Phytolith insights into palaeosol formation and climate dynamics in the Pliocene Karewa deposits, Kashmir Himalaya, India

Abstract

The phytolith study of sedimentary deposits serves as a valuable tool for reconstructing past vegetation and environmental changes. In this study, we carried out a phytolith analysis of a palaeosol and a clay bed from the Pliocene Lower Karewa deposits of the Kashmir Himalaya, India. The palaeosol lies directly over the hard rock basement. The material that forms the palaeosol is thought to represent sedimentation at the time of Kashmir Valley formation around 4 Ma owing to the uplift of the Pir Panjal Range. The phytolith assemblages suggest the area supported a complex vegetation structure during palaeosol formation and clay bed deposition. The phytolith assemblages, commonly associated with C₄ grasses — characteristic of warm, arid, and low CO₂ environments, and some woody plants and shrubs, suggest warmer and drier climatic conditions during palaeosol formation. However, micromorphological analysis and detailed field observations suggest that the material that forms the palaeosol was deposited much later than the commencement of valley formation. The co–occurrence of phytoliths of diverse climate and vegetation types along the depth of palaeosol indicates a thorough mixing of material during its deposition, possibly by pedogenic, glaciotectonic or mass–wasting processes. Our study provides a renewed viewpoint on the oxidized palaeosol, suggesting that previous interpretations about its formation during basin formation need reconsideration. On the other hand, the clay bed depicts less diverse phytolith assemblages, suggesting a possibly harsher, colder environment. The phytolith morphotypes of the clay bed depict a more controlled climate, and each lamina suggests the phytolith of a particular time period.