Utilizing new Mammal faunas for calibration of paleomagnetostratigraphy in the Kochkor basin, Kyrgyzstan.

Abstract:

Kyrgyzstan is the most seismically active nation in the world, owning to the uplift of the Tien Shan mountain range. This record of faulting is far from simple though, with different dates of initiation spanning tens of millions of years in the published literature. Differentiating between these extremes is vital in terms of constructing earthquake hazard maps for the country. Much of the high degree of uncertainty comes from a lack of datable rocks within the time frame associated with the faulting. While paleomagnetic stratigraphic analyses provide highly accurate ages, they in turn need calibration points to preclude multiple possible matches to a global geochronological framework. Herein I provide the first description of Neogene fossil mammal faunas to act as biostratigraphic control for the paleomagnetic data. Dominating the faunal assemblage is rhinoceros species, Chilotherium anderssoni. This taxon is globally only known from 8.7-5.3 million years ago, constraining much of the stratigraphy to the latest Miocene to Pliocene. Additional taxa include Gazella, Samotherium, Hipparion, Hyaenaictithirium, Paleolagus, and Pliocervidae. As fossils are limited to the Miocene/Pliocene Chu Formation, we have also collected additional paleomagnetic samples from the lower Shamsi Formation to extend the age range covered and constraint the initiation of faulting.