphologic shape at ~25 Ma. Layer 3 and Layer 4 accumulated beyond the foreland basin, while the southwestern limit of Layer 4 migrated northeastwards by an anticline zone relative to that of Layer 3. Each depozone of the western Kunlun foreland basin migrated northeastwards over time. The reflector terminations significantly retreated to the hinterland from ~40 Ma-~30 Ma. This retreat suggests that the Tarim lithosphere behaves as a viscoelastic body. The linear fitting of the upper envelop of the distribution of reflector terminations since ~30 Ma suggests that the foreland basin migrated northeastwards at an

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average rate of ~8.18 mm/yr, i.e. the rate of the Tarim lithosphere underthrusting beneath western Kunlun. This underthrusting rate comprises a crustal shortening rate of ~3.8-5.7 mm/yr, and a latitudinal propagation rate of western Kunlun of ~4.4-2.5 mm/yr. The abrupt increases in sedimentary accumulation rates in the entire basin suggest that western Kunlun has reached its current elevation since ~11 Ma.

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This article is protected by copyright. All rights reserved. [START_REF] Jia | Stratigraphy of the Tarim Basin and adjacent area, volume II, stratigraphic charts of sub-areas[END_REF][START_REF] Zhang | Phanerozoic stratigraphy in covered area of Tarim basin, petroleum Industry Press[END_REF]Bosboom et al., 2014a[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF]. 3b and3c, respectively, to present the entire profile. The vertical scale approximates to the horizontal one. Figures 3a,3b and 3c share the same vertical and horizontal scales. Figure 6 is marked in Figure 3b. [START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF] and Aertashi (Bosboom et al., 2014a) magnetostratigraphic sections. See Figure 1b for their locations. Five matching boundaries are correlated based on the comparable lithology. Referenced in the text and formation boundary reflectors are denoted to the right side of borehole K column. ATS, Aerertashi Formation; QMG, Qimugen Formation; KLT, Kalataer Formation; WLG, Wulagen Formation.

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indicative of the bottom boundary of the middle Eocene-Quaternary foreland unit. The western Kunlun range slightly predated the deposition time of R23′.

Figure 7. River-cut section of the northern limb of the Fusha-Keliyang (F-K) anticline along the eastern bank of the Wuluwusitang River (modified from Zhou, 1983), showing the growth unconformity occurring in the Pakabulak Formation that supports the hiatus interpretation of the northern limb of the F-K anticline in Figures 3a and4a. See Figure 1b for its location. 5 for the correlation between the borehole K stratigraphic column and timing results, and Figures 1b and3a and 4a for the borehole K location. This curve shows that the sedimentation rates of the site increased from ~40 Ma to 22 ~Ma, decreased from ~22 Ma to ~11 Ma, and reached to its minimum since ~11 Ma, indicating that the borehole K site has swept over the foreland basin system from the distal foredeep depozone to the wedge top one. This curve is concordant with that of the classic foreland basin, suggesting that the age correlation is admissible and viable. S1 for all the measured values. The dashed fold line is a distribution envelope established by connecting the maximum values within about one million of years. The solid line is fitted by values connected by the dashed fold line. The linear fitting of the upper envelop of the distribution area of reflector terminations indicates that the western Kunlun foreland basin system migrated forelandward at a rate of ~8.18 mm/yr since ~30 Ma, consisting of the present shortening rates of ~3.8-5.7 mm/yr derived from GPS measurements [START_REF] Gan | Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[END_REF][START_REF] Liang | Threedimensional velocity field of present-day crustal motion of the Tibetan Plateau derived from GPS measurements[END_REF][START_REF] Wang | Present-day velocity field and block kinematics of Tibetan Plateau from GPS measurements[END_REF][START_REF] Wang | Present-day crustal deformation of continental China derived from GPS and its tectonic implications[END_REF] and the western Kunlun latitudinal propagation rate of ~4.4-2.5 mm/yr. From ~40 Ma to ~30 Ma, the foreland basin retreated toward the hinterland. The retreat of the foreland basin suggests that the Tarim lithosphere behaves as a viscoelastic body. The grey histogram at lower part of Figure 10a shows that sedimentation rate of the whole basin, represented by formations rates of seismic reflector, increased in a stepwise fashion, 1 reflector per million years from ~40 Ma to ~33 Ma, 2-3 reflectors per million years from ~33 Ma to ~12 Ma, 4 reflector per million years from ~12 Ma to ~11 Ma, and 7-9 reflectors per million years since ~11 Ma. The rates reached its maximum and have maintained constant since ~11 Ma, suggesting that western Kunlun reached its current effective elevation at that time. (b) Migration of a classic foreland basin with the underthrusting of its underlying lithosphere. Migration of the western Kunlun foreland basin is consistent with this classic type. (c) Stratal onlaps in the foreland basin that records its lateral migration (after DeCelles, 2012). This type of onlaps has been identified in the seismic profile of Figures 3,4

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  and S1) are divided into four tectonostratigraphic units in an ascending order: (a) the Paleozoic rift, (b) the Jurassic-Cretaceous foredeep, (c) the Paleocene-early Eocene continental platform, and (d) the middle Eocene-Quaternary foreland tectonostratigraphic units (SI Text). Given that the filling sequence of the foreland basin records the Cenozoic underthrusting of the Tarim lithosphere, we only finely depicted the architecture of the middle Eocene-Quaternary foreland unit.

Figure 1 .

 1 Figure 1. (a) Topographic map of Central Asia showing the Tibetan Plateau and other active mountain belts as responses to the India-Asia collision. The shown major faults were adopted from Yin (2010). (b) Geologic map of the southwestern Tarim Basin and the western Kunlun range modified from Xinjiang BGMR (1993) and Wang and Peng (2013).

Figure 2 .

 2 Figure 2. Simplified Cenozoic stratigraphic chart of the western Kunlun foreland front (simplified from[START_REF] Jia | Stratigraphy of the Tarim Basin and adjacent area, volume II, stratigraphic charts of sub-areas[END_REF][START_REF] Zhang | Phanerozoic stratigraphy in covered area of Tarim basin, petroleum Industry Press[END_REF] Bosboom et al., 2014a[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF].

Figure 3 .

 3 Figure3. Uninterpreted seismic reflection profile crossing the western Kunlun foreland region and the southwestern Tarim Basin. This profile is composed of three segments of seismic profiles. Common Middle Points (CMP) are plotted along the top of each segment. See Figure1bfor its location and FigureS1for its undivided high-solution and large-scale version. The right ends of Figures3a and 3bcorrespond to the left ends of Figures3b and 3c, respectively, to present the entire profile. The vertical scale approximates to the horizontal one. Figures3a, 3band 3c share the same vertical and horizontal scales. Figure6is marked in Figure3b.

Figure 4 .

 4 Figure 4. Interpretation of the seismic reflection profile and key seismic reflectors tracing lines. The right ends of Figure 4a and Figure 4b correspond to the left ends of Figure 4b and Figure 4c respectively, to comprise the whole profile. See Figure 1b for its location and Figure S1 for its undivided large-scaled version. Figures 4a, 4b and 4c correspond one-to-one to Figures 3a, 3b and 3c, respectively. The vertical and horizontal scales are the same as the ones of Figure 3. Solid circles represent seismic reflector terminations. PKBLK Fm, the Pakabulak Formation; AJ Fm, the Anjuan Formation; KZLY Fm, the Keziluoyi Formation; WLG & BSBLK Fms, the Wulagen and Bashibulak Formations; KLT, the Kalataer Formation; ATS & QMG Fms, the Aertashi and Qimugen Formations; K, Cretaceous strata; J, Jurassic strata; P, Permian strata; Pre-P, pre-Permian strata; C, Carboniferous strata; D, Devonian strata; S, Silurian strata; M & U O, middle and upper Ordovician strata; Є, Cambrian strata; Pre-Є, pre-Cambrian rocks.

Figure 5 .

 5 Figure5. Correlation between the stratigraphic column of borehole K, the Kekeya[START_REF] Zheng | Late Oligocene-early Miocene birth of the Taklimakan Desert[END_REF] and Aertashi(Bosboom et al., 2014a) magnetostratigraphic sections. See Figure1bfor their locations. Five matching boundaries are correlated based on the comparable lithology. Referenced in the text and formation boundary reflectors are denoted to the right side of borehole K column. ATS, Aerertashi Formation; QMG, Qimugen Formation; KLT, Kalataer Formation; WLG, Wulagen Formation.

Figure 6 .

 6 Figure 6. Enlarged portion of the seismic reflection profile from Figure 3b that images the reflector of R24 lapping on R23'. (a) Clear seismic profile and (b) Interpreted seismic profile. R23' represents the top boundary of the Paleocene-middle Eocene platform unit and R24 is

Figure 8 .

 8 Figure 8.Natural gamma ray and spontaneous potential logging curves of borehole K from the depth ~300 m to ~450 m. The natural gamma ray curve shows that a ~2-meter-thick mudstone bed from the depth of ~371.5 m to ~373.5 m displays a significantly high natural gamma ray value of ~167 API, while the other mudstone beds at ~416.7 m and ~447.3 m have natural gamma ray values close to the background one. See Figures1b and 3aand 4a for the location of orehole K and Figure5for its relative depth in the stratigraphic column of borehole K.

Figure 9 .

 9 Figure 9. Sedimentation curve of the borehole K drilled at the crest of the Kekeya anticline almost in the seismic profile. See Figure5for the correlation between the borehole K stratigraphic column and timing results, and Figures 1b and 3a and 4a for the borehole K location. This curve shows that the sedimentation rates of the site increased from ~40 Ma to 22 ~Ma, decreased from ~22 Ma to ~11 Ma, and reached to its minimum since ~11 Ma, indicating that the borehole K site has swept over the foreland basin system from the distal foredeep depozone to the wedge top one. This curve is concordant with that of the classic foreland basin, suggesting that the age correlation is admissible and viable.

Figure 10 .

 10 Figure 10. (a) Plot of distances from the range versus the reflector terminations and their correlating ages, and plot of seismic reflector formation rates (number of reflectors per million years) through time (the gray histogram in the lower part of Figure 10a). Open symbols indicate values measured from the crest of the Kekeya anticline to terminations on Figure S1. See TableS1for all the measured values. The dashed fold line is a distribution envelope established by connecting the maximum values within about one million of years. The solid line is fitted by values connected by the dashed fold line. The linear fitting of the upper envelop of the distribution area of reflector terminations indicates that the western Kunlun foreland basin system migrated forelandward at a rate of ~8.18 mm/yr since ~30 Ma, consisting of the present shortening rates of ~3.8-5.7 mm/yr derived from GPS measurements[START_REF] Gan | Present-day crustal motion within the Tibetan Plateau inferred from GPS measurements[END_REF][START_REF] Liang | Threedimensional velocity field of present-day crustal motion of the Tibetan Plateau derived from GPS measurements[END_REF][START_REF] Wang | Present-day velocity field and block kinematics of Tibetan Plateau from GPS measurements[END_REF][START_REF] Wang | Present-day crustal deformation of continental China derived from GPS and its tectonic implications[END_REF] and the western Kunlun latitudinal propagation rate of ~4.4-2.5 mm/yr. From ~40 Ma to ~30 Ma, the foreland basin retreated toward the hinterland. The retreat of the foreland basin suggests that the Tarim lithosphere behaves as a viscoelastic body. The grey histogram at lower part of Figure10ashows that sedimentation rate of the whole basin, represented by formations rates of seismic reflector, increased in a stepwise fashion, 1 reflector per million years from ~40 Ma to ~33 Ma, 2-3 reflectors per million years from ~33 Ma to ~12 Ma, 4 reflector per million years from ~12 Ma to ~11 Ma, and 7-9 reflectors per million years since ~11 Ma. The rates reached its maximum

  and S1.

Figure 11 .

 11 Figure 11. Sketch views of the physiographical evolution of the Tarim Block since the middle Eocene (a) before 40 Ma, (b) 40 Ma -25 Ma, (c) at 25Ma, and (d) at present. Main observations that constrain this study are from the analyses of the seismic profile of Figures 3 and S1 and its interpretation of Figure 4, and Li et al.'s (2019; 2020) work.

F

  Figure1b

  Figure 5

  Figure 7

Acknowledgments

The manuscript benefited from discussions with Prof. Mingjie Xu. We greatly appreciate the valuable comments and insightful suggestions from Editor John Geissman, the Associate Editor, and four anonymous reviewers. This work was sponsored by National Key R&D Plan of China (Grant No.2017YFC0601402), grants 41372201 and 41672198 from the National Natural Science Foundation of China. The support to YC from LABEX VOLTAIRE (ANR-10-LABX-100-01), Région Centre ARGON, and EQUIPEX PLANET (ANR-11-EQPX-0036) is also appreciated. The supporting information on the interpretation of the seismic profile, the division of the tectonostratigraphic units, the layer division of the middle Eocene-Quaternary foreland tectonostratigraphic unit, Figure S1, and Table S1 presented in this manuscript can be found online via Mendley (https://www.mendeley.com/) at http://dx.doi.org/10.17632/s8ws6vf7wr.2.

Accepted Article

This article is protected by copyright. All rights reserved.

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Marija Roglić
email: marija.roglic@umontpellier.fr

The antenarrative of sensemaking: building participation via LEADER

Keywords: participation, antenarrative, sensemaking, Europeanization, LEADER

We look at a LEADER organizations as storytelling organizations that unfold around the understanding and praxis of participation.

European Union LEADER programme is defined as a territorially based and participative approach to development. Since its mainstreaming into the European Union Programmes it has been progressively bureaucratized and is being perceived as a tool of Europeanization. A tool framed on the level of European Union by its seven features: bottom-up approach, area-based approach, the local partnership, an integrated and multi-sectoral strategy, networking, innovation and cooperation. The implementation of these features is left to each Member State. The understanding and praxis of these features is everyday work of LAG managers.

We ask how is participation built in everyday life of such organizations?

We employ an antenarrative research design that directs our analytic attention to the flow of lived experience (Boje, 2001) so as to investigate the sensemaking process between the organizational actors that frame the understanding and praxis of participation. Embedded in the experience of the author as a LAG manager we hypothesize that the understanding of participation, one that is underlining seven features of LEADER, lies in the sensemaking practices of all the actors involved in the management of these organizations.

 . We present our results in a form of a non-linear narrative that delineates recurring types of practices that embody the understanding and praxis of participation within one LEADER organization from 2013-2019.

I. Introduction

Research in management studies has started paying increased attention to multistakeholder initiatives (MSIs). They are defined as private governance mechanisms involving corporations, civil society organizations, and sometimes other actors, such as governments, academia or unions to cope with social and environmental challenges (Moog, Spicer, & Böhm, 2015, p. 2). They have been seen crucial for development [START_REF] Bosworth | Empowering Local Action through Neo-Endogenous Development; The Case of LEADER in England[END_REF]Ray, 1999). Researchers in development studies have argued that a development process is seen as based on local resources and community participation and is stimulated via an simultaneous or individual interaction of (a) local actors, (b) outside actors such as national governments, (c) mid -level actors such as local non-governmental organizations supported by various external entities. (Ray, 2000a).

We know that these initiatives are potentially very positive, but we know less on how to make them work. Evidence both from development, and from management studies points out that sometimes they work, and sometimes not.

One of the central problems here is the problem of participation. Development studies, see participation as involvement of a significant number of persons in situations or actions that enhance their well-being, such as their income, security, self-esteem etc. (Nawaz, 2013, p.27) so as to increase the receptivity and ability of rural people to respond to development programs as well as to encourage local initiatives (ibid.)

Initially at the core of development projects in the poorer regions of the world researchers on community-based development have seen that participation in the absence of state facilitation can result in a closed village economy that limits the possibility for improved public action (Mansuri & Rao, 2004, p. 26). And that this community involvement is almost dominated by the elites as they tend to be better educated and have fewer opportunity costs on their time (ibid, p.30). Participation has been seen as an instrument for promoting pragmatic policy interests, such as cost-effective delivery or low-cost maintenance, rather than a vehicle for radical social transformation (ibid). MSI's and their standards interact with the local political and economic contexts and are often "seized" by powerful actors embedded in hierarchical local power structures. The result is often a reinforcement of existing local power inequalities (Cheyns & Risgaard, 2014, p. 7) Research on community-based development within the European Union has encountered similar critiques in the EU where it was seen is seen as redistributing political power by giving preference to rural/local actors, and partially discriminating in favour of actor networks and against state bureaucracy (Kovach 2000, p.183) . [START_REF] Maurel | Local development stakeholders and the european model: learning the leader approach in the new member states[END_REF] has observed low level of citizen's participation, the formation of interest groups monopolising access to grants, and the action of consultancy offices and development agencies ( ibid, p. 528) within the Hungarian, Czech and Polish LAGs. Koutsouris (2008, p. 252) Meaning that by tapping into multiple sources of knowledge and expertise of various actors , that is the human and social capital existing within the territory, we manage to find better solutions to things.

However, the problem is that the fact that different actors make part of this multistakeholder setting doesn't necessarily mean that they participate. They dedicate time, energy, resources to advance the goals of MSIs -if they are allowed and enabled to participate by contributing. So participation, how to stimulate it and how to sustain it towards the accomplishment of the goals of MSI is a crucial question to which we still don't have any good answers.

Literature on development studies says they have began to address this problem and we know certain things. Maurel (2008, p. 528) points out that the actions of consultancy offices and development agencies have monopolized participation. Furthermore, that programmes of community development have become a tool of hegemony where experts and managers neglect local knowledge and local perplexities (Koutsouris 2008, 252). Literature on strategic research within the field of management studies defines participation as an activity comprising structures, practices and processes that help lower level organizational actors to take part in strategy work (Laine and Vaara, 2007;Mantere andVaara, 2008 in Tavella, 2020, p. 1). Participation around MSIs is constructed in the form of multistakeholder alliances, partnerships, standards and round tables following different procedural approaches that can results in a dialogue platform or an independent organisation with its own governance structure. (Martens et all., 2018, p. 3) such as powersharing rules that allow for equal participation (Luttrel et all. 2018), establishment of working groups (Schouten et all., 2012) or public consultation (Cheyns & Risgaard, 2014).

Development studies scholars have investigated participation techniques either from the perspective of international organizations such as World Bank or with a more national focus, looking into the participation techniques that unfold around the European Union LEADER programme. Participation is constructed through the process of involvement in decision making processes, implementing programs, sharing in the benefits of development programs or involvement in evaluation of such programs (Nawaz, 2013 p;27). Researchers looking into LEADER (Mueller et all. 2020, 226) describe participation as a social practice that is negotiated and legitimised through ritual-like situations.

I would like to demonstrate what are the type of activities and practices that build participation and how they define the meaning of participation, one that is depended on its performance.

Based on my analysis of different LEADER organizations is that in MSIs how you define participation will affect performance. The question I ask is therefore: how is participation built in day-to-day operations of an MSI organization? I argue that participation is based on the day-to-day activities of the organization. Real participation has to be built in day to day operations of the organization and on the example of "LAG 5" I will show you how and why. Therefore, my real question is based in the fact that MSIs are formed. They have a specific organizational design, structure and roles, but the literature on LEADER show us that there is a problem with this. There is a difference between the formally assigned set of roles and responsibilities and the actual participation.

Participation means that roles are enacted. That this formal structure within which these various stakeholders actually dedicate time, energy, resources, attention to perform the roles they are set to do enacts a form of participation that will allow for real contribution. By drawing on the example of LAG 5 members who have built and voluntarily worked on implementing development project in their territory with this organisation.

Our presentation is structured as follows. Multistakeholder initiatives are defined in the context of participative modes of development, such is the LEADER programme. Drawing on the analytical framework developed by Martens et all (2018) we investigate the sensemaking process between the organizational actors that frame the understanding and praxis of participation. Before coming to our empirical findings, we present our research context, case study approach and methodology. Participation as an everyday practice of the organisation is analysed on the example of an LEADER organization lead author has worked in. In the discussion and conclusion we interpret the findings and provide insight into avenues for further research.

  goes as far as to define LEADER as a tool of hegemony where experts and managers on one hand neglect local knowledge and local perplexities and particularities and on the other (…) endorse changes without paying due attention to their systemic effects as challenges to local structures. Kovach &Kucherova (2009) question the participative practices of LAG professionals arguing participation is simply a formality not a practice. Thuesen (2010) looked into the structure of the governing boards of LAGs discussing the issue of representative democracy and participation of mostly well educated, rich, older men in Danish LAG governing boards. Lukic & Obad (2016) analyse the emergence of LAGs in Croatia indicating the emergence of new project class that either manages participation or is absorbed by local politics. Hubbart & Gorton (2011, p. 92) refer to the Austrian case that suggest adopting the practice of participation requires several years of learning by doing of local actors. By observing participatory practices within LAG territories Mueller et all (2020) deduct that participation as a social practice is constantly negotiated in specific physical-spatial settings that are defined in a performative way.All this points out that membership within MSIs, such would be local action groups (LAGs) does not necessarily guarantee participation. Success is predicated on the fact that you manage to have multiple interests. The ideology behind community-led local developments stresses that development needs to be embedded in endogenous resources. Resources which should be activated and harnessed through targeted bottom-up, participatory development programmes(Herbert-Chesire & Higgins 2004, p. 290 in Mueller et all. P. 224).

  Esparcia et all. (2015, p. 33) have began addressing this problem by delineating three view on LEADER as a community-based development programme 1) LEADER as an instrument of power in the hands of power-groups within LAGs and their clientelist networks; (2) LEADER as an instrument of local economic development; (3) LEADER as a tool for social networking, capacity building, local empowerment and local democracy. But there are still important aspects of this phenomenon that are still not very well understood.Therefore, we ask what are the actions that build participation via contributions of various actors that take part in these multistakeholder initiatives, LAGs.