Differential sedimentary evolution of typical aulacogens of Meso-Neoproterozoic in North China craton

Many countries and regions in the world have obtained industrial oil flow in the Meso-Neoproterozoic sedimentary strata and formed commercial exploitation in recent years. The development horizon of high-quality source rocks in the Proterozoic in North China can be compared with the international, indicating that the Meso-Neoproterozoic in North China has great exploration potential. The sedimentary characteristics of typical aulacogen in multiple cratons in the Meso-Neoproterozoic North China Craton are compared and studied by using field outcrop data, drilling data and analysis and test data, aiming to provide sedimentary support for the prediction of oil and gas distribution and evaluation of exploration field in the Meso-Neoproterozoic in this area. The results show that there are four sedimentary systems in the study area, including Marine clastic rock sedimentary system, Marine carbonate sedimentary system, Marine-continental transitional facies sedimentary system and glacial sedimentary system. They are divided into seven sedimentary facies types: barrier coastal facies, non-barrier coast facies, shallow shelf facies, carbonate platform facies, reef facies, fan delta facies and glacial facies, and further divided into 15 subfacies and 21 microfacies. On this basis, the Meso-Neoproterozoic sedimentary filling sequences of two typical aulacogens, Yanliao and Xiong 'er, in the study area are clarified, showing that the formation time of each sedimentary filling sequence stage of different aulacogens is different, and the rock characteristics, lithology combination, lithologic structure, contact relationship, vertical sequence and sedimentary facies assemblage of the same sedimentary filling sequence stage are obviously different. The filling characteristics of the two aulacogens completely record the geological events related to the breakup of the Colombian supercontinent.


Materials and methods
The research data is composed of field profiles, cores, and analytical test data in the two aulacogens of Yanliao and Xiong ' er.The focus of this study is based on a large number of outcrops.The division and comparison of the Meso-Neoproterozoic strata in the typical aulacogens in the study area, the types and characteristics of sedimentary facies, and sedimentary filling sequences were analyzed.Based on the study of the Typical section facies, lateral comparison section facies, and sedimentary filling sequences in the two aulacogens of Yanliao and Xiong ' er, the sedimentary evolution difference comparison is carried out, and the response characteristics of geological events are discussed.

Sedimentary filling sequence of Meso-Neoproterozoic in Yanliao aulacogen
On the basis of observation and analysis of the two backbone sections of Jibei Depression and Xuanlong Depression in the Yanliao aulacogen, and in combination with regional stratigraphic and structural background data [47][48][49] , it is believed that the Yanliao Aulacogen experienced four stages in the Mesoproterozoic and one stage in Neoproterozoic.The four stages of Mesoproterozoic are continental rift deposition, transformation from continental rift to passive continental margin, passive continental margin and active continental margin.The formation of the Neoproterozoic Qingbaikou System (starting from the Luotuoling Formation) is the result of a new continental extension, which is a passive continental margin stage (Fig. 3).Five sedimentary sequences are identified in the study area.www.nature.com/scientificreports/ (1) Sequence I includes Changzhougou Formation-Tuanshanzi Formation, which was deposited in continental rift stage.It is between the unconformable surface UC-I (Fig. 3①) and UC-II (Fig. 3②) 50 of the Yanliao aulacogen basement.Among them, the unconformity surface UC-I is the angular unconformity between the sandy conglomerate at the bottom of the Changzhou Formation and the underlying Archean Metamorphic rock series, which is the product of the Luliang movement.The Changzhougou Formation is mainly a set of clastic rock deposits dominated by quartz sandstone with parallel and staggered layers.At the bottom, there are laterally discontinuous gravels, and the overall sedimentary environment is Clastic rock shore-shallow sea-shelf Clastic rock shore (Fig. 3g).The lithology of the Chuanlinggou Formation is dark horizontal layered mudstone, with fine-grained sandstone in the form of lenses or normal-graded bedding.It is an anoxic barrier coastal sedimentary environment (Fig. 3f).The Tuanshanzi Formation develops a set of Carbonate rock intercalated with fine Clastic rock deposits, and the sedimentary environment becomes Carbonate rock tidal flat.The distribution range of them is relatively limited, and their sedimentary thickness varies greatly [51][52][53] .
(2) Sequence II includes the Dahongyu Formation, representing the transformation sedimentary from continental rift to passive continental margin.It was deposited on the top of the Great Wall System in the Yanliao Aulacogen, and generally distributed in the NE direction, between the unconformity surface UC-II and UC-III (Fig. 3③).Unconformity surface UC-II is an overlap unconformity between Dahongyu Formation and old strata.It is mainly a set of clastic rocks intercalated with volcanic rocks and dolomite deposits.In the early sedimentary period of Dahongyu Formation, it is mainly a set of clastic rocks with volcanic rocks.The grain size at the bottom is coarse and the hydrodynamic force is strong, indicating the beginning of basin expansion, extensive transgression and thermal subsidence.Upward, it is mainly composed of medium-fine grained sediments, with dolomite and a large number of volcanic rock interlayers.It is a foreshore sedimentary environment of no-barrier coast facies.The upper part is interbedded with sandy dolomite and argillaceous dolomite, which is a supralittoral-intertidal zone sedimentary environment of carbonate rock, indicating that the crust is relatively rising and sea level is falling.
(3) Sequence III includes Gaoyuzhuang Formation-Tieling Formation, which represents passive continental margin deposits, with a sedimentary system dominated by tidal flat and bay-lagoon sedimentary environments.It is between unconformity surface UC-III and UC-IV (Fig. 3④).Unconformity surface UC-III is the unconformity between Gaoyuzhuang Formation and old strata.During the sedimentary period of Gaoyuzhuang Formation, the whole sedimentary environment is carbonate tidal flat, containing a lot of stromatolites, with siliceous or algae ash clumps and nodules (Fig. 3e).The Yangzhuang Formation is characterized by purple-red silty argillaceous dolomite, which is generally intertidal-supralittoral zone deposit of carbonate rock tidal flat.The sea level gradually rises from bottom to top.The Wumishan period inherits the late trend of Yangzhuang Formation, with typical sedimentary rhythm layer.During the deposition period of the Hongshuizhuang Formation, the sedimentary environment was a bay-lagoon sedimentary environment.The sediments were mainly gray-black shale, and the sea level gradually decreased.During the sedimentary period of Tieling Formation, the sediments were dominated by limestone and dolomite limestone, with a large number of stromatolites.With the rise of sea level, the environment changes from intertidal-supralittoral zone to subtidal zone (Fig. 3d).( 4) Sequence IV includes Xiamaling Formation, which represents active continental margin deposits.It is between unconformity surface UC-IV and UC-V.The Xiamaling Formation is mainly a set of shale, mudstone, occasionally intercalated with marl, argillaceous dolomite and sandstone, and a large number of diabase sheets (Fig. 3c).It shows that the Yanliao aulacogen was in an obvious extension state during this period.
(5) Sequence V includes the Luotuoling Formation-Jing ' eryu Formation, which is a passive continental margin deposit.It is between the unconformity surface UC-V and UC-VI.The unconformity surface UC-V is a parallel unconformity between the Luotuoling Formation and the Xiamaling Formation (Fig. 3⑤), and even a micro-angular unconformity.The Luotuoling Formation is mainly a set of containing glauconite quartzarenite and silty shale, which is a clastic rock littoral-shallow marine shelf environment (Fig. 3b).The Jing ' eryu Formation is mainly a set of marine carbonate subtidal deposits (Fig. 3a).The sedimentary range of the two should be wider than the present residual part, reflecting a relatively stable environment of Epicontinental sea.

Sedimentary filling sequence of Middle-Neoproterozoic in Xiong ' er aulacogen
On the basis of the lithological characteristics, contact relationship, vertical sequence, and structural background of the Meso-Neoproterozoic strata in the Xionger Aulacogen field section, and in combination with the sedimentary characteristics of three typical backbone sections and one horizontal correlation section [51][52][53] , it is considered that the Meso-Neoproterozoic strata in Xiong ' er aulacogen have experienced three stages: early continental rift, late continental rift and passive continental margin (Fig. 4).Four sedimentary sequences are identified in the study area.
(1) Sequence I includes the whole Xiong ' er Group, which is located at the bottom of Changcheng System of Xiong ' er Aulacogen.It is between the unconformity surface UC-I and UC-II.Unconformity surface UC-I is angular unconformity contact between Xiong ' er group and underlying Archean Taihua Group Gneiss basement or paleoproterozoic Shuangfang Group biotite quartz schist (Fig. 4①) 54 .Sequence I is a set of volcanic lava with a small amount of sedimentary rocks or pyroclastic rock depositions (Xiong ' er Group).From bottom to top, alluvial fan-fan delta deposits of Dagushi Formation are successively developed.The Xushan Formation, Jidanping Formation and Majiahe Formation are volcanic rock deposits.And upward, the sedimentary rock interlayer thickens and increases.It indicates that this is the early stage of the rift and the transgression has reached the Xiong ' er aulacogen.
(2) Sequence II mainly includes the Xiaogoubei Formation and the Yunmengshan Formation.It develops above the unconformable surface UC-II (Fig. 4②) and below the Baicaoping Formation.Although the Yunmengshan Formation and the overlying Baicaoping Formation in the study area are mostly in integrated contact, in the Zhongtiao Mountains area, the Baicaoping Formation overlaps and unconformably above the Xionger Group.The Xiaogoubei Formation and Yunmengshan Formation are characterized by a set of coarse clastic sediments, among which the Xiaogoubei Formation is fan delta of marine-continental transitional sedimentary  system (Fig. 4e,f).As sea level continues to rise, a coastal sedimentary environment is formed during the transgression of the Yunmengshan Formation.The whole sequence II is characterized by the late rift deposition in the transgression environment.
(3) Sequence III includes the Baicaoping Formation-Huanglianduo Formation, which developed under the unconformity surface UC-III.The unconformity surface UC-III is a parallel unconformity between the Huanglianduo Formation and the Dongjia Formation (Fig. 4③).During the sedimentary period of Baicaoping Formation, a set of mud shale with a small amount of sandstone deposits was formed (Fig. 4d).The water body of the Cuizhuang Formation continues to deepen, gradually evolving from the early nearshore-foreshore sedimentary environment to the late shallow sea shelf sedimentation.During the sedimentary period of the Sanjiaotang Formation, a set of fine-grained quartz sandstone deposits was formed, belonging to coastal sedimentation (Fig. 4b).During the sedimentary period of Luoyukou Formation, the sediments changed from clastic rocks to carbonate rocks, and the sedimentary environment changed from transitional zone to Carbonate rock tidal flat.The sedimentary environment of the whole sequence is mainly clastic rock shore-shallow sea shelf-carbonate platform, representing passive continental margin deposits.
(4) A large number of strata are missing in sequence IV, which is between the unconformity surface UC-III and UC-IV.It includes the Dongjia Formation-Dongpo Formation.The unconformity surface UC-IV is the parallel unconformity between the Dongpo Formation and the overlying Cambrian Xinji Formation.The early and middle stages of the Qingbaikou period are mainly clastic rock deposits, and its gravels are mainly composed of dolomite, banded siliceous rock, vein quartz, etc. (Fig. 4a), which reflects the sedimentary environment of clastic rock littoral.The Luoquan Formation of Sinian System is a typical set of glacier deposits.At the end of Sinian, the Dongpo Formation experienced another large-scale transgression, with fine sandstone at the bottom and shale mixed with Siltstone at the top, which is a coastal-shallow sea shelf sedimentary environment.Sequence IV developed clastic rock littoral-carbonate platform-glacier-clastic rock littoral-shallow marine shelf sedimentary environment, which represents passive continental margin deposits.

Discussion
In this study, the horizontal comparison section of sedimentary facies is selected for comparative analysis, which is Shanxi Luonan-Shanxi Yongji-Shanxi Licheng-Hebei Quyang-Hebei Yixian-Hebei Kuancheng (Fig. 5).In combination with the distribution characteristics of the Meso-Neoproterozoic strata in each Aulacogen, the sedimentary filling sequence has obvious differences, mainly in three aspects:

Comparison of the formation time of each sedimentary filling sequence stage of different aulacogens
The rifting of the Yanliao Aulacogen started in the Changzhougou period of the Changcheng period in the Mesoproterozoic (~ 1650 Ma).The continental rift stage occurred in the Changzhougou-Tuanshanzi period of the Changcheng period.The Dahongyu period of the Changcheng period is the transformation stage from continental rift to passive continental margin.The passive continental margin stage occurred in the Gaoyuzhuang-Tielingian Jixianian period.The Daijian period is a active continental margin stage.The Neoproterozoic Qingbaikouan is the second passive continental margin stage.The rifting of Xiong ' er aulacogen began in the early Changcheng period of Mesoproterozoic (~ 1780 Ma).The sedimentary period of the Xiong' er Group during the Changcheng period is the early stage of the continental rift.The Xiaogoubei-Yunmengshan period of the Changcheng period is the late stage of the continental rift.From the Baicaoping period of the Changcheng period to Jixianian period, it is in the passive continental margin stage.The sedimentary strata of the Daijian period are missing, speculating that it is the active continental margin stage.Qingbaikou period is the second passive continental margin stage.

Comparison of characteristics of each sedimentary filling sequence of different aulacogens
The continental rift stage: The lower part of Yanliao aulacogen (the Changzhougou Formation) is mainly a set of clastic rock deposits, and the conglomerate layer is developed at the bottom.The Chuanlinggou Formation is dark horizontal layered mudstone.The Tuanshanzi Formation is a set of carbonate rocks with fine clastic rocks, and volcanic rocks are widely developed locally.The whole is clastic rock shore-anoxic barrier coast sedimentarycarbonate tidal flat sedimentary environment.During early stage of rifting in the Xionger Aulacogen depression, a set of ultra thick andesitic volcanic rocks of Xiong ' er Group were developed in Xiong ' er Formation.A set of www.nature.com/scientificreports/coarse clastic sedimentary rocks developed in Xiaogoubei Formation and Yunmengshan Formation during late stage of rifting.The whole is fan delta-clastic rock shore sedimentary environment.The transition period (the transformation from continental rift to passive continental margin): It is obvious only in the Yanliao aulacogen, which develops a set of clastic rock with volcanic rock deposition.In the late sedimentary period, the sediments were mainly dolomite.In the late stage, although the rifting and volcanism continued, its intensity decreased significantly.The environment changes from no-barrier coast facies to carbonate rock platform facies.However, no developmental characteristics were found about this stage in the Xiong ' er aulacogen.
The passive continental margin stage: the Jixian System in Yanliao aulacogen is mainly composed of thick carbonate rocks and mudstones, and the overall sedimentary environment is carbonate tidal flat-shallow marine shelf-carbonate tidal flat.In the Xiong ' er aulacogen, the early stage (Baicaoping Formation-Sanjiaotang Formation) develop a set of fine clastic rock deposits dominated by quartz sandstone, siltstone and shale.In the late stage (Luoyukou Formation and Huanglianduo Formation), a set of carbonate deposits was developed.The whole is clastic rock littoral-shallow marine shelf-carbonate platform sedimentary environment.
The active continental margin stage: The Yanliao aulacogen is mainly a set of shale and mudstone, occasionally intercalated with marl, argillaceous dolomite and sandstone.And a large number of diabase sheets appeared.It is a shallow marine shelf sedimentary environment.In Xiong ' er aulacogen, it is speculated that the sedimentary stratum is missing due to Continental collision and Tectonic uplift in this stage.
The second passive continental margin stage: The Yanliao aulacogen is mainly composed of clastic rocks and carbonate rocks, which developed in clastic rock littoral-carbonate tidal flat sedimentary environment.In Xiong ' er aulacogen, the Dongjia Formation of Qingbaikou System is a set of terrigenous clastic-carbonate rock formation.After that, there was one set of stratigraphic deposits only in Yuku Formation of the Nanhua period in the Xiaoqinling-Luanchuan stratigraphic area, which is mainly a set of metamorphic rocks constructed by volcanic rocks and carbonate rocks.In the late stage (Luoquan Formation and Dongpo Formation in Sinian period), a set of moraine glutenite, (gravel-bearing) fine sandstone, siltstone and shale were developed 51,52 .The whole is clastic rock littoral-carbonate platform-glacier-clastic rock littoral -shallow marine shelf sedimentary environment.

Response characteristics of sedimentary filling to important geological events
The deposition process of the North China Craton in the middle Proterozoic (about 1.8 ~ 1.35 Ga) completely recorded the breakup process of the Columbia supercontinent 55 .Following the convergence and formation of the Colombian Supercontinent, the North China Craton experienced a series of convergence, collision, amalgamation and unified crystallization in the Paleoproterozoic, and the North China Craton basement formed [56][57][58] .Subsequently, the North China Craton was incorporated into the Colombian supercontinent and remained relatively stable for a long time (Fig. 6) 59 .This series of tectonic movements make obvious differences in sedimentary filling in different aulacogens.

The Yanliao aulacogen
The Changcheng period of Yanliao aulacogen is dominated by a large set of terrigenous clastic rock deposits, which are unconformable on the underlying Archean Metamorphic rock series at an angle, with a sedimentary thickness of 2670 m.It indicates that the rifting is obvious.The stratigraphic distribution characteristics show that the basin has the characteristics of continental rift and aulacogen.The Changzhougou-Tuanshanzi period is the continental rift stage.With the eruption of volcanic rocks, a set of clastic rock with volcanic sedimentary formation is developed in Dahongyu Formation.As the intensity of activity decreases, the basin transforms from a continental rift to a passive continental margin during the Dahongyu period (Fig. 7).Dahongyu Formation is in parallel unconformity with the underlying Tuanshanzi Formation, or in direct overlap unconformity with Archean crystalline rocks.The overlap unconformity is a geological response record of the 'Xingcheng Uplift' tectonic event (Fig. 7).
The tectonic environment of Jixian period tends to be stable and has turned into a passive continental margin stage.A set of extremely thick carbonate rocks with muddy is developed, which is dominated by a large area of carbonate platform sedimentary environment (Fig. 7).The regional discordant contact at the bottom of the Jixian system is a geological response record of the 'Qinglong Uplift' tectonic event in the area.In the late Gaoyuzhuang period, the Taihang highland gradually expanded and the sea level decreased relatively.The sea water retreats northward, resulting in a reduction in the area of land surface sea basins.As a result, sedimentary hiatus occurred in Gaoyuzhuang Formation and Yangzhuang Formation at the edge of the basin, which is the geological response record of the 'Luanxian Uplift' tectonic event in this area.At the end of the deposition of the Tieling Formation of the Pending Period, the crust uplifts as a whole, and the area of the epicontinental sea basin is further reduced.As a result, it led to the uplift and erosion of the Tieling Formation, forming a large area of ancient weathering crust.Subsequently, a set of shale intercalated with argillaceous carbonate rock or fine sandstone deposits were deposited in the upper part.During the sedimentary period of the Xiamaling Formation, the Yanliao aulacogen is in an obvious extensional state and it belongs to active continental margin deposition (Fig. 7).Due to the overall uplift of the crust, the distributions of the Xiamaling Formation in this area are small, which is parallel to the Tieling Formation.It is the geological response record of the 'Qinyu Uplift' tectonic event.After that, the crust of North China uplifted and squeezed.
It led to a long period of denudation (erosion) and planation after the deposition of Xiamaling Formation and before the deposition of Luotuoling Formation.It leads to the loss of strata, which is the geological response record of the 'Yuxian Uplift' tectonic event in this area.In Qingbaikou period, the North China Block began to subside again, and the Qingbaikou System is mainly composed of clastic rocks and carbonate rocks, which www.nature.com/scientificreports/www.nature.com/scientificreports/reflects a relatively stable epicontinental sea structure-sedimentary environment and belongs to passive continental margin deposition (Fig. 7).

The Xiong ' er aulacogen
The development of the Xiong ' er aulacogen is also considered to be a geological response record of the North China Craton in the Columbia supercontinent breakup event.At early stage of the Xiong ' er-Yunmengshan Period of Changcheng Period, the southern margin of the North China Craton experienced a short period of initial crustal cracking, with rapid uplift of the mantle plume, intense stretching and thinning of the Lithosphere, and eruption of a large amount of magmatic materials.A set of thick volcanic lava sediments that deposited, which is in angular unconformable contact with the underlying strata and is the product of the 'Zhongtiao Mountains Movement' in this area (Fig. 8).
Late continental rift deposition, The coarse debris deposits (Xiaogoubei Formation and Yunmengshan Formation) with a thickness of over one kilometer have been deposited, forming in a fan delta coastal sedimentary environment (Fig. 8).It is in angular unconformable contact with the underlying Xiong ' er Group, which is a geological response record of the 'Mount Wangwushan Movement' tectonic event in this area.
With the continuation of the breakup of the Columbia Supercontinent and the extrusion between continents, the tectonic environment became stable during the Baicaoping-Jixian period of the Changcheng Period, and mainly developed clastic rock shore-shallow sea shelf-carbonate rock platform sedimentary environments.Subsequently, the rifting ended and the whole was transformed into passive continental margin deposition.In the early sedimentary stage of the passive continental margin (Baicaoping Formation-Sanjiaotang Formation), a set of quartz sandstone, siltstone and shale has developed.In the late passive continental margin (Luoyukou Formation-Huanglianduo Formation), it is epicontinental sea and sediments mainly are carbonate rocks.
During the Daijian period of Mesoproterozoic, the North China Craton was further uplifted, resulting in extensive loss of Daijian System strata and further narrowing of the sedimentary range of Xiong' er Aulacogen.Only developed the Dazhuang Formation of in the Luonan region of Shanxi Province (Fig. 8).Therefore, this period in the Xiong ' er aulacogen is considered to be the active continental margin stage.
The North China Craton experienced the evolution and breakup of the Rodinia supercontinent in the Neoproterozoic.During the Qingbaikou-Sinian Period, the Xiong ' er aulacogen was a passive continental margin sedimentary stage (Fig. 8).In the Mianchi-Queshan stratigraphic area, it occurred a small-scale transgression during the Dongjia Period.The sedimentary environment changed from clastic rock barrier-free coast to carbonate tidal flat environment.In Xiaoqinling-Luanchuan area, the Qingbaikou System is a set of terrigenous clastic rock-carbonate rock formation.In Songji area, regional tectonic movements led to crustal uplift and loss of strata during the Jixian and Qingbaikou periods.During the Nanhua period, it is only developed the Yuku Formation in

Conclusions
(1) Guided by the theory of sedimentology, through a large number of outcrops measurement and observation, core observation and description, the sedimentary facies division marks such as lithology, structural marks and sedimentary structure marks were analyzed, and the division schemes of sedimentary facies, subfacies and microfacies were established.The sedimentary facies types of the Meso-Neoproterozoic in the study

Figure 1 .
Figure 1.Schematic diagram of Tectonic framework in China (showing the major Precambrian cratons, landmass and Phanerozoic orogenic belt (modified from 44 ).

Table 1 .
Meso-Neoproterozoic strata correlation table of stratigraphic division in the typical aulacogens of the North China Craton.

Table 2 .
Sedimentary facies types and sedimentary characteristics of Meso-Neoproterozoic strata in the study area.