According to detrital zircons ages spectra and Hf isotopes in the matrix of the ophiolitic melange, the Ailaoshan-Song Ma-Song Chay Indosinian suture zone can be divided into four units, namely M1, M2, M3, and M4. Different deposition ages (310-270 Ma, 260-255 Ma, similar to 245 Ma, and >255 Ma) demonstrate temporal heterogeneity. The M1 unit is in the middle and south segments, and inner part of the NW segment of the Ailaoshan ophiolitic melange, and the southernmost part of Song Ma ophiolitic melange. The Silurian and Devonian sedimentary rocks of the Indochina block are the major provenance of the M1 unit. The M2 unit is located in the southwest part of the NW segment of the Ailaoshan ophiolitic melange. At least half of the 270-250 Ma detrital zircons might come from the South China block. The M3 unit is mainly located in the Ailaoshan-Song Ma ophiolitic melange and sourced from Indochina block. M4 is mainly located in the Song Chay ophiolitic melange, and its detrital zircons are mainly sourced from the South China block. The strike-parallel heterogeneity refers to the different distributions along the orogenic belt with various provenances. The strike-perpendicular heterogeneity characterises the geometry of M1, M2, and M3 units and is attributed to a Cenozoic positive-flower structure of the Red River Fault showing sinistral strike-slip tectonic event with SW-ward thrusting. These temporal and spatial heterogeneities correspond well to the different evolutionary stages of the eastern Paleo-Tethys.

The short-term climate and environmental consequences (<~1.0–10 Kyr) immediately following the end-Cretaceous extinction have been attributed to transient effects originating from Deccan volcanism and the Chicxulub impact. These two events have received significant attention for their role in precipitating extreme climate conditions. In contrast, the long-term (> ~100 Kyr) climate and environmental changes of the post-extinction have been extensively studied in the marine systems, yet their ramifications within terrestrial ecosystems are less well-characterized and require further elucidation. This study presents a carbon isotope analysis of pedogenic carbonates from matured calcisols in the Nanxiong Basin, South China, to reconstruct carbon cycles and atmospheric CO2 concentrations (pCO2) spanning from 76.0 Ma to 62.0 Ma, aiming to decipher the long-term terrestrial environmental and climatic conditions. Results show that δ13C values range from −12.4‰ to −5.0‰ (mean − 9.0‰) and pCO2 varies between ~250 ppmV and ~ 2200 ppmV (mean 920 ppmV). When combined with δ13C data from Songliao Basin, NE China, the carbon cycle variation exhibits a 13C collapse and smooth towards subsequent rebound, indicating a process of ~600 Kyr deterioration, ~600 Kyr stabilization and ~ 400 Kyr recovery in the terrestrial ecosystem. The fluctuation of estimated pCO2 aligns with the change pattern of sea surface temperatures, attesting to the strong perturbation of climate and environment at the same pace as the carbon cycle variations. It is proposed that ecosystems and environments in both terrestrial and surface ocean experienced a more unstable, difficult and erratic recovery process and were much more sensitive to climatic changes than in deep ocean for ~1.5 million years in the aftermath of the end-Cretaceous mass extinction. In addition, the divergence of proxy variations from expected effects implies the Deccan eruption and Chicxulub impact could not have played a long-term role in governing the climatic and environmental perturbations following the Cretaceous-Paleogene Boundary.

Based on the large-scale Late Triassic angular unconformity in northern Vietnam, French geologists proposed the Indosinian Movement in the early 20(th) century. The Song Chay tectonic belt in northern Vietnam, where the Indosinian orogeny was named, records a lot of information about the classical Indosinian orogenic belt and is the key area to understanding its tectonic evolution. According to our ten-year work on the Song Chay area and previous research results, this paper systematically reviews the geometry, kinematics, timing and evolution of the Song Chay tectonic belt. Detailed field work shows that the Song Chay tectonic belt can be divided into the Cenozoic Day Noi Con Voi unit, the Song Chay ophiolitic melange unit and the NE Vietnam fold and thrust unit from SW to NE. In the ophiolitic melange unit and the fold and thrust unit, NE-SW mineral and stretching lineations with top-to-the-NE kinematics indicate a SW-ward subduction and the corresponding NE-ward thrust of the Song Chay Ocean crust. Precise geochronological work shows that the crystallization age of the plagiogranite in the ophiolitic melange unit is 356.4 +/- 2.9 Ma, indicating that the Song Chay Ocean opened before the Early Carboniferous. The low-temperature geochronological data in the fold and thrust unit constrain the top-to-the-NE shearing between 250 Ma and 245 Ma, indicating the collision timing of 250 similar to 245 Ma. In addition, the detrital zircons of the Song Chay ophiolitic melange matrix were sourced from the downgoing South China block, and only a few ones were derived from the overriding Indochina block, so the Song Chay Ocean may be a very limited ocean basin. Structural analysis and detrital zircon dating suggest that the geometry and kinematics on both sides of the "Dian-Qion suture zone" are the same. Therefore, the "Dian-Qion suture zone" is hardly interpreted as a suture zone. Based on our and previous works in structural geology, petrology and geochronology, we proposed a tectonic evolution model of the Song Chay Ocean from Late Carboniferous to Middle Triassic: (1) 310 similar to 270 Ma, the Song Chay Ocean SW-ward subducted beneath the Indochina block, the magmatic arc was not developed at this time, and the ophiolitic melange matrix was mainly sourced from the South China block; (2) 270 similar to 250 Ma, the Song Chay Ocean subduction continued, during which the magmatic arc developed well, and ophiolitic melange received materials from both arc and South China block at the same time; (3) 250 similar to 245 Ma, the Song Chay Ocean closed and the South China block collided with the Indochina block; (4) 245 similar to 230 Ma, the Indochina orogenic belt entered the post-collision extension stage.

We provide the results of anisotropy of magnetic susceptibility (AMS) and zircon U-Pb dating for the Linglong (Luanjiahe)-Guojialing (Congjia)-Aishan batholith in the Jiaodong Peninsula, east of North China block. According to these data, we reveal the link between Late Mesozoic granite emplacement and regional tectonics. Then, we talk about the role of the overriding plate process on magmatic tempos.

In comparison with ophiolite, ophiolitic me ' lange, especially its matrix, contains more information about the evolution of the relevant ocean. The evolution of the eastern Palaeo-Tethys recorded a whole Wilson cycle of numerous continental blocks such as the South China Block and Indochina Block, including rifting away from the Gondwana continent, subsequent northward migration and final collage with the Laurasia continent. Based on structural geology, detrital zircon, and related geochemical analyses, the Ailaoshan-Song Ma ophiolitic me ' lange can be divided into M1, M2, and M3 units with distinct detrital zircon age spectra and eHf(t) values suggesting for different provenances. These units are in faults-contact along the orogenic belt, indicating a strike-parallel heterogeneity of the ophiolitic me ' lange. To further understand the heterogeneity of these ophiolitic melanges, five samples from the matrix of the Ailaoshan ophiolitic melange were collected to be conducted detrital zircon U-Pb dating and Lu-Hf isotope analyses. All samples share the same zircon age spectrum, with two obvious age peaks at 430 and 960 Ma, which is comparable with the M1 unit. These results imply that the northwestern Ailaoshan ophiolitic me ' lange segment can be subdivided into M1 in the interior and M2 in the exterior rather than the previous division, indicating a strike-perpendicular heterogeneity. Based on their geometries (NE-dipping) and depositional ages (M1, 310-270 Ma; M2, 260-240 Ma), the elder M1 unit was thrusted upon the younger M2 unit, indicating a tectonic inversion. This inversion, which is associated with the whole geometry of the Ailaoshan belt, is ascribed to the transpressive deformation of the Cenozoic Red River Fault. These spatial heterogeneities well match the different evolutionary stages of the eastern Palaeo-Tethys.

The timing and mechanism of the combination between the South China Block (SCB) and the Indochina Block (IB) are controversial. Three ophiolitic me ' lange zones (Ailaoshan, Song Ma, and Song Chay) have been proposed as suture zones within this collisional orogen. However, the relationships among the three corresponding tectonic belts are unclear. In this study, we present detailed structural data for the three tectonic belts. The bulk architectures of the Ailaoshan, Song Ma, and Song Chay belts correlate well with one another. This similarity is also revealed by our new zircon U-Pb geochronological results from the Song Ma and Song Chay ophiolites. The regional deformation age is constrained to between 250 and 240 Ma by our new muscovite 40Ar/39Ar ages, and the medium-low temperature conditions are revealed by the quartz c-axis fabric. Considering the transformation effect of the Cenozoic large-scale sinistral strike-slip of the RRF and DBF, the Early Mesozoic Ailaoshan, Song Ma, and Song Chay suture zones should represent different segments of the same belt. Based on this hypothesis, we compiled the ages of the magmatism in this region, which allows us to propose an evolutional model as follows: i) -380-310 Ma continental rifting and subsequent Ailaoshan-Song Ma-Song Chay ocean spreading as a branch of the Paleo-Tethys, ii) -310-250 Ma oceanic subduction coeval with continental-arc magmatism, iii) -250-240 Ma continental collision, iv) -240-220 Ma post-collisional extension.

蛇绿岩是恢复大洋演化最直接的证据,是识别板块汇聚边界的一级地质学标志.相比于蛇绿岩,蛇绿混杂岩的基质记录了更多关于大洋板块演化的信息.为了深入理解蛇绿混杂岩基质组成的构造内涵,我们选择了位于越南北部—中国滇东南地区的古特提斯哀牢山-Song Ma(马江)-Song Chay(斋江)缝合带开展研究.本文综合了前人有关该带蛇绿混杂岩基质碎屑锆石U-Pb定年和Hf同位素分析的结果,认为哀牢山-Song Ma-Song Chay蛇绿混杂岩基质具有强烈的横向不均一性,可以划分为M1、M2、M3和Song Chay单元.其中,M1位于哀牢山-Song Ma蛇绿混杂岩中部,构成了哀牢山蛇绿混杂岩的主体,具有440 Ma和960 Ma的特征碎屑锆石年龄峰值,结合其Hf同位素特征,我们认为M1的物源为印支板块.M2位于哀牢山-Song Ma蛇绿混杂岩的NW部,显示出单一的260 Ma左右的碎屑锆石年龄峰值,结合其Hf同位素特征,我们认为M2主要来自于华南板块上的峨眉山大火成岩省.M3位于哀牢山-Song Ma蛇绿混杂岩的SE部,碎屑锆石年龄结果显示出250 Ma的主要峰值以及370 Ma和780 Ma的次要峰值,结合其Hf同位素特征,我们认为M3的主要物源为印支板块的弧岩浆岩,少量来自华南板块.Song Chay蛇绿混杂岩基质中的碎屑锆石主要是来自作为被动陆缘的华南板块,只有很少一部分来自上覆的印支板块.上述蛇绿混杂岩组成的横向不均一性,指示了洋盆关闭过程中物源的变化.更重要的是,基质中鲜明的俯冲板块(华南)被动陆缘的信息,使我们推断古特提斯东部在某一阶段或某一部位表现为有限洋盆,其对我们理解东古特提斯板块拼合过程具有重要意义.

The Cretaceous extensional province of the South China Block (SCB), and the decratonization-induced extension in the North China Block (NCB), were both controlled by the Late Mesozoic subduction of the Izanagi/Paleo-Pacific Plate. Different from the metamorphic core complexes exhuming deep crustal rocks of the NCB, extension of the SCB is expressed by numerous half-graben basins and detachment of upper-middle crustal rocks, but its mode and mechanism remain unclarified. At the westernmost of this extensional province, the Early Paleozoic Yuechengling-Miao'ershan Massif, composed of the ductilely deformed Yuechengling pluton and undeformed Miao'ershan pluton, records Late Mesozoic detachment and exhumation. Magnetic fabrics of the western Yuechengling pluton are consistent with structural fabrics, while the NE-SW trending magnetic lineation and NE-SW striking magnetic foliation of the Miao'ershan pluton and the undeformed Yuechengling pluton reflect a pre-existing magma flow structure. Integrating our structural observation, anisotropy of magnetic susceptibility (AMS) results with gravity modeling, we reveal the deep geometry of the extensional dome and restore the original structure before the Late Mesozoic Ziyuan detachment. The mode of extension argues for a single batholith split into two separate massifs, thinning the crust of the central SCB. The shallow-dipping Ziyuan detachment fault (10°-30°) may account for the large horizontal extension but low exhumation of mid-crustal rocks in the SCB, in contrast to the large exhumation of deep crustal rocks in the NCB.

In response to the craton destruction, the North China Craton (NCC) underwent the Early Cretaceous extensional tectonics. During this period, the eastern NCC has also experienced numerous plutonism, volcanism, and extensional structures. Particularly, half-graben or graben, Early Cretaceous extensional domes, metamorphic core complex, and syn-kinematic plutons are widespread throughout the NCC and its surrounding area, with a peaking age of 125 Ma, pointing to a large-scale severe NW-SE extension. However, it remains unknown when and how the large-scale extension is initiated. To answer this key issue, we choose two plutons (Fengjiayu-Xibailianyu and Gubeikou plutons) with the age of early stage of the Early Cretaceous (130-127 Ma) as the target of this study. The Fengjiayu-Xibailianyu pluton is close to, while the Gubeikou pluton is far away from the Early Cretaceous intensive extensional region. A multidisciplinary study, including structural geology, anisotropy of magnetic susceptibility (AMS), and gravity modeling, has been carried out on these two plutons to reveal the tectonic regime coeval with their emplacement. Both of these two plutons share similar features of concentric magnetic foliations and variable magnetic lineations which are decoupled with the ductile fabric in their country rocks. Accordingly, we considered that they intruded in a permissive way at a weak extension regime during the Early Cretaceous (130-127 Ma), just before the Late Mesozoic peak of the magma flare-up and large-scale extensional tectonics of the NCC. Combined with our previous works, the Early Cretaceous NW-SE trending extension in NCC was further subdivided into the early-stage weak extension during 130-127 Ma and the late-stage intensive extension during 127-110 Ma, namely the large-scale extension initiated after 127 Ma. The early-stage extension could be ascribed to the westward subduction of the Izanagi plate under the Eurasian continent.

To understand the post-orogenic tectonics related to collision between the North China Craton (NCC) and the South China Block (SCB), the Northern Sulu massif is a representative area. It experienced a complex evolution marked by exhumation of ultra-high-pressure metamorphism rocks, migmatization, and alkaline magmatism in the Latest Triassic, and felsic magmatism in the Late Jurassic. In this contribution, we carried out a combined study including structural analysis, anisotropy of magnetic susceptibility (AMS), and gravity survey on the Northern Sulu massif. According to our structural analysis, it is interpreted as an extensional dome, exhibiting dominantly SE-dipping foliations in its east and center and NW-dipping ones closer to its northwestern margin, NW-SE mineral and stretching lineations, and top-to-the-NW kinematics. The Latest Triassic pyroxene syenite has dominantly SE-dipping mesoscopic/magnetic foliations, NW-SE magnetic lineations, and wedge shape at depth, and the Latest Triassic quartz syenite has variable magnetic fabric. Considering geometric relations of plutons and country rocks, the former is a "syn-kinematic" pluton, while the latter post-dates the regional tectonics, constraining the timing of the top-to-the-NW shearing at 220-210 Ma. Compared with the syn-orogenic tectonic events, the Latest Triassic ductile deformation points to a NW-SE extension related to lithospheric delamination. Late Jurassic isotropic monzogranite is characterized by "onion-skin" magnetic foliations with NE-SW trending magnetic lineations, and NE- or SW-ward decrease of thickness at depth. On the basis of regional understanding, we link its emplacement with the Late Jurassic NE-SW extensional tectonics attributed to the oblique subduction of the Paleo-Pacific plate. Such two episodes of crustal extensions with magmatism reformed the crustal architecture of the SE-margin of the NCC, which considerably facilitated stress-transmission from plate-boundary to intraplate during the development of subsequent Late Mesozoic intracontinental deformations.

The location of the suture zone between the South China Block (SCB) and the Indochina Block (IB) is disputed. Recently, along the Song Chay (Chay river) belt, a mélange zone was proposed as a potential suture zone of the SCB and IB. However, the provenance and age of the Song Chay mélange is poorly known. In order to better constrain the age and provenance of the elements forming the Song Chay mélange, nine samples of detrital material, and one orthogneiss were subjected to zircon U‐Pb and Hf isotope analysis. Detrital zircons from the silty matrix of the Song Chay mélange record three major Neoproterozoic age clusters at 580–650, 700–800, and 900–1,000 Ma, which correspond well to the substratum of the SCB. Two minor Late and Early Paleozoic age groups at 270–330, and 420–500 Ma, with mainly negative ε Hf (t) values were also recovered. We consider that the zircons in the matrix of the mélange were mainly derived from the subducting plate, namely the SCB. This interpretation is supported by the occurrence of lensoid sandstone blocks, representing the substratum of the SCB, included into the mélange. The deposition age of the Song Chay mélange is between 310 and 250 Ma. Our results demonstrate that in an ophiolitic mélange, the detrital material does not invariably come from the overriding plate, but at the onset of the collision, the subducting continental plate may also supply the terrigenous material.

The magmatism (including volcanism) in East Asia (or China) could provide key clues and age constraints for the subduction and dynamical process of the Paleo-Pacific Plate. Although many absolute isotope ages of extrusive rocks have been published in the 1980s–2000s, large uncertainties and large errors prevent the magmatism in southeast (SE) China from being well understood. In this study, we investigate the zircon geochronology of extrusive rocks and temporospatial variations in the late Mesozoic volcanism in SE China. We reported zircon U–Pb ages of new 48 extrusive rock samples in the Shi-Hang tectonic belt. Together with the published data in the past decade, ages of 291 rock samples from ∼40 lithostratigraphic units were compiled, potentially documenting a relatively complete history and spatial distribution of the late Mesozoic volcanism in SE China. The results show that the extrusive rocks spanned ∼95 Myr (177–82 Ma), but dominantly ∼70 Myr (160–90 Ma), within which the volcanism in the early Early Cretaceous (145–125 Ma) was the most intensive and widespread eruption. We propose that these ages represent the intervals of the Yanshanian volcanism in SE China. Spatially, the age geographic pattern of extrusive rocks shows that both the oldest and youngest age clusters occur in the coastal magmatic arc (eastern Zhejiang and Fujian), and the most intensive and widespread age group (145–125 Ma) occurs in a back arc or rifting basin (eastern Jiangxi, central Zhejiang, and northern Guangdong), implying that the late Mesozoic volcanism migrated northwest and subsequently retreated southeast. This volcanic migration pattern may imply that the Paleo-Pacific Plate subducted northwestward and the roll-back subduction did not begin until the Aptian (∼125 Ma) of the mid-Cretaceous.

Abstract. The westward subduction of Paleo-Pacific plate (PPP) played a governing role in tectonic evolution of East Asia. Although various PPP subduction models have been proposed, the subduction age and dynamical process of the PPP remain controversial. In this study, we investigate the geochronology of extrusive rocks and tempo-spatial variations of the late Mesozoic volcanism in Southeast China. We reported zircon U-Pb ages of new 48 extrusive rock samples in the Shi-Hang tectonic zone. Together with the published data, ages of ~ 300 rock samples from ~ 40 lithostratigraphic units were compiled, potentially documenting a relatively complete history and spatial distribution of the late Mesozoic volcanism in Southeast China. The results show that the extrusive rocks spanned ~ 95 Myr (177–82 Ma), but dominantly ~ 70 Myr (160–90 Ma), with two main age populations of 145–125 Ma and 105–95 Ma. We propose that these ages represent the intervals of the Yanshanian volcanism in Southeast China and the western subduction of the PPP, within which two intensive volcanic eruptional pulses happened. Spatially, the age geographic pattern of extrusive rocks is both the oldest and youngest age clusters occurring in the CZ and the younger intensive group in the SHTB, indicating that the late Mesozoic volcanism migrated northwestly from the coast to the inland prior to ~ 145 Ma and subsequently retreated southeastly back to the coast. This migration pattern is interpreted to result from a northwestward subduction followed by a southeastward rollback or retreat of the PPP.

The pre-Eocene history of the region around the present South China Sea is not well known. New multi-channel seismic profiles provide valuable insights into the probable Mesozoic history of this region. Detailed structural and stratigraphic interpretations of the multi-channel seismic profiles, calibrated with relevant drilling and dredging data, show major Mesozoic structural features. A structural restoration was done to remove the Cenozoic tectonic influence and calculate the Mesozoic tectonic compression ratios. The results indicate that two groups of compressive stress with diametrically opposite orientations, S(S)E–N(N)W and N(N)W–S(S)E, were active during the Mesozoic. The compression ratio values gradually decrease from north to south and from west to east in each stress orientation. The phenomena may be related to the opening of the proto-South China Sea (then located in south of the Nansha block) and the rate at which the Nansha block drifted northward in the late Jurassic to late Cretaceous. The Nansha block drifted northward until it collided and sutured with the southern China margin. The opening of the present South China Sea may be related to this suture zone, which was a tectonic zone of weakness.

Nanograins are commonly observed in slip faults and ductile shear zones, and it is more and more widely accepted that nanograins can lubricate the fault, but the role of nanograins in the ductile shear zone is unclear. In order to study this problem, samples taken from the Xiaomei ductile shear zone, Hainan Island, were carefully observed with SEM and TEM. Our observations show that nanograins found in our samples can be divided into three types based on their morphologies: spherical nanograins (S-grain), rod-like nanograins (R-grain) and nanoclays. We find that nanograins are localized in the boundaries of the large minerals, and are likely to localize strain and decrease shear strength in the ductile shear zone. We think S-grains are mainly originated from milling process, and they can also come from solidification of melts and devitrification of amorphous materials. The mirror surfaces can decrease the friction coefficient, and the formation of layered materials is likely to represent the steady state creep.

为了探讨韧性剪切带中纳米颗粒的发育过程和形成机制,进而厘定纳米颗粒对韧性剪切带形成过程和应力机制的指示作用,选取了在小妹韧性剪切带里发育的3种岩石样品(花岗岩、花岗质片麻岩和石英片岩),在扫描电镜下观察其中的纳米颗粒结构及纳米颗粒的聚集形态.观察结果表明:存在2种基本形态——球形的粒状和长条形的柱状,粒状纳米粒子(纳米粒)在3种岩石中都广泛发育,而柱状纳米颗粒(纳米棒)则在花岗质片麻岩中最发育.对纳米颗粒聚集形态研究,可将发育阶段分为:粒化阶段-异化阶段-成层堆积阶段.再次活动时,首先是经过活化阶段,形成复体颗粒,然后再重复上述阶段.结合纳米颗粒形态变化过程,其形成机制可能为脆-韧性变形.

The western part of Qiongnan Paleo-Tethyan Suture Zone in the northern margin of the South China Sea is commonly known as the Jiusuo-Lingshui fault zone. At first, it was deduced as a near EW-direction tectonic boundary zone based on the data of geophysical field. Due to the lack of direct evidence of tectonic deformation, the existence and geological significance of the boundary zone have been controversial for a long time. Through field observation, indoor polarizing microscope and SEM (scanning electron microscope) tests on the basement rocks exposed along the near NS-direction profile of Xiaomei riverbed, Duzong reservoir, Junchang bridge, and Lipen reservoir, and Hainan Island, the authors discovered ductile shear structure in the boundary zone, crystalline quartz schist, granitic gneiss, meta-quartz sandstone, and porphyritic quartz rock. The sha = ear structures were formed by regional dynamic-thermal metamorphism and are the most common ductile deformation metamorphic rock in general orogenic belt. Furthermore, the microstructure and nano structure, which often developed in the ductile shear zone, were found through microscope and SEM. Moreover, the authors discussed nanoscale characteristics of Xiaomei ductile shear zone in Hainan Island. The study results showed that the three rocks of granite, quartz schist and granitic gneiss have many kinds of nano textures and structures. Based on field actual situation of the development degree of nano particles in this shear zone, it is known that these nano textures and structures are related to shearing action. Their formation mechanism may be as follows: one is thermal decomposition of layered silicate under shearing action, the other is brittle fracture after particle plastic deformation and grinding through shearing action. Based on analysis of the Xiaomei ductile shear zone, and after comparison of SEM test results carried out to the rock samples of ductile shear zone of Taroko deep fault zone in Taiwan, we found that the characteristics of the nano particles and ones in Xiaomei ductile shear zone are comparable. According to their relations with the regional deep fault, it could be speculated that Xiaomei ductile shear zone may be closely correlated with Jiusuo-Lingshui deep fault zone in the regional tectonic belonging. These study results can provide important evidence for determination of the tectonic property and spatial position of Jiusuo-Lingshui fault zone.

利用陆源沉积中的碎屑组份(泥岩中的碎屑黏土矿物种类和砂岩中砂、粉砂碎屑类型)相对含量变化,对广东北部和江西南部的南雄盆地晚白垩世-古新世古气候进行了分析.结果显示,砂岩碎屑组份含量气候指数(长石/石英比,F/Q)介于0.02～0.14之间;(碎屑)黏土矿物组合主要以伊利石为主,平均79％;伊利石结晶度指数与化学指数分别为0.25～0.39、0.31 ～0.7.进一步分析表明,研究区这一时期以干旱气候为主,存在暖湿气候间断,古气候演化可分为三个阶段:晚白垩世马斯特里赫特期以干旱一半干旱性气候为主,古新世丹尼期早期转变为相对湿热或与干旱-半干旱气候交替,古新世丹尼期晚期恢复到半干旱性气候,但比第一阶段湿度可能稍有增加.这一总体干旱-半干旱气候格局及其变化总体与同期全球气候变化一致.

AbstractLower Cretaceous pedogenic carbonates exposed in SE China have been dated by U–Pb isotope measurements on single zircons taken from intercalated volcanic rocks, and the ages integrated with existing stratigraphy. δ13C values of calcretes range from –7.0‰ to –3.0‰ and can be grouped into five episodes of increasing–decreasing values. The carbon isotope proxy derived from these palaeosol carbonates suggests pCO2 mostly in the range 1000–2000 parts per million by volume (ppmV) at S(z) (CO2 contributed by soil respiration) = 2500 ppmV and 25°C during the Hauterivian–Albian interval (c. 30 Ma duration). Such atmospheric CO2 levels are 4–8 times pre-industrial values, almost double those estimated by geochemical modelling and much higher than those established from stomatal indices in fossil plants. Rapid rises in pCO2 are identified for early Hauterivian, middle Barremian, late Aptian, early Albian and middle Albian time, and rapid falls for intervening periods. These episodic cyclic changes in pCO2 are not attributed to local tectonism and volcanism but rather to global changes. The relationship between reconstructed pCO2 and the development of large igneous provinces (LIPs) remains unclear, although large-scale extrusion of basalt may well be responsible for relatively high atmospheric levels of this greenhouse gas. Suggested levels of relatively low pCO2 correspond in timing to intervals of regional to global enrichment of marine carbon in sediments and negative carbon isotope (δ13C) excursions characteristic of the oceanic anoxic events OAE1a (Selli Event), Kilian and Paquier events (constituting part of the OAE 1b cluster) and OAE1d. Short-term episodes of high pCO2 coincide with negligible carbon isotope excursions associated with the Faraoni Event and the Jacob Event. Given that episodes of regional organic carbon burial would draw down CO2 and negative δ13C excursions indicate the addition of isotopically light carbon to the ocean–atmosphere system, controls on the carbon cycle in controlling pCO2 during Early Cretaceous time were clearly complex and made more so by atmospheric composition also being affected by changes in silicate weathering intensity.