Characteristics and paleoenvironmental indications of caddisfly larval cases-stromatolite bioherms in the Lower Cretaceous in Liupanshan Basin, Central China

Abstract

Fossil caddisfly larval cases (CLCs) are of great significance for reflecting the habits of ancient caddisfly and indicating the paleoenvironment. Multiple layers with bioherms formed by fossil CLCs and stromatolites were found to be distributed in the Lower Cretaceous in Liupanshan Basin, Central China. In order to deeply understand the characteristics and formation environment of the CLCs-stromatolite bioherms, a series studies were conducted on the Yaoshan section in the northeastern of the basin. Morphological anatomy, mineralogy, element geochemistry, and isotope geochemistry are included in the studies. It reveals that the CLCs-stromatolite bioherms in Yaoshan are mainly composed of calcite and dolomite mineralogically, and CLCs and stromatolite morphologically.

In the bioherms, a large number of fossil CLCs stacked orderly, with a conical shape perpendicular to the stratum distribution. The bioherms were deposited in a semi-enclosed saline lake in hot and dry paleoclimate, and they were mainly formed during the periods when the evaporation increased, the water body became shallower, and the supply of terrestrial material increased.