Shock deformation and volcanism across the Cretaceous-Tertiary transition
Abstract
The cause of the Cretaceous-Tertiary (K/T) transition remains one of the most controversial scientific topics in the geosciences. Paleontologic, mineralogic, geochemical, and geophysical evidence associated with the K/T boundary have been used to argue that the extinctions were caused by meteor impact or volcanism. To assess the viability of a volcanic model for the K/T transition, a study was undertaken to: (1) determine the character of shock-induced microstructures in silicates from previously shocked experimentally; (2) complete a series of shock-recovery experiments on granite and quartzite at elevated temperatures and variable pulse duration to determine temperature- and rate-dependent effects on microstructural development; (3) determine the distribution of shocked minerals at DSDP Site 527, Walvis Ridge, and ODP Holes 689B and 690C, Maud Rise, Wedell Sea; and (4) develop a volcanic model that can account for all of the evidence at the K/T transition. Comparison of natural and experimentally-shocked quartz and feldspar using optical and transmission electron microscopy (TEM) revealed that the optical and statistical character of shock-induced microstructures in volcanic rocks are different from both classic impact microstructures, and from the Raton K/T samples. Comparison of the Manson and Raton samples reveals similarities sufficient to support the contention of Izett (1987b) that Manson is a possible source for shocked quartz in the Raton deposits. A series of 31 high-explosive (HE) shock-recovery experiments at pressures to 25 GPa and temperatures to 750°C were completed on samples of Westerly granite and Hospital Hill quartzite. TEM and optical microscopy reveal that both pre-shock temperature and pulse duration have a first-order effect on the nature and development of shock-induced microstructure in quartz and feldspar. Application of the experimental results to natural shock-induced microstructures indicates that the volcanic microstructures are probably produced at elevated temperatures and shock pressures that do not exceed 15 GPa. The results also suggest that the Raton K/T deposits probably represent a moderate impact event at pressures below about 25 GPa...
Description
Typescript (photocopy).Subject
Cretaceous Geologic PeriodGeology, Stratigraphic
Tertiary Geologic Period
Major geophysics
1990 Dissertation H889
Geology, Stratigraphic
Cretaceous
Geology, Stratigraphic
Tertiary
Shock waves
Rock deformation
Collections
Citation
Huffman, Alan Royce (1990). Shock deformation and volcanism across the Cretaceous-Tertiary transition. Texas A&M University. Texas A&M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1109000.