More From Cretaceous Research

["Jerry D. Harris" <jharris@dixie.edu>]

ANOTHER new issue...

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
http://cactus.dixie.edu/jharris/

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