Cambrian microfossils from the Tethyan Himalaya

Abstract

AbstractCambrian biostratigraphy of the Indian subcontinent is best documented from the Parahio Formation of the Tethyan Himalaya. Recently established trilobite biostratigraphy shows that the formation encompasses the latest part of unnamed Stage 4 and much of unnamed Stage 5. A variety of small shelly fossils have been recovered via acid digestion of carbonate beds and include tetract and pentact hexactinellid sponge spicules, chancelloriid spicules belonging toChancelloriasp. and a new species,Archiasterella dhiraji, shells of an helcionelloid comparable toIgorella maidipingensis, a meraspid ptychopariid trilobite, the tubularCupithecasp., a poorly preserved hyolith, and an assortment of spinose microfossils of uncertain affinity. These newly recovered microfossils are consistent with the trilobite-based lower and middle Cambrian age determination and do not support a late Cambrian age for the top of the Parahio Formation advocated in some recent literature. The microfossils reported herein significantly expand the known diversity of such fossils from Cambrian strata in the Himalayan region, and allow for comparison of this fauna with others from Gondwanaland and elsewhere. Integration with trilobite data indicate that the stratigraphic ranges of many small shelly fossils described in this study are greater than previously recognized.