Geological Society of America

T26 The Ediacaran-Cambrian Ecosphere (R)evolution: Emerging Records from Central and East Asia

Sunday, 19 October 2014
8:00 AM - 12:00 PM
207

REFINING THE EDIACARAN-CAMBRIAN TRANSITION IN WESTERN MONGOLIA AND SOUTH CHINA

Paper number: T26-7
Program: Technical Sessions
Time: 9:30 AM – 9:45 AM

Authors

Emily F. Smith Presenting Author
Harvard University, Cambridge, MA
Francis A. Macdonald
Harvard University, Cambridge, MA
Tanya N. Petach
Harvard University, Cambridge, MA
Maoyan Zhu
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing
Guoxiang Li
Nanjing Institute of Geology and Palaeontology, Nanjing, N/A
Uyanga Bold
Harvard University, Cambridge, MA

Abstract

The Ediacaran-Cambrian transition is one of the most fundamental biological transitions in Earth History, recording the abrupt appearance and diversification of multiple metazoan clades. However, despite its importance, integrating, characterizing and precisely calibrating biological and geochemical changes across this transition has proven to be difficult, due in part to uncertainties in correlations between records globally and a lack of absolute age constraints.

The Zavkhan Basin in western Mongolia hosts well-exposed, thick, carbonate-rich, fossiliferous late Ediacaran through early Cambrian strata. These successions provide an excellent record of the geochemical and paleontological changes that occur during this time. However, without absolute age constraints from the Zavkhan Basin, it is necessary to use relative dating techniques to correlate between sections in Mongolia with those elsewhere. South China is one such region that not only contains U-Pb ash ages, but also small shelly fossils, and carbon isotope chemostratigraphic data, allowing for the potential to refine the correlation between these two regions.

Here we present high resolution carbon isotope chemostratigraphy from multiple sections across the Zavkhan Basin and use these to create a refined age model for the late Ediacaran through early Cambrian strata. Using this refined age model and new geological mapping, we refine the small shelly fossil biostratigraphic record for this basin. Finally, we correlate these refined records from Mongolia with those from South China to better characterize the Precambrian-Cambrian boundary in Asia and tempo of the Cambrian explosion of metazoan diversity.