Discovery of Triassic microfaunas at Mae-Sot, NW Thailand (Preliminary report)

The Middle and Late Triassic radiolarian faunas were extracted from a vitric tuff rich laminated bedded-chert in the Mae-Sot and Umphang areas of NW Thailand. The radiolarian faunas from the bedded-chert succession are characterized by Triassocampe postdeweveri (Early Ladinian), Pachus multinodosus (Early Norian), Sarla natividadensis (Middle Norian) and Canoptum rhaeticum (Norian-Rhaetian), individually. The Triassic chert-sequence is overlain by the ‘Jurassic base-conglomerate’, an ill-sorted breccia in a reddish-silt matrix. 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 like Pachus multinodosus and Canoptum rhaeticum, while Early - Late Triassic conodonts as Platyvillosus costatus, Cratognathodus cf. cuspidatus, Metapolygnathus polygnathiformis, M. carpathicus, Ancyrogondolella quadrata and A. spatulata are found in limestone clasts. The silici-pelagic origin of the clasts suggests the presence of an ocean before the end Triassic orogeny along the Mae Sariang Zone that amalgamated the parts of the Shan-Thai block. This first finding of Late Triassic (Norian - Rhaetian) radiolarians from bedded-cherts, 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, W of the Nan-Uttaradit Suture. The occurrence of Triassic limestone, as that of the Chaiburi Formation in the Phatthalung area of the Mae Sariang Zone or the Kodiang Limestone in the ‘Western zones’, 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

Marbles from Tokushima Prefecture, used in the National Diet Building : Part 1: locality and geological framework

The quarries of marbles for the construction of the National Diet Building (Nagata-cho, Chiyodaku, Tokyo) were identified in Tokushima Prefecture. The geological setting and microfossil age of the marbles were studied. Seven brands, "Akebono", "Kito-ishi ", "Hototogisu", "Kamo-sarasa", "Awayuki ", "Kotajima" and "Shin-awayuki" were used in the House of Councilors and the Central part of the building. The "Akebono", used for the wall along the Councilor's Second Stairway, is Silurian limestone from the Hiakari-yama lenticular body of the Kurosegawa Tectonic Zone in the Koyama-daira area (Kisawa Village). The "Kito-ishi" from the Misago-yama area (Kisawa Village), used for the fireplace in the reception room of the Vice-president of the House of Councilors, is the limestone and greenstone breccia intercalated in the Upper Carboniferous alternation of chert and pelagic limestone in the Permian accretion terrene (Masaki Belt of the Kurosegawa Terrane). The "Hototogisu", used for the well-ornamented entrance gate of the Emperor's room "Gokyujo", is the Upper Triassic dolimitic limestone in the Late Jurassic-earliest Cretaceous accretion mélange of the South Chichibu Terrane (Tsunomine Subbelt) from the Arida area (Asebi-cho, Anan City). The "Kamo-sarasa", used for the inside wall of the central entrance of the building, is the Upper Triassic limestone with some green reticulation in Late Jurassic-earliest Cretaceous accretion mélange of the South Chichibu Terrane (Tsunomine Subbelt) from the Oji area (Kuwano-cho, Anan City). The "Awayuki", used for the lower part of the wall along the square in front of the Emperor's room, and the lower part of the wall around the assembly hall of the House of Councilors, presumed to be a kind of "Kamo-sarasa", is proved to be the Upper Triassic Megalodon limestone with hexacoral-bearing dark limestone blocks in the accretion mélange of the South Chichibu Terrane (Tsunomine Subbelt) from the Kurogo area (Kamo-cho, Anan City). The "Kotajima", used for the lower part of the wall along the passage of the second floor, and the wall along the "Kisha Kaidan" stairway, is proved to be the Upper Triassic limestone with reticulation of black cleavages in Late Jurassic-earliest Cretaceous accretion mélange of the South Chichibu Terrane (Tsunomine Subbelt) from the Higashibun area (Tsunomine-cho, Anan City). The "Shin-awayuki", used for the mosaic on the floor of the Central Hall and the lower part of the wall along the passage of the southern central part of the first floor, is the Upper Carboniferous limestone in Jurassic accretion mélange of the South Chichibu Belt (Hosono Subbelt) from the Izeki area (Takarada-cho, Anan City)