NW Thailand Research Articles

Zircon U-Pb geochronology of the Lan Sang gneisses and its tectonic implications for the Mae Ping shear zone, NW Thailand

The Mae Ping shear zone (MPSZ), a major shear zone trending NW-SE in Thailand, is responsible for the left-lateral displacement of the N-S Triassic-Jurassic granitoid and gneiss belt. This displacement is postulated to have contributed to Cenozoic extrusion tectonics. Within the Lan Sang National Park, the MPSZ exposes several intensely deformed lithologies, collectively known as the Lan Sang gneisses. These gneisses have attracted considerable attention for their potential to substantiate the extrusion model. However, the timing of the emplacement of the orthogneiss protolith is still debated. Moreover, the origin and distribution of the Eocene syn-shearing granodiorite within this shear zone are not well understood. To shed light on the magmatic history of the MPSZ, this study utilized zircon U-Pb geochronology to systematically investigate the Lan Sang gneisses. Our findings demonstrate that these gneisses can be categorized into paragneiss and orthogneiss groups. Paragneiss samples feature zircons displaying rounded detrital cores ranging from 3,078 to 450 Ma, with metamorphic rim overgrowth of ca. 200 Ma (most Th/U <0.01). This indicates that their Paleozoic sedimentary protoliths experienced high-grade metamorphism during the Triassic-Jurassic Indosinian orogeny. On the other hand, zircon from orthogneiss samples shows that their magmatic protoliths were predominantly emplaced either around ∼200 Ma or within 45-32 Ma. The Eocene-Oligocene magmatism likely coincided with the proposed Eocene metamorphism. Since these samples were deformed by left-lateral shearing, the left-lateral motion of the MPSZ probably ended after 32 Ma. Eocene-Oligocene magmatic events have also been identified in granite, mylonite, and gneiss samples from other regions along the Sibumasu terrane, including the Three Pagodas, Klaeng, Ranong, Khlong Marui shear zones, and the Doi Inthanon area. The Eocene-Oligocene magmatism was likely linked with the movement of the shear zones and may be responsible for the regional cooling pattern. The spatial and temporal distribution of the Eocene-Oligocene magmatism within the Sibumasu terrane supports the hypothesis that the inward migration of magmatism in the overriding plate resulted from the shallowing of the Neo-Tethyan slab.

Dating deformation using sheared leucogranite: temporal constraints by 40Ar/39Ar thermochronology for the Mae Ping shear zone, NW Thailand

Dating deformation using sheared leucogranite: temporal constraints by 40Ar/39Ar thermochronology for the Mae Ping shear zone, NW Thailand

Southern extension of the Paleotethyan zone in SE Asia: Evidence from the Permo-Triassic granitoids in Malaysia and West Indonesia

The consumption of the East Paleotethyan Ocean was the final step in creating the united SE Asia continent. However, uncertainties remain as to the significance of Paleotethyan-associated granitoids and when ocean closure finally occurred in west Indonesia and Malaysia. This paper presents new U-Pb geochronological, petrologic, elemental and Sr-Nd-Pb-Hf isotopic results for granitoids from west Kalimantan, West Java, Bangka-Belitung and Peninsular Malaysia. These granitoids are geochemically subdivided into the Eastern and Main Range granites. The Eastern granites include the granitoids from west Kalimantan, West Java and East Peninsular Malaysia and are dated at ~256–207 Ma, ~208–207 Ma and ~289–217 Ma, respectively. They have εNd(t) = +0.2 ~ −9.1, with two-peaks of +0.1 and −5.6, (206Pb/204Pb)i = 18.64–19.49, (207Pb/204Pb)i = 15.61–15.78 and (208Pb/204Pb)i = 38.56–39.47, and originated from a mixed source involving juvenile crust and Indochina basement. The Main Range granites occur in Bangka-Belitung (West Indonesia) and West Peninsular Malaysia, and have crystallization ages of ~226–198 Ma. They share the similar Sr-Nd-Pb-Hf isotopic compositions with those in the South China and Inthanon Triassic granites, with 87Sr/86Sr(t) = 0.70725–0.72652, εNd(t) = −5.6 ~ −10.8, ∆8/4 = 28.1–109 and ∆7/4 = 13.7–23.6, and were derived from a meta-greywacke source. Our data reveals the development of the Paleotethyan-associated Permo-Triassic granitoids in West Java, Belitung and west Kalimantan. The Bentong-Raub suture forms the East Paleotethyan suture boundary in Peninsular Malaysia, and extends southwards into the easternmost Bangka-Belitung Islands (and even West Java). To the north, it links to the Inthanon-Changning-Menglian suture in NW Thailand and SW China. It is concluded that the temporal pattern of the East Paleotethyan Ocean in west Indonesia and Malaysia correlates with that in NW Thailand and SW China. Its evolution switched from subduction to assembly of the Indochina-East Malaysia and Sibumasu at ~230 Ma. The Eastern granites might reflect active margin processes in response to the eastward subduction of the Paleotethyan Ocean, and the Main Range granites represent the post-collisional igneous rocks.

Revision of the family Metarbelidae (Lepidoptera) of the Oriental Region. III. Genus Stueningeria Lehmann, 2019

In the third part of the revision of the family Metarbelidae (Lepidoptera) of South-Eastern Asia, we provide a revision of the genus Stueningeria Lehmann, 2019 with description of six new species: Stueningeria htetae sp. nov. (Type locality: Mynmar, 21 km E Putao), Stueningeria csovarii sp. nov. (Type locality: Thailand, Changwat Nan, 15 km N of Bo Luang), Stueningeria loeffleri sp. nov. (Type locality: Thailand, Sakhon Nakhon Prov., Phu Pan NP), Stueningeria ihlei sp. nov. (Type locality: Vietnam (C.), Prov. Thua-Thien-Hue, Kreis A Luoi, Gemeinde A Rong, Passastrasse ca. 30 km S A Luoi.), Stueningeria murzini sp. nov. (Type locality: China, SW Yunnan, Xishuanbanna, Guanping env., 60 km N Jinghong), and Stueningeria pinratanai sp. nov. (Type locality: NW Thailand, Chiangmai, Doi Pui Forest Res. Stat.) Two new combinations are established: Stueningeria campbelli (Hampson, 1910) comb. nov. and Stueningeria phaga (Swinhoe, 1894) comb. nov. Both species are redescribed. The type species of the genus Stueningeria nepalensis Lehmann, 2019 is reported for the first time for the fauna of India (Uttarakhand). We also give for the first time the description of female genitalia of the genus Stueningeria. The genus distribution map is provided.

Age and provenance of the Chaung Magyi Group, Yeywa Dome, Myanmar, based on U-Pb dating of detrital zircons

The unfossiliferous Chaung Magyi Group of the Northern Shan Plateau of Myanmar, comprises metasedimentary rocks, in particular greywacke, slates, phyllites and schists, of inferred Proterozoic age that unconformably underlie the late Cambrian Pangyun Formation. To address the problem of the youngest stratigraphic extent of the group, four samples of the Chaung Magyi Group from the Yeywa Dome, East of Kyaukse, Mandalay Division, were collected for U-Pb dating of detrital zircons. Based on the youngest detrital zircons present in sandstone samples from the western Yeywa Dome area, at least the upper part of the Chaung Magyi Group is of latest Proterozoic age and possibly extends to the late Cambrian (~500 Ma). Comparison of detrital zircon age-frequency histogram distributions show only slight differences in distributions of detrital zircons in the Cambrian of NW Thailand and the Chaung Magyi Group samples (Sibumasu Terrane), with a concentration of ages between 1300 Ma and 820 Ma, with two major peaks at 1086 Ma and 1022 Ma. A younger Cryogenian age peak at 647 Ma is also observed. A spread of older concordant ages ranges from 3093 Ma to 1406 Ma. The minimum depositional age for the Chaung Magyi Group of the west of the Bawdwin Mine (982 Ma) based on ages of cross-cutting dykes (reported in Mitchell, 2018), and the maximum depositional age for Yeywa Dome (~600–500 Ma) based on detrital zircons suggest the age difference (~>400 my) is too great for the Chaung Magyi Group to be considered a single group, the dyke ages require re-investigation.

Pollination-system diversity in Epipactis (Orchidaceae): new insights from studies of E. flava in Thailand

The rewarding orchid Epipactis flava was studied in NW Thailand. Its flowers were visited by a wide range of insects, most of which served as pollinators. The most frequent pollen bearers were (in decreasing order): the cricket Homoeoxipha lycoides, stingless bees of the Tetragonula testaceitarsis/hirashimai complex, hoverflies of subfam. Syrphinae, the wasp Polybioides gracilis and sweat bees of subfam. Halictinae. We found no evidence of a link between the rheophytic habit of E. flava and its pollinator fauna. Whereas most pollinators visited the flowers to feed on nectar, females of Episyrphus alternans (Syrphidae: Syrphinae) were observed to oviposit despite the absence of prey for their young. Hence, we suggest that dual pollination systems contribute to the opportunist strategy of E. flava, and we discuss, in a phylogenetic framework, how the strategy fits in with those previously reported for Epipactis sect. Arthrochilium. The elastic attachment of the epichile (a universal trait in sect. Arthrochilium) was found to promote outcrossing, and we hypothesize that loss of the elastic hinge has provided a key innovation facilitating recurrent evolution of obligate autogamy in sect. Epipactis (which is nested in sect. Arthrochilium).

Late Triassic post-collisional granites related to Paleotethyan evolution in SE Thailand: Geochronological and geochemical constraints

A set of new U–Pb geochronological, elemental and Sr–Nd–Hf isotopic data is presented to constrain the formation age and petrogenesis of granites in SE Thailand, which are significant for understanding eastern Paleotethyan tectonic evolution and regional correlation in SE Asia. Six granite samples from the Chonburi, Rayong–Bang Lamung and Chanthaburi plutons yielded similar crystallization ages of 222–218Ma. These granites can be geochemically classified into S-type (Group 1) and I-type (Group 2) granites. Both groups have similar chondrite-normalized REE and primitive mantle-normalized multi-element patterns but distinctly different Sr–Nd–Hf isotopic compositions. Group 1 is characterized by more enriched initial 87Sr/86Sr (i) ratios (0.7101–0.7272) and lower εNd (t) values (−12.0 to −13.2) compared with those of Group 2 with 87Sr/86Sr (i) of 0.7027–0.7053 and εNd (t) of −0.6 to −1.2. Consistently, zircons from Group 1 yield negative εHf (t) values of −7.3 to −27.4 and Mesoproterozoic or older Hf model ages (TDM=1.53–2.63Ga), distinct from those of Group 2 with positive εHf (t) values (+5.0–+11.3) and younger TDM (0.42–0.67Ga). Group 1 granites mainly originated from ancient greywackes but Group 2 from juvenile mafic crust with the input of meta-sedimentary component. These data, along with available observations, synthetically indicate that these granites formed in the post-collisional gravitational collapse setting of the thickened crust in response to the assemblage of the Indochina with Sibumasu blocks. They linked northerly and easterly to the Late Triassic granitoids in NW Thailand and East Malay Peninsula related to the Paleotethyan tectonic regime, respectively.

Geochronological and geochemical constraints on the intermediate-acid volcanic rocks along the Chiang Khong–Lampang–Tak igneous zone in NW Thailand and their tectonic implications

Volcanic rocks preserved in the Lampang–Den Chai area in NW Thailand are important components of the giant Paleotethyan igneous belt. Constraining their age and petrogenesis is critical for better understanding their temporal-spatial relationship with the Lancangjiang igneous zone and the Paleotethyan tectonic evolution in SE Asia. The volcanic suite is constituted by intermediate to acid rocks with zircon U–Pb ages of 240.4±1.7Ma and 240.6±1.9Ma for the representative andesitic and rhyolitic samples, respectively. Volcanic sequence is dominated by calc-alkaline andesites, dacites and rhyolites. The andesitic and dacitic samples are characterized by high Mg# (37–57) and TiO2 (0.91–1.59wt%), and can be classified as high-Mg series. They are enriched in LILEs and LREEs and depleted in HFSEs. Representative andesitic samples have 87Sr/86Sr (i) ratios of 0.70398–0.70567, εNd (t) values of +3.6–+3.9, zircon εHf (t) values of +2.8–+8.0 and δ18O values of 7.01–8.11‰, respectively. The rhyolitic samples are characterized by high Mg# (38–70) and low TiO2 (0.25–0.61wt%). They are enriched in LILEs and LREEs, along with 87Sr/86Sr (i)=0.70468–0.70645, εNd (t)=+2.0–+4.3 and zircon εHf (t)=+5.7–+13.6. Geochemical signatures suggest that the andesitic and dacitic samples might originate from a newly modified mantle source by slab-derived fluids and recycled sediments, and rhyolitic samples were derived from juvenile mafic crust. It is proposed that the Middle Triassic high-Mg volcanic rocks in the Lampang–Den Chai area formed in response to slab roll-back during transition of tectonic regime from subduction to continental collision between the Sibumasu and Indochina blocks. These rocks constitute part of the Chiang Khong–Lampang–Tak igneous zone, and can northerly link with the Lancangjiang igneous zone and southerly extend to the Chanthaburi, Malaysia and Singapore areas.

Origin of Permian OIB-like basalts in NW Thailand and implication on the Paleotethyan Ocean

The basaltic rocks in NW Thailand belong to part of giant Southeast Asian igneous zone that delineates the extension of the Paleotethyan Ocean from SW China into NW Thailand. The Chiang Mai basaltic samples from the Chiang Dao, Fang, Lamphun and Ban Sahakorn sections are divisible into two groups of high-iron basalt. Group 1 has SiO2 of 38.30–49.18wt.%, FeOt of 13.09–25.37wt.%, MgO of 8.38–1.60wt.%, TiO2 of 3.92–6.30wt.%, which is rarely observed in nature. Group 2 shows SiO2=44.71–49.21wt.%, FeOt=10.88–14.34wt.%, MgO=5.24–16.11wt.%, TiO2=2.22–3.07wt.% and mg#=44–70. Olivine and pyroxene are responsible for the fractionation of the Group 2 magma whereas low oxygen fugacity during the late-stage differentiation of the Group 1 magma prolonged fractionation of ilmenite and magnetite. The onset of ilmenite and magnetite fractionations controls the distinct differentiation commencing at MgO=~7wt.%. Both groups show similar REE and primitive mantle-normalized patterns with insignificant Eu, Nb-Ta and Zr-Hf anomalies. They have similar Nd isotopic compositions with εNd (t) values ranging from +2.8 to +3.7 and similar Nb/La, Nb/U, Th/La, Zr/Nb, Th/Ta, La/Yb, Nb/Th, Nb/Y and Zr/Y, resembling those of OIB-like rocks. The representative basaltic sample yields the argon plateau age of 282.3±1.4Ma, suggestive of Early Permian origin. Our data argue for Group 1 and Group 2 are coeval in the intra-oceanic seamount setting within the Paleotethyan Ocean, which at least continued till 283Ma. These data, along with other observations, suggest that the Inthanon zone defines the main Paleotethyan suture zone, which northerly links with the Changning-Menglian suture zone in SW China.

Geochronological, elemental and Sr-Nd-Hf-O isotopic constraints on the petrogenesis of the Triassic post-collisional granitic rocks in NW Thailand and its Paleotethyan implications

New U-Pb geochronological, petrologic, elemental and Sr-Nd-Hf-O isotopic data for the granites from the Inthanon and Sukhothai zones in NW Thailand in conjunction with correlations with SW China are presented to constrain the age and position of the Paleotethys Ocean in this region and the associated assembly of Southeast Asia. The geochronological data show that the granitic rocks in the Inthanon and Sukhothai zones, herein named Group 1 and Group 2 granites, respectively, yield similar crystallization ages of 230–200Ma. Group 1 samples are characterized by monzogranite and granite with I- and S-type geochemical affinity and Group 2 samples by I-type monzogranite and granodiorite. They have generally similar chondrite-normalized REE and PM-normalized multi-element patterns but distinct Sr-Nd-Hf-O isotopic compositions. Group 1 samples have slightly higher initial 87Sr/86Sr ratios (0.7111–0.7293) but lower εNd(t) values (−11.1 to −14.1) than those of Group 2 samples (87Sr/86Sr(i)=0.7073–0.7278 and εNd(t)=−8.3 to −11.0). Group 1 samples show the lower εHf(t) values (−5.4 to −18.2), older TDM (1.62–2.40Ga) and higher δ18O values (+7.95 to +9.94) than those of Group 2 samples (εHf(t) of −11.1 to +4.80, TDM of 0.96–1.95Ga and δ18O of +4.95 to +7.98) for the Triassic crystallization zircons. These geochemical signatures are similar to the Kwangsian and Indosinian granites in the South China and Indochina blocks but distinct from those of the Gangdese I-type granite and Sibumasu Paleozoic granite. Our data suggest that Group 1 samples mainly originated from the early Paleozoic supracrustal rocks containing metapelite and metavolcanic components, which had previously experienced the surface weathering. Group 2 samples were derived from a hybridized source of an old metamorphic and a newly underplated mafic component. Synthesis of our data with available regional observations indicates that the Inthanon zone represents the main suture zone of the eastern Paleotethyan Ocean in NW Thailand and links with the Changning-Menglian suture zone in SW Yunnan (SW China). In NW Thailand, a switch from the eastward subduction of the Paleotethyan oceanic plate to the collision of the Sibumasu with Indochina blocks occurred at ~237Ma, and syn- and post-collisional time being at ~237–230Ma and ~200–230Ma, respectively. The late Triassic granites in the Inthanon and Sukhothai zones are representative of the post-collisional magmatic products.

Zircon U–Pb geochronology, and elemental and Sr–Nd–Hf–O isotopic geochemistry of post-collisional rhyolite in the Chiang Khong area, NW Thailand and implications for the melting of juvenile crust

Volcanic rocks are widely exposed within the Chiang Khong–Lampang–Tak igneous zone in NW Thailand. A representative rhyolite sample from the Chiang Khong area yielded a zircon U–Pb age of 230.7 ± 1.1 Ma (n = 20, MSWD = 0.98). The Chiang Khong rhyolites are characterized by low TiO2 (0.29–0.62 wt%) and MgO (0.04–0.82 wt%) with A/CNK values of 0.95–1.06 (one outlier at 1.47), and can be classified as highly fractionated I-type rhyolites. They are enriched in LILEs and LREEs, and depleted in HFSEs. Two representative samples have 87Sr/86Sr (i) ratios of 0.70497 and 0.70527, and the eNd (t) values fall at +1.1 and +1.3, respectively. eHf (t) and δ18O in zircon are between +4.7 to +12.0 and 5.3 to 5.9 ‰, respectively. Our geochemical data suggest that the Chiang Khong rhyolites formed by partial melting of juvenile mafic lower crust in a post-collisional setting. Deep crustal anatexis was probably induced by upwelling asthenospheric mantle, shortly after slab detachment subsequent to closure of the Paleo-Tethys.

Petrogenesis for the Chiang Dao Permian high-iron basalt and its implication on the Paleotethyan Ocean in NW Thailand

The Changning-Menglian suture in SW Yunnan has been accepted as the Paleotethyan main ocean. However, it has been a matter of debate as to its southerly extension in NW Thailand (the Chiang Mai-Chiang Rai vs. Nan-Uttaradit zone). Our field investigation identified the high-iron basaltic rocks in the Chiang Dao Permian standard profile in NW Thailand. The high-iron rocks provide crucial records for understanding the controversy on the location of Paleotethyan main ocean in NW Thailand. The Early Permian high-iron samples show extremely high FeOt (20.96 wt.%–25.56 wt.%) and TiO2 (6.07 wt.%–6.34 wt.%) and low SiO2 (38.54 wt.%–43.46 wt.%) and MgO (1.61 wt.%–2.40 wt.%) contents. Such characteristics are similar to those of the Fenner differentiation trend rarely observed in the natural system, distinct from those of the “normal” Bowen trend. Their chondritenormalized REE and primitive mantle-normalized patterns are generally similar to those of typical OIB. The initial 87Sr/86Sr ratios and eNd(t) values range from 0.704 677 to 0.705 103 and 3.16 to 3.48, respectively, falling near the field of typical OIB (oceanic-island basalt). These data synthetically suggest that the Chiang Dao high-iron rocks are the products of high-degree partial melting of peridotite with Fe-rich eclogitic blobs/streaks in response to a seamount setting. In comparison with the Permian tectonic setting in SW Yunnan and NW Thailand, it is inferred that the Paleotethyan Ocean was located between the Shan-Thai terrane of Sibumasu and Sukhothai arc along the Inthanon zone of the Chiang Mai-Chiang Rai rather than Nan-Uttaradit zones.

Petrogenesis and tectonic implication of the Late Triassic post-collisional volcanic rocks in Chiang Khong, NW Thailand

The volcanic rocks exposed within the Chiang Khong–Lampang–Tak igneous zone in NW Thailand provide important constraints on the tectonic evolution of the eastern Paleotethys ocean. An andesite sample from the Chiang Khong area yields a zircon U–Pb age of 229±4Ma, significantly younger than the continental-arc and syn-collisional volcanic rocks (ca. 238–241Ma). The Chiang Khong volcanic rocks are characterized by low MgO (1.71–6.72wt.%) and high Al2O3 (15.03–17.76wt.%). They are enriched in LILEs and LREEs and depleted in HFSEs, and have 87Sr/86Sr (i) ratios of 0.7050–0.7065, εNd (t) of −0.32 to −1.92, zircon εHf (t) and δ18O values of 3.5 to −11.7 and 4.30–9.80 ‰, respectively. The geochemical data for the volcanic rocks are consistent with an origin from the enriched lithospheric mantle that had been modified by slab-derived fluid and recycled sediments. Based on available geochronological and geochemical evidences, we propose that the Late Triassic Chiang Khong volcanic rocks are equivalent to the contemporaneous volcanic rocks in the Lancangjiang igneous zone in SW China. The formation of these volcanic rocks was possibly related to the upwelling of the asthenospheric mantle during the Late Triassic, shortly after slab detachment, which induced the melting of the metasomatized mantle wedge.

East flank of the Sibumasu block in NW Thailand and Myanmar and its possible northward continuation into Yunnan: a review and suggested tectono-stratigraphic interpretation

The east flank of the Sibumasu block was a passive continental margin, and in NW Thailand is marked by the absence of the autochthonous Middle Permian–Triassic platform carbonates which are widespread across the rest of Sibumasu further west. Instead, the carbonates are represented by hemipelagic cherts, mudstones and sandstones including turbidites. During the northward drift of Sibumasu, following its Early Permian rifting from Gondwana, an accretionary complex was present where Palaeotethyan pelagic rocks as old as Devonian were subducted beneath the Sukhothai volcanic arc. At the time of Sibumasu’s collision with the Sukhothai arc, beginning in the Middle Triassic, the accretionary complex was thrust westwards across the east flank of Sibumasu. It is suggested that in the Late Triassic the thrust pile which had been the accretionary complex underwent erosion and was the source of terrigenous clastic rocks deposited further west in a foredeep basin.The boundary of Sibumasu’s east flank with the Permo-Triassic carbonate platform further west is the arcuate Mae Ping-Nam Teng Fault system. Notwithstanding later Cenozoic strike-slip displacement, those faults (as well as the Mae Yuam Fault) are interpreted to have had an earlier history of westward-directed Indosinian thrusting.Northwards in Myanmar and Yunnan the Sibumasu Permo-Triassic carbonate shelf continues as the Shan Plateau and Baoshan Block. The east flank is represented by the Changning–Menglian Belt, and the Palaeotethys ‘cryptic suture’ in Thailand possibly joins with the Lancangjiang Suture.

Diceratotheca, a new genus of Acanthaceae from Thailand

A new genus of Acanthaceae, Diceratotheca, is described from Thailand. The genus is characterised by having unique pollen combined with several unusual morphological characters, of which the 2-spurred anther thecae also appear to be unique within Acanthaceae. Phylogenetic analyses show clearly that the genus belongs within the subtribe Ruelliinae. Further analyses, that include the largest available sample of species from other genera, including the species-rich Strobilanthes and Ruellia, demonstrate that the genus is not nested within other genera and a new genus is therefore required. Analyses show that, of the genera sampled, it is most closely related to Pararuellia Bremek., a herbaceous genus with which it appears to have little in common. The only species Diceratotheca bracteolata is known from a single site in NW Thailand and is probably critically endangered.

Where to Begin?: A Brief Intellectual Biography of F. K. Lehman (F. K. L. U Chit Hlaing)

Where to Begin? A Brief Intellectual Biography of F. K. Lehman (F. K. L. U Chit Hlaing) Juliane Schober F. K. Lehman, (F. K. L. U Chit Hlaing) retired in 2009 at the age of eighty-five from the University of Illinois where he had taught since 1959 and mentored dozens of doctoral students in anthropology, Asian studies, linguistics, and Buddhist studies. His publications include more than sixty articles and his classic study tribal kinship systems, The Structure of Chin Society (University of Illinois Press, 1963 and 1981). Where to begin in tracing such a long and productive trajectory of research and teaching about Theravada Buddhist civilizations and their intersections with tribal societies in the peripheries of lowland kingdoms in Southeast Asia? No one can replicate all that he has come to know over the course of nearly a century about the history, cultures, languages, ethnicity, and religion of the region. His academic journey started with his doctoral work at Columbia on classical Indian civilizations, and later expanded to Tibeto- Burman linguistics, to the anthropology of lowland and upland cultures in Burma and Thailand, and to his most recent work on trade networks in Yunnan, Southwest China. Few scholars today are able to bring to the study of Asia the depth of academic knowledge, transdisciplinary work and personal insight into the region’s history that result from his [End Page 1] lifelong involvement with Asia.1 His exceptional biography spans vast life experiences in colonial India, Southeast Asia, and the global prominence of contemporary Chinese trade patterns. Born in New York City in 1924, he spent his first four years in Calcutta, India, where his family members were gem merchants and subsequently lived with the family in Lashio, in Burma, then a center of the gem trade. He returned to New York in early 1941, and New York University, 1946–49, for his undergraduate education in mathematics, the social sciences, and languages in 1950. He received his doctorate from Columbia University in anthropology and linguistics in 1959, with a dissertation on the cultural history of India. Professor Lehman joined the University of Illinois first in 1952 to work with Julian Steward and then moved to the Human Relations Area Files at Yale, working on the new files for Southeast Asia, thence to a post-doctoral training in Indology at the University of Pennsylvania, only to return to Illinois again in late 1958, when the newly founded Department of Anthropology there recruited him. He returned to Burma in 1957–58 and again in 1961–62 to work with the eminent archeologist of Pagan, Gordon Luce, at Rangoon University and to conduct ethnographic fieldwork among the Chin tribes. Since then, he has continued to return to Southeast Asia many times. He has carried out ethnographic work among the Chin, Kayah, Lushai, Shan, Karen, Burmese, Shan, Thai, and Yunnanese on a wide range of topics that include studies of ethnicity, kinship, religion, cultural history, and linguistics. For most of his tenure at the University of Illinois, Professor Lehman was Director of Graduate Studies and supervised more than two dozen dissertations there. In the course of his career, he also contributed to many professional organizations and has been a dedicated steward of the study of Burma and its ethnic minorities. Since 1974, he has served as Chairman of the Burma Studies Group, a unit within the [End Page 2] Click for larger view View full resolution Fieldwork Sites of the Ethnographic & Linguistic Research of F. K. L. U Chit Hlaing (F. K. Lehman) 1. Chin Hills, Burma. 1957–58 Hakha area/Hrarng,1960–61 Mindat area/NgBong 2. Kayah State, Burma. 1961. Kyebogi 3. Mae Hongsorn, NW Thailand. Summer 1965 and 1967–68. Shan (Mawk Champe) and Eastern Kayah 4. Mandalay, Burma. 1980–81 (Palace dialect and Burmese social organization), 1999 Buddhism 5. Mizoram, India. Winter 1989–90. Mara (Lakher) language and Mizo (Lushai) kinship 6. Yunnan, China. Summer 2001. Wa (Headhunting and other matters) Porok Wa Buddhism 7. China-Burma border, study of cross-border gem trade: Ruili and Tengchong-He Shun (Yunnan, China) Mandalay, Myitkyina, Lashio (Burma) [End Page 3] Southeast Asia Council of the Association for Asian Studies. His efforts were...

Reconstruction of pre-monsoon weather conditions in northwestern Thailand from the tree-ring widths of Pinus merkusii and Pinus kesiya

Two pine species, Pinus merkusii and Pinus kesiya, native in Thailand were studied for their potential to reconstruct past weather conditions from their tree rings. Altogether, cores from 209 Merkus pines and from 205 Khasi pines were sampled at 16 sites. Standard methods were applied to assemble tree-ring chronologies for each site and tree species. The longest site chronology of Merkus pine and Khasi pine covered 314 and 183 years, respectively. Principal component analysis (PCA) illustrated a close clustering of all, except two, site chronologies on the PC1 axis, indicating a strong signal common for both pine species throughout NW Thailand. However, along the PC2 axis, there was a distinct separation between the Merkus pine and the Khasi pine site chronologies, which was possibly due to the species-specific differences in site altitudes. Simple correlations between the PC1 time series and a regionalized climate data set showed a highly negative association with temperature during the pre-monsoon period from March to May. Since, pre-monsoon temperature and rainfall were negatively correlated with each other, we used the PC1 as a direct proxy for pre-monsoon weather conditions (warm/dry vs. cool/wet) back to 1834 AD.

Effects of landuse change on the hydrologic regime of the Mae Chaem river basin, NW Thailand

Summary Conflicts between upland shifting cultivation, upland commercial crops, and lowland irrigated agriculture cause water resource tension in the Mae Chaem watershed in Chiang Mai, Thailand. In this paper, we assess hydrologic regimes of the Mae Chaem River with landuse change. Three plausible future forest-to-crop expansion scenarios and a scenario of crop-to-forest reversal were developed based on the landcover transition from 1989 to 2000, with emphasis on influences of elevation bands and irrigation diversion. Basin hydrologic responses were simulated using the Distributed Hydrology Soil Vegetation Model (DHSVM). Meteorological data from six weather stations inside and adjacent to the Mae Chaem watershed during the period 1993–2000 were the climate inputs. Computed stream flow was compared to observed discharge at Ban Mae Mu gauge on Mae Mu river, Ban Mae Suk gauge on Mae Suk river, and at Kaeng Ob Luang, located downstream from the district town in Mae Chaem. With current assumptions, expansion of highland crop fields led to slightly higher regulated annual and wet-season water yields compared to similar expansion in the lowland–midland zone. Actual downstream water availability was sensitive to irrigation diversion. This modeling approach can be a useful tool for water allocation for small watersheds undergoing rapid commercialization, because it alerts land managers to the potential range of water supply in wet and dry seasons, and provides information on spatial distribution of basin hydrologic components.

Faunal affinity of Toarcian-Aalenian (Early Jurassic) bivalves from Mae Sot and Umphang (Tak Province), Northwestern Thailand

In the Mae Sot and Umphang areas (NW Thailand), Jurassic strata seal the Permian and Triassic substratum of the Shan-Thai terrane with a brecciated conglomerate. Pliensbachian to Early Bajocian shallow marine strata are intercalated within the partly terrestrial Jurassic sequence. Thirty-five Toarcian-Aalenian bivalve species from Mae Sot and Umphang were identified. Among these,Eomiodon chumphonensis Hayami is known only from Thailand, whereasParvamussium donaiense (Mansuy),Myophoriella saurini Hayami,Thracia loducensis Hayami,Pholadomya (Bucardiomya) fontainei Hayami,Thracia loducensis Hayami andModiolus sestiniae Hayami were originally described in Vietnam.M. sestiniae also occurs in Iran. The greater part of the fauna, however, shows varying degrees of affinity with Myanmar (6 species), Cutch (10 species), Japan (13 species) and Europe (9 species), Levant (2 species). In view of these, it appears that these highly endemic Toarcian-Aalenian bivalves from Thailand characterize the Southeastern Asian Province of Tethys.

New micropalaeontological evidence for a Late Triassic Shan-Thai orogeny

The Shan-Thai block is viewed as a remnant of Paleotethys in South East Asia. The general consensus about its origin is that it happened through the rifting from Gondwanaland and final amalgamation to Eurasia, sealed by fluvial-shallow marine Jurassic deposits. As the main Paleotethyan closure, the Nan-Uttaradit/Nan-Chantaburi and Bentong-Raub sutures were proposed by other workers. However, a suture further west, flanked by the Gondwana-Tethys divide (GTD), is advocated here as the main Paleotethyan closure. The Middle and Late Triassic radiolarian faunas were extracted from a chert-sequence in the Mae-Sot and Umphang areas of NW Thailand. The radiolarian faunas indicate early Ladinian, early-middle Norian, and Norian-Rhaetian, individually. The Triassic chert-sequence is overlain by the ‘Jurassic base-conglomerate’. The limestone and chert clasts in the conglomerate yield Early-Late Triassic conodonts and Middle-Late Triassic radiolarians, respectively. Chert clasts in the conglomerate yield among others Norian-Rhaetian radiolarians that are correlative with those from TM3, while Early-Late Triassic conodonts are found in limestone clasts. The silici-pelagic origin of the clasts suggests the Mae Sariang Zone that amalgamated the parts of the Shan-Thai block. This first finding of Late Triassic radiolarians from chert-sequence, next to the Middle Triassic and older radiolarian faunas, adds another element to the reconstruction of the sequence now comprised in the Mae Sariang Zone, west of the Nan-Uttaradit Suture. The occurrence of Triassic limestone, as that of the Chaiburi Formation in the Mae Sariang Zone, or the Kodiang Limestone in the “Western Zone”, may elucidate the question about the provenance of the Triassic conodont-bearing limestone clasts in the Jurassic base-conglomerate that seals the Mae-Sariang Zone. The newly dated Triassic sequence is further sealed by the continental-shelf deposits of the Toarcian-early Bajocian Hua Fai Group.