Turritelline mass accumulations from the Lower Miocene of southern Germany: implications for tidal currents and nutrient transport within the North Alpine Foreland Basin

The mass occurrence of turritelline gastropod shells from the Lower Miocene of southern Germany allows for detailed studies of their palaeoecology, transport mechanisms, preservation potentials and the reconstruction of nutrient regimes. Changes in the fabric of the gastropod-dominated beds are used to reconstruct a generally deepening environment corresponding to the Lower Miocene transgression within the Upper Molasse Sea of the North Alpine Foreland Basin. The sedimentary succession ranges from chaotically arranged, densely packed and near-shore transported; wave-influenced deposits showing bimodal shell orientations; more widely dispersed shells showing a uni-directional orientation; and dispersed shells showing diverse orientations. The shells often show damage to the apex and aperture though it is not clear whether this is due to predation events, pagurisation or abrasion due to transport. An outstanding feature is the replacement of aragonite shells by calcite leading to internal vugs as well as modulating the outer shell surface morphology. The high density of turritelline gastropods indicates a nutrient-rich palaeoenvironment at the northern edge of the Molasse Sea

Precipitate Formation in Low-Temperature Nitrided Cold-Rolled Fe94Ni4Ti2 and Fe93Ni4Cr3 Films

Using various experimental techniques, the formation and evolution of precipitates, the dilation of the matrix, and the nitrogen uptake and release were investigated in cold-rolled Fe94Ni4Ti2 and Fe93Ni4Cr3 materials subjected to nitriding in a gaseous mixture of NH3 + H2 and to reduction in an H2 atmosphere at low (300 °C) to moderate (600 °C) temperatures. Transmission electron microscopy (TEM) revealed that in both alloys the precipitates are thin platelets. In the Ti-containing alloy, the precipitates were also small in the lateral dimensions. The difference in size, aspect ratio of the precipitates, and misfit and coherency on the interface consistently explain the substantial differences in dilation of the matrix and nitrogen uptake for the Ti- and Cr-containing alloys under examination. The results provide evidence for the formation of mixed Fe-Ti-N precipitates (Guinier–Preston (GP) zones) in the early stages of nitriding.