Ken-ichiro Hisada

Erosion and Deposition by the 2004 Indian Ocean Tsunami in Phuket and Phang-nga Provinces, Thailand

Abstract The devastating December 26, 2004, tsunami produced abundant geologic effects along the Andaman coast of Thailand. The tsunami inundated the numerous sandy beaches and flowed over the adjacent aeolian dunes. On some of the dunes, the tsunami scoured circular holes 10–30 cm in diameter, and in its waning phases, it coated the holes with mud. The tsunami locally deposited a sand sheet that ranged from 0–30 cm in thickness, with an average thickness of approximately 10 cm. Sedimentary structures within the sand sheet include ripples from inflow and outflow, graded bedding, parallel lamination, and double-layered deposits. Erosion, locally severe, affected sand beaches and tidal inlets. We use these erosional and depositional features to infer the main processes that acted during inundation from the tsunami.

Triassic radiolarian faunas from the Mae Sariang area, northern Thailand and their paleogeographic significane

Abstract Early to Late Triassic (Spathian to Carnian) radiolarians were obtained from the bedded chert sequence of the Mae Sariang Group distributed in northern Thailand. Based on the similarity of radiolarian fauna and petrographical characteristics, it is inferred that the fine-grained siliceous and calcareous sediments of the Mae Sariang Group are equivalent to those belonging to the eastern marginal facies of the Sibumasu Block. Moreover, the occurrence of an early (?) Carnian radiolarian assemblage from bedded chert shows that the closure of the Paleotethys Ocean between the Sibumasu and Indochina Blocks in northern Thailand occurred after the early Carnian.

Stable isotopic composition of pedogenic carbonates of the Early Cretaceous Shimonoseki Subgroup, western Honshu, Japan

Abstract Abundant pedogenic carbonate nodules are present in the Shimonoseki Subgroup in the Kanmon Basin of Kyushu and Honshu, Japan. The oxygen isotope compositions of these pedogenic carbonates range from −20.1 to −22.8‰ (PDB), which is 7‰ lower than those of the septarian crystallaria in the carbonate nodules. The meteoric water composition estimated from the oxygen isotope composition of the soil water in equilibrium with the carbonates is much depleted compared with the estimate from other sources. This suggests that the oxygen isotope compositions of the Shimonoseki pedogenic carbonates were modified during diagenesis. The carbon isotopic compositions of the Shimonoseki carbonates range from −5.4 to −7.0‰ (PDB), with an average of −6.7‰ (PDB), suggesting carbonate formation in soils dominated by C 3 type of vegetation. An analysis of these values using Cerlings model (Cerling, T.E., Wright, V.P., Vanstone, S.D., 1992. Further comments on using carbon isotopes in paleosols to estimate the CO 2 content of the palaeo-atmosphere. J. Geol. Soc. London 148 (1991), 945–947; 149, 673–676) indicates that the partial pressure of CO 2 in the Early Cretaceous Shimonoseki atmosphere was about 1700–3200 ppmV.

Detrital chrome spinels in the Cretaceous Sanchu sandstone, central Japan: indicator of serpentinite protrusion into a fore-arc region

Abstract The Sanchu Group is regarded as Lower Cretaceous fore-arc basin-fill sediments underlain unconformably by the Jurassic accretionary wedge. This group is accompanied with the Sanchu serpentinite which is probably correlated to the Kurosegawa Tectonic Zone or serpentinite melange of SW Japan. The Sanchu Group is divided into the newly defined Untis 1–3. Sandstones of Unit 1 contain numerous detrital chrome spinel grains which were probably derived from ultramafic and mafic rocks. These chrome spinels are classified into high-Ti and low-Ti groups based on microprobe analysis. The low-Ti group chrome spinels were supplied ultramafic rocks similar to the Sanchu serpentinite, while the high-Ti group ones seem to have been derived from volcanics which are geochemically different from the presently exposed greenstone (120±6 Ma) of the Otchizawa Formation. The spinel chemistry suggests that the source rocks of the low-Ti and the high-Ti groups were originated from the arc to fore-arc upper mantle and the intraplate basalt or E-type MORB, respectively. The serpentinite may have formed a complex together with the volcanics. The sedimentary environment of Unit 1 is presumed to have been the foreshore to nearshore shelf. The graded accumulation of chrome spinels in sandstone suggest that sediment gravity flow such as a storm-generated turbidity current was the transportation mode. The serpentinite-volcanics complex emerged subaerially as a ridge during the sedimentation of Unit 1 (late Hauterivian to early Aptian). This ridge referable to a tranch slope break was produced by the protrusion of serpentinized peridotite (the Sanchu serpentinite and its precursor) associated with E-type MORB or intraplate basalt along the plate boundary in teh fore-arc region. Left lateral slip-fault movements may facilitate the protrusion, which can be considered as phenomena in the “periphery” of the Kurosegawa Tectonic Zone or serpentinite melange.

Late Jurassic radiolarians from pebbles of Lower Cretaceous conglomerates of the Hayang Group, southeastern Korea

Permian to Late Jurassic radiolarians were obtained from granules and pebbles in conglomerates of the Donghwachi and Gisadong formations of the Lower Cretaceous Hayang Group, southeastern Korea. Radiolarian faunas and the petrologic character of the pebbles resemble those of Jurassic accretionary complexes of East Asia. Considering lines of evidence such as the lithologic characters of pebbles, affinity of the radiolarian faunas, reconstructed paleocurrent direction in the Hayang Group, and the paleogeographic position of southwestern Japan, it may be inferred that these pebbles were derived from the accretionary complexes mainly of southwestern Japan and the Far East. New evidence for the occurrence of Late Jurassic radiolarians in the Gisadong Formation suggests that radiolarian-bearing pebbles would be not only chert but also siliceous shale or shale of the Jurassic accretionary complexes, and gives an exhumation age for the latest accreted units of the complexes.

Paleosols in the Cretaceous Goshoura and Mifune groups, SW Japan and their paleoclimate implications

Abstract Cretaceous sedimentary basins in Kyushu Island, Japan, are developed as half-grabens, which accommodated very thick clastic wedges of non-marine to shallow-marine facies. The Albian to Cenomanian Goshoura Group in western Kyushu (ca. 1000 m thick) consists of interbedded channel sandstone, conglomerate, and mudstone. The Cenomanian to Turonian Mifune Group in central Kyushu (ca. 2300 m thick) comprises red and drab sandstone, and intercalated siliceous ash-fall tuff. Different types of paleosols occur in the Goshoura and Mifune groups. Paleosols in the Goshoura Group contain diagnostic vertic features such as subangular blocky peds, irregularly directed slickensides, and downward tapering fissures. Few obvious calcic horizons are developed except for the calcretes of rhizogenic origin. Paleosols in the Upper Formation of the Mifune Group are composed of cyclic acidic tuff–vertic paleosol intervals with abundant pedogenic calcretes. Paleosols of the Goshoura Group belong to the order of vertic Inceptisols, and those of the Mifune Group can be classified as calcic Vertisols. In spite of diagenetic alteration of the paleosols, paleo-vertic soils of the Goshoura and Mifune groups show the exceptional preservation of a number of pedological features. Among various soil-forming factors, diversity in each paleosol is mainly attributed to differences in paleoclimatic conditions during the Middle Cretaceous. Our results show that the paleoclimatic conditions in the subtropical–warm-temperate region had changed from subhumid to semi-arid with time.

Tectonic significance of detrital chromian spinels in the Permian Nam Duk Formation, central Thailand

Detrital chromian spinels in the Permian Nam Duk Formation, Thailand are examined to determine the petrological characteristics of eroded mafic-ultramafic rocks in the Phetchabun area. Detrital chromian spinels are found as one of accessory heavy minerals from turbiditic sandstones of the Nam Duk Formation. The detrital chromian spinels are generally deep brown to almost opaque in thin section due to their wide compositional variation, and are relatively small, about 20–190 microns across. They sometimes exhibit subhedral to euhedral shapes and rarely have inclusions. Thirty–five grains were chosen for microprobe analysis. They have relatively high Cr contents, the Cr#(=Cr/[Cr+Al] atomic ratio), being mostly higher than 0.50, and up to 0.83. TiO2 contents are generally low but variable from 0.02 to 1.16 wt%, and Fe3+ ratios are consistently low. The relatively high Cr# and low TiO2 contents of the Nam Duk detrital chromian spinels in the Permian sediments indicate their derivation from mafic-ultramafic rocks of are origin. The relatively small and euhedral to subhedral spinels with inclusions especially suggest their provenance from volcanic rocks. It is strongly inferred that igneous rocks, namely volcanics and peridotites, of arc origin were exposed in this region at the Permian at least. The Loei-Phetchabun-Ko Chang volcanic belt, interpreted to have been constructed by several magmatic episodes (Devonian, Permian, Triassic, and Late Tertiary), could be a good candidate for the source of detrital chromian spinels in the Nam Duk Formation.

Lithostratigraphy and petrography of marine Jurassic rocks in the Mae Sot area, Tak Province, western Thailand: Implications for depositional environment and tectonics

Geology, lithostratigraphy, petrography, sedimentary structures and depositional environment of marine Jurassic rocks of the Hua Fai Group (HFG) from the Mae Sot area of Tak Province, western Thailand have been studied in detail. Based mainly on five measured sections in the Mae Sot Basin, the group can be divided into three formations: Khun Huai; Doi Yot; and Pha De, in ascending order. Seventeen sedimentary rock units have been established with a total thickness varying from 200 to 832 m. According to the fossil assemblages, the HFG was deposited during Toarcian–Bajocian. Analysis of lithofacies associations in the sedimentary sequences of the group discerns shoreface, fan-delta, protected lagoon, intertidal, subtidal and inner to outer ramp environments with occasional carbonate platforms and reef flats. Toarcian rocks are represented by transgressive–regressive (T–R) cycles that in the Aalenian gradually changed to highest sea level and water depth. During late Aalenian to early Bajocian, sea level was still changing to a transgressive phase, then after early Bajocian, sea level retreated again. The eustatic curves for the Toarcian–early Bajocian in Thailand correspond to the global situation, but differ significantly in the Late Jurassic–Cretaceous, when T–R phases were out of step with the global pattern and instead probably responded to local tectonic movements.

Provenance of the Langjiexue Group to the south of the Yarlung-Tsangpo Suture Zone in southeastern Tibet: Insights on the evolution of the Neo-Tethys Ocean in the Late Triassic

ABSTRACT The Upper Triassic Langjiexue Group, which lies immediately south of the Yarlung-Tsangpo Suture Zone in the Shannan area of southeastern Tibet, represents an important part of the Tethyan Himalayan Sequence (THS). Its provenance and palaeogeography have been the subject of debate. We present new data on petrographic composition, whole-rock geochemistry, and detrital zircon U–Pb geochronology to constrain the provenance of the Langjiexue Group. The dominance of quartz grains and felsic volcanic lithic fragments suggests that the sandstones are litho-quartzose. The trace element geochemical signatures (V–Ni–Th*10, Co/Th–La/Sc, Eu/Eu*–Th/Sc) suggest derivation from felsic igneous sources. The detrital zircon age spectra display three major peaks: a Meso-to-Neoproterozoic peak (1200–900 Ma, 7–18%), a Neoproterozoic-to-Late Cambrian peak (750–500 Ma, 32–65%), and a Late Carboniferous-to-Late Triassic peak (300–200 Ma, 11–33%). The maximum depositional age of early Carnian (236–235 Ma) is obtained by calculating weighted average ages of the youngest zircons (≤250 Ma). The youngest age cluster (300–200 Ma) is incompatible with sources from neighbouring terranes, including the South Qiangtang terrane, Lhasa terrane, THS, and Higher Himalayan Crystalline. Correlations of the Permian–Triassic zircons with those of time-equivalent strata in northwest Australia, west Burma, and the Banda Arc unveil a potential connection to the Tasmanides along the convergent margin of eastern Australia. The New England Orogen (300–230 Ma) could have supplied the Langjiexue Group with magmatic materials via continent-scale drainage systems or a submarine fan complex. This scenario provides a new perspective into the transport of detritus from distal orogens to sedimentary basins thousands of kilometres away. Graphical Abstract

Soil Erosion and Heavy Metal Contamination in the Middle Part of the Songkhla Lake Coastal Area, Southern Thailand

Soil erosion and sources of heavy metal contamination were identified and their distributions were evaluated in the Songkhla Lake Basin, southern Thailand, by analyzing hundreds of soil and stream sediment samples from the middle part of the catchment area. The landforms in the study area are dominated by mountains and hills to the west, gently sloping and undulating terrains in the middle and alluvial plains with rivers flowing eastwards to the lake. The rates and amounts of erosion were determined using the universal soil loss equation (RUSLE) method. Subsequently, the distribution patterns of heavy metals were displayed onto Geographic Information System (GIS) maps to identify the likely sources of pollution and to assess the levels of contamination with the Dutch Standards. The maximum erosion rate of 1.64 mm/yr was found very close to the mountainous areas to the west and was also strong in the foothill areas due to deforestation. The levels of some heavy metals in the soils are mainly controlled by anthropogenic activities; they do not exceed the Dutch standard values in either the soil or the stream sediments. Areas with high Pb, Zn and As values in the stream sediments, especially near abandoned mines in the granite mountains to the west, however, require a follow-up survey because these metals may be transported down stream, especially with the higher current prevalent rate compared to that of the past.