Snail diversity and paleoenvironment of the 12-meter-thick freshwater gastropod bed, Middle Miocene, Mae Moh Basin, Thailand

The purpose of this study is to investigate snail fossils collected from a 12-m-thick freshwater gastropod bed of the Middle Miocene in the Mae Moh Basin, Northern Thailand, in order to investigate gastropod diversity, paleoecology, and paleoenvironment using stable isotope data.Gastropod individuals of 7,532 were analyzed, representing 3 families of freshwater snails (Viviparidae, Bithyniidae, and Planorbidae), indicating freshwater paleoenvironments such as ponds or lakes with intermittent river influx.Bellamya is the most dominant genus (62.75%), followed by Bithynia (28.92%),Idiopoma (7.08%), Cipangopaludina (0.76%), and Mekongia (0.50%), respectively.The stable isotopic analysis of Bellamya shells revealed 13 C values ranging from 2.10 to 5.54 and 18 O values from -2.99 to -6.89 .The positive 13 C values could result from dissolved inorganic carbon uptake from the dissolution of marine limestone surrounding the Mae Moh paleo-lake.The 18 O values confirm that the gastropods inhabited a freshwater environment in a humid climate.The findings provide valuable insights into the Middle Miocene thick gastropod deposition.