DEEP-FREEZE PETROLOGY OF LENA RIVER SAND, SIBERIA

Abstract

Modern sand from the vast (2430000 km2), high-latitude Lena River watershed occupies a low-lying, mostly unglaciated craton covered by thick, widespread permafrost— totally different from the watersheds of large temperate and tropical rivers, whose sands have been previously studied to establish modern baselines for the interpretation of ancient sandstones. Fifty-nine Lena sands are rich in rock fragments and feldspar and reflect well the three major tectonic provinces that underlie it—platform, shield, and collisional suture, although the platform and shield sands are still very immature. Long exposure to cool middle Tertiary climates at first, and dry sub-Arctic to Arctic climates later, is the underlying cause of the mineralogically immature river sands of the Lena River.