Home  |  About JOP  |  Editorial Committee  |  Subscription  |  Message  |  Meetings  |  Call for Papers  |  Contact

For Reviewer   Review Policy   Reviewer Login   EC Member Login   Editorial Office Login   Editor-in-Chief Login   Online First   Current Issue   Archive   Advanced Search   Most Read   Most Download   Free Email Alert   RSS

Current Issue   2014 Vol.  3 No.  3 Published: 2014-07-07 Biopalaeogeography and palaeoecology Lithofacies palaeogeography and sedimentology Geochemistry and sedimentary environment Lithofacies palaeogeography and sedimentology 233 Siliciclastic-carbonate mixing modes in the river-mouth bar palaeogeography of the Upper Cretaceous Garudamangalam Sandstone (Ariyalur, India) Subir Sarkar, Nivedita Chakraborty, Anudeb Mandal, Santanu Banerjee, Pradip K. Bose Mixed siliciclastic-carbonate rocks constitute the Upper Cretaceous Garudamangalam Sandstone Formation, Ariyalur (India), and offer an opportunity to look into the broad spectrum of mixing of compositionally and genetically different components. The palaeogeographic reconstruction indicates that deposition in the nearshore zone differed strongly in energy and active processes operatives due to the presence of a shore-parallel river-mouth bar. The western wing of the Mississippi bird-foot delta is considered to be a present-day analogon. Facies analysis in combination with petrography clearly shows the variability in palaeoenvironmental characteristics, both biogenic and non-biogenic. It also indicates diagenetic uptake of carbonate that filled empty spaces and actively replaced original components. Chemical staining followed by limited application of cathodoluminescence and energy dispersive X-ray analysis (EDAX) hint at intricacies in mixing arising from the compositional variations in the carbonate components. A model of siliciclastic-carbonate sediment mixing, including both the depositional and diagenetic developments, is presented; it is aimed at generating a better overview of, and a deeper insight into, the physical and chemical mechanisms involved. 2014 Vol. 3 (3): 233-256 [Abstract] ( 2090 ) [HTML 1KB] PDF (13892 KB)   ( 465 ) 257 Evolution regularity of the Neogene shallow water delta in the Laibei area, Bohai Bay Basin, northern China Jian-Ping Li, Hao Liu, Cheng-Min Niu, Rui-Bo Guo According to the characteristics of sedimentary microfacies, unique vertical depositional sequences and well logging response, the authors propose that a shallow water delta was widely developed in the Neogene of the Laibei area, Bohai Bay Basin of northern China. Based on seismic minimum amplitude slices, well logging data, test analytical data and so forth, detailed research on the evolution of the shallow water delta of the Neogene Lower Member of Minghuazhen Formation was conducted. The results indicate that the third-order sequence base level controls sandbody types. During a period of low base level, a distributary channel sandbody of shallow water deltaic plain was developed. With base level rising, the sandbody type gradually changed into a subaqueous distributary channel sandbody and a sheet sand can be found as well. The fourth-order sequence base level controls medium-short term evolution of the sandbody. Within a sequence, due to the rising and falling of base level, the sandbody assemblages are identified as an upward-coarsening type, an upward-fining and a compound type respectively. Regionally, from the Laibei Low Uplift to the Huanghekou Sag, the shallow water delta evoluted from a dendritic shape, to a cuspate shape and finally to a sheet shape. 2014 Vol. 3 (3): 257-269 [Abstract] ( 1496 ) [HTML 1KB] PDF (33243 KB)   ( 224 ) 270 Palaeogeography, palaeohydraulics and palaeoclimate of the Mio-Pliocene Siwalik Group, eastern India Sunipa Mandal, Subir Sarkar, Nivedita Chakraborty, Pradip K. Bose South-southwestward palaeocurrent swerved to east-southeast and then broadly to southeast over the transition from alluvial fan to axial channel and then to the flood plain in the Mio-Pliocene foreland system within which the Siwalik Group depositd in Darjeeling-Jalpaiguri Districts, eastern India. Palaeocurrent pattern is found to be multi-modal on the fans, virtually unimodal on the axial channel zone and again multi-modal, more profoundly, on the flood plain. Coarse siliciclastic mass-flows were progressively eliminated and gave way to predominant bed-load transport downfan and the axial river, and then to suspension-load dominance in fine siliciclastics on the flood plain. Distal flood plain lacustrine sediment included most of the coals and the entire bulk of the dolomitic limestone. Further resolution in palaeogeography within the frame of aforementioned foursome facies associations is elicited in twenty-six distinctive facies altogether. Critical evaluation of chemical indices (CIA, CIW, ICV, PIA, as well as Rb/Sr ratio) for weathering and depleted δ18O values indicate a high precipitation rate. The contention is further corroborated by the high discharge rate calculated from cross-set thicknesses within the main channel deposits. Reconciliation of various relevant data sets collected or calculated from all known worksites along the entire 2000 km-long exposure belt of the Siwaliks along the Himalayan foothills reveal confluence of two tributaries, one from the west and the other from the east, close to the present study area before escaping onto the Indian plains. Channel parameters, channel-belt width and discharge thus attained maxima in the present study area. The precipitation rate and temperature increased eastward overall as a prelude to the modern trend in this regard. 13C enrichment indicates that the transition from C3 to C4 vegetation had already set in. 2014 Vol. 3 (3): 270-296 [Abstract] ( 2349 ) [HTML 1KB] PDF (37745 KB)   ( 267 ) 297 Clay minerals in the Pliocene-Quaternary sediments of the southern Yangtze coast, China: Sediment sources and palaeoclimate implications Jing Chen, Zhang-Hua Wang, Tao-Yuan Wei, Bao-Cheng Zhao, Zhong-Yuan Chen Clay mineralogy was used as an indicator of the sediment source and prevailing climate and five suites (I-V) were identified throughout the borehole. Smectite was dominant in the bottom suite of the borehole, indicating the sediment was mainly derived from the local basalt when the study area stood as uplands during the Pliocene. The sharp reduction of smectite in suites II and III (Early Pleistocene) reflects a broader sediment provenance due to neo-tectonic subsidence of the study area. Significant climate fluctuations are indicated by distinct variations in the ratios of illite versus smectite and kaolinite, and by the illite crystallinity in suites II and IV. Especially the suite IV, which forms mottled muddy sediments that underwent pedogenesis, possibly represents glacial/interglacial cycles during the Mid-Pleistocene climate transition (MPT). The rare presence of smectite in suite V which formed during the Late Quaternary suggests a significant contribution of fine-grained sediment derived from the upstream of the Yangtze catchment. Such changes in sediment sources are consistent with the evolution of regional sedimentary environments, which evolved towards an open coast/deltaic setting and imply that the study area became the depositional basin of the Yangtze fine-grained sediment due to the final submergence of the Wu-Nan-Sha and Fukien-Reinan Massifs since the Late Quaternary. 2014 Vol. 3 (3): 297-308 [Abstract] ( 1490 ) [HTML 1KB] PDF (3976 KB)   ( 273 ) Geochemistry and sedimentary environment 309 Coevality of the sea-level fall and main mass extinction in the Permian-Triassic transition in Xiushui, Jiangxi Province, southern China Ya-Sheng Wu, Xiao-Hong Yuan, Hong-Xia Jiang, Li-Jing Liu A continuous Permian-Triassic boundary (PTB) section has been found and studied for the first time in Xiushui, Jiangxi Province, South China. Evidence for a large sea-level fall has been found in the horizon of 0.8 m below the PTB, from the beginning of Hindeodus changxingensis zone (correlatable to Hindeodus typicalis Zone of the Meishan section). Sedimentary record indicates that the sea level kept at lowstand, or occasionally rose slowly during the whole Hindeodus parvus zone, except another substantial sea-level fall in early H. parvus zone. It began a quick rise from the beginning of Isarcicella staeschei zone, kept rising for the whole I. staeschei zone, and probably caused the stagnation of sea water. The first severe change in the biota, marked by the sudden disappearance of all stenotropic organisms such as fusulinids and dasycladacians, happened at the same time as the first sea-level fall, and is regarded as the first and main episode of the end-Permian mass extinction in this area. A microbe-dominated biota followed the first extinction, and spanned the late H. changxingensis zone and the whole H. parvus zone. All the microbes and some other eurytropic organisms including gastropods and ostracods disappeared at the end of the H. parvus zone, and the following biota in the I. staeschei zone is very simple. The coevality of the main sea-level fall and the main extinction episode might be causal: both of them might be caused by a drastic climatic cooling. 2014 Vol. 3 (3): 309-322 [Abstract] ( 1561 ) [HTML 1KB] PDF (24317 KB)   ( 221 ) Biopalaeogeography and palaeoecology 323 Late Miocene wood flora associated with the Yuanmou hominoid fauna from Yunnan, southwestern China and its palaeoenvironmental implication Ye-Ming Cheng, Yu-Fei Wang, Cheng-Sen Li The Upper Miocene Xiaohe Formation of the Yuanmou Basin in Yunnan Province, southwestern China, is famous for its hominoid fauna and is important for studying the Late Cenozoic human and mammal evolution. Abundant fossil wood was found associated with this fauna, which provided important evidence for palaeoenvironmental reconstruction of the basin. Among the fossil wood, two different taxa have been identified namely, Quercoxylon sp. (Fagaceae) and Pterocarya sp. (Juglandaceae). Based on the habitats of their Nearest Living Relatives (NRLs), it is suggested that upland subtropical evergreen broad-leaved forest dominated by Quercus/Lithocarpus was common around the basin, while a lowland deciduous broad-leaved forest dominated by Pterocarya was present on the river bank of the basin during the Late Miocene. 2014 Vol. 3 (3): 323-330 [Abstract] ( 1572 ) [HTML 1KB] PDF (7440 KB)   ( 254 )

Copyright © 2014 JOURNAL OF PALAEOGEOGRAPHY Editorial Office of Journal of Palaeogeography, 20 Xueyuan Road, P. O. Box 902, Beijing 100083, China Tel: +86-10-62394320; +86–10–62396149     Email: Jpalaeo2012@163.com