Search

Eighty-five species belonging to 46 genera of Ostracoda were recovered from 169 samples in three sediment cores (VN, NB, and GA) from the Red River delta plain, northeastern Vietnam. From a Q-mode cluster analysis, we recognized three biofacies (Biofacies A, B, and C). Biofacies B is subdivided into Biofacies BI and BII. The environment of Biofacies A is interpreted as open marine, those of Biofacies BI and BII as marine to brackish water and brackish water, respectively, and that of Biofacies C as oligohaline to mesohaline brackish water. The Holocene sediments consist of estuarine sediments deposited under relatively high sea levels following transgression, deposited during 11–8.5 cal kyr BP, overlain by deltaic sediments deposited under relatively low sea levels following regression, and the ostracod assemblages reflect these changes. The estuarine sediments of the early Holocene transgression are characterized by ostracod Biofacies BI. An erosional surface marks an abrupt change to the shelf environment, accompanied by sediment starvation. The interval around this surface, identified as the maximum flooding surface, is characterized by ostracod Biofacies A. During the subsequent delta progradation, the sedimentary environment changed from a prodelta to delta front, and then to a delta plain, and the corresponding ostracod assemblages changed from Biofacies A to BI, BII, and then C in ascending order. Taken together, our results show that the temporal changes in ostracod assemblages since 10 cal kyr BP are closely related to the evolution of the Red River delta system and can serve as good indicators of paleoenvironmental changes.

熊本県の天草上島の東部には，上部白亜系の姫浦層群が露出しており，姫浦層群は樋の島層と阿村層に区分されている．本調査地域の姫浦層群からは，アンモナイトやイノセラムスに加えて，放散虫や有孔虫などの微化石が多産する．樋の島層からは，有孔虫のDicarinella canaliculataと多くのMarginotruncana pseudolinneianaやイノセラムスのInoceramus amakusensis，アンモナイトのTexanites kawasakiiなどが産出したため，本層はサントニアン階と考えられる．阿村層の上部からは，Grobotruncana linneianaやG. cf. arcaなどからなるカンパニアン階を指示する有孔虫化石群集が産出し，さらにこれらの種は阿村層上部から多産する．したがって，サントニアン/カンパニアン境界は，おそらく阿村層の下部付近にある．なお，Amphipyndax stocki，Dictyomitra formosa，D. koslovaeなどで特徴づけられる樋の島層や阿村層の放散虫化石群集は，サントニアン～中期カンパニアン期を指示する．

Silurian and Devonian chitinozoans and scolecodonts are recorded from strata of the Hida-Gaien Terrane, central Honshu. Silurian chitinozoans include Eisenackitina, Bursachitina, and the species Angochitina elongata. The latter provides a precise biostratigraphical tie between the Japanese succession and the Type Ludlow Series of the Welsh Borderland, UK, and indicates a Ludlow age (Gorstian or early Ludfordian) for the upper member of the Yoshiki Formation in the Ichinotani Valley. Chitinozoans from other Yoshiki Formation localities contain other specimens of Lagenochitinidae. Scolecodonts are more common than chitinozoans in the palynological residues, but are mostly represented by fragments or minor apparatus elements with a low biostratigraphical value. However, material from the Yoshiki and Fukuji Formations includes several species of Mochtyella as well as representatives of Oenonites, Kettnerites, Lunoprionella, Vistulella? and possibly other placognath taxa. Scolecodonts are also present in the Silurian Middle Member of the Gionyama Formation, Kyushu, including a well-preserved jaw of Pistoprion, and fragments of putative Kettnerites and Oenonites. These finds of scolecodonts suggest close similarity in assemblages between Paleozoic polychaete faunas of Japanese terranes and those of Baltica-Laurentia.

Six major groups of trilobites from the Silurian and Devonian of Japan are evaluated for their paleobiogeographical signature. Silurian illaenids and scutelluids show four generic-level and at least two species-level links with the Australian segment of the Gondwana paleocontinent; encrinurids also indicate two generic-level links with Australia and also the South China paleocontinent; whilst Devonian phacopids, and possibly proetids, suggest at least two generic-level links with the North China paleocontinent. These different patterns may reflect the fragmentary biostratigraphical record of Japanese trilobites, but they also appear to reflect paleoenvironmental parameters associated with lithofacies, and paleoecology. Thus, Japanese assemblages of proetids and phacopids occurring in deep-water clastic lithofacies have counterparts in similar settings in North China, and Japanese scutelluids and illaenids are strongly associated with shallow marine carbonate lithofacies that are similar to those of their occurrences in Australia. Japanese encrinurids occur in carbonate rocks indicative of shallow marine settings in the Kurosegawa Terrane, and they demonstrate a consistent paleobiogeographical affinity with Australia and South China. Larval ecology cannot be directly assessed for Japanese trilobite groups. However, proetids have consistently been shown to have planktonic protaspides, whereas illaenids, scutelluids, and encrinurids have benthic protaspides. Planktonic protaspides would have a greater propensity for distribution in ocean currents than benthic ones, and therefore may be of more limited paleobiogeographical utility. The combined data from the six different groups indicates that the complex paleobiogeographical patterns of the Japanese trilobite assemblages need to be interpreted with caution, and similarity of taxa does not necessarily denote paleogeographical proximity to other regions.

Cretaceous 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 Ma...

The discovery of Balatonites sp. in the lower part of the Quy Lang Formation in the Lang Nuoc area, Thanh Hoa Province, Central Vietnam establishes that this portion of the formation is of late Middle Anisian age. This ammonoid's cooccurrence with Costatoria goldfussi mansuyi and Trigonodus tonkinensis suggests that this widely distributed bivalve assemblage in Asian shallow marine facies is at least partly of late Middle Anisian age, and its discovery may provide an important key for the establishment of a precise biostratigraphic framework for the Middle Triassic of Asia.

Conodont-bearing Ordovician and Silurian rocks have a wide geographical distribution in Japan. They are exposed on Honshu, Shikoku, and Kyushu islands. Two recently studied samples from Gionyama, in Kyushu, yield conodont assemblages of Telychian (Distomodus sp., Apsidognathus sp. (cf. A. tuberculatus arcticus), Oulodus cf. rectangulus, Ozarkodina cf. waugoolaensis, Panderodus cf. amplicostatus) and probably the earliest Sheinwoodian (?Distomodus sp. (cf. D. staurognathoides), Ozarkodina sp., Oulodus sp., Walliserodus sp. (cf. Walliserodus sp. nov. c Mannik), Panderodus sp.) ages, providing further biostratigraphical constraints for the age of the Gionyama Formation in the Kurosegawa Terrane. Most of the conodont taxa identified have wide paleobiogeographical distribution, but probable occurrence of Oulodus rectangulus, Ozarkodina waugoolaensis, and Panderodus amplicostatus suggests a relationship between Australia, the South China paleocontinent, and the Kurosegawa Terrane of 'Proto-Japan' during the Silurian. These paleogeographic interpretations agree with the existing notions based on rugose corals.

In North Vietnam, Lower to Middle Triassic storm- and wave-dominated shelf deposits are widely exposed and yield abundant Tethyan bivalves indicating recovery and diversification following the end-Permian mass extinction. We reconstructed the habitats of characteristic bivalve species on the basis of shell preservation and mode of occurrence. Bivalves that diversified in the Middle Triassic Anisian to Ladinian Stages in the Na Khuat Formation, An Chau Basin, can be divided into four fossil assemblages: (1) an autochthonous to parautochthonous Costatoria goldfussi mansuyi and Trigonodus tonkinensis assemblage (sandy bottom of inner shelf facies); (2 and 3) a parautochthonous to allochthonous Costatoria goldfussi mansuyi and Pteria sturi assemblage, and a Costatoria paucicostata and Hoernesia angusta assemblage (muddy bottom of inner to outer shelf facies); and (4) a typical allochthonous Costatoria ngeanensis and Leptochondria albertii assemblage. These assemblages are characterized by a diversity of species of Costatoria and Trigonodus, and by several genera of twisted Bakevellidae, such as Hoernesia, Langsonella, and Lilangina. These bivalve assemblages are composed of shallow-infaunal and semi-infaunal burrowers and epifaunal species, though in Vietnam the Lower Triassic Induan to early Olenekian bivalves are dominated by epifauna. In the eastern part of the Tethys, infaunal bivalves show a remarkable delay in recovering from the end-Permian mass extinction compared to epifaunal bivalves.

The fourth international symposium of IGCP507, “Paleoclimates of the Cretaceous in Asia and their global correlation” was held in Kumamoto, on December 1-6, 2009. The purpose of the symposium, which was organized by the Scientific Committee of the IGCP507 Symposium, was to investigate Cretaceous biodiversity, faunal changes, environments, and climate in Asia through geological analyses of rock and fossil records. Seventy participants registered to attend the conference from 10 countries, and gave 28 oral and 28 poster presentations, two keynote speeches, one workshop “Cretaceous to Recent bryozoans”, and five sessions addressing (1) Vertebrate evolution in Asia during the Cretaceous (thematic session), (2) Paleontology, (3) Paleoclimate, (4) Sedimentology, and (5) Tectonics, on December 4-5. There was a pre-symposium field excursion, “Cretaceous non-marine and shallow marine facies and fossils in western Kumamoto, Kyushu, Japan”, to northern parts of Amakusa Islands (December 1-3). The excursion focused on sedimentary processes, faunal changes in benthic molluscan fossils, and biostratigraphy in the mid-Cretaceous Goshoura and the Upper Cretaceous Himenoura groups. During the post-symposium field excursion, “Mifune Dinosaur Museum and Upper Cretaceous Dinosaur site in the Mifune Group, Kumamoto (December 6)”, participants visited a typical terrestrial vertebrate site and museum exhibitions.

Lower Triassic bivalve assemblages are recognized in the Yinkeng Formation, South China, and the Hong Ngai Formation, North Vietnam. Basinal mudstones and deep ramp carbonates contain the mono- specific Claraia wangi assemblage. The Eumorphotis teilhardi-Towapteria scythica assemblage occurs in deep ramp deposits. The Claraia stachei-"Claraia" phobangensis assemblage is found in shallow ramp deposits. These bivalve assemblages are mainly composed of epifaunal species, and are characterized by low spe- cies diversity and parautochthonous elements. Most species of Claraia probably inhabited shallow to deep marine environments. Besides, Eumorphotis and Towapteria are useful indicators of Lower Triassic shallow marine environments above storm-wave base.

The depositional environments and bivalve assemblages are determined for the Upper Cretaceous Hinoshima Formation of the Himenoura Group, Kamishima, Amakusa Islands, Kyushu, Japan. The Hinoshima Formation is characterized by a thick transgressive succession that varies from incised-valley-fill deposits to submarine slope deposits with high aggradation rates of depositional systems. The incised valley is filled with fluvial, bayhead delta, brackish-water estuary, and marine embayment deposits, and is overlain by thick slope deposits. Shallow marine bivalves are grouped into five fossil assemblages according to species composition: Glycymeris amakusensis (foreset beds of a bayhead delta), Nippononectes tamurai (foreset beds of a bayhead delta), Ezonuculana mactraeformis – Nucula formosa (central bay), Glycymeris amakusensis – Apiotrigonia minor (slope), and Inoceramus higoensis – Parvamussium yubarensis (slope). These bivalve assemblages all represent autochthonous and parautochthonous conditions except for a Glycymeris amakusensis – Apiotrigonia minor assemblage found in debris flow and slump deposits. The life habitats of these bivalves and the compositions of the assemblages are discussed in terms of the ecological history of fossil bivalves of the mid- to Late Cretaceous.

In North Vietnam, the Hua Tat, Pa Khom and Lang Son Formations yield abundant Lower Triassic bivalves. The occurrence of Eumorphotis sp. cf. E. multiformis, represents the first fossil reported from the Hua Tat Formation, while Claraia aurita, C. concentrica, and C. intermedia multistriata are found in the upper Lang Son Formation. The Pa Khom Formation contains C. intermedia multistriata, Claraia sp., and Lopha sp. The occurrence of C. intermedia multistriata indicates that the Pa Khom Formation and the upper Lang Son Formation are Olenekian in age. These Claraia spp. are found in wave-dominated nearshore deposits characterized by hummocky cross stratification and wave-ripple laminations, although Claraia in other areas is generally found in deep-sea mudstone.

Trigonioides goshourensis n. sp. and Trigonioides amakusensis Kikuchi and Tashiro occur in the late Albian Eboshi Formation of the Goshoura Group in Kyushu, Japan. These Albian species are characterized by three radial pseudocardinal teeth on the thick and wide hinge plate, and are probably ancestors of Cenomanian species of Trigonioides ( Kumamotoa ) with four radial pseudocardinal teeth. This chronological relation may be important for the correlation of non-marine Cretaceous strata in East Asia. In addition, the habitat of T . amakusensis is interpreted as estuarine tidal flats under brackish water conditions, although Trigonioides is generally a freshwater bivalve genus.

The non-marine bivalve species Trigonioides (Kumamotoa) quadratus Gu and Ma is described from the Fourth Member of the Hekou Formation in western Fujian, southeastern China. This species previously was regarded to belong to the subgenus Trigonioides (s.s.), which is restricted to the Early Cretaceous. Herein, it is included into the subgenus Kumamotoa. It is compared to Cenomanian (early Late Cretaceous) species from Japan and Korea such as Trigonioides (Kumamotoa) mifunensis Tamura, Trigonioides (Kumamotoa) matsumotoi Kobayashi and Suzuki and Trigonioides (Kumamotoa) paucisulcatus Suzuki. The age of the Fourth Member of the Hekou Formation is discussed.

The oyster-like, dimyarian, cementing bivalve genus Protostrea CHEN in GU et al., 1976 and its type species Protostrea sinensis (Hsu in Hsu & CHEN, 1943) from the upper Anisian (Middle Triassic) of the Qingyan Formation, Guizhou Province, south-western China, are re-described and emended. The genus Most probably is the earliest representative of the family Dimyidae. But Protostrea is a peculiar dimyid because in adult growth stages its shell is fairly large and thick, the resilifer is rectangular, broad, shallow and sometimes multiple, and the crura usually are weak. These features resemble some thick-shelled Prospondylidae. The features of pre-adult growth stages of P. sinensis indicate possible affinities to the order Pectinoida.

The Lower Triassic Hong Ngai Formation crops out in Ha Giang Province, North Vietnam. The lowermost part of this formation is composed of calcareous hummocky cross-stratified sandy mudstone, calcareous mudstone, and marlstone, and is interpreted to have accumulated in a deep ramp environment. Pteria ussurica, Towapteria scythica, Claraia wangi, Eumorphotis teilhardi, and Promyalina sp. are found in these sediments, and indicate parautochthonous occurrences.In Huangzishan, Zhejiang Province, South China, the lower part of the Yinkeng Formation consisting of marlstone and calcareous mudstone yields Lower Triassic bivalves, such as Pteria ussurica variabilis, T. scythica, C. wangi, Claraia sp., Eumorphotis sp., and Promyalina sp., although basal parts yield Permian fossils. Besides, in the Meishan section (GSSP of P-T boundary), Zhejiang Province, the lower part of the Yinkeng Formation is predominated by basin mudstone containing abundant parautochthonous and allochthonous Claraia wangi. C. wangi probably widely inhabits basin to storm-dominated shallow marine environments. T. scythica and most species of Eumorphotis are characteristic bivalves in the Lower Triassic shallow marine environments above the storm wave base.

The geology and the paleontology of the Cretaceous Misakubo Formation have been investigated. The Misakubo Formation is narrowly distributed along the eastern side of the Sambagawa Belt and the Miocene Tokizawa Formation in the northern part of Misakubo, Hamamatsu, Shizuoka Prefecture. This formation consists mainly of black mudstone, fossils yielding bivalves, ammonoids, gastropods and crinoids. Late Albian mid-Cretaceous ammonoids such as Mortoniceras rostratum, Desmoceras latidorsatum, Desmoceras sp., Mariella sp., and Lechites sp. are found in the upper part of the formation. Shallow marine bivalve assemblage yielded in the formation is predominated by Pterotrigonia pustulosa. The fossil bivalve assemblage is compositionally similar to the inner shelf assemblages of the Enokuchi Formation of the Goshoura Group; the Miyanohara Formation, the Fukkoshi Formation and the Nagase Formation of the Sotoizumi Group and the Mikasa Formation of the Yezo Group. The range of these trigoniids might be incorrect, because Pterotrigonia mifunensis and Pterotrigonia monobeana yielded with M. rostratum.

The mid-Cretaceous Goshoura Group, non-marine to shallow marine fossiliferous clastic deposits, is typically exposed on Goshoura Island, Amakusa, western Kyushu, Japan. Based on precise sedimentological analyses, the group is subdivided into the following three formations, the Eboshi, Enokuchi and Karakizaki Formations in ascending order. These formations are herein redefined, and the Eboshi and Enokuchi Formations are newly subdivided into members, i.e., the Eboshi Formation is composed of the Tanoshiri, Hobashiraiwa and Arakuchizaki Members, and the Enokuchi Formation consists of Hokahira and Gannohana Members. Geological age of the group is determined by age-diagnostic ammonite species, e.g., the Late Albian Mortoniceras cf. rostratum from the Hokahira Member, and the Early Cenomanian Graysonites adkinsi from the overlying Gannohana Member. Fifty-eight bivalve species belonging to 42 genera are identified from the group. These bivalve fossils are grouped into 7 fossil assemblages whose occurre...

Several issues in the methods of reconstructing paleoecology of the Mesozoic brackish-water bivalves, the contents of the bivalve assemblages and their paleoenvironments in Japan are discussed. The brackish-water environments can be reconstructed as shallow marine environments associated with fluvial systems on the basis of facies analysis. Paleoecology of bivalve fossils is inferred from their modes of occurrence in each depositional environment. Here, descriptions are given for two examples of paleoecologic analysis of the Mesozoic bivalve faunas : (1) Comparisons between the "mid"-Cretaceous Goshoura Group and the Upper Cretaceous Himenoura Group ; both groups are characterized by brackish-water-influenced tidal flat deposits containing abundant true oyster (Crassostrea). Infaunal bivalves of the "mid"-Cretaceous assemblage are characterized by neomiodontids, although those of the Upper Cretaceous assemblage are represented by venerids. (2) Another example is the taxonomy and paleoecology of the Upper Jurassic to Cretaceous primitive Crassostrea. These oysters are ecologically similar to recent Crassostrea, but compared with recent species, shell sizes of the Upper Jurassic and Lower Cretaceous materials are small. Their shell structures are characterized by poorly developed chambers and chalky deposits, which suggest more archaic conditions.

The Middle Triassic (Anisian) Leidapo Member of the Qingyan Formation, which crops out in southwestern China, consists of basin-floor and slope deposits with abundant benthic fossils and records two transgressions and one regression. The well-preserved bivalves are grouped into four assemblages. The allochthonous Cassianella – Elegantinia and Protostrea – Cassianella assemblages as well as the autochthonous Palaeonucula assemblage are found in slope deposits. The allochthonous assemblages exhibit several modes of occurrence in sediment gravity-flow deposits. The parautochthonous Posidonia assemblage is preserved in slope and basin deposits. The genus-level compositions of these bivalve assemblages are similar to those from the Early Carnian of Tethyan Europe. It is probable that a significant diversification of bivalves took place in the Anisian.

The Middle Triassic (Anisian) Yuqing Member of the Qingyan Formation crops out in Guizhou Province, southwestern China, and consists of storm-dominated inner and outer shelf deposits. It contains Tethyan benthic fossils that are grouped into two fossil assemblages. The allochthonous Mentzelia multi-costata-Mentzelia mentzeli assemblage is characterized by brachiopods in the inner shelf facies. The parautochthonous and allochthonous Posidonia wengensis assemblages, composed mainly of epifaunal bivalves, dominate in the inner and outer shelf facies, although some species of Posidonia generally are characteristic of deep-sea environments or low-oxygen conditions.

A new species of oyster, Crassostrea tetoriensis, is described from the lower part of the Middle Jurassic–Cretaceous Tetori Group. This is the oldest record of the genus and one of the earliest muddy–bottom–dwelling oysters. Characteristics of the species include an elongate spatulate outline and narrow attachment area, an elongate hinge area with deep umbonal cavity, a reniform adductor muscle scar, and a smooth commissural margin without chomata. The oysters are cemented to each other and constitute bouquet–like aggregates or colonies of shells in muddy deposits of inferred brackish–water origin. The shells contain lenticular or blister–like chambers filled with a chalky deposit. These ecological and structural properties are characteristic of Crassostrea, and may be regarded as the result of adaptation of the sessile, suspension feeding animals to soft muddy substrates. Oysters are a group of bivalves that have lost mobility and live cemented mostly to hard substrates. Crassostrea and its allies returned secondarily to soft bottoms. The find of C. tetoriensis indicates that the return occurred early in the history of oysters, 60 myr after the first appearance of ostreid oysters in Late Triassic.

The Upper Cretaceous Himenoura Group in the Amakusa-Kamishima Island area, southwest Japan is subdivided into the Hinoshima and Amura Formations. In order to determine the numerical depositional age of the formations, zircon U–Pb ages were investigated using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) for acidic tuff samples from the lower part of the Hinoshima Formation and the upper part of the Amura Formation. Although the two samples contain some accidental zircons, the samples have a definite youngest age cluster and their weighted mean ages are 85.4 ± 1.3 and 81.5 ± 1.1 Ma, respectively (errors are 95 % confidence interval). These age data indicate that the Himenoura Group in the Amakusa-Kamishima Island area was deposited mainly in the early Santonian to early Campanian which is consistent with biostratigraphic ages. Additionally, zircon age distributions of the two tuff samples from the upper part of the Hinoshima Formation do not show a distinct youngest peak of eruption age but characteristics of detrital zircons suggestive of maximum depositional age of the host sediments. These results demonstrate that the mean age of the youngest zircon age cluster of a tuff sample does not always indicate depositional age of the tuff, and statistical evaluation of age data is effective to determine depositional age of a tuff bed using zircon U–Pb ages.

The Lower Cretaceous Sunjiawan Formation of northeast China consists of non-marine deposits containing abundant Nippononaia yanjiensis Gu. These sedimentary rocks comprise fluvial channel and overbank (levee, crevasse splay, pond and floodplain) accumulations. There are two modes of occurrence of N. yanjiensis . Type 1 is characterized by inferred life positions within the pond deposits, and Type 2 represents poorly preserved fragments and disarticulated valves within the channel deposits. N. yanjiensis was a freshwater mollusc that lived in ponds within abandoned channels in overbank environments. The genus Nippononaia is widely distributed in the Northern Hemisphere, and is a useful indicator of Lower Cretaceous freshwater environments.

The Cretaceous, upper Albian-Cenomanian, Goshoura Group crops out in the Amakusa Islands, Kyushu, Japan. On the basis of facies analysis, the following coastal facies are recognized: shoreface-inner shelf (upper-middle shoreface, lower shoreface and inner shelf), tidal flat on the shoreface, estuary (bay-head delta, central basin, tidal flat and estuary mouth sand body) and fluvial (fluvial channel, flood plain and levee). The group records 4 transgressions and 3 regressions and consists of 4 depositional sequences composed mainly of transgressive and highstand systems tracts. The coastal palaeoenvironments are characterized by tide-and wave-dominated facies. Relative sea-level change estimated from this group is compatible with postulated eustatic sea-level fluctuation around the Albian-Cenomanian boundary.

A theropod tooth found in the Upper Cretaceous Himenoura Group in the Koshikijima Islands, Kagoshima Prefecture, is described. Recent paleontological work in the region suggests a middle Campanian age for the specimen. Lacking a feature diagnostic of any specific theropod clade, this specimen is considered merely as Theropoda incertae sedis. The present finding confirms the potential of the Himenoura Group as a new source of information on the diversity of Theropoda during the Campanian.