The Khorat Group is a stratigraphic group located within the Khorat Plateau in the

Isan Northeast Thailand or Isan (Isan/ th, อีสาน, ; lo, ອີສານ; also written as Isaan, Isarn, Issarn, Issan, Esan, or Esarn; from Pali ''īsānna'' or Sanskrit ईशान्य ''īśānya'' "northeast") consists of 20 provin ...

region of

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is bo ...

. It was first defined as the Khorat Series by Brown et al in 1953 and was redefined as the Khorat Group by Ward and Bunnag in 1964, which gave it its current constituent formations as well as including the

Nam Phong Formation The Nam Phong Formation, which correlates to the Indosinian III Unconformity, is a geological formation in Thailand. It underlies the Khorat Group. It consists of resistant, red-brown micaceous sandstones, conglomerates, siltstones and mudstones ...

, which is now excluded from the group. Subsequently the sequence underwent several different stratigraphic proposals with several alternative divisions, but the formations proposed in Ward and Bunnag are the most widely used. Initially thought to be

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

, the sequence has been shown to be of

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

in age, Dating from the

Berriasian In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago) ...

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

. It overlies the

and is overlain by the evaporitic deposits of the Maha Sarakham Formation. It consists of continental freshwater deposits largely of alternating sandstones and mudstones. The Group is notable for its fossil content, including those of dinosaurs.

References

{{Reflist Geologic groups of Asia Geologic formations of Thailand Lower Cretaceous Series of Asia Cretaceous Thailand