Provenance and tectonic setting of the Upper Palaeozoic sandstones in western Inner Mongolia (the Shalazhashan and Solonker belts), China: insights from detrital zircon U–Pb ages and Hf isotopes

2017 ◽  
Vol 156 (3) ◽  
pp. 547-571 ◽  
Author(s):  
GUANZHONG SHI ◽  
GUANGZENG SONG ◽  
HUA WANG ◽  
CHUANYAN HUANG ◽  
BEN LI
Keyword(s):  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Provenance Analysis ◽  
Northern Margin ◽  
Isotopic Analyses ◽  
Early Palaeozoic ◽  
T Values

AbstractThe Solonker and Shalazhashan belts are hotly debated tectonic units of the Central Asian Orogenic Belt (CAOB), because they may either represent a Permian or Triassic suture zone of the CAOB, or a rifting zone overprinted on an Early Palaeozoic orogen. Provenance analysis of the Upper Palaeozoic sandstones in these belts may provide useful constraints on this issue. This study collected six sandstone samples from three study areas: the Mandula area of the Solonker Belt, the Quagan Qulu area of the Shalazhashan Belt but close to the Alxa block, and the Enger Us area of the Shalazhashan Belt, for framework petrography, zircon morphology, U–Pb and Lu–Hf isotopic analyses. Framework petrography reveals that the Mandula and Enger Us area samples contain high proportions of volcanic fragments, whereas the samples from the Quagan Qulu area include not only volcanic fragments but also significant amounts of biotite and muscovite. The detrital zircons of the Mandula area and the Enger Us area yield two main age groups: (i) 260–330 Ma, with dominant εHf(t) values of –5 to +12; and (ii) 420–550 Ma, with dominant εHf(t) values of –9 to +9, suggesting that Early Palaeozoic arc-related magmatic rocks and Late Palaeozoic syn-depositional volcanic rocks are the main source rocks. The detrital zircons of the Quagan Qulu area have one main age group of 420–500 Ma and some grains of 0.9–1.1 Ga, 1.4–1.5 Ga, 1.8–1.9 Ga and ~ 2.5 Ga, which derive from the northern margin of the Alxa block. The lithological and fossil assemblages of the Upper Palaeozoic sandstones suggest shallow-marine to deep-water depositional environments and a northward-deepening transition. Based on the zircon spectra, sedimentary environment analysis and previous studies, we argue that the Solonker Belt and the Shalazhashan Belt of the CAOB are in extensional basins of a fore-arc or rifting setting.

scholarly journals Finding of Ca. 1.6 Ga Detrital Zircons from the Mesoproterozoic Dagushi Group, Northern Margin of the Yangtze Block

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 371
Author(s):  
Xiaofeng Xie ◽  
Zhenning Yang ◽  
Huan Zhang ◽  
Ali Polat ◽  
Yang Xu ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Yangtze Block ◽  
Northern Margin ◽  
Provenance Studies ◽  
Time Period ◽  
Isotopic Analyses ◽  
History Of ◽  
T Values

The middle Mesoproterozoic is a crucial time period for understanding the Precambrian tectonic evolutionary history of the northern Yangtze Block and its relationship with the supercontinent Columbia. The Dagushi Group (Gp) is one of the Mesoproterozoic strata rarely found at the northern margin of the Yangtze Block. U–Pb geochronology and Lu–Hf isotopic analyses of detrital zircons were analyzed for three metamorphic quartz sandstone samples collected from the Luohanling and Dangpuling formations of the Dagushi Gp. These metasandstones yielded major zircon populations at ~2.65 Ga and ~1.60 Ga, respectively. The ~1.60 Ga ages first discovered yield a narrow range of ɛHf(t) values from −1.8 to +1.8, which lie above the old crust evolutionary line of the Yangtze Block, suggesting the addition of mantle material. Trace element data indicate that ~1.60 Ga detrital zircons share a basic provenance, whereby they have low Hf/Th and high Nb/Yb ratios. Zircon discrimination diagrams suggest that the ~1.60 Ga detrital zircon source rocks formed in an intra-plate rifting environment. Dagushi Gp provenance studies indicate that the ~1.60 Ga detrital zircon was most likely sourced from the interior Yangtze Block. Thus, we suggest that the late Paleoproterozoic to early Mesoproterozoic continental break-up occurred at the northern margin of the Yangtze Block.

Late Paleozoic tectonism of the Bogda region in  Chinese North Tianshan: Insights from sedimentary provenance analysis

2021 ◽  
Author(s):  
Qian Wang ◽  
Guochun Zhao ◽  
Yigui Han ◽  
Jinlong Yao
Keyword(s):  
Detrital Zircon ◽  
Detrital Zircons ◽  
Late Paleozoic ◽  
Provenance Analysis ◽  
The North ◽  
Tectonic Transition ◽  
Isotopic Analyses ◽  
Zircon Morphology ◽  
Detrital Zircon Ages ◽  
T Values

<p>The Chinese North Tianshan (CNTS) extends E-W along the southern part of the Central Asian Orogenic Belt and has undergone complicated accretion-collision processes in the Paleozoic. This study attempts to clarify the late Paleozoic tectonism in the region by investigating the provenance of the Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS by U-Pb dating and Lu-Hf isotopic analyses of detrital zircons. Detrital zircon U-Pb ages (N=519) from seven samples range from 261 ± 4 Ma to 2827 ± 32 Ma, with the most prominent age peak at 313 Ma. There are Precambrian detrital zircon ages (~7%) ranged from 694 to 1024 Ma. The youngest age components in each sample yielded weighted mean ages ranging from 272 ± 9 Ma to 288 ± 5 Ma, representing the maximum depositional ages. These and literature data indicate that some previously-assumed “Carboniferous” strata in the Bogda area were deposited in the Early Permian, including the Qijiaojing, Julideneng, Shaleisaierke, Yangbulake, Shamaershayi, Liushugou, Qijiagou, and Aoertu formations. The low maturity of the sandstones, zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East ­Junggar Arc and the Harlik-Dananhu Arc in the CNTS. The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc. Zircon ɛ<sub>Hf</sub>(t) values have increased since ~408 Ma, probably reflecting a tectonic transition from regional compression to extension. This event might correspond to the opening of the Bogda intra-arc/back arc rift basin, possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean. A decrease of zircon ɛ<sub>Hf</sub>(t) values at ~300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision, which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous. This research was financially supported by the Youth Program of Shaanxi Natural Science Foundation (2020JQ-589), the NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).</p>

Internal versus external locations of the South China Craton within Rodinia during the Cryogenian: Provenance history of the Nanhua Basin

2020 ◽  
Author(s):  
Guangyou Zhu ◽  
Huichuan Liu ◽  
Tingting Zhang ◽  
Weiyan Chen ◽  
Jianwei Xiao ◽  
...  
Keyword(s):  
Mantle Plume ◽  
South China ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Yangtze Block ◽  
The South ◽  
Isotopic Analyses ◽  
South China Craton ◽  
Late Neoproterozoic ◽  
T Values

Contrasting models for internal versus external locations of the South China Craton (SCC) in the supercontinent Rodinia and associated mantle plume or ocean subduction dominated tectonic processes can be resolved by detrital zircon U-Pb dating and Lu-Hf isotopic analyses on the Cryogenian Nanhua Supergroup in the central SCC. Our results show that samples from the lower Liantuo, Tiesi’ao, and Datangpo formations of the Nanhua Supergroup show three age peaks at 2.50 Ga, 2.05 Ga, and 0.85 Ga, and those of the upper Nantuo Formation yield four peaks at 2.50 Ga, 2.05 Ga, 0.85 Ga, and 0.65 Ga. The Archean and Paleoproterozoic (1.80−2.10 Ga) zircons have εHf(t) values of −16.3 to +4.7 and −23.0 to +4.2, and may be sourced from the Kongling and Douling complexes and Paleoproterozoic intrusions in the northern Yangtze Block, respectively. Early Neoproterozoic (0.70−0.96 Ga) zircon grains show variable εHf(t) values of −20.0 to +15.0. In combination with the absence of Mesoproterozoic detrital zircons in the Nanhua Supergroup, huge volumes of Neoproterozoic granitic intrusions in the northern Yangtze Block are the potential sources for the 0.70−0.96 Ga detrital zircons. Only the siltstone of the Nantuo Formation has late Neoproterozoic (0.63−0.69 Ga) detrital zircons with high and positive εHf(t) values (+7.9 to +9.4). Several granitoid intrusions (0.63−0.68 Ga) in the Wudang and Ankang uplift of the South Qinling belt in the northern Yangtze Block provide the late Neoproterozoic detrital zircons of the Nantuo Formation. These provenance analyses of the Nanhua Supergroup indicate an interior source from the SCC, rather than an exterior source from the Laurentia and Australia cratons. The Neoproterozoic rift basins and magmatic rocks in the SCC were produced by secular episodic subductions and back-arc extensions, rather than a Neoproterozoic super-mantle plume. The SCC occupied a peripheral position adjacent to northern India in Rodinia during the Neoproterozoic. These conclusions will promote our understanding of genetic mechanism and distribution prediction of the several Cryogenian−Cambrian black-shale layers and excellent source rocks in the SCC.

Protracted northward drifting of South China during the assembly of Gondwana: Constraints from the spatial-temporal provenance comparison of Neoproterozoic−Cambrian strata

2021 ◽  
Author(s):  
Qiong Chen ◽  
Guochun Zhao ◽  
Min Sun
Keyword(s):  
South China ◽  
Detrital Zircons ◽  
Northern Margin ◽  
Northern India ◽  
Geological Evolution ◽  
System 2 ◽  
Sedimentary System ◽  
Provenance Variations ◽  
Late Neoproterozoic ◽  
T Values

Neoproterozoic to Paleozoic sedimentation shows systematic temporal-spatial variations within South China, which must be considered in reconstructing geological evolution of South China in response to global plate reorganization from the breakup of Rodinia to the assembly of Gondwana. We use >1000 new U-Pb and Hf isotopic data for detrital zircons from Neoproterozoic−Cambrian strata across the western (i.e., Longmenshan) and eastern (i.e., Wuyishan) margins of South China, coupled with compiled stratigraphic and magmatic information, to constrain change in provenance through time. First-order conclusions are as follows: (1) detrital zircons from the Neoproterozoic strata of the two margins were mainly sourced from the Panxi-Hannan arc and the Jiangnan orogen, signaling a rough self-sufficient sedimentary system; (2) newly identified Cambrian molasse-like sediments in the western margin, in which abundant detrital zircons are 550−500 Ma old with positive εHf(t) values, were mainly derived from the 580−500 Ma Cadomian arc belt along the Iran-Turkey margin; and (3) the Cambrian sediments in the eastern margin document more increased contributions from the Grenvillian-age provinces most possibly in Australia. Such spatial-temporal provenance variations signal the northward drifting of South China, from a position connecting with Iran-Turkey and northern India to that approaching Australia during the late Neoproterozoic−Cambrian period. We highlight that the activity of oblique oceanic-continental convergence accreted Asian terranes onto the northern margin of Gondwana, hence contributing to the ultimate Gondwana architecture under global plate reorganization.

Petrography and geochemistry of the siliciclastic Araba Formation (Cambrian), east Sinai, Egypt: implications for provenance, tectonic setting and source weathering

2015 ◽  
Vol 154 (1) ◽  
pp. 1-23 ◽  
Author(s):  
HOSSAM A. TAWFIK ◽  
IBRAHIM M. GHANDOUR ◽  
WATARU MAEJIMA ◽  
JOHN S. ARMSTRONG-ALTRIN ◽  
ABDEL-MONEM T. ABDEL-HAMEED
Keyword(s):  
Tectonic Setting ◽  
Source Area ◽  
Xrd Analysis ◽  
Climatic Conditions ◽  
Source Rocks ◽  
Northern Margin ◽  
Rock Fragments ◽  
Geochemical Parameters ◽  
Clastic Sediments ◽  
Chemical Index

AbstractCombined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

SOUTHERN GEORGINA BASIN: A NEW PERSPECTIVE

1990 ◽  
Vol 30 (1) ◽  
pp. 137 ◽  
Author(s):  
W.R. Lodwick ◽  
J.F. Lindsay
Keyword(s):  
Mirror Image ◽  
Source Rocks ◽  
Carbonate Production ◽  
Northern Margin ◽  
Middle Ordovician ◽  
Upper Proterozoic ◽  
Clastic Sediments ◽  
Early Palaeozoic ◽  
New Perspective ◽  
Reservoir Potential

The Georgina Basin formed as a shallow intracratonic depression on the Australian craton along with a number of other basins in the Proterozoic and early Palaeozoic, probably in response to the break up of the Proterozoic supercontinent. Since all of these basins evolved under similar tectonic and sea-level controls, the basins all have similar sediment successions and, it might thus be assumed, similar petroleum prospectivity. One basin, the Amadeus Basin, currently has petroleum production, suggesting a potential for exploration success in the other intracratonic basins.In the Amadeus Basin the main petroleum prospects lie within or adjacent to major sub-basins that formed along the Basin's northern margin. The Georgina Basin has sub-basins that formed along its southern margin, almost as a mirror image of the Amadeus Basin. The lower Palaeozoic section of the Toko Syncline in the southern Georgina Basin has hydrocarbon shows in Middle Cambrian to Middle Ordovician rocks. Source rocks appear to have developed within the transgressive systems tract and the condensed interval of the highstand systems tract, at times when the basin was starved for clastic sediments and carbonate production was restricted.Seismic data acquired in the 1988 survey are of a higher quality than that previously obtained in the area. Its interpretation portrays the westward thrusting French Fault at the eastern edge of the Toko Syncline with potential hangingwall and footwall traps. Cambro- Ordovician Georgina Basin sediments subcrop the overlying Eromanga Basin with angularity, providing potentially large stratigraphic traps. Fracturing of the Cambrian and Ordovician carbonates within fault zones, and solution porosity at the unconformity, would also enhance reservoir potential in the area. Perhaps most significantly, the new data also shows an earlier, apparently independent basin completely buried beneath the Georgina section. The concealed section may simply be a very thick, early Upper Proterozoic section, or perhaps an equivalent to, or a lateral extension of the McArthur Basin. Recent work in the McArthur Basin has shown considerable source potential in the McArthur and Roper Groups, which may support the possibility of an additional, as yet unrecognised, source beneath the Georgina Basin.

scholarly journals Hydrocarbon source rock potential of Miocene diatomaceous sequences in Szurdokpüspöki (Hungary) and Parisdorf/Limberg (Austria)

2020 ◽  
Vol 113 (1) ◽  
pp. 24-42
Author(s):  
Emilia Tulan ◽  
Michaela S. Radl ◽  
Reinhard F. Sachsenhofer ◽  
Gabor Tari ◽  
Jakub Witkowski
Keyword(s):  
Source Rock ◽  
Pannonian Basin ◽  
High Energy ◽  
Depositional Environments ◽  
Source Rocks ◽  
Hydrocarbon Source Rock ◽  
Petroleum Potential ◽  
Northern Margin ◽  
Geochemical Parameters ◽  
Study Sites

AbstractDiatomaceous sediments are often prolific hydrocarbon source rocks. In the Paratethys area, diatomaceous rocks are widespread in the Oligo-Miocene strata. Diatomites from three locations, Szurdokpüspöki (Hungary) and Limberg and Parisdorf (Austria), were selected for this study, together with core materials from rocks underlying diatomites in the Limberg area. Bulk geochemical parameters (total organic carbon [TOC], carbonate and sulphur contents and hydrogen index [HI]) were determined for a total of 44 samples in order to study their petroleum potential. Additionally, 24 samples were prepared to investigate diatom assemblages.The middle Miocene diatomite from Szurdokpüspöki (Pannonian Basin) formed in a restricted basin near a volcanic silica source. The diatom-rich succession is separated by a rhyolitic tuff into a lower non-marine and an upper marine layer. An approximately 12-m thick interval in the lower part has been investigated. It contains carbonate-rich diatomaceous rocks with a fair to good oil potential (average TOC: 1.28% wt.; HI: 178 to 723 mg HC/g TOC) in its lower part and carbonate-free sediments without oil potential in its upper part (average TOC: 0.14% wt.). The composition of the well-preserved diatom flora supports a near-shore brackish environment. The studied succession is thermally immature. If mature, the carbonate-rich part of the succession may generate about 0.25 tons of hydrocarbons per square meter. The diatomaceous Limberg Member of the lower Miocene Zellerndorf Formation reflects upwelling along the northern margin of the Alpine-Carpathian Foreland. TOC contents are very low (average TOC: 0.13% wt.) and demonstrate that the Limberg Member is a very poor source rock. The same is true for the underlying and over-lying rocks of the Zellerndorf Formation (average TOC: 0.78% wt.). Diatom preservation was found to differ considerably between the study sites. The Szurdokpüspöki section is characterised by excellent diatom preservation, while the diatom valves from Parisdorf/Limberg are highly broken. One reason for this contrast could be the different depositional environments. Volcanic input is also likely to have contributed to the excellent diatom preservation in Szurdokpüspöki. In contrast, high-energy upwelling currents and wave action may have contributed to the poor diatom preservation in Parisdorf. The hydrocarbon potential of diatomaceous rocks of Oligocene (Chert Member; Western Carpathians) and Miocene ages (Groisenbach Member, Aflenz Basin; Kozakhurian sediments, Kaliakra canyon of the western Black Sea) has been studied previously. The comparison shows that diatomaceous rocks deposited in similar depositional settings may hold largely varying petroleum potential and that the petroleum potential is mainly controlled by local factors. For example, both the Kozakhurian sediments and the Limberg Member accumulated in upwelling environments but differ greatly in source rock potential. Moreover, the petroleum potential of the Szurdokpüspöki diatomite, the Chert Member and the Groisenbach Member differs greatly, although all units are deposited in silled basins.

scholarly journals Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1023
Author(s):  
Hyojong Lee ◽  
Min Gyu Kwon ◽  
Seungwon Shin ◽  
Hyeongseong Cho ◽  
Jong-Sun Kim ◽  
...  
Keyword(s):  
Continental Margin ◽  
Detrital Zircon ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Bulk Rock ◽  
Zircon Age ◽  
Margin Setting ◽  
Weathering Intensity

Zircon U-Pb geochronology and bulk-rock geochemistry analyses were carried out to investigate their relationship with depositional environments of the non-marine Neungju Basin sediments in South Korea. The Neungju Basin was formed in an active continental margin setting during the Late Cretaceous with associated volcanism. Detrital zircon age distributions of the Neungju Basin reveal that the source rocks surrounding the basin supplied sediments into the basin from all directions, making different zircon age populations according to the depositional environments. Mudstone geochemistry with support of detrital zircon U-Pb age data reveals how the heterogeneity affects the geochemical characteristics of tectonic setting and weathering intensity. The sediments in the proximal (alluvial fan to sandflat) and distal (playa lake) environments differ compositionally because sediment mixing occurred exclusively in the distal environment. The proximal deposits show a passive margin signature, reflecting their derivation from the adjacent metamorphic and granitic basement rocks. The distal deposits properly indicate an active continental margin setting due to the additional supply of reworked volcaniclastic sediments. The proximal deposits indicate a minor degree of chemical weathering corresponding to fossil and sedimentological records of the basin, whereas the distal deposits show lower weathering intensity by reworking of unaltered volcaniclastic detritus from unstable volcanic and volcaniclastic terranes. Overall, this study highlights that compositional data obtained from a specific location and depositional environments may not describe the overall characteristic of the basin.

scholarly journals Preservational, paleoecological, and evolutionary patterns in the Wyoming-Montana Paleogene and Siwalik Neogene records

1992 ◽  
Vol 6 ◽  
pp. 13-13
Author(s):  
Catherine Badgley ◽  
Anna Kay Behrensmeyer ◽  
William S. Bartels ◽  
Thomas M. Bown
Keyword(s):  
Spatial Distribution ◽  
Species Richness ◽  
Fossil Record ◽  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Depositional Environments ◽  
Taxonomic Resolution ◽  
Faunal Composition ◽  
Faunal Turnover ◽  
Historical Series

The Paleocene to early Eocene sequence of Wyoming-Montana and the Miocene to Pleistocene Siwalik record of Pakistan are exceptionally long, continental sequences, each containing a rich and well documented fossil record, especially of mammals. The two sequences are broadly similar in tectonic setting and sedimentary environment, in duration and facies changes, and in diversity of fossils. Each contains a paleoclimatic record in stable isotopes and, in the Paleogene, floras. Comparison of these two sequences has focused our attention on the interaction of tectonic, climatic, sedimentologic, and taphonomic factors that produce a particular fossil record and on the co-occurring ecological and evolutionary changes that result in a historical series of biotas, each the product of local and global events.In the Paleogene record, the geographic scope of the record encompasses much of the floodbasin, and the spatial distribution of paleoenvironments formed fairly straightforward gradients from channel to distal floodplain. The Siwalik record has a smaller window onto a larger, heterogeneous fluvial system often with multiple, contemporaneous river systems that differ in magnitude. The spatial distribution of paleoenvironments was a mosaic without long proximal to distal gradients. In both records, major facies changes are correlated with striking changes in fossil productivity.The overall pattern of fossil preservation by depositional environment differs substantially in the two areas. The Siwalik sequence has a greater variety of depositional environments that produce fossils throughout the section. The primary productive environment in the older part of the Paleocene record declined in productivity upsection, while a previously unproductive facies became the major source of fossils. Much of the record represents attritional accumulation in each area, but a significant portion is transported. The taphonomic processes that created fossil concentrations led to better taxonomic resolution for most Paleogene localities than in most Siwalik localities.In each record, both aquatic and terrestrial components of the vertebrate faunas are correlated with facies. Since facies varied in productivity over time, some changes in faunal composition may have resulted from change in the prevalence or productivity of particular facies. At least one faunal turnover coincided with major facies changes in each sequence.For mammals in each record, immigration rather than speciation in situ was the primary means of appearance of new species. Episodes of immigration were not closely followed by extinctions of resident species. Mean species longevity appears to have been more than twice as great in the Neogene than in the Paleogene record. Changes in faunal composition and species richness occurred during times of global climatic change; causal connections are still being explored. Changes in species richness did not track changes in relative abundance of taxa or changes in size within lineages or faunas. In terms of guild structure, the herbivore guild had high relative generic diversity through most of both sequences. The Paleogene record had a more even distribution of taxa in the five principal guilds, while the Siwalik record was heavily dominated by the herbivore guild. Size distributions differed substantially, reflecting the early and late windows into the mammalian radiation, rather than sampling bias.

Reassessment of the Mesozoic metasedimentary rocks and tectonic setting of Taiwan and the adjacent continental margin of eastern Asia

2016 ◽  
Vol 154 (5) ◽  
pp. 1127-1154 ◽  
Author(s):  
YU WANG ◽  
CHIN-HO TSAI ◽  
LIYUN ZHOU ◽  
YAN QIU ◽  
GUIHUA SUN
Keyword(s):  
Continental Margin ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Crystalline Basement ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Metamorphic Belt ◽  
Late Mesozoic ◽  
Sedimentary Sequences ◽  
Se China

AbstractIt remains unclear whether a crystalline basement exists in SE China (including Taiwan), whether the formation of the Tananao metamorphic belt in Taiwan was linked to subduction of the Palaeo-Pacific Plate, and whether the source rocks of the sedimentary sequences in the metamorphic belts are late Mesozoic or Palaeozoic in age. Field investigations and zircon age data in the present study indicate that there is no pre-Palaeozoic gneiss (crystalline basement) in Taiwan (although orthogneisses were produced during deformation and metamorphism of Mesozoic granites), and investigations of the metasediments show that the sedimentary sequences in the Tailuko and Yuli belts are similar. Moreover, LA-ICP-MS dating of detrital zircons from the Pingtan–Dongshan belt in Fujian Province yields a cluster of 206Pb–238U ages at ~ 210–190 Ma, and the Tailuko and Yuli belts in Taiwan have similar clusters of detrital zircon ages at 200 Ma, 160 Ma, 120 Ma and 110 Ma, as well as a later overprinting caused by arc–continent collision. The cathodoluminescence images and trace-element characteristics of the zircons show that they were originally magmatic in origin. This finding, combined with the Hf isotope data, indicates that the sources of sediments in the Tananao belt (Tailuko and Yuli belts) were relatively close to an active continental margin, and that both the Tailuko and Yuli belts have similar sedimentary sources. From the margin of the Chinese mainland to Taiwan, the metasediments seem to represent a continuous sequence of deposits ranging in age from Jurassic to Cretaceous, but with the sediments becoming progressively younger towards the east. It can be inferred that the sediments in the Tailuko and Yuli belts were continental-shelf sequences with sources in SE China.

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