December 2008 Geology and GSA Today media ...(ging seawater chemistry and climate exer...)

Date:11/26/2008

ging seawater chemistry and climate exerted considerable control over the mineralogy of emerging skeletal metazoans. The earliest skeletons known were composed exclusively of aragonite or high-magnesium calcite, but these were replaced by lineages with low-magnesium calcite mineralogies. These changes were controlled by the changing magnesium-calcium ratio of seawater, and probably also by increasing partial pressure of CO2 in the atmosphere as a result of the onset of greenhouse conditions.

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Newly recognized eastern extension of the Nile deep-sea fan

Yehoshua Folkman and Yossi Mart, Geological Survey of Israel, 30 Malkhei Yisrael St., Jerusalem 95501, Israel. Pages 939-942.

The Nile River deep-sea fan is currently a prime exploration objective in the Mediterranean Sea due to major gas discoveries in its channel complexes offshore Egypt. Folkman and Mart present a newly recognized easternmost segment of the Nile deep-sea fan that has been revealed recently in the deep Mediterranean Sea offshore Israel, based on high resolution, three-dimensional seismic imaging. This segment is vertically divided into two sequences: basal sand-rich sequence deposited in a basin floor setting, and an overlying younger mud-rich sequence, characterized by densely spaced seabed and sub-seabed distributary slope channel complexes.

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Earthworms produce granules of intricately zoned calcite

Martin R. Lee et al., Department of Geographical and Earth Sciences, Gregory Building, Lilybank Gardens, University of Glasgow, Glasgow G12 8QQ, UK. Pages 943-946.

In the 19th century, Charles Darwin first found that common species of earthworms produce millimeter-sized clusters of the mineral calcite. Darwin was unable to explain how or why these calcite "granules" are formed, and this question has remained unanswered despite the fact that granules are very abundant in soils and so make an important, albeit poorly understood, c
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Contact: Christa Stratton cstratton@geosociety.org 303-357-1093 Geological Society of America Source:Eurekalert

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