Heavy Minerals and Sedimentary Organic Matter in Pleistocene and CretaceousSediments on Long Island, New York, with Emphasis on Pyrite and Marcasite in the Magothy Aquifer

摘要

Abundance and distribution of iron-bearing and other heavy minerals in sedimentsof Long Island, N.Y., were examined to identify sources and sinks of dissolved iron and other ground-water constituents along a deep flow path from the ground-water divide to the southern shore along the Nassau-Suffolk County border. The occurrence and reactivity of many iron-bearing minerals in the aquifer system are affected by terminal electron-accepting processes, which are a function of depth below land surface, distance from the ground-water divide, and organic-matter content of the sediment. The lateral distribution of heavy minerals within lithologic sediments is not uniform throughout Long Island, or even along the 30-kilometer study section at the Nassau-Suffolk County border. Mineralogy and mineral abundance in Pleistocene units differ from those in Cretaceous sediments, and some of the trends vary with depth as well as from north to south.