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2018 Vol.  7 No.  1
Published: 2018-02-01

Biopalaeogeography and palaeoecology
Lithofacies palaeogeography and sedimentology
Tectonopalaeogeography and palaeotectonics
Biopalaeogeography and palaeoecology
1 Late Triassic sauropodomorph and Middle Jurassic theropod tracks from the Xichang Basin, Sichuan Province, southwestern China: First report of the ichnogenus Carmelopodus
Li-Da Xing, Jin Ba, Martin G. Lockley, Hendrik Klein, Sheng-Wu Yan, Anthony Romilio, Chun-Yong Chou, W. Scott Persons IV
Upper Triassic and Middle Jurassic strata of the Xichang Basin in Sichuan Province, southwestern China, yielded important dinosaur ichnofossils. From the Xujiahe Formation of the Yiguojiao tracksite, we report a Late Triassic footprint assemblage in China and the first discovery of diagnostic Triassic sauropodomorph tracks in this region. The tracks share a number of features in common with the ichnogenera Eosauropus (Late Triassic) and Liujianpus (Early Jurassic). The neighboring Bingtu tracksite is stratigraphically younger (Shaximiao Formation, Middle Jurassic) and preserves small tridactyl theropod tracks that represent the first occurrence of the ichnotaxon Carmelopodus in China and Asia. While these tracks are morphologically comparable to those from the Middle Jurassic type locality in North America, the specimens from China show the proximal margin of the digit IV impression in a more cranial position, which may indicate a trackmaker with a relatively short metatarsal IV. In addition to the skeletal record, the Carmelopodus footprints document the presence of small theropods in the dinosaur fauna of the Middle Jurassic Shaximiao Formation.
2018 Vol. 7 (1): 1-13 [Abstract] ( 232 ) [HTML 1KB] PDF (2870 KB)   ( 52 )
14 Trace fossils of an amalgamated storm-bed succession from the Jurassic of the Kachchh Basin, India: The significance of time-averaging in ichnology
Franz T. Fürsich, Alfred Uchman, Matthias Alberti, Dhirendra K. Pandey
The uppermost part of the Upper Bathonian Sponge Limestone member, Patcham Formation, of the Jhura Dome of Kachchh Mainland is a thickening- and shallowing-upward succession topped by medium- to thick-bedded hummocky cross-stratified grainstones deposited by storm waves. Occasionally, thin, commonly lenticular, intraclastic-bioclastic silty marl intercalations between the grainstones are highly bioturbated, in contrast to the grainstones, in which, for the most part, trace fossils occur scattered. Large exposures of bedding planes of the grainstones allow the detailed investigation of ichnological features, whereas the high density of traces in the soft marls precludes the identification of any ichnotaxa. Eighteen ichnotaxa have been recorded including Ophiomorpha, Thalassinoides, Taenidium, Gyrophyllites, Chondrites, Dactyloidites, Teichichnus, Bolonia, and Ancorichnus. Except for Ophiomorpha nodosa and Thalassinoides, which generally indicate moderate to high energy conditions and are the dwelling burrows of suspension-feeding to omnivorous crustaceans, the ichnotaxa represent a deposit-feeding behaviour of their producers and thus are characteristic of low-energy environments. The trace fossils form three ichnoassemblages characterized by (1) Ophiomorpha nodosa and Thalassinoides suevicus, (2) ?Thalassinoides isp. A, Taenidium, and Bolonia lata, and (3) Ancorichnus. The dominance of traces of deposit-feeders in rocks indicative of high-energy events is counterintuitive and points to their non-contemporaneity. The sediments were deposited during brief high-energy events, whereas the trace fossils were produced when, after waning of storms low-energy conditions prevailed. This time-averaging is particularly pronounced in trace fossils that extend vertically downwards and may reach strata deposited under distinctly different conditions. Thus, environmental interpretations based on trace fossils should refer to colonisation surfaces rather than to the sediment surrounding the trace fossils. In the latter case, interpretations may be erroneous, especially when erosion subsequently destroyed sedimentary evidence of their original environment.
2018 Vol. 7 (1): 14-31 [Abstract] ( 170 ) [HTML 1KB] PDF (7339 KB)   ( 48 )
32 Oxygenation in carbonate microbialites and associated facies after the end-Permian mass extinction: Problems and potential solutions
Stephen Kershaw, Hao Tang, Yue Li, Li Guo

Carbonate sediments deposited in normally-oxygenated shallow ocean waters of the latest Permian period, immediately prior to the end-Permian mass extinction, contain well-developed diverse shelly faunas. After the extinction of these skeletal metazoans, the sediments commonly comprise microbialites (regarded by most authors as benthic) and associated facies bearing evidence interpreted by many authors to indicate reduced oxygenation of the shallow ocean waters. However, the evidence of oxygenation state is inconsistent and the sequences have gaps, indicated in the following 5 points:
1) Shelly fossils occur commonly in post-extinction shallow marine limestones, and likely to have been aerated in contact with the atmosphere. Nevertheless, although the largest mass extinction in Earth history may have caused reduced body size in shelly organisms, such reduction is arguably due to environmental stress of lowered oxygenation. Discriminating between these controls remains a challenge.
2) Abundant pyrite framboids in many post-extinction limestones are interpreted by several authors as indicating dysoxic contemporaneous waters, so the organisms that lived there, now shelly fossils, were dysaerobic. However, verification is problematic because pyrite framboids scattered amongst shelly fossils cannot have formed amongst living organisms, which need at least some oxygen; synsedimentary framboid formation requires anoxic conditions in the redox boundary where sulphate-reducing processes work. Thus, framboids and shelly fossils found together means taphonomic mixing of sediments, destroying original depositional relationships so that it is not possible to determine whether the shells were aerobic or dysaerobic prior to sediment mixing. Furthermore, diagenetic growth of framboids is possible, as is import of previously-formed framboids from deeper water during upwelling. Thus, there is no proof of an environmental link between framboid size and occurrence, and contemporaneous oxygenation in these post-extinction shallow water facies, so we question the validity of this model in those facies, but consider that the model is valid for deeper water facies.
3) Some publications provide evidence of oxygenation, from redox-sensitive elements in post-extinction limestones, while others indicate low oxygen conditions. Redox-sensitive geochemistry requires further work to explore this issue at higher resolution of sampling than has been so far applied.
4) Biomarkers recorded in some post-extinction facies contain evidence of anoxic conditions (including green sulphur bacteria) but other examples lack these, which may be indicate fluctuations of water oxygenation. However, a key issue that has not yet been resolved is determination of whether biomarkers were imported into the sites of deposition, for example by upwelling currents, or formed where they are found. Thus, there is currently no verification that biomarkers of low oxygen organisms in shallow water settings actually formed in the places where they are sampled.
5) The common occurrence of small erosion surfaces and stylolites represents loss of evidence, and must be accounted for in future studies.
The oxygenation state of post-end-Permian extinction shallow marine facies continues to present a challenge of interpretation, and requires high-resolution sampling and careful attention to small-scale changes, as well as loss of rock through pressure solution, as the next step to resolve the issue.

2018 Vol. 7 (1): 32-47 [Abstract] ( 159 ) [HTML 1KB] PDF (5629 KB)   ( 42 )
48 Evolution of sedimentary facies and fossil communities in the Middle Permian Maokou Formation in Zigui County, Hubei Province, South China
Ke-Yu Zhu, Tan Wang, Zhi-Xing Yi, Yong-Biao Wang
A geological event that happened at the end of the Middle Permian resulted in different levels of erosion in a shallow-water platform of South China, which led to diverse geological records in different sections. The Lianziya section in western Hubei Province of South China has a well-exposed stratigraphic sequence of the late Middle Permian rocks with abundant fossils and sedimentary facies types, providing new evidences for understanding the evolution of marine biota and environment in the late Middle Permian. Our study shows that four fossil communities can be recognized with the change of sedimentary facies in the late Middle Permian: Foraminiferal-algal community, phylloid algal community, bryozoan community and Ungdarella community. The foraminiferal-algal community is dominated by fusulinids and calcareous algae, but was soon replaced by the phylloid algal community. With an increase of terrestrial input, the phylloid algal community was again replaced by the bryozoan community. Near the end of the Middle Permian, with a decrease of terrestrial input, the bryozoan fossil community disappeared while the Ungdarella community became dominant. A 10 cm-thick weathered crust occurred at the top of the Middle Permian limestone, marking a large amplitude fall in sea-level and the beginning of a terrestrial erosion stage. The sedimentary facies and fossil community changes in the Lianziya section indicates that the Middle Permian crisis was a gradual process while the sea-level fall mainly occurred in the latest Middle Permian.
2018 Vol. 7 (1): 48-57 [Abstract] ( 213 ) [HTML 1KB] PDF (4854 KB)   ( 50 )
58 A redescription of the ichnospecies Koreanaornis anhuiensis (Aves) from the Lower Cretaceous Qiuzhuang Formation at Mingguang City, Anhui Province, China
Li-Da Xing, Yuan-Chao Hu, Jian-Dong Huang, Qing He, Martin G. Lockley, Michael E. Burns, Jun Fang

The Cretaceous bird trackway originally labelled Aquatilavipes anhuiensis, in 1994, had previously been examined, photographed and replicated, but never described or illustrated in detail. However, it has been part of a widening discussion about the distribution of Aquatilavipes and Koreanaornis in China (and Korea). Here we illustrate and formally describe the holotype in detail and assign it to Koreanaornis (K. anhuiensis) as informally proposed by previous authors. We also demonstrate that most authenticated reports of Koreanaornis, including the Anhui occurrence, are from the Lower Cretaceous, not from the Upper Cretaceous as previously reported.

2018 Vol. 7 (1): 58-65 [Abstract] ( 255 ) [HTML 1KB] PDF (1548 KB)   ( 30 )
Lithofacies palaeogeography and sedimentology
66 Geologic-seismic models, prediction of shaol-water lacustrine delta sandbody and hydrocarbon accumulation significance in the Late Miocene, Huanghekou Sag, Bohai Bay Basin, northern China
Hao Liu, Qing-Long Xia, Xin-Huai Zhou

The Huanghekou Sag is located in the southeast part of the Bohai Bay Basin, northern China. Large-scale shallow lake delta developed in the Neogene provided suitable geological conditions for the formation of subtle oil-gas reservoirs in this area. The key for analyzing sandstone reservoir and sedimentary facies is by using seismic attributes (amplitude) to establish the relationship between lithology combination and seismic attributes. The lower unit of Late Miocene Minghuazhen Formationat of BZ34 block in the Huanghekou Sag was subdivided into 10 parasequence sets (PSS). Thicker sandstones mainly occurred in PSS1 and PSS10, whereas thin sandstones were mostly observed within other parasequence sets. Based on statistics and analyses of lithology, i.e., statistics of root-mean-square (RMS) amplitude and lithology of well locations in different parasequence sets of the study area, as well as 1-D forward seismic models of 7 types of lithology combinations, the establishment of a spatial distribution of 2-D sandbody, forward seismic models etc., we found that high amplitude peaks correspond to thicker sandbodies, while low amplitude indicates non-development of sandbodies (generally less than 2 m), and medium amplitude agrees well with large sets of mudstones interbedded with medium and thinner sandstones. Different sand-mudstone combinations genetically reflect a combination of multiple micro-facies, therefore, amplitude features can predict sandbodies as well as facies characteristics.

2018 Vol. 7 (1): 66-87 [Abstract] ( 150 ) [HTML 1KB] PDF (13797 KB)   ( 44 )
Tectonopalaeogeography and palaeotectonics
88 Deeply concealed half-graben at the SW margin of the East European Craton (SE Poland) — Evidence for Neoproterozoic rifting prior to the break-up of Rodinia
P. Krzywiec, P. Poprawa, M. Mikołajczak, S. Mazur, M. Malinowski

Baltica was one of continents formed as a result of Rodinia break-up 850-550 Ma. It was separated from Amazonia (?) by the Tornquist Ocean, the opening of which was preceded by Neoproterozoic extension in a network of continental rifts. Some of these rifts were subsequently aborted whereas the Tornquist Rift gave rise to splitting of Rodinia and formation of the Tornquist Ocean. The results of 1-D subsidence analysis at the fossil passive margin of Baltica provided insight in the timing and kinematics of continental rifting that led to break-up of Rodinia. Rifting was associated with Neoproterozoic syn-rift subsidence accompanied by deposition of continental coarse-grained sediments and emplacement of continental basalts. Transition from a syn-rift to post-rift phase in the latest Ediacaran to earliest early Cambrian was concomitant with deposition of continental conglomerates and arkoses, laterally passing into mudstones. An extensional scenario of the break-up of Rodinia along the Tornquist Rift is based on the character of tectonic subsidence curves, evolution of syn-rift and post-rift depocenters in time, as well as geochemistry and geochronology of the syn-rift volcanics. Itisadditionally reinforced by the high-quality deep seismic reflection data from SE Poland, located above the SW edge of the East European Craton. The seismic data allowed for identification of a deeply buried (11-18 km), well-preserved extensional half-graben, developed in the Palaeoproterozoic crystalline basement and filled with a Neoproterozoic syn-rift volcano-sedimentary succession. The results of depth-to-basement study based on integration of seismic and gravity data show the distribution of local NE-SW elongated Neoproterozoic depocenters within the SW slope of the East European Craton. Furthermore, they document the rapid south-eastwards thickness increase of the Neoproterozoic succession towards the NW-SE oriented craton margin. This provides evidencefor extensive crustal thinning occurring prior to the break-up of Rodinia and formation of the Tornquist Ocean.

2018 Vol. 7 (1): 88-97 [Abstract] ( 180 ) [HTML 1KB] PDF (3178 KB)   ( 35 )
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