Abstract

Studies of the heavy minerals in 9 samples of Recent sand, 18 samples of Glacial sand, and 8 samples of Cretaceous sand reveal that the Glacial sands and the Recent lake and river sands derived from glacial deposits are characterized primarily by hornblende, pyroxenes, garnet and magnetite, usually in comparatively large amounts, with minor amounts of epidote, tourmaline, and zircon. Noteworthy also is the uniformity of the heavy mineral assemblages of the Pleistocene and Recent sands with reference to mineralogic composition and relative abundance of the different mineral grains. It suggests a similar ultimate source area for all these deposits. The suite of minerals indicates that igneous rocks were dominant in the source area. The heavy mineral assemblages of the Cretaceous sands are very different from those of the Glacial sands or of the lake and river sands derived from Glacial deposits and are characterized primarily by kyanite, muscovite, tourmaline, zircon, staurolite, and rutile, with minor amounts of ilmenite, leucoxene, and sillimanite. The rare earth minerals, monazite and xenotime, although present only in small amounts, are consistently found in the Cretaceous sands and only very occasionally found in the non-Cretaceous sands. The source area for these sediments differed from the source of the Pleistocene and Recent sands. Metamorphic rocks such as schists and slates are indicated by the abundant stress minerals.

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