湖北当阳白垩纪风成石英砂

风成沉积是干旱或半干旱气候下的一种典型产物,包括石漠戈壁滩,沙漠和风成黄土。世界上研究得较详细的古代沙漠沉积的地质时代是侏罗纪、二叠-三叠纪、泥盆纪、下寒武世和前寒武纪,尤其是二叠纪最佳。在我国,已经报道的古风成沉积时代不老于白垩纪。1963年张步春和王景钵首次报道在广东河源红色盆地地层中,发现了风成斜层理和风棱石。后来,笔者在湖南沅麻红色盆地的白垩系中也发现有风成砂。

OBSERVATION ON CRETACEOUS EOLIAN QUARTZ SANDS FROM DANGYANG COUNTY, HUBEI PROVINCE

The sand samples for SEM were taken from the Upper Cretaceous Honghuatwoun Formation in Dangyang, Hubei Province. According to scanning electron microphotographs the quartz sand surface textures can be divided into following types:1)rounded grain with rounded corners and edges. The flatten part of grain appears to have imprint of eolian abrasion(Fig. 1);2)irregular depressions and meandering ridges on rounded grain(Fig. 2);3)chemical solution and precipitates of SiO2(Fig. 3);4)disordered conchoidal breakage patterns caused probably by grain-to-grain collision in an eolian environment; and5)the remained striated groovs(Fig. 2, a)and imbricated breakage blocks(Fig. 2, b). Types 1 to 4 are shown as evidence for eolian origin; Type 5 may indicate the source of debris mudflow deposits in mountain apron environment.