Late Mesozoic Intracontinental Deformation in the Northern Margin of the North China Craton: A Case Study From the Shangyi Basin, Northwestern Hebei Province, China

During the late Mesozoic, the East Asian continent underwent a complex tectonic history due to multiple episodes of plate convergence. How the crust responds to the multiple plate convergence in the North China Craton (NCC) remains unclear. Here we undertook field geological investigations and fault-slip vectors analysis of the Shangyi Basin in the western Yanshan fold and thrust belt, northern margin of the NCC. Combined with new geochronological data, we delineate three phases of intracontinental deformation in the area: 1) NW-SE compression during the Late Jurassic to earliest Cretaceous (ca. 151–141 Ma); 2) NW-SE extension during the middle–late Early Cretaceous (ca. 135–110 Ma); and 3) NE-SW compressional deformation later than 110 Ma. The early NW-SE compression controlled the present bulk architecture of the basin, and the subsequent two tectonic events only caused limited reworking of the previous structures. Through balanced cross-section restoration, we estimate the horizontal shortening ratio of the crust in the study area is over 27% due to the NW-SE compression. Moreover, the contribution of tectonic shortening from the north side of the basin is greater than that from the south side. NW-SE compressional deformation is consistent in time with the episode B of the Yanshanian movement (Yanshanian B), which may be influenced by the subduction of the Paleo-Pacific plate beneath East Asia and the closure of the Mongol-Okhosk Ocean. Subsequent NW–SE extension is likely to be associated with the destruction of the NCC during the Early Cretaceous. Extension may result from the roll-back of the Paleo-Pacific plate and post-orogenic collapse of the Mongol-Okhotsk belt. The last NE-SW compressional event may be linked to the remote effect of the final collision between the Qiangtang and Lhasa terranes.


INTRODUCTION
The North China Craton (NCC), located in the interior of the East Asian continent, has experienced a multi-phase intracontinental deformation since the Mesozoic (Liu, 1998;Liu and Yang, 2000;Zheng et al., 2000;Davis et al., 2001;Cui and Wu, 2002;Cope et al., 2007;Zhang et al., 2007;Li et al., 2012;Liu et al., 2013Liu et al., , 2018Huang et al., 2015;Li et al., 2016;Y. C. Wang et al., 2018;Yang and Dong, 2018;Clinkscales and Kapp, 2019;Meng et al., 2019;S. F. Liu et al., 2021). These deformations might be related with the convergence of several independent plates or blocks at the same time, including the Siberian Plate to the north, the Paleo-Pacific Plate to the southeast, and the Qiangtang-Lhasa block to the southwest ( Figure 1A) Shi et al., 2015). The Yanshanian intracontinental orogeny (Zheng et al., 2000;Davis et al., 2001;Cope et al., 2007;Zhang et al., 2007;Lin et al., 2013;Huang, 2019) and the subsequent large-scale lithospheric extension and thinning of the NCC (Meng, 2003;Zhu et al., 2011;Zhu and Xu, 2019;Wang et al., , 2012Lin and Wei, 2018;Liu et al., 2020) are the most representative during the complex Mesozoic tectonic evolution, attracting extensive attention from a large amount of geologists. Multiple research approaches, such as analysis of structural geometry and kinematics Li et al., 2016;Clinkscales and Kapp, 2019), study of palaeo-stress field based on fault-slip data Huang et al., 2015;Yang and Dong, 2018;, study on basin-mountain coupling (Liu and Yang, 2000;Cope et al., 2007;Liu et al., , 2018; Y. C. Lin et al., 2019;, geochronology (Wu et al., 2005;Wang et al., 2012Wang et al., , 2015, lithogeochemistry (Dai et al., 2016;Li and Wang, 2018), geophysics (Zheng et al., 2009;Zhu et al., 2011;Zhu and Xu, 2019) and numerical simulation analysis (Hou et al., 2010;Liu et al., 2017;Li and Hou, 2018), have been applied to try to reconstruct the history of intracontinental evolution of the NCC during the late Mesozoic. However, detailed structural analysis of key areas remains inadequate. The timing of the late Mesozoic tectonic regime transition within the NCC was defined on late Middle Jurassic (160 ± 5 Ma) , the Late Jurassic-Early Cretaceous (ca. 150-140 Ma) (Zhai et al., 2004) and the Early Cretaceous (ca. 136 Ma) (Niu et al., 2003). Besides, the related geodynamic mechanisms was attributed to the subduction of the Paleo-Pacific plate (Ren et al., 2002;Zhu et al., 2011;Zhu et al., 2018;Zhu and Xu, 2019), a combined effect from the Paleo-Pacific subducting plate and the closure of the Mongol-Okhosk Ocean (Meng, 2003;, and a multi-plate convergence around East Asia . In general, the tectonic evolution of the basins records the process of the regional stress propagation and transition (Shi et al., 2006(Shi et al., , 2013Li and Hou, 2018;S. F. Liu et al., 2021). Abundant late Mesozoic intracontinental basins were developed along the northern margin of the NCC (He et al., 1998;Liu et al., 2004;J. Liu et al., 2015;Xu et al., 2016;Lin et al., 2019) and were considered as natural laboratories for studying on intracontinental deformation. In this paper, a multidisciplinary survey has been conducted in the Shangyi Basin, which is a typical area in the northern edge of the NCC that recorded late Mesozoic polyphase deformation events. A multi-technique approach, including field structural measurement, stress inversion of fault-slip vectors, crosssection restoration and balancing, and analysis of zircon U-Pb geochronology, has been performed with the aim to reconstruct the tectonic evolution history of the Shangyi Basin. The new results lead us to delineate at least three-phase of tectonic deformation for the study area during the Late Jurassic to Cretaceous. NW-SE compression in the Late Jurassic-Early Cretaceous controlled the basic tectonic framework of the basin. Furthermore, combined with previous studies, we also discussed the relationship between the paleostress regimes of the Shangyi Basin and different plate tectonic configurations and varying driving forces.

GEOLOGICAL SETTING
The Sino-Mongolian block formed due to the final closure of the Paleo-Asian Ocean along the Solonker-Linxi Suture during the late Paleozoic to early Mesozoic (Davis et al., 2001;Xiao et al., 2003;Eizenhöfer et al., 2014;. Meanwhile, the South China block in the south was also final collided with the NCC (Liu et al., 2005;Dong et al., 2011;S. F. Liu et al., 2015;Zhang et al., 2019). These large-scale tectonic events marked the beginning of intracontinental deformation of the NCC. During the late Mesozoic, located between the Sino-Mongolian block and the Siberian plate, the Mongol-Okhotsk Ocean began to close from west to east in a scissor-like fashion (Zorin, 1999;Metelkin et al., 2010). In the meantime, the NCC experienced a remarkable intracontinental orogeny, which is generally referred to as the Yanshan Movement S. F. Liu et al., 2021). The term Yanshan Movement, which was named by Wong (1927) and was initially employed to describe to Late Jurassic-Early Cretaceous unconformities, magmatism, and mineralization in the Yanshan area, is currently used to define a period of significant tectonism that affected East Asia continent during the late Mesozoic Dong et al., 2015Dong et al., , 2018. The Yinshan-Yanshan fold and thrust belt in the northern margin of the NCC, which extend west-east from the western Inner Mongolia to western Liaoning province along over 1000 km (Zheng et al., 2000;Davis et al., 2001;Cope et al., 2007;Zhang et al., 2007;Lin et al., 2013), has been known as the most representative product of this intracontinental tectonic event. The Yanshan Movement can usually be divided into three sub-stages. The early stage (Yanshanian A) is marked by the disconformities at the base of the Tiaojishan Formation (Late Jurassic) and expressed by some gentle folds and local thrusts (Hao et al., 2021). The intermediate stage is characterized by the Tiaojishan Formation volcanic rocks . And the last stage (Yanshanian B) is represented by a regional unconformity at the base of the Zhangjiakou Formation volcanic rocks (Early Cretaceous) and involved diffuse folding and thrust faulting (Y. Lin et al., 2019). Following the Yanshan Movement, the northern NCC has experienced widespread extension and thinning of the continental lithosphere during the Early Cretaceous, expressed by remarkable magmatism S. H. Zhang et al., 2014;Wang et al., 2015), graben and half-graben basins (Zorin, 1999;Graham et al., 2001;Ren et al., 2002;Meng, 2003;Liu et al., 2004;Y. Q. Zhang et al., 2004;Li and Hou, 2018; and low-angle detachment systems or metamorphic core complexes (MCCs) Wang et al., , 2012Lin and Wei, 2018). Furthermore, a short phase of compression occurred after the late Early Cretaceous, which resulted in an extensive tectonic reverse of the Early Cretaceous faulted basin in Eastern China and adjacent areas (Y. Q. . Some works consider this compressional event as the episode C of the Yanshanian Movement, which indicates termination of the NCC peak destruction Zhu et al., 2012).
The Shangyi Basin in the northwest of Hebei province, China, is situated on the intersection area between the ∼E-W-trending Yinshan-Yanshan fold and thrust belt and NNE-trending Dahingganling (or Greater Khingan Range) -Taihang Mountain structural belt ( Figure 1B). The basin, about 800 km 2 in area, is bounded by the ∼E-W-striking Shangyi-Pingquan Fault (SPF) to the north and the NE-to NNEstriking Banshen-Shuiquangou Fault (BSF) to the south, respectively ( Figures 1B, 2A). The SPF, as the tectonic boundary between the Yanshan fold and thrust belt and the Inner Mongolia Palaeo-uplift, has a long evolutionary history and was marked by significant thrust and dextral strike-slip movement in the late Mesozoic (Wang et al., 1992;Hu and Song, 2002;Zhang et al., 2006). The BSF, about 40 km in length, was formed as the important component of a basement-involved thrust system in the western part of the Yanshan structural belt during the late Mesozoic . In a map view, the Shangyi Basin appears as a salient projecting to the east.
The basement rocks are mostly exposed on the northern, western and southern parts of the study area ( Figure 2A). Among them, the Neoarchean Hongqiyingzi Complex (ca. 2.53 Ga; Peng et al., 2012) is exposed in the north of the study area, and consists predominantly of the biotite plagioclase gneiss, biotite granulite, garnet-bearing biotite schist, plagioclase amphibolite and a small amount of quartzite, marble. The Paleoproterozoic Khondalite (ca. 2.0 Ga; Dong et al., 2013) is present in the west part. In the southern part, the Neoarchean to Paleoproterozoic Huai'an Complex (ca. 2500Zhao et al., 2008;H. F. Zhang et al., 2011) is well-exposed and mainly composed of Tonalite-Trondhjemite-Granodiorite (TTG) rocks, granitic gneiss, mafic granulite and moyite. In addition, the Mesoproterozoic rocks, including carbonate rocks, quartzite, quartzose sandstone and shale, are present sporadically in the northern and southern sides of the basin (Figure 2A).
Most of the magmatic intrusions are exposed along the SPF (Figure 2A), and consists of Paleoproterozoic syenite, Late Paleozoic diorite and Early Mesozoic granite, diorite and FIGURE 3 | Late Mesozoic stratigraphic units in the Shangyi Basin and its correlation with other typical late Mesozoic basins in the North China Carton. Beipiao, Shiguai, and Yungang basins were modified from J. , Y.C.  and Y. , respectively. The geochronological data of the late Mesozoic stratigraphic units in the Beipiao Basin were obtained from Yang et al. (2007), Chang et al. (2009Chang et al. ( , 2013 and Wang et al. (2013).
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 5 monzonite. Besides, minor amounts of Paleoproterozoic and Late Mesozoic intrusive bodies were emplaced in the western and southwestern basement rocks of the basin (Figure 2A). Among them, Late Paleozoic magmatism may be related to the closure of the Paleo-Asian Ocean (F. . Recent research shows that the Huangyuwa granitic pluton, located about 10 km to the northeast of Xinghe, formed at 135-123 Ma, and it represents the product of magmatic activity in the Early Cretaceous (Zhang, 2019).
The basin Mesozoic stratigraphic sequence, in ascending order, comprises the Early Jurassic Xiahuayuan Formation, the Middle-Late Jurassic Jiulongshan Formation and the Late Jurassic-Early Cretaceous Tuchengzi Formation (Figure 3). The Xiahuayuan Formation present in the north part of the basin is characterized by a set of coal-bearing terrigenous sedimentation unit, which contains plentiful paleontological fossils, and it unconformably overlies the Khondalite series in the northwest side ( Figure 2A). The Jiulongshan Formation is a set of variegated fluvial deposition accompany with small amount of basaltic andesite and pyroclastic rocks, which is mainly distributed in Hongtuliang, Xiajing and Dawangmaogou, as well as in the west side of the basin ( Figure 2A). It unconformably contact with the underlying Xiahuayuan Formation and basement rocks. The Tuchengzi Formation is marked by the purple-red coarse-grained clastic sediments and widely distributed in the north, east, south and middle part of the basin. And it usually unconformably overlies the underlying older rock units. However, the Tuchengzi Formation in the north and south edges of the basin is also covered by Precambrian strata due to the influence of the boundary faults ( Figure 2A). Broadly speaking, the Shangyi Basin is similar in lithological association with other typical Mesozoic basins in the northern margin of the NCC ( Figure 3). Nevertheless, it is worth mentioning that the late Mesozoic volcanic rocks, including the Late Jurassic Tiaojishan Formation, the Early Cretaceous Zhanjiakou Formation and Yixian Formation are absent in our study area ( Figure 3).
In addition, the Cenozoic stratigraphic units are widespread in the north of the SPF, the eastern side of the basin and the west of Xinghe. A large area of the Miocene clastic deposits and basalt are unconformable contact with the underlying pre-Cenozoic strata in the easternmost region.
Previous studies have revealed that the evolution of the Shangyi Basin was controlled by the SPF. Relevant investigations, such as the basin-fill sequence, sedimentary environment, and lithofacies palaeogeography, have been conducted (He et al., 2008;Xu et al., 2016). Whereas, not enough attention was paid to the research of the multi-phase activity characteristics of the basin-controlling faults and the evolution of regional tectonic stress, as well as the effective isotope chronological constraints on the Late Mesozoic strata of the basin.

Stress Inversion of Fault-slip Vectors
We can determine the stress tensor associated with fault movements by analysing fault nature and slip direction.
Considering that fault slip data, including dip directions and angles of fault planes, pitch directions and angles of striations, and strike-slip directions, are easy to obtain, this method has been extensively applied to the study of tectonic evolution (Angelier, 1979(Angelier, , 1984Delvaux et al., 1995;Delvaux and Sperner, 2003;Zhang et al., 2003;Allmendinger et al., 2012;Riller et al., 2017;Lin et al., 2015;Shi et al., 2015Shi et al., , 2020. The stress inversion method is usually based on the Wallace-Bott hypothesis, which suggests that the fault-slip vector (s) is parallel to the orientation of the maximum shearing stress (τ) under the influence of a regional uniform stress tensor (Wallace, 1951;Bott, 1959). Some other conditions also need to be considered, for example 1) the stress field remain constant during a tectonic event (Angelier, 1979); 2) the faults do not interfere with each other, with no rotation of the fault planes (Lacombe, 2012); and 3) the protoliths of the deformed rocks are homogeneous and isotropic (Lacombe, 2012). In practice, there is usual an angle between the slip vector (s) and shear stress vector (τ). Therefore, this angle should be kept as small as possible so that the stress tensor we get is more accurate . The stress state or stress ellipsoid can be expressed by three principal stress axes (maximum (σ 1 ), intermediate (σ 2 ), and minimum (σ 3 ) stresses, where σ 1 > σ 2 > σ 3 ) and stress difference ratio (R (σ 2 − σ 3 )/(σ 1 − σ 3 ), 0 ≤ R ≤ 1). Theoretically, we need at least four independent fault-slip data to calculate a stress field (Etchecopar et al., 1981;Chen and Shi, 2015;. In this work, we use Win-Tensor software (Delvaux et al., 1995;Delvaux and Sperner, 2003) for paleo-stress inversion. 314 fault-slip data were obtained from 34 observation sites in the field ( Table 1). The relative sequences of multi-stage tectonic deformation can be determined by identifying the youngest strata that involved in various stages of deformation, by analyzing the superposition relationships of multiple slip vectors on a single fault surface, and by observing the cross-cutting relationships of truncated fault planes . According to the above analysis, together with the attitude of the fold hinges and the angular bisector orientations of the X-type conjugate shear fractures from different strata, we are able to reconstruct the evolutionary sequence of the late Mesozoic tectonic stress field in the Shangyi Basin.

Balanced Cross-section Restoration
In order to carry out the quantitative analysis to tectonic deformation of the basin, we use the technique of balanced cross-section to restore the deformation and structure to its initial state based on the reliable geologic section and related geometrical rules (Dahlstrom, 1969;Hosseck, 1979;Li et al., 2011;Nakapelukh et al., 2017;. Because of the lack of seismic and borehole data in our study area, we mainly based our cross-sections on detailed field geological investigations. Generally speaking, the cross-sections should theoretically be kept orthogonal to the strikes and axes of faults and folds (or parallel to the direction of regional principal stress) (Hosseck, 1979;Song, 1985) so that the deformation behavior and the amount of shortening can be defined more accurately. Taking into account the major structural features of the basin, the sections A-A' with NW-SE-trending and B-B' with NNW-SSE-trending were selected for balancing and restoration (Figures 2A,B). Here we took the 2D-Move software to restore the deformation and estimate the crustal shortening. Meanwhile, the layer length conservation principle and plane strain should be considered during the analysis process (Dahlstrom, 1969;Li et al., 2011;Li et al., 2019).

LA-ICP-MS Zircon U-Pb Dating
To constrain the timing of tectonic deformation in the Shangyi Basin, we analyzed zircon grains from two selected rock samples (for sample locations, see Figure 2A) using LA-ICP-MS U-Pb dating. Zircon grains were extracted from crushed blocks using heavy liquid and magnetic separation techniques. Zircons were handpicked under a binocular microscope, mounted in epoxy resin, polished to expose approximately half of the grains, and gold coated. Cathodoluminescence (CL) images of zircon grains were acquired using an Analytical Scanning Electron Microscope (JSM−IT100) connected to a GATAN MINICL system. LA-ICP-MS zircon U-Pb dating was conducted at the Key   Figures 1B, 2A). Principal stress axes (σ 1 , σ 2 and σ 3 ) of regional stress field are also shown on the map. Lower hemisphere, equal-area projections.
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 8 FIGURE 5 | Representative outcrop photographs related to regional NW-SE compression. (A) Mesoproterozoic carbonate rocks are overthrust southeastward over the Jiulongshan Formation along the Shangyi-Pingquan Fault (SPF) accompanied by related drag fold exposed in the footwall. (B) Two sets of striations, including dip-direction striations with reverse faulting and sub-horizontal dextral strike-slip striations, are simultaneously exposed on one fault surface in the Xiahuayuan Formation sandstones from the footwall of the SPF, corresponding to NW-SE and NE-SW compression, respectively. Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resources, Beijing. The spot size and laser frequency were set to 32 µm and 5 Hz, respectively. Zircon 91500 was taken as an external standard for the U-Pb dating, and glass NIST610 was used as a standard for the traceelement calibration. The ICPMSDataCal software was used to calibrate the trace-element analysis and U-Pb dating (Liu et al., , 2010. Weighted mean calculations and concordia diagrams were acquired using Isoplot/Ex_ver3 (Ludwig, 2003).

Major Faults and Folds
The major faults and related folds are exposed along the north and south edges of the basin. Along the northern boundary of the basin, the SPF from west of Houfugou to east of Daxigou is striking WNW-ESE and dipping towards the north or northnortheast, in spite of its whole orientation in the Yanshan belt as ∼E-W ( Figures 1B, 2A). Along the SPF, Neoarchean-Paleoproterozoic Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 10 FIGURE 7 | Representative outcrop photographs related to regional NW-SE extension. Photo (A-C) shows that some small-scale normal and strike-slip faults are developed in the Tuchengzi Formation and reflect NW-SE extensional deformation. (D) At the south of Xiajing, the later SE-or NW-dipping normal faults dislocate the early tight folds in the coal-bearing sandstones in the Xiahuayuan Formation. (E) Two groups of faults crop out in the Xiahuayuan Formation sandy conglomerates at the southwest of Shangyi. And the dextral strike-slip faults are cut by the SSW-dipping transtensional faults, corresponding to NW-SE compression and NW-SE extension, respectively. (F) Two-phase faults are exposed in the Jiulongshan Formation at the northeast of Hongtuliang, and the early NW-dipping reverse faults are truncated by the lather SE-dipping normal faults, corresponding to NW-SE compression and NW-SE extension, respectively. (G) Some NW-and SE-dipping extension faults and well-developed horst are marked in the Jiulongshan Formation at the northeast of Hongtuliang. Lower hemisphere, equal-area projections.
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 11 basement and a few Mesoproterozoic caprock are overthrust southward onto Late Mesozoic strata. Within the footwall of the SPF, near Dawangmaogou, Xiajing and Hongtuliang, some ∼E-Wand NE-striking secondary thrusts show tectonic vergence towards the south (or the southeast). These secondary faults extend towards the northeast and eventually merge into the SPF (Figure 2A), indicating that the former are controlled by the latter. In the south margin, the BSF from Banshen to Shuiquangou is striking NE, whereas east of Shuiquangou, its direction changes into NNE (Figure 2A), and it finally disappeared in the Tuchengzi Formation of the east of Xiaosuangou. The BSF is generally steeply dipping (>60°) towards the southeast. Along the BSF, the basement rocks are thrust northwestward over the Tuchengzi Formation ( Figure 2B). According to the variation trend of the attitude of the rock stratum in geological map, some folds with the NE-trending axes are mainly observed in the north and south parts of the basin, showing the asymmetric syncline or anticline controlled by the boundary faults ( Figure 2B). Additionally, a WNW-trending gentle syncline occurs between Yanjiayao and Tumulu (Figure 2A), which represents a structural style different from the asymmetric folds described above.

Multi-phase Deformations and Paleo-stress Fields
Based on detailed field measurements from the Shangyi Basin, together with the superposition and cross-cutting relationships of different structures, three-stage deformation can be identified. In this part, we mainly introduced the structural deformation characteristics of each stage, as well as the corresponding inversion results of fault slip data. Relevant interpretations of their deformation sequences were presented in the Discussion section.

First Set of Structures: NW-SE Compression
We collected abundant evidence associated with this compression from 23 sites in the margins and interior of the basin (Figure 4). On the northern edge, the Neoarchean Hongqiyingzi Complex and the Mesoproterozoic quartz sandstones and carbonate rocks are usually thrust over the late Mesozoic strata along the SPF ( Figures 5A,B). Slickensides and steps of the faults, asymmetric folds and fault-related drag structures all indicate a reverse faulting with the top-to-the-SE slip sense, and a NW-SE maximum principal stress (σ 1 ) inferred by relevant fault-slip vectors ( Figures 5A,B). On the southern fringe, approaching the northeast of Shuiquangou (site SY11) (Figure 4), a medium-scale NE-trending asymmetric syncline unconformably covered by the near-horizontal Cenozoic basalts can be noticed in the purple-red sandstones (Tuchengzi Formation) from the lower plate of the BSF ( Figure 5C). The southeast limb of the syncline is short and sub-vertical (even overturned), but its northwest limb is long and gentle, which suggests the BSF has the kinematics with the top-to-the-NW slip sense ( Figure 2B). Some other small-scale folds with the sub-horizontal NE-oriented hinges can be observed in the Tuchengzi Formation from the south of Jiashihe (site SY29) (Figures 4, 5E). Furthermore, a SE-dipping reverse fault with low dip angle has occurred along the unconformable contact between the conglomerates of the Tuchengzi Formation and the Mesoproterozoic quartz sandstones at the site SY32 (Figures 4, 5F). The fault-slip data collected along the BSF and adjacent secondary fractures were used for stress inversion, defining a uniform NW-SE maximum principal stress (σ 1 ) (Figures 4, 5C-G). We made a systematic analysis to 149 fault-slip data points from 22 sites ( Table 1) and gained a stress regime with a regional 134°/02°for σ 1 , 208°/35°for σ 2 , and 210°/72°f or σ 3 (Figure 4), indicating a stress regime dominated by NW-SE compression.
In addition, two sets of striations can be recognized on the same NW-dipping fault plane in the sandstones (Xiahuayuan Formation) from the footwall of the SPF. One group is marked by thrust faulting and the other group is characterized by dextral strike-slip faulting, corresponding to the NW-SE and NE-SW principal compressive stresses, respectively ( Figure 5B). Approaching the west of Jiucaigou, two-phase faults were identified in the Tuchengzi Formation, and the early ENE-striking dextral strike-slip faults were cut by the later SE-dipping normal ones, corresponding to a NW-SE principal compressive stress and a NW-SE principal tensile stress, respectively ( Figure 5G).

Second Set of Structures: NW-SE Extension
Remarkable structural styles related to the second set of structures may not be easily discernible on the map, but we still obtained some related clues from 13 artificial and natural outcrops (Figures 6, 7A-G). As the same with the first set of structures, all the late Mesozoic clastic sediments filled in the basin were involved in this extensional event, expressed by a series of SE-or NW-dipping normal faults ( Figures 7A,C,D,F,G), transtensional faults ( Figures 7B,E), and some typical grabens and horsts ( Figure 7G). Here the systematic analysis from 107 fault-slip vectors ( Table 1) shows a regional maximum principal stress axis (σ 1 ) at 241°/77°, intermediate principal stress axis (σ 2 ) at 049°/13°, and minimum principal stress axis (σ 3 ) at 144°/02° (Figure 6), suggesting a stress regime of NW-SE extension.
Moreover, some evidence reveals that the early structures were reworked by this extensional deformation, for example some NW-or SE-dipping normal faults dislocated the early NEtrending tight folds ( Figure 7D) and cut the pre-existing NEstriking reverse faults ( Figure 7F). At site SY40, near the southwest of Shangyi County, two groups of faults developed in the Xiahuayuan Formation with different activity times, where the early WNW-striking dextral strike-slip faults were severed by the later SSW-dipping transtensional faults, corresponding to a NW-SE compressive stress state and a NW-SE stretching stress state, respectively ( Figure 7E).

Third Set of Structures: NE-SW Compression
In our research area, the third set of structural deformation is weaker than the previous two sets of structures that we described above in terms of the scale and activity intensity. Related deformational behaviors were found from 11 field outcrops (Figures 8, 9A-F), expressed by some miniature transpressional faults ( Figures 9A,E), X-type conjugate shear fractures ( Figure 9B), conjugate strike-slip faults ( Figures 9C,D), and outcrop-scale folds. Both the acute-angled bisector direction of the X-type conjugate shear fractures and the azimuth of the horizontal orthogonal line of fold axes are NE-or SW-directed, Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 which also represents the orientation of maximum principal stress axis (σ 1 ). The systematic analysis from 58 fault-slip vectors ( Table 1) indicates a regional stress field with σ 1 of 044°/07°, σ 2 of 319°/56°, and σ 3 of 130°/34° (Figure 8), implying a territorial NE-SW principal compressive stress. Moreover, at the north of Tumulu (site SY68), a few evidence of multiphase tectonic activity is recorded in the conglomerates of the Tuchengzi Formation. The early SE-dipping normal faults were dislocated by the later N-dipping sinistral strike-slip faults. Inversion of fault-slip data shows that these two deformations represent separately the influence of the NW-SE extension and NE-SW compression ( Figure 9F).

ANALYSES OF CROSS-SECTION RESTORATION AND CRUSTAL SHORTENING RATIO
The geological cross-sections A-A' and B-B' (Figures 2A,B) are restored, aiming to estimate crustal shortening in the study area due to the NW-SE compressive stress field. Since the youngest strata involved in the NW-SE compressional deformation is the Tuchengzi Formation, which is widely distributed in the basin, we can take the lower boundary of the Tuchengzi Formation as the marker bed for cross-section restoration. To make the operation easier, it is usually assumed that the same layer is a constant thickness along the entire section. However, our field investigations do not support such a hypothesis. For instance, in the section A-A', the stratigraphic sequence in the footwall of the BSF is successively the Neoarchean-Paleoproterozoic basement unit, the Jiulongshan Formation, and the Tuchengzi Formation from the bottom up, which is quite different from that in the hanging wall, including the basement rocks, the Mesoproterozoic quartz sandstones and the Tuchengzi Formation in ascending order ( Figures 2B, 10). The Jiulongshan Formation is only developed in the footwall of the BSF, which is absent in the upper wall. Here we can speculate that the palaeotopographical effect may trigger the pinch-out of the Jiulongshan Formation in the lower plate of the BSF and then may cause a directly unconformable contact between the Tuchengzi Formation and the underlying older strata. The similar case may occur in the Mesoproterozoic unit of the section A-A', as well as in other related strata of the section B-B' ( Figures  2B, 10). Therefore, taking the bottom boundary of the Tuchengzi Formation as the marker layer can avoid the above problem effectively. Besides, given the tectonic denudation, we can't confirm the original depositional thickness of the Tuchengzi Formation, and only replace it with the maximum layer thickness on the sections. Finally, the layer length conservation principle was used to estimate the minimum crustal shortening . Additionally, we ignore the effects of the NW-SE extension and NE-SW compression, as these tectonic events generated limited reshaping of the present-day cross-sections (the sections A-A' and B-B').
Our results show that the present lengths of the sections A-A' and B-B' are independently 18.7 and 42.1 km, and their restored FIGURE 10 | The results of balance and restoration of the sections A-A' and B-B'. Subsurface geometries are largely schematic due to lack of geophysical data. The legends are the same as Figure 2B. The rest figure captions are the same as Figure 1B.
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 lengths are separately 21.5 and 57.6 km, indicating their minimum shortening ratios are 13 and 27%, respectively ( Figure 10). The crustal shortening was mainly accommodated by the boundary thrust faulting and internal folding of the basin. In addition, most of the deformation occurred in the north and south margins of the basin accompanied with weak tectonic response in the interior region. Combined with the space geometries and shortening ratios of the two cross-sections (Figures 2A,B, 10), we discovered that the contribution of tectonic shortening from the north part of the basin obviously exceeded that from the south side.

GEOCHRONOLOGICAL RESULTS
Two rock samples were collected for zircon U-Pb dating to constrain the timing of deformation in the basin. Sample locations are shown in Figures 2A, 11A,E. The detailed results are presented in Figure 12 and in the Appendix (Supplementary Table A1).
Sample SY86 was collected from a pyroclastic interlayer within the sandstones of the Jiulongshan Formation near the Beicaonian. This interlayer (10-15 m thick) is predominantly the andesitic volcanics mixed with bits of clastic deposit, and it's gently inclined to the northeast. Based on field observations, the apparent sedimentary contact between the andesitic pyroclastic rocks and the surrounding sandstone can be defined clearly (Figures 11A,B). The results show that apparent ages of 102 zircon grains are between 2533 ± 23 Ma and 152 ± 4 Ma ( Figures 12C,E), with the younger ages (n 21) defining a weighted mean 206 Pb/ 238 U age of 161.3 ± 2.3 Ma (MSWD 4.7) ( Figure 12C). These younger zircon grains are mostly subhedral, and a magmatic origin of them is inferred based on the recognition of oscillatory zoning in CL images ( Figure 12A) and the Th/U ratios (0.54-1.26; Supplementary Table A1) (Belousova et al., 2002). The weighted mean 206 Pb/ 238 U age is interpreted as the formation age of the andesitic pyroclastic rocks, and also reflecting the formation age of the Jiulongshan Formation. Other older ages are possibly the detrital zircon ages (Figures 12A,C,E).  Wang et al., 2017). SLB, Songliao Basin; HB, Huabei Basin; OB, Ordos Basin; SSZ, Solonker-Linxi suture zone; SLSZ, Sulu suture zone; SDSZ, Shangdan suture zone; MLSZ, Mianlue suture zone. The rest figure captions are the same as Figures 1A,B. See text for more details.
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 18 Sample SY57 was acquired from a NE-trending mafic dike intruded into the sandstones (Tuchengzi Formation) at the north of Jiashihe (Figures 2A, 11E,F). This mafic dike, over 1 km in length and 1-2 m in width, may belong to the product of regional NW-SE extensional deformation. We intended to take the formation age of the dike to constrain the timing of NW-SE extension. Unfortunately, it did not work. Apparent ages of zircons (n 84) are between 2596 ± 20 Ma and 186 ± 2 Ma ( Figures 12B,D,F and Supplementary Table A1). The youngest age of 186 ± 2 Ma represents the Early Jurassic, which is overtly earlier than the age of surrounding Tuchengzi Formation and also precede the formation age of 161 Ma obtained from the Jiulongshan Formation. In consequence, all the ages may reflect the ages of the captured detrital zircons from the wall rocks rather than indicate the formation age of this mafic dike.

Timing of Three-phase Deformation
According to the analysis of multi-stage deformation, we established a relative evolutionary sequence of the basin during the late Mesozoic, including the early NW-SE compression, the middle NW-SE extension and the later NE-SW compression. The present bulk architecture of the basin was controlled by the early NW-SE compressional stress, and the subsequent two tectonic events only caused limited destruction to the previous tectonic framework.
Some fault striations associated with NW-SE compression and the X-type conjugate shear fractures resulted from NE-SW compression were simultaneously observed in the pyroclastic interlayer at the location of sample SY86 ( Figures 11B-D), indicating that both of the two compressional events commenced posterior to 161 Ma. Our structural analysis has revealed that the Tuchengzi Formation is the youngest strata suffered from NW-SE compressional deformation. Many investigations suggest that the Tuchengzi Formation in the Yanshan belt is commonly marked by the molasse-like formations or synorogenic deposits (Zhao, 1990;Zhang, 1999;He et al., 2008), whose lower limit age has been usually constrained to 157-151 Ma (Cope, 2003;Xu et al., 2012;Qi et al., 2015;Fu et al., 2018). Furthermore, despite we failed to define the emplacement age of the NE-oriented mafic dike at the east edge of the basin from our sample SY57, Xu et al. (2016) reported a SHRIMP zircon U-Pb age of 141 ± 1 Ma from the mafic dikes that intrude in the upper part of the Tuchengzi Formation in the eastern Shangyi basin. Many other mafic dikes intruded in the Tuchengzi Formation were widely recognized in North China and Northeast China. Their ages of emplacement are concentrated in 144-140 Ma, indicating a regional extensional tectonic setting during the Early Cretaceous (Xu et al., 2017). Based on the analysis above, the timing of NW-SE compressional deformation can therefore be constrained to ca. 151-141 Ma. In the light of regional tectonic evolution, NW-SE compressional deformation was closely related to the episode B of the Yanshanian movement (Yanshanian B) in the NCC, expressed by territorial Late Jurassic-Early Cretaceous disconformities, series of fold-thrust structures and transpressional fault systems (Wong, 1927;Davis et al., 1998;Zhao et al., 2004;Zhang and Dong, 2008;Li et al., 2016;Zhu et al., 2018;Lin et al., 2019), which has been constrained to 160-135 Ma Zhu et al., 2015;Clinkscales and Kapp, 2019;Lin et al., 2019). Niu et al. (2003) used the SHRIMP zircons U-Pb dating from the base of the Zhangjiakou Formation volcanics in the basin of the central Yanshan belt to determine the change in regional tectonic regime from compression to extension occurred at 136 Ma. As is well-known, during the Early Cretaceous, regional NW-SE extension was matched with widespread lithospheric extension and destruction in eastern China, manifested by massive magmatism and remarkable NE-trending basin-range structures, which has been normally constrained to 135-110 Ma (Wu et al., 2005;Wang et al., 2012Wang et al., , 2015Daoudene et al., 2013;Zhu et al., 2018). The Early Cretaceous volcanics are absent in the Shangyi Basin. Whereas, Zhang (2019) recently provided new evidence of the magmatic activity in Shangyi area during the middle-late Early Cretaceous based on the zircons U-Pb ages of 135-123 Ma from the Huangyuwa granitic pluton (or the Xiaodaqingshan granites) at the northeast of Xinghe (Figure 2A). The above descriptions allows us to constrain the timing of NW-SE extension to ca. 135-110 Ma. In the northern margin of North China, correlational studies of NE-SW compression during the late Mesozoic were rarely reported. Based on the comprehensive analysis of the intracontinental transform structures in the joint part of the Yanshan and Taihang Mountain belts during the Early Cretaceous, Lin et al. (2020) suggested that the Yanshan belt was marked by ∼E-Woriented sinistral extension after 129 Ma. A local NE-SW compressive stress field may be derived from this sinistral transtensional structure, whereas the multi-stage tectonic evolution sequences established in this paper cannot support this pattern. Actually, C. H.  investigated the NWstriking Taiying-Lengkou-Shangying Fault Zone in the central part of the Yanshan belt, which has experienced multi-phase tectonic movements in the late Mesozoic, including thrusting, extension and strike-slip faulting. A significant reversal faulting with the top-to-the-SW slip sense along the Taiying-Lengkou-Shangying Fault Zone occurred after the generated age of the late Early Cretaceous Jiufotang Formation, causing an asymmetric syncline with the NE-dipping axial plane was formed in the Jiufotang Formation in the footwall (C. H. . Moreover, Yang (2015) conducted the analysis of Mesozoic tectonic deformation and palaeostress field in the southern area of Jianchang, Western Liaoning Province, China and established a model of four-phase tectonic evolution. The NW-to NNW-oriented fold and fault system was considered as the result of the latest NE-SW compression, whose activity age was identified as later than the Jiufotang Formation (Yang, 2015). The Jiufotang Formation in the northern NCC is predominantly a set of fossil-bearing lacustrine sediments, whose age constraints was still lacking in reliable geochronology data and was generally defined by the research of Paleontology and Stratigraphy. He et al. (2004) reported the K-feldspars 40 Ar/ 39 Ar date of 120.3 ± 0.7 Ma from the tuff interlayer within the shale of the Jiufotang Formation at the Shangheshou section in Chaoyang, Liaoning, northeastern China. Another radioisotopic age of the Jiufotang Formation has been dated from Tebch, Inner Mongolia, with a 40 Ar/ 39 Ar age of 110.59 ± 0.52 Ma got from intrusive basalt within the Jiufotang Formation (Eberth et al., 1993), which may provide a Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 top limit for the Jiufotang Formation. In consequence, NE-SW compression may commence posterior to 110 Ma. Given that the Cenozoic strata in the study area were not involved in NE-SW compressional deformation, this tectonic event may occur at the late Early Cretaceous-Late Cretaceous.

Tectonic Origin of the Tuchengzi Formation
In addition to the Shangyi Basin, the Tuchengzi Formation is also extensively exposed in other typical late Mesozoic basins in the northern margin of the NCC. The origin of the Tuchengzi Formation was variously interpreted to be related to 1) the flexural basin controlled by compression and thrusting (He et al., 2008;J. Liu et al., 2015;Liu et al., 2018;Lin et al., 2019); or 2) intraplate rift environment (Shao et al., 2003;Xu et al., 2016). According to this study, integrated with previous achievements, we believe that the Tuchengzi Formation of the Shangyi Basin developed during a compression environment. The reasons are as follows. 1) Abundant chronological data show that the Tuchengzi Formation was formed in the Late Jurassic-Early Cretaceous (157-137 Ma) (Cope, 2003;Zhang et al., 2009；;Xu et al., 2012;Wang et al., 2013;Qi et al., 2015;Li et al., 2016;Fu et al., 2018;Lin et al., 2019;Shi et al., 2019), which is consistent in time with the Yanshanian B. 2) Since the lack of accurate chronological data, P.  and Xu et al. (2016) assigned the pyroclastic interlayer within the sandstones near the west edge of the basin to the Tuchengzi Formation, and they considered the pyroclastic deposit reflected an extensional environment during the depositional stage of the Tuchengzi Formation. However, our chronological results confirmed this set of pyroclastic rocks was formed at 161 Ma (Figures 3, 12C), corresponding to the sedimentation time of 164-158 Ma from the lower part of the Jiulongshan Formation (Chen et al., 2014;Li et al., 2014;Lin, 2019). Meanwhile, numerous studies have shown that the molasse-like characteristics of the Tuchengzi Formation represent the thrust faulting from the basin-controlling faults (J. Liu et al., 2018;Lin et al., 2019. 3) The overall tectonic framework of the basin is controlled by NW-SE compressional stress, and the synsedimentary normal faults associated with the Tuchengzi Formation are not found on the edges of the basin (He et al., 2008). Xu et al. (2016) took the Early Cretaceous mafic dikes intrude in the upper part of the Tuchengzi Formation in the Shangyi basin as the result of syntectonic emplacement during the late sedimentary stage of this formation, suggesting an extensional tectonic setting. Nevertheless, based on our fieldwork, these mafic dikes are not appeared as the interlayers but manifested as evident cross-cutting relationships with the surrounding strata ( Figures  11E,F), which implies that the regional extension may later than the Tuchengzi Formation. 4) The stratigraphic succession of the Tuchengzi Formation in Shangyi area is characterized by an upward decrease in grain size (Figure 3), which is inconsistent in sedimentary characteristics with that in others Mesozoic basins (such as the Luanping Basin, the Chicheng Basin, and the Qianjiadian Baisn) in the Yanshan belt, expressed by a sequence with fining-upward first and then coarsening-upward in grain size (J. Lin et al., 2019;Shi et al., 2019). This difference may be related to the geotectonic location of the study area. Related research reveals that the Taihang Mountains might have experienced two significant tectonic uplifts during the late Middle Jurassic to Early Cretaceous Cao et al., 2013;Yang et al., 2014), which may result in the denudation of the upper part of the Tuchengzi Formation and the lack of late Mesozoic volcanic rocks in Shangyi region. Of course, we are not ruling out that some transitory tectonic quiet periods (even the short-lived weak extensional episodes) may occur in the depositional phase of the Tuchengzi Formation. Shi et al. (2019) confirmed that the middle and upper part of the Tuchengzi Formation in the Qianjiadian Basin in the western Yanshan fold and thrust belt was controlled by the NE-striking Qianjiadian thrust fault and the SPF. Before that, the basin has experienced an obvious lake transgression event during the early deposition of the Tuchengzi Formation, suggesting a temporary tectonic quiet period .

Implications of Crustal Shortening-thickening to Craton Destruction
Based on restoration of the section B-B', we obtained the minimum crustal shortening ratio of 27% in Shangyi area under the control of NW-SE compression during the late Late Jurassic to earliest Cretaceous. Horizontal shortening of the crust was principally accommodated by vertical crust thickening resulted from the thrust faulting and the buckle folding. Numerous studies confirmed that the Yanshanian movement caused conspicuous thickening of the lithosphere in eastern China during the late Mesozoic Dong et al., 2015Dong et al., , 2018. Based on balanced cross-section reconstructions,  estimated the north-south-directed shortening of the central part of the Yanshan belt before 135 Ma was around 38%, causing crustal thickening up to 12-15 km. Subsequently, the tectonic regime in eastern China and its adjacent areas underwent a remarkable transition from compression to extension, generating extensive lithospheric destruction and thinning. In recent years, some significant evidence of early crustal shortening-thickening has been discovered from some representative low-angle detachment systems or metamorphic core complexes developed in the northern margin of the NCC Zhu et al., 2015), indicating an intimate relationship between crustal shortening-thickening and lithospheric destruction. On the one hand, the thickened crust may usually give rise to deep-seated partial melting, and then continuous melting may cause the weakening of deep-seated rocks and may further trigger crust-mantle decoupling . On the other hand, lithospheric isostasy and the coeval magmatism caused the thickened crust uplifted significantly accompanied with increasing gravitational potential energy, which incurred the destruction of the original stability of the craton and also provided favorable conditions for the subsequent intense extensional collapse of the middle and upper crust (Zheng and Wang, 2005;.

Tectonic Evolution and Geodynamic Interpretation
Intracontinental deformation events occurred at pre-Late Jurassic in the north edge of the NCC had been recognized in many studies.
Frontiers in Earth Science | www.frontiersin.org August 2021 | Volume 9 | Article 710758 20 For instance, some significant ∼E-W-striking faults in Yanshan belt, including the Fengning-Longhua Fault, the Gubeikou-Pingquan Fault (namely the eastern the Shangyi-Pingquan Fault) ( Figure 1B) and so on, were characterized by thrusting towards the south of hanging wall during the pre-Middle Jurassic (J. Liu et al., 2012;Li et al., 2016;S. F. Liu et al., 2021), indicating the ∼N-S crustal shortening. Afterwards, a regional unconformity interface formed between the Tiaojishan Formation and the underlying older stratigraphic units, which reflects the episode A of the Yanshanian movement. Furthermore, a set of molasse-like formations represented by the Longmen Formation conglomerates from the Western Hills of Beijing acted as the crucial sedimentary response of this tectonic movement (Xu et al., 2016). However, in view of limited structural data in this work, here we mainly discuss the Late Jurassic-Cretaceous tectonic deformation in the northern margin of North China.
During the Late Jurassic to earliest Cretaceous (ca. 151-141 Ma), after the short tectonic quiet period, another intense intracontinental deformation event, namely the episode B of the Yanshanian movement, occurred in northern margin of the NCC. The SPF, as the north boundary of the Shangyi Basin, reactivated under the influence of regional NW-SE compression, expressed by obvious dextral strike-slip movement. Meanwhile, the BSF was formed on the southern edge of the basin and was marked by a reverse fault with the top-to-the-NW slip sense. These thrust structures have shown as the basement-involved thick-skinned tectonics, which made all the late Mesozoic strata in the basin subject to folding and thrusting and formed a structural style of facing thrusts ( Figure 13A1). In addition, some evidence related to the ∼N-S contraction deformation has also been identified simultaneously in the north margin of the NCC. For example, Zhu et al. (2015) reported that the Sihetang ductile shear zone in the middle of the Yanshan belt was a thrusting zone with the top-to-the-SSW shear sense during the early Early Cretaceous (140-137 Ma); Davis et al. (2001) deemed that the high-angle Gubeikou Fault shown as a thrust fault with the top-to-the-south slip sense during the Late Jurassic to earliest Cretaceous (148-132 Ma). The above information demonstrates that the north edge of the North China might be affected by multiple tectonic domains in this period.
The geodynamics of NW-SE compression in this stage was normally considered as the subduction of the Paleo-Pacific plate beneath the East Asian continent Zhu et al., 2018;Clinkscales and Kapp, 2019;Lin et al., 2019). However, this suggestion cannot explain the simultaneous ∼N-S or NNE compressional deformation in the northern margin of the NCC (Lin et al., 2013), which was usually attributed to the closure of the Mongol-Okhosk Ocean (Zorin, 1999;Davis et al., 2001;Meng, 2003;Donskaya et al., 2008;Wang et al., , 2015Zhu et al., 2015). Some studies suggest that the Mongol-Okhotsk Ocean began to close from west to east in a scissor-like fashion during the late Mesozoic, and the final collision may occur in the Early Cretaceous (Metelkin et al., 2010). Under the influence of the closure of the Mongol-Okhosk Ocean in the north, series of N-S-directed tectonic shortening were marked in the northern margin of the NCC (He et al., 1998). Therefore, this stage of tectonic event (namely the Yanshanian B) may be driven by a combined effect from both of the subduction of the Paleo-Pacific plate beneath East Asia and the closure of the Mongol-Okhosk Ocean ( Figure 13A2).
During the middle-late Early Cretaceous (ca. 135-110 Ma), the NCC underwent widespread lithospheric extension and destruction, expressed by vast magmatism and the development of abundant extensional structures. Due to previous compression and uplifting, the Early Cretaceous volcanics are quite undeveloped in Shangyi area. Nevertheless, under the control of regional NW-SE extension, some outcrop-scale extensional structures were formed in margins and interior of the basin, and some coeval mafic dikes and intermediate-acid granites were also invaded sporadically in the east and west sides ( Figure 13B1). Compared with the contemporaneous representative extensional basins and lowangle detachment systems (or metamorphic core complexes) in the northern margin of the NCC Lin and Wei, 2018), the strength and influence of NW-SE extensional deformation in the Shangyi Basin are very limited and are not change the previous tectonic framework, which may reflect the inhomogeneous extension and thinning of the lithosphere (Xu, 2004;Liu et al., 2009). Many researchers linked far-ranging NW-SE extensional deformation in North China during the Early Cretaceous to the roll-back of the Paleo-Pacific subducting plate (Griffin et al., 1998;Davis et al., 2001;Ren et al., 2002;Zhu et al., 2011;Liu et al., 2017;. However, many extensional structures, such as half-graben basins, metamorphic core complexes, and syntectonic plutons bounded by low-angle normal faults, were also recognized in Transbaikalia and adjacent areas in the northern Central Asian Orogenic Belt, whose origin was owed to post-orogenic extensional collapse of the Mongol-Okhotsk belt (Zorin, 1999;Meng, 2003;Donskaya et al., 2008;. These extensional structures show the highly consistent in activity age with the lithospheric extension and thinning of the NCC (Donskaya et al., 2008;Wang et al., 2012Wang et al., , 2015Daoudene et al., 2013;Lin and Wei, 2018). Furthermore, in terms of the geotectonic position, the distance between the northern margin of the NCC and the subducting edge in the east is roughly the same as the distance from the northern margin of the NCC to the Mongol-Okhotsk belt in the north ( Figure 1A). The geodynamic context of this far-ranging NW-SE extensional event is thus likely associated with back-arc extension triggered by the roll-back of the Paleo-Pacific subducting plate and post-orogenic extensional collapse of the Mongol-Okhotsk belt ( Figure 13B2).
After the late Early Cretaceous (<110 Ma) (or may be during the late Early Cretaceous-Late Cretaceous), the Shangyi Basin experienced NE-SW compression. This compressional event, whereas, only caused limited destruction and transformation to the early structures, which was shown as local strike-slip displacement along the boundary faults, some outcrop-scale X-type conjugate shear fractures, and NW-trending open fold ( Figure 13C1). It should be noted that the Cretaceous faulted basin in Eastern China experienced an important tectonic reverse associated with another NW-SE compressive stress field during the late Early Cretaceous-Late Cretaceous (Y. Q. Liu et al., 2017;, which reflects termination of the NCC peak destruction. Here NW-SE compression is inconsistent in orientation with the contemporaneous NE-SW compression, implying a complex tectonic situation of intracontinental multidirectional compressional deformation in the north edge of the NCC during this period. About the driving mechanism, on the one hand, this stage of NW-SE compression may be linked to the change of velocity and angle of the subducting plate Zhu et al., 2018;. After further analysis, some researchers have argued that an undefined ocean block or plateau collided with the southeast margin of East Asia continent during the Late Cretaceous (ca. 100 Ma) (Yang, 2013;Niu et al., 2015;J. Zhang et al., 2020). Then this unknown block continued moving to the north along the east margin of East Asia, which affected the compressionshear structural environment in the east edge of East Asia. In this process, Paleo-Pacific Plate changed into low-angle subduction again ( Figure 13C2) (Yang, 2013;J. Zhang et al., 2020). However, on the other hand, NE-SW compression is almost perpendicular in orientation to the subduction of the Paleo-Pacific plate, so the latter is unlikely to be the geodynamic background of the former. Simultaneously, the Mongol-Okhosk Ocean has closed, suggesting the driving force may not be from the north. Actually, the Qiangtang and Lhasa terranes at the southwest of the NCC ( Figure 1A) experienced collision and collage during the Mesozoic (Guynn et al., 2006;Kapp et al., 2007;Ma et al., 2017). The Bangong-Nujiang suture zone, as the boundary between the Qiangtang and Lhasa terranes, represents the relic of the Mesozoic Bangong-Nujiang Tethyan Ocean (Wang et al., 2016). Recently, Peng et al. (2020) conducted a systematic petrologic, geochemical and isotope chronological investigation in Tongka area, which is located in the eastern section of the Bangong-Nujiang suture. They deemed that the initial subduction of the Bangong-Nujiang Tethyan Ocean may start at 190 Ma, and its eventual closure may continue to the Late Cretaceous (Peng et al., 2020). Considering that the subduction and closure of the Bangong-Nujiang Tethyan Ocean is consistent in direction with regional NE-SW compression, we can speculate that the NE-SW compression may be linked to the remote effect of the final collision between the Qiangtang and Lhasa terranes ( Figure 13C2).

CONCLUSION
According to our results, the following conclusions can be drawn.
(1) We delineate three phases of intracontinental deformation in the Shangyi Basin during the late Mesozoic in the following chronological order: NW-SE compression during the Late Jurassic to earliest Cretaceous (ca. 151-141 Ma); NW-SE extension during the middle-late Early Cretaceous (ca. 135-110 Ma); and NE-SW compressional deformation later than 110 Ma. NW-SE compression controlled the present basic tectonic framework of the basin, and the subsequent two tectonic deformations only caused limited destruction to the previous structures.
(2) Based on balanced cross-section restoration, we estimate the minimum crustal shortening ratio of 27% in Shangyi area under the control of NW-SE compression. Moreover, the contribution of tectonic shortening from the north side of the basin is greater than that from the south side. (3) NW-SE compression is consistent in activity age with the episode B of the Yanshanian movement, and the latter may be related to the subduction of the Paleo-Pacific plate beneath East Asia and the closure of the Mongol-Okhosk Ocean. The subsequent NW-SE extensional event is likely to be reflects the destruction of the NCC during the Early Cretaceous, which may result from the rollback of the Paleo-Pacific plate and post-orogenic extensional collapse of the Mongol-Okhotsk belt. The NE-SW compressional deformation may be related to the remote effect of the final collision between the Qiangtang and Lhasa terranes.

DATA AVAILABILITY STATEMENT
The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.

ETHICS STATEMENT
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