Friday, January 23, 2015

A Look Back…25 Years: Ireland Ice Sheet Collapse

The nature and rate of decay of ice sheets is central to understanding possible impacts of climate change. Twenty-five years ago, McCabe and Dardis documented the character and distribution of Late Pleistocene drumlins, deposited in association with the melt of the ice sheet in western Ireland. The results illustrated several lithofacies associations, interpreted in the context of depositional environment in association with the ice sheet. These insights provided a conceptual model for ice-distal to ice-contact subaqueous deposition, modified by till deposition and drumlinization. The results provided a detailed documentation of rapid facies changes associated with a dynamic ice margin, and how these details “may not therefore be linked directly to climatic change.”

Tuesday, January 6, 2015

A Look Back…50 Years: Analcime in the Record

Sedimentary rocks are mineralogically diverse, the result of depositional and diagenetic variability. Fifty years ago, Teruggi reported a new occurrence of sedimentary analcime, which he suggested was “one of the most important so far recorded in the geological literature.” His results, based on the study of a single section, revealed “considerable quantities of sedimentary analcime” in Argentina. He interpreted the analcime to be a diagenetic alteration of “altered vitroclastic matrix.”