Geological Characteristics of Tempestite from Cambrian Abuqiehai Formation in Middle Helan Mountain and Its Geological Significance

A suite of typical storm deposition has been discovered for the first time in Helanshan area of Ningxia, which was developed in the middle and lower parts of upper Cambrian. Bottom-erosion texture, bio-disturbed texture, imbricate-boulder texture and radial fabric can be found in these storm sediments, indicating a typical shallow-water storm deposition. The lower part of this formation consists of oolitic limestone, bamboo-like limestone and argillaceous banded limestone. The oolite shows an evident decline in the middle part, which mainly consists of calcirudite, algal limestone and argillaceous banded limestone. Dolomite lime appears in the top part of this formation, indicating a shallow subtidal sedimentary environment. The discovery of storm rock has a great significance for the reconstruction of middle and late Cambrian paleogeography and the comparison of regional strata in Helanshan area of Ningxia.