Early Paleozoic mantle diapirism in Galicia

Comparison of the geological outcrop and the Bouguer map of the Ordenes Complex in Galicia (NW Spain), gives substantial evidence for a subdivision of the peripheral belt into separate units. These units, high-grade metamorphic complexes, appear to have their origin in diapiric movements of upper-mantle material into a crystalline lower crust of continental type.     

Relations between stream sediment and source-rock mineralogy,Piney Creek Basin,Wyoming

The areal distribution of stream sediment and source-rock heavy mineralogy was studied to determine the mineralogical relations between source and derived sediment in the Piney Creek drainage basin of Wyoming. Heavy-mineral distribution in the streams was characterized using factor analysis. The results of analyses show that for an actively degrading stream system, the heavy-mineral composition of stream sediment is controlled to a considerable extent by the composition of local sediment sources and by continuous addition of detritus from bank cutting. Only the most common minerals from upstream sources persist as statistically significant variables downstream. In some cases the heavy-mineral mineral composition of stream sediment can be controlled by comparatively few, or volumetrically rare source rocks, even though more abundant source rocks supply a wide range of heavy minerals. Specific drainage configurations such as lakes and proximity of streams to major sediment sources significantly modify sediment mineralogy immediately downstream.