Quartz-Grain Surface Features of Mesozoic-Cenozoic Sands from the Labrador and Western Greenland Continental Margins

Abstract

ABSTRACT The quartz-grain surface features of 39 Cretaceous and Paleocene sand samples from offshore Labrador and onshore western Greenland were examined by scanning electron microscope. The results of this study and those of other workers reveal the existence of 30 distinct surface features. The Labrador-Greenland sand grains show an abundance of pre-transportational surface features, imparted during liberation of the grains from crystalline source rocks. Impact features are relatively scarce, and features indicative of deltaic, aeolian and glacial environments are absent altogether. Among chemically produced surface features, those of precipitational origin far outweigh those due to silica dissolution. It is concluded that the Labrador-Greenland sands were derived, under acidic weathering conditions, from local crystalline parents and deposited in both marine and non-marine environments. Quartz overgrowths are present in all stages of development. A distinctive, high-relief surface texture (gullying), thought to originate by marine decapitation of pre-transportational pedologic overgrowths, is described and illustrated. Authigenic minerals adhering to quartz-grain surfaces include kaolinite, illite, dolomite, potassium feldspar, and pyrite.