Wan, X., Scott, R., Chen, W., Gao, L. & Zhang, Y. 2011: Early Cretaceous stratigraphy and SHRIMP U‐Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet. Lethaia, Vol. 44, pp. 231–244. The Late Jurassic to the Early Cretaceous marine strata are extensively distributed in southern Tibet. In Gyangze, the strata are divided into the Weimei and Jiabula formations. In Nagarze, they are divided into the Weimei and Sangxiu formations. Previous work has reported diverse ammonite species of Haplophylloceras and Himalayites in the Weimei Formation, and a few species of Spiticeras in the lower Jiabula and Sangxiu formations. The present study has found the bivalve Inoceramus and nannofossil assemblages in the lower Jiabula and Sangxiu formations. The nannofossil assemblage of Nannoconus steimannii steinmannii, N. steinmannii minor and Watznaueria barnesae indicates Berriasian age, and the Calcicalathina oblongata–Speetonia colligata assemblage is Valanginian in age. Numerical ages for the Jiabula and Jiabula‐goukou sections in Gyangze have been interpolated by comparing the fossil ranges with ages calibrated in other sections. The correlation experiment plots fossil ranges in the two sections to the CRET1 Database. The estimated rate of sediment accumulation of the lower Sangxiu Formation is 22.6 m/myr. The Jurassic–Cretaceous (J/K) boundary is at the bottom of the Jiabula Formation in Gyangze, and the base of the Sangxiu Formation in Nagarze. The boundary is marked by the appearance of the ammonite Spiticeras and the nannofossil assemblage of Nannoconus st. steinmannii–N. st. minor–Watznaueria barnesae. The radiometric age in Tibet is the first to be integrated with upper Valanginian fossils. The volcanic rocks of the upper Sangxiu Formation are dated at 136 ± 3.0 Ma deduced from zircon SHRIMP age of rhyolite. By consideration of the rate of sediment accumulation of the underlying sedimentary deposits, the J/K boundary in the Gyangze–Nagarze area is approximately 145 Ma as suggested by the newly issued International Stratigraphic Chart, and the Valanginian/Hauterivian boundary lies between 134 Ma and 136 Ma. □ Biostratigraphy, graphic plot, Jurassic/Cretaceous boundary, nannofossil, SHRIMP U‐Pb age, Southern Tibet, Valanginian/Hauterivian boundary.
The Cretaceous/Tertiary boundary in the Gamba and Tingri regions of Tibet occurs between the Zongshan and Jidula Formations. Arenaceous facies similar to those of the Jidula Formation are widespread in Tibet and Pakistan; collectively, these represen! the diachronous deposits of the Latest Cretaceous-Early Tertiary regression. Major faunal changes took place in Tibet during the Late Cretaceous. Ali of the Cretaceous ammonoids, planktonic and benthonic foraminifera, rudistid and inoceramid bivalves became extinct over the Campanian Maastrichtian interval in a stepwise patte rn, with abrupt Late Campanian and Late Maastrichtian extinction events (Tabs. 3, 4). A large number of new laxa appeared during the Danian (Tabs. 3, 4). These fa una! changes in the shallow-water marine facies of Tibet demonstrate that this region was not isolated from major global fauna l changes taking place in the Cretaceous/Tertiary boundary mass extinction inte rval.
<p>A series of ICDP deep boreholes of SK1), SK2 and SK3 have been drilled in the Songliao Basin of NE China during 2006 to 2021. The deepest and the most attractive SK2 is with bottom depth of 7108m and super long Continuous coring footage of 4380m. With the long-term working process, we have some special experiences that may be useful to others. The first is that ICDP financial support may cover only a small part of the total cost. But the fishing effect is crucial. That is to say, when we are trying to get financial support, the most important thing above all is generally the reason why do we want to spend the money for. Because of its widely accepted peer review international level program, ICDP funding ,no matter big or small, can always give us strong and convictive argument for the money usage, especially when we are trying to get funded from government organizations and/or companies those are interested in high level research of global aspects. The second is that an ICDP project can be forward in different ways. A step by step procedure is also a very functional way. For example, at the beginning of our ICDP long marching, we got ICDP technical support when we worked on SK1 in 2006. This turned to a key step for the following procedure. Three years later in 2009, we got ICDP funded. The third is that drilling and coring are costly. We may save a lot of money if we can combine ICDP pure research of global aspects with local industry interests. Petroleum companies related to the Songliao Basin kindly provided us all the available data including well-logs, core samples and 3D-seismic data for free. So that, we did not spend any money for the pre-drilling research. And more so, based on these precise data we got very good prediction of the subsurface stratigraphic sections we may meet while drilling, which are very important information for the plans of drilling engineering.</p><p>Why we want to drill the deep boreholes of the SK2 coupled with SK1 and SK3.</p><p>At first, we hope to obtain a continuous and complete Cretaceous terrestrial coring succession. Situated on the eastern margin of the Eurasian Plate, the Songliao Basin accumulated the most continuous and the highest resolution geological records of Cretaceous terrestrial sedimentary-volcanic successions in the world. The whole Cretaceous sequence is over 10km thick.</p><p>Secondly, we hope to establish a high-precision terrestrial stratigraphic framework of the region.</p><p>Thirdly, we hope to study the Cretaceous conditions concerning paleo-environment of the lakes in the Songliao Basin and adjacent areas. At last, research on paleoclimatic aspects in northeastern Asia based on the collected precise lake deposits. And then, According to the knowledge acquired from the global warming process in the Cretaceous in NE Asia, especially during the stages of intense fossil fuel accumulation episodes, we may have the opportunity try to find some similarities to the global warming trend that human being is facing now.</p>
Although the paleoclimate of the marine Cretaceous has been well studied, the paleoclimate of the non-marine is still not well understood. The Songliao Basin was one of the largest non-marine rift basins during Cretaceous. The Well-preserved Cretaceous lacustrine deposits in this basin provide a unique opportunity to study terrestrial paleoenvironments and paleoclimate during the Late Cretaceous. Here, the microfossils from the Late Turonian Qingshankou Formation of the Songliao Basin were used to investigate the paleoenvironments and paleoclimate of east Asia. There are two spore and pollen assemblages recognized: a Cedripites-Cyathidites-Classopollis assemblage from Upper Member 1, and a Cedripites-Cyathidites-Classopollis assemblage from Lower Member 2 of the Qingshankou Formation, respectively. Besides, relatively abundant ostracods have been identified. In the Songliao Basin, the climate was relatively warm and wet during Late Turonian, with good source rock deposited in the Songliao lake.
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