Khorat Group Research Articles

New goniopholidid specimens from the Lower Cretaceous Kitadani Formation, Tetori Group, Japan

New crocodyliform fossils have been discovered from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. They include skull elements (premaxilla, maxilla, parietal, quadrate and dentary), postcranium elements (dorsal vertebra, caudal vertebra, femur and osteoderm) and isolated teeth, and are described as goniopholidid crocodyliforms. Phylogenetic analysis resulted in nesting the Kitadani goniopholidid at the basal position of Goniopholididae and one autapomorphy is recognized: presence of the parietal sagittal crest. In addition, the narrow snout and a heterodont dentition in jaws of this goniopholidid is a unique combination of rostral morphology among Goniopholididae. Generally, the basal taxa bear a narrow snout with homodont dentition, and the heterodont dentition is seen in derived broad-snouted taxa. Judging from those rostral shape and dentitions, the Kitadani form possessing acute caniniform and blunt teeth tends to be more opportunistic as foraging strategy than other basal narrow-snouted goniopholidids with only acute caniniforms throughout. Our new discovery is the first osteological report of Japanese Cretaceous crocodyliform. Siamosuchus phuphokensis from the Early Cretaceous Sao Khua Formation, Khorat Group also shows combination of basal and derived cranial characters. Transitional species from Asia suggest allopatric speciation of goniopholidid in geographically intermediate Asian area.

The hydrocarbon source potential of Permo-Triassic rocks of the Indochina Block adjacent to the Paleo-Tethys suture in Thailand

The main Thailand petroleum systems are found in the syn-rift and post rift sections of Cenozoic rift basins. The Khorat Plateau area is a separate gas province with Permian limestone reservoirs possibly sourced from Triassic lacustrine, and Permo-Carboniferous marine shales. However, these source rocks and those of equivalent age west of the Khorat Plateau are not well described in the literature. This study investigated the source potential of outcropping Permo-Triassic shales from the western margin of the Khorat Plateau and the Khao Khwang Fold and Thrust Belt (KKFTB). The key formations sampled are: Permian: Alum Shale, Nong Pong, Sap Bon, Khao Khad, and Nam Duk formations; Triassic: Pang Asok and Hua Hin Lat Formation. Most potential Permo-Triassic source rocks sampled exhibited little potential due to the dominance of Type IV, non fluorescent amorphous, vitrinite and intertinite mascerals and low <1 % TOC content. Probably the Type IV kerogens are not original, but the product of subsurface alteration of other kerogen types (most likely Type III). The complex burial histories of the formations indicates such alteration could have occurred post-maturation. Probably maximum burial in the KKFTB was attained during the Triassic Indosinian Orogeny when upper diagenetic to anchizone conditions were attained. Significant burial also occurred when the Jurassic-Cretaceous Khorat Group (>2 km thick) was deposited. This later burial could be responsible for later maturation in areas north of the KKFTB. Simply in terms of TOC content >1, the Hua Hin Lat and Khao Khad formations have the most promising source potential.

Geochemistry and provenance of Mesozoic sandstones in Khon Kaen Geopark: Implication for tectonics of the western Khorat Plateau of Thailand.

Khon Kaen Geopark, representing an area of dinosaur fossil diversity, was selected for investigations to reveal the origin and tectonic setting of the Khorat Group. The area occupied by Mesozoic sedimentary rocks of four formal formations of the Khorat Group, namely the Phra Wihan Formation (PWF), Sao Khua Formation (SKF), Phu Phan Formation (PPF), and Khok Kruat Formation (KKF). A field investigation and macroscopic observations suggested that the immature sedimentary rocks of the study area are mainly clast-supported, pebbly sandstone and siltstone with few calcretes. The 50 rock samples that were selected for petrographical and geochemical investigations revealed that the sandstones of the PWF and PPF are quartz arenite and sublitharenite, with some subarkose, whereas those of the SKF are mainly subarkose and sublitharenite. In addition, the KKF dominantly presents sublitharenite with pebbles and calcretes. Mesozoic sandstones contain quartz, feldspars, various types of rock fragments, and accessory minerals (biotite, muscovite, zircon, and tourmaline), with siliceous, ferrous, and calcareous cement. Petrographic (Q-F-L) and geochemical (major and trace element) data suggested that the sources of sediments are mostly quartzose sedimentary rocks and some felsic-intermediate igneous rocks. Chondrite-normalized rare earth element patterns indicated that the origins of the studied sandstones are quartzose sedimentary rocks deposited in a passive continental margin or an upper continental crust. Geochemical traits of the sedimentary successions demonstrated that the provenance of the Khorat Basin prior to reworking by fluvial processes was situated in the passive continental margin or recycled orogen of the paleo-volcanic arc during the Mesozoic period.

Geodiversity in Khorat Geopark, Thailand: Approaches to geoconservation and sustainable development

This work aims to investigate the geodiversity of the Khorat Geopark area, Northeastern Thailand, and assess the geological sites that are connected to biological and cultural heritage, as well as community activities that enhance geoconservation and sustainable development. The geological diversity of Khorat Geopark dates back to the late Jurassic period and continues to the present day, resulting from the deposition of terrestrial sedimentary rocks from the Khorat Group. The Khorat rock group has been uplifted and eroded to form the Khorat Plateau with a unique landscape and important geological features of the cuesta landform on the western part of the Khorat Geopark. On the four corners of Nakhon Ratchasima City, there are numerous fossils of outstanding Early Cretaceous dinosaurs and other reptiles and Cenozoic fossils of both flora and fauna, mainly mammalian remains and, in particular, ancient elephants. Geological sites in the Khorat Geopark area were weighted and scored based on their scientific value (SV), potential value for education (EV), potential value for tourism (TV), and degradation risk variables (DV). According to the assessment, the Khorat Geopark's 24 geosites are of moderate to high value, with 7 sites having 301–400 scores and 5 sites having a high level of international value. Most of them are related to fossils and cuestas. Thus, the fossil diversity of the Khorat Geopark is of international scientific significance. Khorat Geopark is managed under the conservation, education, and sustainable development initiatives using a bottom-up method with multiple networks, both local communities and local governments, especially through the Home-Temple-School (HTS) model.

A preliminary assessment of geological CO2 storage in the Khorat Plateau, Thailand

The main carbon dioxide (CO2) emissions in Thailand come from the energy sector. Gas-based power plants, including natural gas and biogas, are CO2 point sources, and are mostly located in the Khorat Plateau. Geological CO2 storage is an important element in the effort to reduce CO2 emissions from CO2 point sources. This study is a preliminary assessment of the geological CO2 storage potential of the onshore Khorat Plateau. A potential geological formation is screened and ranked in terms of its suitability as a CO2 storage site (storage optimization, risk minimization and feasibility). The results of this screening and ranking indicate that, among the tested sites in this study, the Khorat Permian carbonate is the most suitable for geological CO2 storage, followed by the Khorat Group sandstone, and Khorat evaporite. However, the Khorat Cenozoic basalts are not suitable for geological CO2 storage in the Khorat Plateau. The results from this study should advance the understanding of petroleum exploration and carbon capture and storage technology in Thailand, especially in the Khorat area. However, it should be noted that more subsurface studies are needed, and more criteria should be included in the future to improve the reliability of the assessment of geological CO2 storage potential in the Khorat Plateau.

Age, depositional history, and paleoclimatic setting of Early Cretaceous dinosaur assemblages from the Sao Khua Formation (Khorat Group), Thailand

We describe the sedimentology, geochronology, and geochemistry of the Early Cretaceus Sao Khua Formation of the Khorat Basin, northeastern Thailand, and report a temporal range adjustment for its dinosaurian assemblage. Facies analysis and architectural studies reveal that sedimentation occurred within a floodplain setting fed by large meandering bedload-rich channels. Interfluve areas comprised freshwater lakes and emergent areas subject to pedogenic modification. Multiple paleosol types are identified and geochemistry is indicative of a stable humid subtropical climate regime. Based on radiometric dating of detrital zircons (via LA-ICP-MS), we interpret that the middle part of the Sao Khua Formation was deposited no later than 133.8 (±1.8) Ma (late Valanginian), and grain ages collected from the overlying lowermost Phu Phan Fm constrain sedimentation of the upper part of the Sao Khua Formation to no earlier than 132.4 (±2.0) Ma (early Hauterivian). In consideration of the Early Cretaceous regional tectonic framework, we interpret that youthful igneous zircon grains are derived from the adjacent South China-Vietnam South Borneo Volcanic Arc. We establish that the entombed dinosaur biota (including members of the Ornithomimosauria, Spinosauridae, Megaraptora, and Somphospondylia) is ~5–9 million years older than previously recognized and that these records are among the oldest known globally for these clades. Constraining the age of the Sao Khua Formation indicates that the shift from sauropod-dominated, ornithischian depauperate ecosystems of the Sao Khua Formation to iguanodontian-rich ecosystems of the Khok Kruat Formation occurred sometime between the early Hauterivian and Aptian on the Khorat Plateau.

Characterisation of potholes formed on bedrock sandstones at Loei Dun, Phetchabun Geopark, Thailand

Abstract Phetchabun National Geopark comprises varied geosites; one of the fluvial bedrock landforms distinguished here is Loei Dun. This shows many potholes in Mesozoic sandstone of the Nam Phong Formation (Khorat Group). A genetic study of the occurrence of the Loei Dun potholes lends it a higher geoheritage value. For the present study we did fieldwork and carried out petrographical and geotechnical analyses so as to classify and characterise the potholes and consider geotourism potentials. Petrographically, the bedrock sandstone is a lithic arenite which consists of 82-96 percent very fine to coarse, well-sorted subangular sand with low sphericity and calcite cementation. Our geotechnical analysis of the bedrock sandstone suggests that pothole occurrence may be linked to low rock strength and slake durability index with high rock absorption and porosity at Loei Dun. Field studies confirmed the impact of other factors such as joints/faults, fluvial conditions and biological weathering. There are five types of pothole, viz., simple ones, potholes with external furrows, compound potholes, breached potholes and lateral ones. The present study adds educational value to the Loei Dun geosite at Phetchabun Geoparks and cultural and economic aspects can be further strengthened through the development of geotourism in the area.

Fossil assemblage from the Khok Pha Suam locality of northeastern, Thailand: an overview of vertebrate diversity from the Early Cretaceous Khok Kruat Formation (Aptian-Albian)

The Khok Pha Suam locality in the province of Ubon Ratchathani, northeastern, Thailand, is known as “the last home of Thai dinosaurs”, because it belongs to the Lower Cretaceous Khok Kruat Formation (Aptian-Albian) which is currently the youngest Mesozoic vertebrate fossil producing formation in the Khorat Group. Here, we describe a diverse vertebrate assemblage, including hybodonts, ray-finned fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs from the Khok Pha Suam locality. The updated data on the Khok Kruat fauna provides a better understanding of the variety and distribution of Early Cretaceous continental ecosystems, which are useful for palaeoenvironmental reconstruction. In addition to consolidating unincorporated data on fauna, this study also provides the palaeontological data necessary to illustrate the palaeoecosystem to the general public, as well as improving the academic value of the Pha Chan-Sam Phan Bok Geopark.

Geology of Hin Chang Si Sandstone Geoheritage in Khon Kaen Province for Geotourism Planning of Northeastern Thailand

One of the most distinguished sandstone geoheritage resources in the Khorat Plateau is Hin Chang Si located in the Nam Phong National Park, Khon Kaen Province. The clastic sedimentary rocks of the Phra Wihan Formation of the Khorat Group covered this area. As a result of the lithologic study, the Hin Chang Si consists of pebbly sandstone, moderately sorted medium- to coarse-grained sandstone, and a small amount of siltstone interbedded with laminated shale. The characteristics (colors, cementation, and degrees of weathering) divided sandstones into two groups, including white grain-supported sandstone with silica cement and matrix-supported sandstone with Fe-rich cement. In addition, these sandstones present primary sedimentary structures, which comprise tabular cross-bedding and normal grading as well as bioturbation. Hin Chang Si demonstrates many geomorphological features, including cliffs, potholes, rock pillars, polygonal cracks, caves, tafoni, runnels, and natural arches according to inventory. The weathering and degradation processes in humid tropical conditions are the main processes that caused these geomorphological features. Whereas many primary factors affected various types of morphology that are composed of joints, folds, and faults. The national park provides the natural trail map, tourism information, and biodiversity data to visitors; however, geological information about sandstone landforms should be actualized for geotourism development.

Turtle remains from the Early Cretaceous of Kut Island, Gulf of Thailand

An isolated first costal turtle plate from the Early Cretaceous of Kut Island, Gulf of Thailand, is reported and assigned to Trionychoidae gen. et sp. indet. The morphology of the plate and comparison with turtle assemblages of the Khorat Group support the correlation of the vertebrates-bearing beds of Kut Island with the Sao Khua Formation, as already suggested by the studies on sharks and dinosaurs.

Frequent Polarity Reversals in the Cretaceous Normal Superchron

AbstractThe Cretaceous Normal Superchron (CNS), defined as a magnetic quiet zone spanning from ∼126 to ∼84 Myr, is often used to understand the Earth’s geodynamo processes. However, whether there were polarity reversals within the CNS remains contentious. This paper presents the youngest detrital zircon U‐Pb age‐constrained magnetostratigraphic study of the Cretaceous Khorat Group for two sections (i.e., Ban Phonngam (BP) and Ban Nongpen (BN)) in Vientiane, Laos. Both sections are characterized by the prominent long normal‐polarity zones that are correlated to the CNS. Interestingly, six (four) short primary reversed horizons were identified within the BP (BN) section. Integrated with other reported reversed events, there likely at least five globally and two single reported reversed‐polarity events or clusters of events have happened within the CNS. The confirmation of frequent reversed polarities within the two parallel sections will provide a new comprehensive understanding of the Earth’s geodynamic behavior during the CNS.

A Review of the Lithostratigraphy of the Early Cretaceous Sao Khua Formation, Khorat Group in Northeastern Thailand

Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation is in the upper half of the Khorat Group which is comprised of six formations. This formation was named and defined at the type section for the rocks between the restricted PhraWihan Formation and the Phu Phan Formation in the drainage area of the Huai Sao Khua, an intermittent stream that flows westward parallel to the highway between Nong Bua Lamphu and UdonThani Provinces. It contains richest and most diverse vertebrate and invertebrate Mesozoic fossils in Thailand. The Sao Khua Formation is characterized by the sequence of the fining-upward successions of at least 4-5 megacycles throughout the formation with the total thickness ranging between 400-700 meters. Each cycle starts with a channel lag conglomerate which the clasts consist totally of re-worked calcrete nodules. The conglomerates were overlain by fine-to medium-grained sandstones of point bar deposit. Finally, the top part of each cycle was covered by a succession of fine-grained floodplain deposit that makes up 60%-70% of the formation. Paleosols are commonly found in the Sao Khua Formation within the floodplain sequence and their geochemistry indicates a semi-arid paleoclimate. Based on lithostratigraphy, the Sao Khua Formation is interpreted to have been deposited by a meandering river system under a semi-arid climate condition. The age of the formation is assigned as the Hauterivian-Late Barremian based on vertebrate and bivalves fossils.

Xenoxylon, a boreal fossil wood in the Mesozoic redbeds of Southeast Asia: Potential for the stratigraphy of the Khorat group and the palinspatic reconstruction of Southeast Asia

The fossil wood genus Xenoxylon is reported in-situ for the first time in Thailand. It originates from the Indosinian terrane, from the Mesozoic continental redbeds of the Phu Kradung Formation (Khorat Group). Palinspatic reconstruction, palaeobiogeography and correlation with other occurrences of the genus, in southern China as well as in Vietnam, suggest a middle to late Jurassic age for the Phu Kradung Formation level yielding the fossil wood. The dating of this formation is still controversial and thus our data is an important step towards a better understanding of its geological history and palaeoecology, as well as of the Southeast Asia Mesozoic continental redbeds significance for the evolution of the vertebrates.

Phu Din Daeng, a new Early Cretaceous vertebrate locality on the Khorat Plateau, NE Thailand

In this paper, we report on a new Early Cretaceous vertebrate locality, Phu Din Daeng, in Nakhon Phanom Province, NE Thailand. The Phu Din Daeng site has yielded a diverse vertebrate assemblage, including sharks (Heteroptychodus steinmanni), bony fishes (Pycnodontiformes; Sinamiidae cf. Siamamia and ?Vidalamiinae, and Ginglymodi), adocid turtles, indeterminate neosuchian crocodiles, pterosaurs and dinosaurs (spinosaurids and indeterminate theropods). A new adocid turtle, Protoshachemys rubra n. g. n. sp. is described on the basis of shell material. Field investigations on the geology and comparisons with other vertebrate faunas place Phu Din Daeng in the Sao Khua Formation (Barremian) of the Khorat Group.

タイ国東北部のコラート層群より産する恐竜足跡化石について ―足跡相の 概要とその特徴―

タイ国東北部のコラート層群より産する恐竜足跡化石について ―足跡相の 概要とその特徴―

First Cretaceous fish fauna from Malaysia

ABSTRACTCretaceous fish fossils are reported from Malaysia for the first time. They were found with dinosaur and turtle remains in nonmarine sediments in the interior of Pahang State, Peninsular Malaysia. This fish assemblage consists mostly of isolated teeth, with minor amounts of noncranial remains, including vertebral centra, scales, coprolites, and hybodont fin spines. Over 100 fish teeth were examined. Nine taxa were confirmed from this fish assemblage: six (identified and unidentified) species of hybodont sharks, Heteroptychodus kokutensis, Isanodus paladeji, Lonchidion aff. khoratensis, Mukdahanodus aff. trisivakulii, Egertonodus sp., and Hybodontidae indet., and three species of actinopterygians (ray-finned fishes): ‘Lepidotes’ sp., Halecomorphi indet., and Ginglymodi indet. This fish assemblage has strong affinities with Early Cretaceous (Barremian–early Aptian) faunas of Thailand, because the four hybodont species, H. kokutensis, I. paladeji, L. khoratensis, and M. trisivakulii, were previously known only from the Sao Khua Formation (Khorat Group) and equivalent strata of Ko Kut (Kut Island). Egertonodus has been confirmed in Asia for the first time. Overall, this fish assemblage shows a close linkage to Early Cretaceous (Barremian–early Aptian) faunas of Thailand. Based on faunal composition and biostratigraphic correlation, we suggest a Barremian–early Aptian age for this new fauna from Malaysia.

Sedimentology and Stratigraphy of Phu Sung Fossil Site of the Lower Cretaceous Sao Khua Formation, Sakon Nakhon Province, Northeastern Thailand

“Phu Sung”, a new fossil site in Sakon Nakhon Province was recently reported. Phu Sung fossils are very complete and in very well-preserved condition. They were found in reddish micaceous silty mudstone. The stratigraphy and sedimentology show that Phu Sung succession is a continental deposit in the fluvial system and it is in the Early Cretaceous Sao Khua Formation of the Khorat Group. According to lithology, fossils were deposited in a quiet environment, such as overbank deposit, small pond or oxbow lake margin. Sedimentary structures such as desiccation crack and calcrete indicate semi-arid to arid paleoclimate condition which probably corresponds to the taphonomy or preservation of the fossils.

Landslide Hazard Zoning in Na Heaw District, Loei Province, Northeastern Thailand

Nahaew District in northeastern Thailand, where crops out the Cretaceous Khorat Group, is a priority area for landslide hazard assessment through landslide susceptibility and hazard zoning. Through an interpretation of Google Earth imagery, several landslides were mapped to create landslide inventory map. Parameter maps were constructed and compiled into a database with the landslide inventory. The bivariate (frequency ratio) statistical analysis was used to establish landslide susceptibility maps, which were classified into five susceptibility classes. Another approach was landslide hazard zonation. Urban and rural planning and engineering construction need especially hazard zonation map in medium and local scale. GIS and remote sensing techniques have many advantages in the preparation of the map including regional, medium and local scales. In this study, landslide zonation map was prepared using runout model by assigning engineering properties and Digital Elevation Model (DEM) as well as rainfall data. The result was landslide hazard zonation of the area and can be used for urban planning. The report and recommendation have contributed to local authority.

New Vertebrate Fossil Site from the Early Cretaceous Sao Khua Formation, Sakon Nakhon Province, Northeastern Thailand

A new vertebrate fossil site, “Phu Sung” in Sakon Nakhon Province was discovered. Various vertebrate fossils belonging to fresh water shark, bony fish, turtle, crocodile and dinosaur were found in reddish silty mudstone of the Early Cretaceous Sao Khua Formation of the Khorat Group. Crocodilian remains including a complete skull and partial articulated skeleton are very well preserved associated with turtle remains. Moreover, well preserved 19 turtle shells were found accumulated together. These discoveries will certainly fulfill our knowledge about these aquatic taxa from the Early Cretaceous Sao Khua Formation. The exceptional preservation of Phu Sung fossils could probably relate to the paleoenvironment in the Early Cretaceous of Thailand.

Sandstone provenance and U–Pb ages of detrital zircons from Permian–Triassic forearc sediments within the Sukhothai Arc, northern Thailand: Record of volcanic-arc evolution in response to Paleo-Tethys subduction

Provenance analysis and U–Pb dating of detrital zircons in Permian–Triassic forearc sediments from the Sukhothai Arc in northern Thailand clarify the evolution of a missing arc system associated with Paleo-Tethys subduction. The turbidite-dominant formations within the forearc sediments include the Permian Ngao Group (Kiu Lom, Pha Huat, and Huai Thak formations), the Early to earliest Late Triassic Lampang Group (Phra That and Hong Hoi formations), and the Late Triassic Song Group (Pha Daeng and Wang Chin formations). The sandstones are quartzose in the Pha Huat, Huai Thak, and Wang Chin formations, and lithic wacke in the Kiu Lom, Phra That, Hong Hoi and Pha Daeng formations. The quartzose sandstones contain abundant quartz, felsic volcanic and plutonic fragments, whereas the lithic sandstones contain mainly basaltic to felsic volcanic fragments. The youngest single-grain (YSG) zircon U–Pb age generally approximates the depositional age in the study area, but in the case of the limestone-dominant Pha Huat Formation the YSG age is clearly older. On the other hand, the youngest cluster U–Pb age (YC1σ) represents the peak of igneous activity in the source area. Geological evidence, geochemical signatures, and the YC1σ ages of the sandstones have allowed us to reconstruct the Sukhothai arc evolution. The initial Sukhothai Arc (Late Carboniferous–Early Permian) developed as a continental island arc. Subsequently, there was general magmatic quiescence with minor I-type granitic activity during the Middle to early Late Permian. In the latest Permian to early Late Triassic, the Sukhothai Arc developed in tandem with Early to Middle Triassic I-type granitic activity, Middle to Late Triassic volcanism, evolution of an accretionary complex, and an abundant supply of sediments from the volcanic rocks to the trench through a forearc basin. Subsequently, the Sukhothai Arc became quiescent as the Paleo-Tethys closed after the Late Triassic. In addition, parts of sediments of supposed Devonian–Carboniferous age within the Sukhothai Arc were revised as the Triassic Lampang Group, and the Early Cretaceous Khorat Group.