7 specimens of sirenians from the Tethys-Mediterranean and adjacent seas spanning the Eocene to Pliocene. Enamel delta-13C values across this time interval were consistently high and indicative of diets composed mostly of marine seagrasses. In contrast, enamel delta-18O values showed significant change over time and across the region. Sirenians from southern sites (i.e., Egypt, Libya) had significantly higher mean delta-18O values than specimens from most European locations, suggesting variation in salinity within the Tethys-Mediterranean. The range in enamel delta-18O values increased from the Paleogene through the Neogene, but enamel delta-13C values remained steady, indicating that changes in environmental conditions did not necessarily coincide with major changes in dietary preferences. Declines in sirenian taxonomic diversity in the late Miocene were likely due to the rapid climate and oceanographic changes during the latter half of the Cenozoic and their impacts on available dietary resources. Elevated delta-13C and delta-18O values in Mediterranean sirenians during the Messinian Salinity Crisis corroborate the hypothesis of ecophenotypic dwarfing in these animals.
Seismic and geodetic evidence for extensive, long-lived fault damage zones
Elizabeth S. Cochran et al., Dept. of Earth Sciences, University of California-Riverside, Riverside, California 92521, USA. Pages 315-318.
Growing evidence suggests that the crust adjacent to active faults suffers an incredible amount of damage and cracking during earthquakes. Using seismic and geodetic data, Cochran et al. have found a wide, sustained damage zone along the Calico fault, located in the Mojave Desert, California. The damage zone extends for 1.5 km across the fault, with seismic velocities reduced by up to 50%. This zone of damaged rock has not recovered in the hundreds, or perhaps thousands, of years since the last large earthquake occurred on the Calico fault. ThePage: 1 2 3 4 5 6 7 8 9 10 11 Related biology news :1
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