The Palaeo-Productivity Signals Chronicled from the Buxa Formation, North-East Lesser Himalaya, India

ABSTRACT The Mesoproterozoic era is known for its relatively stable ecological conditions and limited atmospheric oxygen. Despite this understanding, uncertainties remain about how ocean chemistry evolved during this time and its potential impact on the development of complex eukaryotic life forms. In response to these uncertainties; we have undertaken a study to investigate indicators of ancient productivity within the Buxa Formation of the Lesser Himalaya in Sikkim. By analyzing the isotopic values ( δ13 C and δ 18Ο values) as well as Rare Earth Element (REE) composition, a total n = 151 carbonate samples were investigated across three sections of the Buxa Formation: Jorethang to Mangalbare, Legship to Naya Bazar, and Reshi to Mangalbare, Sikkim. The study’s findings show that there was minimal variation in δ13C values, consistently ranging between –0.5 and +2.5 ‰ VPDB. This pattern suggests a relatively steady and moderately high level of productivity during that time. This productivity might have been influenced by a temporary increase in atmospheric oxygen levels. Additionally, we have also reviewed and examined stromatolites as part of the investigation.