Mid-Tertiary paleoenvironments in Thailand: pollen evidence
1Laboratoire des Sciences du Climat et de l'Environnement/Institut Pierre Simon Laplace, UMR 8212 CEA/CNRS/UVSQ, Orme des Merisiers, bât. 709, 91191 Gif-sur-Yvette cedex, France
2Laboratory of Paleoenvironments, ISE-M, UMR 5554, Case 61, Université Montpellier II, 34095 Montpellier Cedex 05, France
3Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements, UMR 6046 CNRS, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Poitiers, France
4Paleontology Section, Department of Mineral Resources, Rama VI Road, Bangkok 10400 Thailand
*formerly at: Laboratory of Paleoenvironments, ISE-M, UMR 5554, Case 61, Université Montpellier II, 34095 Montpellier Cedex 05, France
Abstract. Only few well-dated records document the evolution of Southeast Asian paleoenvironments during the Cenozoic. Here we analyse continental pollen assemblages from Late Oligocene and Miocene fossil sites of Thailand. In agreement with previous studies, palynoflora from the Oligocene suggests warm temperate forested habitats at 24–26 Ma, whereas Middle Miocene assemblages are made of thermophilous taxa. This change can be linked to the major climate reorganization that brought warmer and wetter conditions over Southeast Asia around 22 Ma. This study also provides the first submillional records from the Middle Miocene of Thailand. Thirteen samples of lignite layers from the sivaladapid-bearing Mae Moh site, dated between 13.3 and 13.1 Ma, and six samples from the hominoid-bearing Chiang Muan deposit, dated between 12.4 and 12.2 Ma, document oscillations between tropical woodlands and grasslands in northern Thailand. These pollen records likely reflect climate variations linked to insolation variations. Late Miocene palynological assemblages from Khorat, northeastern Thailand, document fluviolacustrine paleoenvironments alternatively covered by thermophilous trees and grasslands. These records show that both sivaladapids and early hominoids from Thailand have evolved in tropical environments with high variability in the vegetation cover.