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More From Cretaceous Research

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Haggart, J.W., Matsukawa, M., and Ito, M. 2006. Paleogeographic and paleoclimatic setting of Lower Cretaceous basins of East Asia and western North America, with reference to the nonmarine strata. Cretaceous Research 27(2):149-167. doi: 10.1016/j.cretres.2005.11.008.

ABSTRACT: Lower Cretaceous strata are widespread in East Asia and along the western coast of North America. In both regions, Cretaceous basins contain significant stratigraphic accumulations and can be thought of as along-strike equivalents. In East Asia, fore-arc basins were oriented parallel to and east of active magmatic arcs while in western North America extensive fore-arc successions accumulated west of the arc complexes. The greater extent of nonmarine, rift and back-arc basins in the East Asian region, and overall lower topographic development, was likely related to movement of the region away from ongoing subduction to the east. In western North America, by contrast, movement of the North American plate westwards towards the active subduction zone resulted in development of a volumetrically larger and topographically higher orogen than in East Asia.
The active arc complexes in both regions exerted significant controls on paleoclimate. Interior basins of both Asia and North America, landward of arc complexes, were significantly drier than the coastal areas, due to rain-shadow phenomena in both regions. Although the proto-Pacific Ocean was likely much wider during Early Cretaceous time than it is today, we infer that similar oceanic circulation patterns existed and significantly affected climate and molluscan biogeographic assemblages of both East Asia and western North America: East Asia was dominated by warm water derived from the Tethyan regions, whereas west coast North America was influenced by cooler waters derived from high-latitudes.

Lucas, S.G. 2006. The Psittacosaurus biochron, Early Cretaceous of Asia. Cretaceous Research 27(2):189-198. doi: 10.1016/j.cretres.2005.11.011.

ABSTRACT: Fossils of the primitive ceratopsian dinosaur Psittacosaurus are widely distributed in Asia in Russia (western Siberia), Mongolia, China (Liaoning, Nei Monggol, Gansu, Ningxia, Xinjiang, Shandong, and Hebei provinces), Thailand, and possibly Japan. All Psittacosaurus records are of Early Cretaceous age, and a Psittacosaurus biochron can be recognized equivalent to the Tsagantsabian and Khukhtekian land-vertebrate faunachrons (LVF). The Tsagantsabian LVF is defined as the time interval between the first appearance datum (FAD) of Psittacosaurus, and the FAD of the turtle Peishanemys. The Khukhtekian LVF is the time between the FAD of Peishanemys and the FAD of the ceratopsian dinosaur Microceratops (=beginning of the Baynshirenian LVF). Cross correlation to the standard global chronostratigraphic scale, mostly by radioisotopic dates and palynology, indicates the Tsagantsabian is Barremian-early Aptian, and the Khukhtekian is late Aptian-Albian. The duration of the Psittacosaurus biochron thus is about 20 myr of Barremian-Albian time.

Matsukawa, M., Ito, M., Nishida, N., Koarai, K., Lockley, M.G., and Nichols, D.J. 2006. The Cretaceous Tetori biota in Japan and its evolutionary significance for terrestrial ecosystems in Asia. Cretaceous Research 27(2):199-225. doi: 10.1016/j.cretres.2005.11.006.

ABSTRACT: Cretaceous nonmarine deposits are widely distributed on the Asian continent and include various kinds of zoo- and phyto-assemblages. The Tetori Group is one of the most important Mesozoic terrestrial deposits in East Asia, and for this reason its geology, stratigraphy, and biota have been studied intensively by our group for more than a decade. We present the main results herein.
We confirm that formations as lithostratigraphic units are the best geological correlation tools for the Tetori Group and the best tools for a geological mapping of the group. Although subgroups have previously been used for correlation, proper designation and evaluation of subgroups is required if they are to be used effectively, and we show that previous geological correlation of the Tetori Group has been confused by inappropriate definition of these subgroups. We located fossil localities including reported zoo- and phyto-assemblages in the framework of formations correlated by our stratigraphy. The occurrence of zoo-assemblages was probably controlled by environments (i.e., most are in situ), but phyto-assemblages were mostly transported and rapidly buried by high-energy river systems. Although two distinct dinosaur faunas and four floras have been named for the zoo- and phyto-assemblages in the Tetori Group, in reality there is only one Tetori Dinosaur Fauna and one Tetori Flora, as proved by careful correlation. Two types of zoo-assemblages co-occur in the Tetori Group: vertebrate species whose ancestors flourished in the Jurassic (as found in China), and their descendants from the Late Cretaceous. As the latter modern type of assemblage is more abundant than the former, changeable environments at the continental margin probably accelerated evolution of more modern species.
We can employ nonmarine molluscan species as geological correlation tools in some cases, i.e., when their taxon ranges are well-confirmed by independent evidence. However, because freshwater molluscan species and terrestrial vertebrate species had many opportunities to move to optimum habitat as environments changed through time on the Cretaceous Asian continent, their correlation potential is uncertain. Many nonmarine molluscan species from the Japanese and Chinese Cretaceous had their stratigraphic occurrences controlled by changing environments.

Nichols, D.J., Matsukawa, M., and Ito, M. 2006. Palynology and age of some Cretaceous nonmarine deposits in Mongolia and China. Cretaceous Research 27(2):241-251. doi: 10.1016/j.cretres.2005.11.004.

ABSTRACT: To provide biostratigraphic and paleoecologic data for a major international project studying dinosaur trackways in eastern Asia, samples were collected for palynological analysis from the Choyr Basin of southeastern Mongolia and the Yanji Basin, Jilin Province, northeastern China. Palynologically productive samples from the Choyr Basin are from strata previously identified as either the Shinekhudag Formation or the Zuunbayan Formation but recently renamed the Khuren Dukh Formation; productive samples from the Yanji Basin are from the Tongfosi Formation. The biostratigraphically most important palynomorphs from both units are angiosperm pollen. The Khuren Dukh Formation is determined to be middle to late Albian in age. The Tongfosi Formation is determined to be early Cenomanian in age. These results conflict with some previously published interpretations of the ages of these units. Lacustrine depositional environments are indicated for both units by the presence of freshwater algae in both deposits.

Sha, J., Lin, L., Chen, S., and Matsukawa, M. 2006. Some Lower Cretaceous nonmarine bivalves from fluvio-lacustrine deposits bearing dinosaur fossils in Mongolia and northeast China. Cretaceous Research 27(2):262-278. doi: 10.1016/j.cretres.2005.11.002.

ABSTRACT: One species of Unio and three species of Sphaerium, the typical nonmarine bivalves in East Asia, from the Lower Cretaceous fluvio-lacustrine deposits of Choyr Basin of southeastern Mongolia and the Beipiao area of Jehol in northeastern China, are described. The assemblage of Unio longus (Zhu), Sphaerium chientaoense Suzuki, and S. coreanicum (Kobayashi and Suzuki) from the Khuren Dukh Formation of the Choyr Basin of southeastern Mongolia can be compared with the Nakamuranaia-Margaritifera (Menyinaia)-Neomiodonoides assemblage in China. The four nonmarine bivalve species described herein are found in numerous formations in East Asia suggesting Valanginian to Albian age.

Matsukawa, M., Saiki, K., Ito, M., Obata, I., Nichols, D.J., Lockley, M.G., Kukihara, R., and Shibata, K. 2006. Early Cretaceous terrestrial ecosystems in East Asia based on food-web and energy-flow models. Cretaceous Research 27(2):285-307. doi: 10.1016/j.cretres.2005.11.010.

ABSTRACT: In recent years, there has been global interest in the environments and ecosystems around the world. It is helpful to reconstruct past environments and ecosystems to help understand them in the present and the future. The present environments and ecosystems are an evolving continuum with those of the past and the future. This paper demonstrates the contribution of geology and paleontology to such continua.
Using fossils, we can make an estimation of past population density as an ecosystem index based on food-web and energy-flow models. Late Mesozoic nonmarine deposits are distributed widely on the eastern Asian continent and contain various kinds of fossils such as fishes, amphibians, reptiles, dinosaurs, mammals, bivalves, gastropods, insects, ostracodes, conchostracans, terrestrial plants, and others. These fossil organisms are useful for late Mesozoic terrestrial ecosystem reconstruction using food-web and energy-flow models. We chose Early Cretaceous fluvio-lacustrine basins in the Choyr area, southeastern Mongolia, and the Tetori area, Japan, for these analyses and as a potential model for reconstruction of other similar basins in East Asia. The food-web models are restored based on taxa that occurred in these basins. They form four or five trophic levels in an energy pyramid consisting of rich primary producers at its base and smaller biotas higher in the food web. This is the general energy pyramid of a typical ecosystem. Concerning the population densities of vertebrate taxa in 1 km2 in these basins, some differences are recognized between Early Cretaceous and the present. For example, Cretaceous estimates suggest 2.3 to 4.8 times as many herbivores and 26.0 to 105.5 times the carnivore population. These differences are useful for the evaluation of past population densities of vertebrate taxa. Such differences may also be caused by the different metabolism of different taxa. Preservation may also be a factor, and we recognize that various problems occur in past ecosystem reconstructions.
Counts of small numbers of confirmed species and estimates of maximum numbers of species present in the basin are used for the analysis and estimation of energy flow. This approach applies the methods of modern ecosystem analysis.

Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@gmail.com

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