RUI: COLLABORATIVE RESEARCH: The Neoproterozoic and Cambrian of the Tethyan Himalaya: A Test of Models of Core Gondwanan Construction

Colorado College, Colorado Springs CO

Investigators

Abstract

EAR 9980376 Myrow EAR 9980426 Hughes Collaborative Research: THE NEOPROTEROZOIC AND CAMBRIAN OF THE TETHYAN HIMALAYA: A TEST OF MODELS OF CORE GONDWANAN CONSTRUCTION The nature and timing of the assembly of core Gondwanaland remains a matter of vigorous debate. The traditional view is that East Gondwana, consisting of India, Australia and Antarctica collided with the combined African cratons (Kalahari and Congo) as one block sometime during the late Neoproterozoic. An alternative model suggests that the accretion of East Gondwana to the African craton was a two part process. In this model, India broke off from Australia and Antarctic, swept across the Mozambique Ocean, and collided with the African craton at approximately 680 Ma. This was purportedly followed sometime later by collision of Australia/Antarctica around 550 to 530 Ma. Our study of the Tethyan Himalaya will test tectonic models of the assembly of core Gondwanaland using a combined stratigraphic, macrofaunal and sedimentological approach. Of primary importance is the stratigraphic signature of sediment input from adjacent orogenic belts. A record of major increases of siliclastic sediment, with abrupt changes in paleocurrents would accompany orogenesis. A key component of the proposed models is that they have predictable patterns of detrital zircon ages. A Late Cambrian-Early Ordovician tectonic event is recorded in the Tethyan Himalaya and in other places in East Gondwanaland. The nature of this event is unclear, but two possibilities include: (1) it represents a somewhat delayed expression of the Australia/Antarctica collision in the two-stage model, or (2) it represents the docking of an outboard microcontinent (e.g., the Lhasa Block of Tibet) subsequent to the formation of core Gondwanaland. The biostratigraphic patterns of trilobites provide the basis of testable predictions of these hypotheses. In the first case, we expect to find a stratigraphic increase in similarity in faunas between India and the rest of East Antarctica throughout the Cambrian. If faunal similarity with the rest of East Gondwana was constant throughout the trilobite-bearing Cambrian, we may infer that Gondwanan construction was complete prior to 520 Ma. In addition, if the ~500 Ma tectonic event in the Tethyan Himalaya records microcontinental collision, then the identification of the outboard terrane may be approached through biogeographic patterns established in this study. Myrow's RUI proposal will involve undergraduates at Colorado College as junior collaborators in all components of the research. This will provide a much-needed opportunity for students to experience scientific research in diverse geographical and cultural environments. A key aspect of this proposal is the close research collaboration with Indian and Chinese scientists.