The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon) in the diversification of the marine biosphere. Nutrient availability and phytoplank...

in order to investigate deformation history preserved in the calcite twins in the hinterland of zagros, several samples have been collected from calcschists of the paleozoic sargaz complex in the faryab area, se iran. these samples are related to f1-recumbent folding and thrust shear zones. the twin width is about 1 and 3.8 µm (thin-twin regime); the twin strain amounts 5 and 10%; twin intensit...

Shifts in the taxonomic composition of Paleozoic communities are commomly ascribed to selective extinctions. Suppression realized speciation rates owing shrinkage available adaptive space (lowering potential niche number), even though unselective, results differential diversity losses, greatest losses being sustained by clades with highest and extinction (the high-turnover caldes). The resultin...

The Ancient Pacific Margin NATMAP project (Thompson et al., 2000) is a collaboration between the British Columbia Geological Survey Branch, the Geological Survey of Canada and the Yukon Geoscience Office. It aims to advance understanding of the Cordillera-long belt of complexly deformed pericratonic rocks that made up the Pacific margin of North America in Paleozoic to early Mesozoic time (Figu...

Recent evidence quite convincingly indicates that the Late Permian biotic crisis was in fact a binary extinction with a distinct end-Guadalupian extinction pulse preceding the major terminal end-Permian Tartarian event by 5 million years. In addition anoxia appears to be closely associated with each of these end-Paleozoic binary extinctions. Most leading models cannot explain both anoxia and th...

Many of the late Paleozoic granitoid plutons of the southern Appalachians are composite bodies with coarsegrained amphibole + biotite and biotite varietal facies (Speer et al., 1980). From field relations, these facies appear closely related, and multiple intrusion or differentiation comes to mind as an explanation for the relationship. In the Liberty Hill pluton, the coarse-grained central amp...