Phra Wihan Research Articles

Fracture Characterization Explores Potential of Phra Wihan Formation, Thailand

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22845, “Fracture Characterization and Basement Reservoir Potential of Phra Wihan Formation in Southern Part of Uttaradit Province, Northern Thailand,” by Watcharapong Piewmoh, SPE, PTTEP, and Pitsanupong Kanjanapayont, Chulalongkorn University. The paper has not been peer reviewed. Copyright 2023 International Petroleum Technology Conference. Reproduced by permission. _ The complete paper describes the characterization of fractures in the Mesozoic sandstones of the Phra Wihan Formation in northern Thailand. Fracture characterization of outcrop analogs is important to determine the potential of subsurface reservoirs. The methodology used field study and petrography analysis to determine the relationship of fractures and other structures such as bedding planes and fold geometry. In addition, microstructure analysis can assist in the evaluation of a reservoir’s potential. Introduction Basement reservoir sandstones are one of the main targets in a mature onshore oil field in Thailand. But most basement reservoirs of the onshore Tertiary basin are pre-Tertiary and are associated with low quality. Prediction of reservoir quality in low-porosity and -permeability conditions requires an understanding of fractures in the subsurface. Outcrop analogs are key in characterizing fractured reservoirs. Geological Setting The tectonic evolution of Thailand is detailed in the complete paper. The country’s primary geological provinces are subdivided into the following five components, from west to east: - Sibumasu terrane - Inthanon zone - Sukhothai terrane - Nan and Sra Keao sutures - Indochina terrane The Sibumasu and Indochina terranes are major continental masses that collided during the Devonian-Triassic. Two subparallel suture zones exist along the convergence between the Sibumasu and Indochina terranes; one is an accretionary complex defined by the Inthanon zone. Another is a closed back-arc basin defined by the Nan and Sra Keao sutures. The Sukhothai terrane is an island-arc system formed along the margin of the Indochina terrane.

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.

Possibly Oxfordian (Upper Jurassic) cockroach assemblage (Insecta: Blattaria) from the Phra Wihan Formation in Thailand

Possibly Oxfordian (Upper Jurassic) cockroach assemblage (Insecta: Blattaria) from the Phra Wihan Formation in Thailand

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.

Frictional behavior of sandstone fractures under forward-backward pre-peak cyclic loading

The objective of this study is to determine the effect of cyclic loading under pre-peak condition on shearing behavior of fractures in Phra Wihan sandstone, primarily to improve an understanding of the stability conditions of slope embankments along roadways and railways in the north of Thailand where seismic activities have often occurred. The fractures were artificially made in the laboratory by tension inducing method and cyclically sheared under forward to fully backward loading paths with constant normal stresses between 1 and 4 MPa. Two cyclic loading conditions were used on separate sets of specimens: constant stress amplitude and constant displacement amplitude. Fifty shear cycles were applied. The results indicated that the pre-peak cyclic loading under both loading conditions slightly reduce shear strengths and stiffness of the sandstone fractures due to the degradation of the second order fracture asperities. Fracture roughness notably reduced particularly under large shear stress and displacement amplitudes due to the deposition and packing of rock power. The subsequent monotonic loading performed after cyclic loading showed further reduction of fracture roughness due to the degradations of the first order asperities.

To Belong or Not to Belong. Affective Self‐Nationalization in Thailand

Through analyzing conflict narratives regarding Khao Phra Wihan, a territorial conflict important for nationalists in Thailand, this article aims to detangle how nationalization is experienced and performed on an individual level. In this article, the concept “affective self‐nationalization” is proposed to analyze the emotional and embodied practices through which individuals fashion themselves into nationalized subjects. In Thailand, self‐nationalization is instigated by the governing agency through repeated, regular, mandatory, public performances of loyalty through which individuals create the nation collectively. These performances create automatic feelings to the nation, establishes national others as fearsome, and rule through the basic human need of belonging. At the same time, individuals’ emotions shape the society through how they decide to perform nationalization. The concept of “affective self‐nationalization” captures the connections between the official nationalizing program of “outside” society in a form of nationalist emotional socialization with individual experience of nationalizing.

Disturbing the nationalist imaginary: everyday resistance to nationalism in the Thai-Cambodian borderland

ABSTRACTBased on narratives from civil societal actors that have been involved in some way in the conflict over Khao Phra Wihan, this paper concerns the construction of the Thai nation, and how that is resisted. The paper brings together social constructivist views on nationalism with research on everyday, low-scale, individual, non-organized, covert, low-profile forms of resistance. The way nationalism is resisted in the borderland can be categorized into three main themes: (1) Everyday resistance through evasion, (2) Everyday resistance through re-categorization, and (3) Everyday resistance through re-imagination.

Puangthong R. Pawakapan. State and Uncivil Society in Thailand at the Temple of Preah Vihear. Singapore: Institute of Southeast Asian Studies, 2013, xiv+125p.; bibliography, index. Charnvit Kasetsiri, Pou Sothirak, and Pavin Chachavalpongpun. Preah Vihear: A Guide to the Thai-Cambodian Conflict and Its Solutions. Bangkok: White Lotus, 2013, xiv+104p.; bibliography, no index.

State and Uncivil Society in Thailand at Temple of Preah Vihear Puangthong R. Pawakapan Singapore: Institute of Southeast Asian Studies, 2013, xiv+125p.; bibliography, index.Preah Vihear: A Guide to Thai-Cambodian Conflict and Its Solutions Charnvit Kasetsiri, Pou Sothirak, and Pavin Chachavalpongpun Bangkok: White Lotus, 2013, xiv+104p.; bibliography, no index.In recent years, instead of being a place for peace, meditation, contemplation, and prayer, ancient Khmer temple of Prasat Preah Vihear (Phra Wihan to Thai) has become an object of political dispute and military clashes between two ASEAN members: Thailand and Cambodia. two short books under review are a welcome addition to growing corpus of literature on temple dispute which arose after controversial decision by UNESCO in July 2008 to inscribe Preah Vihear on its World Heritage list. author of first volume, Puangthong R. Pawakapan, is Associate Professor in International Relations Department of Chulalongkorn University's Faculty of Political Science and best qualified to write on this subject as she has in past conducted extensive research on Thai-Cambodian relations.1) main purpose of this well-written booklet, however, is not only to provide a comprehensive overview of historical background of conflict, but also to analyze actions, strategy, and objectives of campaign of Thailand's People's Alliance for Democracy's (PAD) to exploit border conflict for its own anti-Thaksin agenda.The PAD, also known as Yellow Shirt movement, is seen in State and Uncivil Society in Thailand as stakeholder mainly responsible for sowing seeds of hatred between Thais and Cambodians and derailing successful economic and political cooperation between two countries between 2000-08. PAD is portrayed as an ultra-nationalist social supported by various civic groups and institutions, mainly in Thai capital Bangkok. In first of four chapters author tries to conceptualize term uncivil as an appropriate characterization of movements such as PAD whose behavior and ideology run contrary to democratic principles. Puangthong argues that the exclusion of certain organisations from definition of society is theoretically untenable because all social movements and organisations, Ku Klux Klan, claim that their actions are right and legitimate (p. 9). It is also a matter of fact that same civil movement might be considered a progressive force when fighting communist regimes or other authoritarian dictatorships and viewed as reactionary when opposing a democratically elected government, even though its confrontational tactics may have been same all along (p. 9). author tries to overcome this contradiction by defining uncivil as a sub-set of civil society. This argument is not fully convincing as electoral democracies with a strong society are by no means immune to nationalism and may be pressured by public opinion in their respective countries to stage wars against neighboring states. As European history in nineteenth and twentieth century amply demonstrates, liberal-civic democracies sometimes seem to be less inclined to preserve peace than certain autocratic regimes which appear to be more determined to keep chauvinistic masses at bay.The chapter entitled The Post-Cold War Regional Integration is based on premise that after end of Cambodian conflict (Third Indochina War) in 1991, it was economic cooperation and exchange that fostered improved relations between Thailand and her Indochinese neighbors, including Cambodia. author persuasively argues that Cambodia became an important market and investment area for Thai economy. cross-border trade between two countries grew impressively between 1992 to 2008, with exports from Thailand exceeding imports from Cambodia by a factor of 10. …

Petrography, mineralogy and geochemistry of Cretaceous sediment samples from western Khorat Plateau, Thailand, and considerations on their provenance

At Mo Hin Khao on the western flank of Khorat Plateau, Thailand, the Phra Wihan Formation reveals litharenite and sublitharenite with some subarkose and arkose. A cuesta in the eroded sedimentary sequence exhibits spectacular rock pillars of considerable geotourist potential. The rock sequence is high in silica (SiO2 67–98wt%) and contains quartz, mica, magnetite, chert fragments and accessory minerals such as zircon and tourmaline and amphibole species. These accessory minerals suggest felsic rocks, such as granite, granodiorite and pegmatite, were sources for the sandstones. Geochemical analyses of the sedimentary sequence suggest that source rocks may lie in the passive continental margin, before sediment transport and deposition in the Khorat Basin by rivers flowing across a large flood plain. Many depositional sequences/episodes formed thick beds of cross bedded clastic rocks. A high average maturity index (>5) indicates sedimentary reworking/recycling. Chemical Index of Alteration (CIA) values range from 47 to 98, suggesting variable chemical weathering within the source area rocks, largely representing moderate to high degrees of weathering. The average CIA value of these sediments (78) suggests that relatively extreme alteration factors were involved.

ASEAN's weak role in bilateral dispute settlement: The case of Preah Vihear (Phra Wihan)

ASEAN's weak role in bilateral dispute settlement: The case of Preah Vihear (Phra Wihan)

Use of isotope hydrology for groundwater resources study in Upper Chi river basin

The Upper Chi river basin is located in the vicinity of Chaiyaphum province, northeastern Thailand. Groundwater management in the drought affected area of fractured Mesozoic siliciclastic rocks groundwater system was challenged by the approaches of isotope and chemical techniques. The local meteoric water line (LMWL) of the study area provide lower slope (δD = 6.8508δ18O − 0.8013) and more depleted average annual rainfall (δ18O = −7.6 %ο) when compare to LMWL of Bangkok due to higher evaporation. The surface water mainly exhibits an evaporation effect and can be clearly divided into two groups, the upper reaches and the downstream areas, with approximate separated in δ18O by −4.0 %ο. The groundwater system in the area can be divided into seven subareas based on the stable isotope characteristics and groundwater dating by radiocarbon and tritium methods. Nong Bua Deang subarea, Kang Kro subarea, and Thep Satit subarea, the most upstream system which were separated by thick aquitards of Phra Wihan sandstones, are classified as the upper reach area. The groundwater samples are characterized in two traits: the upstream group shows older groundwater ages (<80.0 % modern carbon, PMC) because of less interaction with surface water and the downstream group, near main channels and reservoirs, exhibit younger groundwater ages because of contribution of surface water in the recharge area. Bamnet Narong subarea and Muang Chaiyaphum subarea are classified as the middle reach area. The groundwater shows rapidly recharge from rainfall, the results of radiocarbon provide younger ages. The downstream characteristic which is closely interaction of extremely evaporated surface, were found in Kon Sawan-Mancha Kiri subarea and Ban Phai subarea. Almost all the groundwater samples are related to younger ages except the wells near the upper tributaries. The groundwater management can be proposed by attending to conservation policy in the upper reach area, and some parts of Ban Phai subarea in which groundwater is slowly replenished slowly, as well as groundwater exploration will be expanded in the Bamnet Narong subarea and the Muang Chaiyaphum subarea which is the most effective zones for groundwater developments.

ASEAN's weak role in bilateral dispute settlement: The case of Preah Vihear (Phra Wihan)

ASEAN's weak role in bilateral dispute settlement: The case of Preah Vihear (Phra Wihan)

Identification of an anastomosing river system in the Early Cretaceous Khorat Basin, northeastern Thailand, using stratigraphy and paleosols

The Phu Kradung and Phra Wihan formations of the Early Cretaceous Khorat Group were investigated to characterize the depositional system and paleoclimate, based on stratigraphy, paleosol features, paleosol profiles, and reworked deposits. The sediments of both formations are classified into 12 facies on the basis of their primary depositional attributes, such as bedding, grain size, texture, and sedimentary structures. Furthermore, these facies are grouped into eight architectural elements based on stratigraphic relationships and outcrop-scale macroforms. The proportions of each architectural element indicate that the depositional system was that of an anastomosing river. The anastomosing river system in the studied section is characterized by a high rate of vertical floodplain aggradation and the development of a relatively stable crevasse channel. Paleosols are developed mainly in floodplain deposits, and are characterized by the development of calcretes. A semi-arid to sub-humid paleoclimate is deduced from the occurrence of the calcretes. In addition, their microstructures suggest that these calcretes were formed under several different conditions, with micritic carbonate precipitating under relatively arid climates, and alveolar septal structures under semi-arid to sub-humid conditions. Using the thicknesses of the calcrete horizons, we conclude that the difference in the amount of precipitation between the wet and dry periods was highly variable, without any order, during deposition of the studied section. The thicknesses of intervals between successive calcrete horizons indicate that the inflow of fine materials occurred randomly across the floodplain. Partly superimposed, multiple calcrete horizons were developed during periods of low sediment supply. A random deposition of floodplain sediments appears to characterize the anastomosing river system of the Khorat Basin.

タイ国北東部に分布する中生界コラート層群Phu KradungおよびPhra Wihan層の堆積システムと古環境

タイ国北東部に分布する中生界コラート層群Phu KradungおよびPhra Wihan層の堆積システムと古環境

PROVENANCE OF THE SANDSTONE USED IN THE CONSTRUCTION OF THE KHMER MONUMENTS IN THAILAND

We investigated the sandstone used in the construction of the Khmer monuments situated upon and around the Khorat Plateau in north‐east Thailand in order to clarify the provenance. The sandstones of the 22 investigated Khmer monuments can be classified into three groups. The sandstone of Group 1 is lithic and is derived mainly from the Khok Kruat Formation. This group includes the sandstone used at Phimai, Phnom Wan, Muang Khaek etc. The sandstone of Group 2 is siliceous and can be subdivided into three further groups. The sandstone of Group 2 is considered to have been derived from the Phu Phan, Phra Wihan or Sao Khua Formations. The sandstone used at Muang Tam, Phnom Rung, Sdok Kok Thom, Preah Vihear (Khao Phra Wihan), Narai Jaeng Waeng etc. belongs to Group 2. The sandstone of Group 3 is feldspathic and is correlated with the grey to yellowish‐brown sandstone that is commonly used in the Angkor monuments in Cambodia. This sandstone is used at Wat Phu and Hong Nang Sida in Laos. The above results reveal that the choice of sandstone used for the Khmer monuments, including the Angkor monuments, was dictated by the surrounding geology.

Palynology and stratigraphy of the Mesozoic Khorat Group red bed sequences from Thailand

Abstract New palynological results are presented and integrated with previous data for the Mesozoic Khorat Group continental red bed succession of NE Thailand. The Khorat Group is traditionally considered to comprise, from bottom to top, the Nam Phong, Phu Kradung, Phra Wihan, Sao Khua, Phu Phan and Khok Kruat Formations. The group is unconformably overlain by the continental evaporitic Maha Sarakham Formation, which has been palynologically dated as mid-Albian–Cenomanian, therefore giving a minimum age for the underlying Khorat Group. Traditionally the Nam Phong Formation is considered to be Late Triassic, the Phu Kradung, Phra Wihan and Sao Khua Formations are assigned to the Jurassic, and the Phu Phan and Khok Kruat Formations to the Early Cretaceous. This age dating has mainly been based on plant macrofossil and vertebrate studies. Palynology supports the Late Triassic age for the Lower Nam Phong and underlying Huai Hin Lat Formations but suggests an Early Cretaceous (Berriasian–Barremian) age for the Phu Kradung, Sao Khua and Phra Wihan Formations, and an Aptian age for the Khok Kruat Formation. The Phu Phan has yet to yield useful age-diagnostic palynomorphs but must also be Early Cretaceous based on the age of the under- and overlying formations. The key palynomorph present for ascribing an Early Cretaceous age is Dicheiropollis etruscus , a taxon that is restricted to this age interval and has been found in the Phu Kradung (both at outcrop and in subsurface exploration wells), Phra Wihan and Sao Khua Formations. The lithostratigraphy and age of the Nam Phong Formation is, at present, still problematic. From subsurface seismic data it is clear that the Nam Phong Formation comprises two distinct units separated by an unconformity, referred to herein as the Lower and Upper Nam Phong Formations. The age of the Lower Nam Phong Formation based on palynology is Late Triassic (Rhaetian) whereas the age of the Upper Nam Phong Formation is poorly constrained but can be no older than Pliensbachian based on data from the Phu Horm-1 well. The absence of the Early Cretaceous marker D. etruscus may be taken as indirect evidence for a Jurassic age for the Upper Nam Phong Formation in the Phu Horm-1 well. This revised age dating suggests the presence of a significant depositional hiatus within the Nam Phong Formation, and consequently the Lower Nam Phong Formation should be removed from the Khorat Group. Overall the palynomorph assemblages of the Khorat Group are dominated by the gymnosperm pollen Corollina (synonymous with Classopollis ) and Dicheiropollis , both of which belong to the Cheirolepidaceae and would indicate deposition in a warm, dominantly seasonally dry subtropical climate.

Internal deformation of the Shan-Thai block inferred from paleomagnetism of Jurassic sedimentary rocks in Northern Thailand

Paleomagnetic samples of red sandstones were collected at 16 sites from the Lower to Upper Jurassic Phu Kradung formation and the Upper Jurassic Phra Wihan formation around Nan City (19.2°N, 101.0°E) in the southern region of the Shan-Thai block. After stepwise thermal demagnetization, a high-temperature component with an unblocking temperature of about 680 °C is isolated from 11 sites. We interpret this to be a prefold characteristic remanent magnetization because of a positive fold test at the 95% confidence level. The tilt-corrected mean paleomagnetic direction from 11 sites is D = 32.3°, I = 33.3°, α 95 = 12.2°, k = 15.0, which gives a paleomagnetic pole for this area of 60.1°N, 186.5°E with A 95 = 11.7°. Compared with a Jurassic paleopole for the stable part of the Yangtze block, we observe a clockwise tectonic rotation of 12.8°, which is similar to the observed rotation (18–28°) of the northern region of the Shan-Thai block. This amount contrasts with a large rotation of more than 45° that is estimated from the narrow zone extending from Luxi to Mengla in the central region of this block. This declination aspect suggests that a coherent whole block rotation by about 20° of the Shan-Thai block took place in an earlier phase during indentation of India into Asia and that an internal deformation with additional local rotation between 25° and 77° followed within a limited zone in the central part. The internal deformation of the Shan-Thai block absorbed the stress on the Asian continent induced by indentation of India as well as its coherent whole block motions of clockwise rotation and southward displacement.

Non-marine Jurassic rocks of Thailand: A summary

Abstract Non-marine Jurassic rocks are widespread in the northeastern part (Khorat Plateau), and partly in the northern, eastern, and southern part of Thailand. In the Khorat Plateau, the rocks, more than 1000 m thick, are represented by the Phu Kradung and Phra Wihan Formations of the Khorat Group but are less extensive in the north, east, and south. Reddish brown o grayish purple sandstones, siltstones, claystones, conglometric sandstones and conglomerates are the main lithologies; calcrete nodules are also present in claystones only in the Phu Kradung Formation. Deposition occurred mostly in meandering and braided rivers in semi-arid and slightly humid conditions for the Phu Kradung and Phra Wihan Formations, respectively, expect for the southern rocks, where lacustrine deposits dominate. Age determinations are based mainly on vertebrates, bivalves and palynomorphs indicating reassignment to the Jurassic-possibly Early Cretaceous. *Supported by Chinese Academy of sciences (Grant No. GJH20522) and this ...

Linking hinterland evolution and continental basin sedimentation by using detrital zircon thermochronology: a study of the Khorat Plateau Basin, eastern Thailand

AbstractThe effectiveness of detrital zircon thermochronology as a means of linking hinterland evolution and continental basin sedimentation studies is assessed by using Mesozoic continental sediments from the poorly understood Khorat Plateau Basin in eastern Thailand. New uranium lead (U‐Pb) and fission‐track (FT) zircon data from the Phu Kradung Formation identify age modes at 141 ± 17 and 210 ± 24 Ma (FT) and 2456 ± 4, 2001 ± 4, 251 ± 3, and 168 ± 2 Ma (U‐Pb), which are closely similar to data from the overlying formations. The FT data record post‐metamorphic cooling, whereas the U‐Pb data record zircon growth events in the hinterland. Comparison is made between detrital zircon U‐Pb data from ancient and modern sources across Southeast Asia. The inherent stability of the zircon U‐Pb system means that 250 Myr of post‐orogenic sedimentary recycling fails to change the regional zircon U‐Pb age signature and this precludes use of the U‐Pb approach alone for providing unique provenance information.Although the U‐Pb zircon results are consistent with (but not uniquely diagnostic of) the Qinling Orogenic Belt as the original source terrane for the Khorat Plateau Basin sediments, the zircon FT cooling data are more useful as they provide the key temporal link between basin and hinterland. The youngest zircon FT modes from the Khorat sequence range between 114 ± 6 (Phra Wihan Formation) and 141 ± 17 Ma (Phu Kradung Formation) that correspond to a Late Jurassic/Early Cretaceous reactivation event, which affected the Qinling Belt and adjacent foreland basins. The mechanism for regional Early Cretaceous erosion is identified as Cretaceous collision between the Lhasa Block and Eurasia. Thus, the Khorat Plateau Basin sediments might have originated from a reactivation event that affected a mature hinterland and not an active orogenic belt as postulated in previous models.

Dinosaur footprints from the Phra Wihan Formation (Early Cretaceous of Thailand)

The ichnological assemblage of the Phra Wihan Formation (early Early Cretaceous of northeastern Thailand) includes the first sauropod tracks ever found in Thailand. It is reminiscent of the fauna of the underlying Jurassic Phu Kradung Formation with theropods, small ornithischians of uncertain affinities (possibly Hypsilophodon-like ornithopods) and sauropods. It suggests that, in southeastern Asia, an important faunal change occurred in the Early Cretaceous among continental vertebrates, whereas little happened at the Jurassic–Cretaceous boundary.