Waagenoperna was a genus of epi-byssate, marine to brackish-water/littoral bivalves. It used to be regarded as Late Permian–Late Triassic in age. However, a review of the genus reveals that it did not occur until the Late Triassic, and in the Early Jurassic some species of Waagenoperna (i.e. W. lilingensis, W. mytiloides and W. cf. lilingensis) had a wide distribution in the areas southwest of the Shanghai–Altay Mountain Range, including parts of southern China. The sediments hosting these bivalves are intercalated with non-marine strata including coal. The geographic and stratigraphic distribution patterns of Waagenoperna can not only aid in the correlation of the non-marine coal-bearing strata, spanning the Triassic–Jurassic transition, and constrain their age, but also particularly demonstrate a history of transgressions, flooding the areas southwest of Shanghai–Altay during the Sinemurian. These extensive transgressions influenced the climate and changed the palaeo-topography of southwestern Shanghai–Altay: they ensured a humid climate and resulted in the formation of marsh and even paralic swamp environments. These environments allowed the flora and fauna to thrive and led to the accumulation of large quantities of organic matter that eventually formed coal and probably oil as well.

Three continuous cores acquired in the Sihetun area of Liaoning Province, famous for feathered non-avian dinosaurs of the Jehol Biota, reveal the stratigraphic and facies relationships of the divisions of the Early Cretaceous Yixian and underlying ?Jurassic-Early Cretaceous Tuchengzi formations. Based on these cores, we propose a modified lithostratigraphic nomenclature in the Sihetun Sub-basin in which the Yixian Formation is divided into three members: the Lujiatun Member, a fluvial and alluvial volcaniclastic sandstone and conglomerate, unconformably overlying the Tuchengzi Formation, with articulated tetrapods plausibly preserved in burrows; the Xiatulaigou Member, an extrusive basaltic flow and breccia comprising the only true lavas in the area; and the Jianshangou Member, a cyclical lacustrine mudstone containing a taphocoenosis of articulated compression fossils with soft tissue preservation including non-avian dinosaurs, birds, pterosaurs, mammals, fish, crustaceans, insects, mollusks, and plants. The latter, is divided into 4 units: the basal Dajianshanzi Bed, a shallow-water lacustrine unit with abundant mollusks and rooted zones; the Anjiagou Bed, the main tetrapod-bearing unit, consisting of microlaminated dark gray mudstones with many interbedded airfall ashes deposited in a meromictic lake; the Hengdaozi Bed comprised of thin and rhythmically to medium bedded light gray to tan mudstones and sandstones with few discrete ashes, famous for its diverse insects and plants, including early angiosperms deposited in alternating dysoxic and oxygenated bottom water; and the Huangbanjigou Bed, the most obviously cyclical of the units, with dark gray microlaminated intervals with articulated vertebrates alternating with more massive lighter colored mudstones and volcaniclastic sandstones deposited in lakes that oscillated in depth. Cyclicity in the Jianshangou Member is dominated by meter-scale cycles that may be paced by orbital variations. Unambiguous, relatively rapid, lateral facies changes within the Yixian Formation are suggestive of local relief, not the bottom of a giant flat-bottomed basin.

Significance Geological records of paleoclimate provide the only constraints on Solar System orbital solutions extending beyond the ∼50-Ma limit imposed by chaotic diffusion. Examples of such constraints are coupled high and low latitude, Triassic–Jurassic (∼198–202 Ma) sedimentary cyclicity in coal-bearing outcrops from the ∼60° N-paleolatitude Junggar Basin (Western China), and contemporaneous tropical basins. Analysis reveals climate variability dominated by obliquity-scale cyclicity in the Junggar Basin and precession-scale cyclicity in the tropics. Together, these geological records empirically constrain orbital solutions by providing joint g4 − g3 and s4 − s3 secular frequency estimates of the Earth–Mars orbital resonance. These results demonstrate the opportunity for developing a new class of solutions grounded by geological data extending hundreds of millions of years into the geologic past.

Pan, Y., Sha, J., Fursich, F.T., Wang, Y., Zhang, X. & Yao, X. 2011: Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation, China: implications of volcanic and climatic factors. Lethaia, Vol. 45, pp. 299314. The taphonomy and palaeoecology of the famous Lower Cretaceous Jehol biota of northeastern China are two of its least resolved aspects. The biota occurs in lacustrine sediments characterized by abundant volcanic ash layers. The general view is that these tuff layers correlate strongly with vertebrate mass mortality events. However, though aquatic invertebrates also suffered mass mortality, in the majority of cases individuals tend to occur on bedding planes of finely laminated sediments, suggesting that each mass mortality event is not related to volcanic activity. Based on data collected in the course of two excavations at Zhangjiagou and Erdaougou, the role of volcanic activity and other factors that could have controlled the dynamics of the fauna were investigated. Cluster analyses of fossil assemblages from both localities show similar results, and eight fossil communities are recognized. In the lacustrine Yixian Formation, frequent and often severe volcanic activity represented by the abundant tuff layers influenced the water quality, causing repeated collapse of the aquatic ecosystem. Bedding planes with remains of the eight different communities were analysed, each recording the community dynamics of a shallow eutrophic lake system that was most probably controlled by fluctuations of oxygen level related to climate. A mortality model, in which oxygen-level fluctuations play the decisive role, is proposed to explain the existence and distribution of the fossil communities, as well as the unfossiliferous layers. ?China, Jehol biota, lacustrine community, mass mortality, palaeoclimate, volcanic activity.

The Early Cretaceous Yixian Formation at Sihetun, Beipiao, western Liaoning, northeastern China, is well-known for yielding diverse and excellently preserved fossils of the Jehol Biota. The lower unit of Yixian Formation, dominated by lacustrine deposits, is rich in concentrations of two freshwater bivalves: Sphaerium anderssoni and Arguniella ventricosa. These bivalve concentrations can be divided into three types that comprise either paucispecific A. vencricosa or S. anderssoni, or both bivalves in similar amounts. The lithological, biotic, and taphonomic features of 12 bivalve concentrations are recorded, and the taphonomic signatures (such as shell articulation, size-frequency distribution, and orientation) are analyzed. Autochthonous as opposed to allochthonous bivalve concentrations are discriminated. A very short time-averaging effect is recognized in some concentrations, which was probably caused by seasonal or episodic water-level fluctuations and hypoxia. Three factors operated on the bivalve concentrations before final burial: in-situ reworking, transport, and time-averaging. Although time-averaging of the death assemblages was limited to several years, it is in this way that several generations of the two bivalve species could become preserved together. Reworking of the bivalve concentrations was most likely caused by storm action. (C) 2011 Elsevier Ltd. All rights reserved.

A comparative analysis of Late Jurassic-Early Cretaceous strata have been done for the Sanjiang-Middle Amur basin, a coal- and oil-bearing area spanning the eastern Heilongjiang of northeastern China and southeastern Far East of Russia. On the basis of various fossils occurring in the formations, particularly by means of the Tithonian-Valanginian index Buchia and the late Barremian-middle Albian indicator Aucellina assemblages, the marine and non-marine Late Jurassic-Early Cretaceous strata in the basin are correlated. The Mesozoic international chronostratigraphic chart (http://www.stratigra-phy.org) is established basically based on the marine rocks. To accurately date the non-marine strata, it is necessary to correlate them with the marine deposits. This study sheds new light on the dating and correlation of non-marine Upper Mesozoic. Additionally, the results would help understand the tectonics and paleogeography and thus aid the exploration of energy resources.

The spatial and temporal distribution of Late Mesozoic marine and brackish-water sediments in eastern Heilongjiang records three main transgressive interludes: The late Middle Callovian–Valanginian, Barremian–Aptian and Albian marine invasion phases. The Callovian–Valanginian transgressions were limited to the northeastern corner of eastern Heilongjiang, but the others intermittently extended northwest-, southwest- and westwards along the Yunshan shallow embayment, which opened into and deepened towards the northwestern Palaeo-Pacific. They not only flooded almost all of the subsiding basins surrounding the embayment, but during peak transgressions also widely flooded areas outside eastern Heilongjiang, such as the Yanji, Beipiao–Fuxin and Songliao basins along the Tan–Lu fault system of northeast China. All the transgressions came from the northwestern Palaeo-Pacific Ocean, and probably the Arctic Sea as well. In addition to the eustatic sea level changes, the late Early Cretaceous transgressions of northeast China were closely related to the tectonic movements within the Tan–Lu fault system and the circum-Paleo-Pacific, which were very pronounced and went hand in hand with a strong volcanic activity and ongoing subsidence. During the late Early Cretaceous, the long-term existence of a marine embayment in eastern Heilongjiang, successive marine transgressions, and flooding along the Tan–Lu fault system in northeast China ensured a humid climate across all of northeast China. These transgression and climatic conditions produced a number of extensive and long-lasting swamps and marsh lands in both paralic and limnic environments. Luxuriant plant and thriving animal growth led to the accumulation of abundant organic matter in the deposits. As a result, a number of late Early Cretaceous coal basins and oil fields formed in eastern Heilongjiang, the Yanji basin of eastern Jilin, Beipiao–Fuxin basin of western Liaoning, and the Songliao basin, northeast China.

Global environments changed greatly during the Late Jurassic and Early Cretaceous, particularly during the Jurassic-Cretaceous boundary interval. Separation of the world into Tethyan, Boreal and other biogeographic realms complicates international correlation, and even the pelagic ammonites cannot play their characteristic role of principle correlation criteria. In the Boreal and North Pacific realms, the Late Jurassic and Cretaceous buchiid bivalve zones have very good calibration to Boreal ammonite zones, which, in turn, have approximate correlations to Tethyan ammonite zones. Therefore, buchiid bivalves provide a means to identify Upper Jurassic-Lower Cretaceous stages and the Jurassic-Cretaceous boundary interval. The base of the Buchia unschensis Zone is roughly coincident with the Boreal ammonite Craspedites exoticus subzone, Upper Volgian Craspedites okensis Zone, which in turn closely corresponds to the base of the Tethyan ammonite basal Berriasian Berriasella jacobi Zone. The top of the underlying Buchia russiensis Zone approximately coincides with that of the uppermost Middle Volgian, Boreal ammonite Epivirgatites variabilis Zone, which approximately corresponds to the Tethyan ammonite Durangites Zone of uppermost Tithonian. Buchia and dinoflagellate cyst assemblages from two regions in eastern Heilongiiang of northeastern China indicate the presence of the Jurassic-Cretaceous boundary interval. The Dong'anzhen Formation of Dong' an, Raohe County contains Middle Volgian-Lower Valanginian Buchia assemblages and the Jurassic-Cretaceous boundary is tentatively assigned to either the base of the Buchia fischeriana-Buchia unschensis assemblage or between the Buchia fischeriana-Buchia unschensis and Buchia russiensis-Buchia fischeriana assemblages. The Dongrong Formation from boreholes at Suibin, Suibin County, yields uppermost Oxfordian to basal Berriasian Buchia assemblages and Oxfordian-Barremian dinoflagellate cyst assemblages. Here, the Jurassic-Cretaceous boundary interval is probably between the Buchia cf. mosquensis-Buchia cf. rugosa assemblage (including Buchia ex gr. russiensis and Buchia ex gr. taimyrensis) and the overlying non-Buchia-bearing deposits.