The Triassic Inai Group in the Karakuwa area, southern Kitakami Mountains, Japan (Part I):Stratigraphy and paleogeography

耕太郎, 鎌田

doi:10.5575/geosoc.85.737

Cited by 4 publications

(9 citation statements)

References 7 publications

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“…Cross-stratifications or current ripples in sandstone show an almost westward paleocurrent direction (Kamada 1979), which is concordant with the supposed landslide directions (Kamada 1979). However, several paleocurrents in turbiditic sandstone are directed toward the north, suggesting multiple provenance directions for the sandstone beds (Kamada 1979). Based on lithological studies of conglomerates and lithic The numbers in squares to the left of the columnar sections are equivalent to the outcrop numbers (Online Supplemental File Fig.…”

Section: Geological Settingsupporting

confidence: 76%

“…In the sandy laminated mudstone of the Osawa Formation, the laminations are not horizontal but are cross-stratified at a low angle (Kamada 1979). These structures are considered to have been formed by low-density turbidity flows (Kamada 1979). Kawakami and Kawamura (2002) mentioned examples of sedimentary settings in which thick coarsegrained sandstone a few meters thick intercalated with sandy laminated mudstone could be formed by the flooding of channels in flat basin (Hesse and Dalton 1995), in continental slope and in prodelta environments (Pickering 1984;Stow and Piper 1984;Kamada 1991).…”

Section: Geological Settingmentioning

confidence: 99%

“…In the case of the Osawa Formation, the sequence indicates abundant supply of sediment from the hinterland via the probable fan delta system. The large siliciclastic supply was probably sourced from Permian siliciclastic strata (Okawa et al 2013), which may be associated with local uplift and denudation of this area (Kamada 1979). Given the abundant supply of materials from the hinterland, large amounts of organic matter were deposited there, facilitating development of anoxic conditions at the seafloor.…”

Section: Ocean Redox Stratification In the Early Triassicmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

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Sedimentary Environment and Redox Conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane, Japan: Insights Into Ocean Redox Stratification and Faunal Recovery

Ishizaki

Shiino

2023

Palaios

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The sedimentary environments and redox conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane were reconstructed based on lithofacies, trace fossils, and other paleontological content. The muddy and sandy lithofacies of the Osawa Formation lack evidence of storm waves despite the presence of storm-induced turbidites, suggesting that the oldest deposits of the Osawa Formation were deposited in the proximal part of the outer shelf. In turn, water depth increased from the lower to upper part of the formation, ultimately recording the distal part of the outer shelf. In addition to sandy lithofacies caused by turbidity and traction currents, multiple sandy layers within the muddy lithofacies would have originated via supply into the prodelta setting from a fan delta system. Collapses of the delta front or river system floods could have generated hyperpycnal flows, resulting in abundant supplies of mud and organic matter. Trace fossil analyses revealed that the degree of bioturbation (ichnofabric indices) dramatically decreased as water-depth increased, indicating a steep oxic-dysoxic gradient along the onshore-offshore transect. Diagenetic pyrite framboids indicative of dysoxic/anoxic benthic conditions are abundant at greater water depths. Abundant pyrite framboids less than 6 μm in diameter suggest intermittent euxinicity. With an increase in global weathering, abundant sediment supply including organic matter from the fan delta system could have contributed to the development of ocean redox stratification, which appears to have impacted on the adaptation of both nektic and benthic animals of this area during the Early Triassic.

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Section: Geological Settingsupporting

confidence: 76%

Section: Geological Settingmentioning

confidence: 99%

Section: Ocean Redox Stratification In the Early Triassicmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

See 2 more Smart Citations

Sedimentary Environment and Redox Conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane, Japan: Insights Into Ocean Redox Stratification and Faunal Recovery

Ishizaki

Shiino

2023

Palaios

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“…The refugium archetype is the oceanic island, where shallow-water taxa can¯ee from continental shelves at times of environmental crisis. However, Vermeij (1986) warned that the role of oceanic islands as refugia is not supported by strong evidence, and many failures to discover Lazarus taxa in such locations seem to con®rm his views (Kamada 1979;Tamura 1981Tamura , 1982Vermeij 1986;Sano and Nakashima 1997). Phacelostylophyllum and Neoguadalupia are exceptions.…”

mentioning

confidence: 99%

What are Lazarus taxa?

Fara

2001

Geological Journal

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The many de®nitions and interpretations associated with the`Lazarus effect' have considerably confused this notion. While several authors regard the Lazarus effect as the temporary disappearance of taxa from the fossil record in any given time interval, many others consider the Lazarus effect as a pattern restricted to mass extinction episodes. The adequacy of the fossil record is the key for interpreting the Lazarus pattern: either Lazarus taxa re¯ect the incompleteness of the fossil record (the`stratigraphic alternative'), or they illustrate genuine extinction-linked phenomena (the`biological alternative'). The latter option includes two traditional hypotheses implying existence of refugia and post-extinction low population diversity. Differences between these two biological explanations seem to be more rhetorical than substantiated. In addition, the sampling intensity is an external factor commonly linked with both the stratigraphic and the biological alternatives. Interpreting the Lazarus effect is an asymmetrical procedure because the biological alternative is only favoured when the stratigraphic one cannot be documented. Consequently, analytical techniques assessing the completeness of the fossil record are critical to understand the meaning of Lazarus taxa. In particular, gap distributions are better compared with extinction and origination rates rather than with total diversity estimates. Finally, the Lazarus effect should be de®ned broadly to include range gaps from any given time interval.

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Provenance of Permian sandstones, South Kitakami Terrane, Northeast Japan: implications for Permian arc evolution

Yoshida

Machiyama

2004

Sedimentary Geology

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The Triassic Inai Group in the Karakuwa area, southern Kitakami Mountains, Japan (Part I):Stratigraphy and paleogeography

Cited by 4 publications

References 7 publications

Sedimentary Environment and Redox Conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane, Japan: Insights Into Ocean Redox Stratification and Faunal Recovery

Sedimentary Environment and Redox Conditions of the Lower Triassic Osawa Formation in the Southern Kitakami Terrane, Japan: Insights Into Ocean Redox Stratification and Faunal Recovery

What are Lazarus taxa?

Provenance of Permian sandstones, South Kitakami Terrane, Northeast Japan: implications for Permian arc evolution

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