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ID 117471
Title Alternative
Upper Triassic Sabudani Formation and Sakashu Unconformity of the South Kurosegawa Terrane, East Shikoku : stratigraphy, sedimentary facies and faunas
南部黒瀬川帯寒谷層と坂州不整合
Author
Okamoto, Haruka University of Tokushima
Tsujino, Yasuyuki Tokushima Prefectural Museum
Nakao, Ken-ichi Tokushima Prefectural Museum
Kozai, Takeshi Naruto University of Education
Hirsch, Francis Naruto University of Education
Keywords
stratigraphy
sedimentary facies
Permo-Triassic unconformity
hummocky cross-stratification
molluscus
provenance
reworked fauna
conodont
radiolarians
Kurosegawa Terrane
Outer Zone of SW Japan
Content Type
Departmental Bulletin Paper
Description
The Sakashu Unconformity, a representative unconformity between Late Permian accretionary comprex and Late Triassic shallow-marine sediments in the South Kurosegawa Terrane, has investigated in stratigraphy, sedimentary facies, allochthonous and autochthonous faunas with the view point of post-accretional environmental changes. The accretion mélange of the Hisone Group, basement of the unconformity, yields Late Permian radiolarians. The lower member of the Upper Triassic Sabudani Formation is associated with two types of debris flows. One contains blocks of pelagic chert, carbonates, and greestones. The other is composed of mylonitized granitic breccias and fragments. The latter probably derived from the Mitaki Granites (400+ Ma) of the Kurosegawa Tectonic Zone that form the substratum of the Silurian limestone. The basal middle member of the Sabudani Formation contains huge blocks of weathered limestone/chert that yields late Early Permian conodont fauna (M. bisseli - S. whitei Zone). The hummocky cross-stratification in the middle member of the Sabudani Formation indicates a lower off-shore facies. Existence of the Permian conodont-bearing huge eroded limestone/chert blocks, and early Late Permian radiolarians in chert pebbles of the hummocky cross-stratified lag sediments suggests probable derivation of the conglomerates from the blocks in the Permian accretionary complexes. The Triassic mollusk fauna of the middle and upper members of the Sabudani Formation is correlative with the Carnian (-Norian) Kochigatani bivalve-fauna in the clastic facies of the Kurosegawa Terrane (Outer Zone of SW Japan) as well as with the Mine and Nabae groups, Primorye, Zabaikal and NE Siberia. From a paleobiogeographic point of view, the bivalve-fauna of the clastic sand- and marlstone Kochigatani facies is regarded to differ from that of the carbonate Tethyan facies in the South Chichibu Jurassic Accretionary Terrane.
Journal Title
Natural Science Research
ISSN
09146385
NCID
AN10065859
Publisher
徳島大学総合科学部
Volume
19
Start Page
19
End Page
29
Sort Key
19
Published Date
2005-12-24
EDB ID
FullText File
language
jpn
TextVersion
Publisher
departments
Science and Technology