The Sao Khua Formation () is a middle member of the

Khorat Group The Khorat Group is a Group (stratigraphy), stratigraphic group located within the Khorat Plateau in the Isan region of Thailand. It was first defined as the Khorat Series by Brown et al in 1953 and was redefined as the Khorat Group by Ward and B ...

. It consists of an alteration of pale red to yellowish-gray, fine to medium-grained sandstone and grayish-reddish brown siltstone and clay. Rare pale red to light gray conglomerates, containing carbonate pebbles, are also characteristic of this formation. This geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in Thailand dates to the Early Cretaceous age, specifically the

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...

through

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the ...

stages. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 563-570. .

Depositional environment

Baser on

paleosol In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geolo ...

s and

lithostratigraphy Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous ...

, the Sao Khua Formation is believed to have been deposited in a warm to slightly cool

semi-arid climate A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of sem ...

by a meandering river system.

Geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...

is indicative of a stable humid subtropical climate regime, and sedimentation is thought to have occurred in a

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

setting which was fed by bedload-rich large

meandering A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank (cut bank) and deposits sediments on an inner, convex bank ...

channels.

Paleocurrent A paleocurrent or paleocurrent indicator is a geological feature (typically a sedimentary structure) that helps one determine the direction of flowing water in the geologic past. This is an invaluable tool in the reconstruction of ancient deposit ...

analysis suggests the sand channels at the time of deposition of the formation probably formed a

braided channel A braided river, or braided channel, consists of a network of river channel (geography), channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers ...

environment.

Fossil content

Amphibians

Reptiles

Dinosaurs

* Sauropoda indet. 1 and 2

Lizards

Pseudosuchians

Pterosaurs

Turtles

Fish

Bony fish

Cartilaginous fish

Invertebrates

Bivalves

References

{{Reflist Geologic formations of Thailand Lower Cretaceous Series of Asia Cretaceous Thailand Sandstone formations Conglomerate formations Paleontology in Thailand Valanginian Stage Hauterivian Stage