Paleomagnetism of Neoproterozoic through to Lower Paleozoic rocks on microcontinents of Central Asia: implications for the Precambrian glacial Paradox and amalgamation of Eurasia

Tillite at the Base of the Tsagaan Oloom Fm (Gobi-Altai area)

Supported by the National Science Foundation EAR05-08597

Project Summary

The latest Neoproterozoic through the Cambrian is one of the most remarkable intervals in geologic time. It marks the onset of biodiversity at the Vendian-Cambrian boundary, major transitions in seawater chemistry, major plate reorganization, the breakup of the Rodinia supercontinent and Gondwana assembly and a possible change from severe climate with low-latitude glaciations to Phanerozoic circumpolar pattern. Existing paleomagnetic data suggest that at least some of the Neoproterozoic glaciogenic sediments were deposited at low paleolatitudes in sharp contrast to their Pleistocene counterparts. Several competing models vie for explanation of this unusual paleoclimatic record (e.g. Snowball, Slushball and High Obliquity models).  The extant paleomagnetic database does not allow a clear distinction amongst these models. The Ural-Mongol fold belt, which separates the Baltica, Siberia, North China and Tarim blocks, is the largest in Eurasia. Its central part comprises a number of microcontinents with Precambrian basement. On several of these microcontinents, the Vendian section includes well-preserved glacial relicts that can add a significant increase in our knowledge of depositional paleolatitudes as well as providing age control on the glaciations.  In addition, paleomagnetic studies of Neoproterozoic to Early Phanerozoic rocks on the microcontinents of the Ural-Mongol mobile belt will allow us to address another problem. The tectonic evolution of the entire Ural-Mongol belt and the assembly of Eurasia will be better understood if the development of the central part of this belt and can be determined. We will trace the origin and subsequent motion of the microcontinents included into the mosaic structure of the central part of the belt that will in turn impose strong constraints on general style of tectonic evolution of this belt.

Intellectual Merit

The Precambrian paleoclimatic paradox is a long-standing debate, but the extant paleomagnetic dataset available to date is of limited use in distinguishing from amongst the prevailing models for the extensive glaciations (Snowball Earth, High-Obliquity Earth or Phanerozoic paradigm). As the number of yet unstudied sequences of late Neoproterozoic to Vendian to Cambrian age is limited on major cratons, the proposed research on sequences of these ages on microcontinents will considerably increase the corresponding dataset and will improve our knowledge of paleogeography for this interval.  A comprehensive model for the tectonic evolution of the central part of the Ural-Mongol fold is crucial for understanding of the amalgamation of the Eurasian supercontinent throughout the Paleozoic. Combining geological data with the results we plan to obtain, our project will establish the origin and subsequent motions of the microcontinents and will thus impose strong constraints on the general style of tectonic evolution of the entire Ural-Mongol belt. In the broadest geological sense, it is noteworthy that the Variscan belt of southern Europe and several Late Precambrian belts (e.g., arc sequences of Saudi Arabia and other large Pan-African domains) show important similarities with central part of the Ural-Mongol fold belt. A successful model for this region may serve as a useful analog for other pre-Mesozoic accretion processes during the amalgamation of supercontinents.

Broader Impacts

            The University of Florida is committed to enhancing geologic education in the USA through the active recruitment of under-represented groups. We will also involve undergraduate students in this research in order to train future generations of geologists and have requested funds to support undergraduate research projects within the current proposal.  Our work also involves the substantial collaboration of Russian colleagues and students. These types of collaborative efforts allow the Russian scientists access to western scientists and their laboratories and vice-versa.  We would like to emphasize the training that this grant will provide to undergraduate, graduate and postdoctoral scholars. Also, our international collaboration with scientists in Russia fosters integration of the latter into the international scientific community. Results from this project will be shared via the published literature (i.e. with other scientists); with undergraduate and graduate students (via formal and informal departmental seminars) and with the general public. 

Project Participants
Dr. Joseph G. Meert (Project Director and downright ugly)
Dr. Natasha Levashova (Co-Project Director)
Vimal Pradhan (Ph.D. student and Inspirational Leader)
Shawn Malone (M.S. student and field guide)
Laura Gregory (M.S. student and finder of lost souls)
Jessica Yff (undergraduate researcher and moral compass)

Major Findings:

   Our first field season took place during August-September of 2005.  Our team collected more than 1100 drill core and hand samples from the Dzabkhan Fm, the Tsagaan Oloom Fm, Bayan Gol Fm and from the Ulanshandin arc.  We are currently in the process of analyzing the samples and hope to generate our first report later this spring. 

Shawn Malone (M.S. Student) and Munkh-Erdene (Mongolian Survey) orient limestone samples
from the Bayan Gol Formation along the Zavkhan river.

Mongolian Airways Super Luxury Liner (a Soviet Antonov-24 prop) that took us from Ulaan Bataar
to Gobi Altai in western Mongolia.  The runway was dirt and the parking space was the only paved
section of the airport.

Field Crew in front of a ovoo.  Front (relaxed) driver Uri (Novosibirsk), back (from right) Alexander Rybanin
(aka Sasha- Novosibirsk), Natasha Levashova (Moscow), Roman Shelepaev (Novosibirsk), Munkh-
Erdene (Mongolian Survey), Valery Kalugin (Novosibirsk) and Shawn Malone (Florida).

Shawn Malone standing in front of red and grey shales in the Bayan Gol formation.