The emergence of soft-bodied metazoans and the radiation of the earliest skeletal organisms substantially changed the ecological dynamics of Ediacaran environments, leading to the genesis of biogenic hard-part deposits for the first time in Earth's history. The impact of bioclasts origin on sedimentary processes is analyzed herein, focusing on the sedimentology and taphonomy of shell concentrations dominated by the Ediacaran index-fossil Cloudina from the Itapucum Group, Paraguay. At that time, Cloudina was the critical source of durable biomineralized hard parts in an environment nearly free of other bioclasts. Despite their Precambrian age, the simple fabric and geometry of these accumulations are typical of Cambrian-style shell-beds. Furthermore, these deposits indicate that the establishment of the Phanerozoic style of marine substrates and preservation was determined more by the acquisition of hard parts rather than environmental changes.
Potentially induced earthquakes in Oklahoma, USA: Links between wastewater injection and the 2011 Mw 5.7 earthquake sequence
Katie M. Keranen et al., ConocoPhillips School of Geology and Geophysics, University of Oklahoma, 100 E. Boyd Street, Norman, Oklahoma 73069, USA. Posted online ahead of print of 26 March 2013; http://dx.doi.org/10.1130/G34045.1.
In this study, Katie M. Keranen and colleagues demonstrate a relationship between the 2011 magnitude 5.7 Oklahoma earthquake sequence with wastewater disposal in nearby wells. Keranen and her co-authors use the locations of nearly 800 aftershocks to delineate the faults that ruptured, showing progressive rupture on three separate fault segments. The first rupture
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