Explosive arc volcanism can have significant environmental impact because of the discharge of ash and volatiles directly into the atmosphere and oceans. Jicha et al. compile 2,814 age determinations from four circum-Pacific arcs and show that peak periods and subsequent lulls in arc magmatism over the past 50 million years are coeval with major fluctuations in global climate. Hundreds of intermediate-to-silicic eruptions occurred during an extremely vigorous period of circum-Pacific volcanism beginning in the late Eocene, about 34 million years ago, which likely led to the production of sulfur aerosols in the stratosphere and fertilization of surface waters of the Pacific Ocean. The findings suggest that abundant arc volcanism may be partly responsible for the climatic preconditioning that must have preceded and ultimately promoted the first widespread glaciation of Antarctica.
Evidence of Cenozoic environmental and ecological change from stable isotope analysis of Sirenian remains from the Tethys-Mediterranean region
Mark T. Clementz et al., Dept. of Geology and Geophysics, University of Wyoming, 1000 E. University Ave., Laramie, Wyoming 82071, USA. Pages 307-310.
Sirenians (sea cows; manatees and dugongs) have been primary consumers in tropical and subtropical shallow-water marine ecosystems for over 50 million years. Though fossils of the earliest sirenians have been recovered from the Caribbean, sirenians are thought to have originated in the Tethys-Mediterranean region, which experienced significant climate change over the course of the Cenozoic. Application of stable isotope analysis can provide new insight into how diet and habitat preferences were impacted by climate change and, in turn, how these ecological changes correlate with diversity patterns for this region. Tooth enamel was sampled by Clementz et al. from 5
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Geological Society of America