March/April Geological Society of America Bulletin media highlights

Boulder, CO – Articles are now posted in the GSA BULLETIN "In Press" area of the journal Web site (http://www.gsajournals.org/perlserv/?request=get-toc-aop&issn=0016-7606). Geology topics of interest include: evidence from New Zealand challenging the hypothesis that the Northern Hemisphere drives global climate; evidence of two catastrophic volcanic eruptions in the Hannegan Pass area of Washington state's North Cascades National Park; origins of the highly productive topsoil of America's Great Plains; and new insights into hotspots in the Hawaiian-Emperor Island seamount chain.

The middle Eocene climatic optimum event in the Contessa Highway section, Umbrian Apennines, Italy
Fabio Florindo, Istituto Nazionale di Geofisica e Vulcanologia, Paleomagnetism, Roma I-00143, Italy; et al. Pages 413-427.

Keywords: Eocene, middle Eocene climatic optimum, MECO, magnetostratigraphy, biostratigraphy, stable isotope stratigraphy, Contessa Highway section, Italy.

Recently, a distinct negative shift in oxygen isotope records at ca. 40 million years ago (designated as the middle Eocene climatic optimum) has been observed in cores from the Indian and Atlantic sectors of the Southern Ocean. It has been interpreted primarily as a temperature signal that affected both surface waters and middle bathyal deep waters. Jovane et al.’s results from the Contessa section, in the Umbrian region, central Italy, provide the first evidence of this climatic event beyond the Southern Ocean, which suggests a global response of the oceanic carbon cycle to the same forcing.

Chronology and controls of avulsion along a mixed bedrock-alluvial river
Stephen Tooth, University of Wales, Aberystwyth, Institute of Geography and Earth Sciences, Ceredigion SY23 3DB, UK; et al. Pages 452-461.

Keywords: aggradation, avulsion, bedrock, incision, meanders, luminescence dating.