Selected Trace Fossils in Core and Outcrop

Knaust, Dirk

doi:10.1007/978-3-319-49837-9_5

Cited by 5 publications

(9 citation statements)

References 342 publications

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“…13). The predominance of shallow-tier burrowing Nereites (Knaust 2017) may also occur in seemingly stratified rocks (Bromley 1996), traditionally described as “slate” in the present study area. Given that the frequency of homogenized sandy siltstone layers increases as the number of Nereites -bearing layers increases, lithofacies B–D could have been similar to each other originally and subsequently bioturbated, resulting in different ichnofabric indices.…”

Section: Discussionmentioning

confidence: 69%

“…Using observations of outcrops and polished rock samples in horizontal and vertical views (Online Supplemental File Fig. S5), genera of trace fossils were identified in accordance with the morphological characteristics presented by Knaust (2017). The degree of bioturbation is expressed as five levels of the ichnofabric index, based on the density of trace fossils and the degree of homogenization caused by bioturbation.…”

Section: Methodsmentioning

confidence: 93%

“…Among the trace fossils present, Rhizocorallium is a deeper tier structure with a complex morphology of feeding behaviors (Knaust 2017). The occurrence of the Rhizocorallium herein is one of the oldest examples thereof as it is known from the late Spathian onwards (Chen et al 2011).…”

Section: Discussionmentioning

confidence: 99%

“…In horizontal view, it forms a U-shaped tube without branches with spreite structures between the limbs of the “U”; i.e., it is an enclosed spreite (Fig. 6B, 6C; Knaust 2017). In vertical view, the possible initial tube is short and vertically oriented, and subsequently, its direction changes to horizontal (Fig.…”

Section: Lithofacies and Paleontological Contentsmentioning

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: Discussionmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Lithofacies and Paleontological Contentsmentioning

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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“…Even though Helminthopsis is commonly reported from other Cretaceous–Cenozoic thin-bedded turbidite settings (e.g., Wetzel and Uchman 1997; Heard and Pickering 2008; Cummings and Hodgson 2011), in these settings it is to the authors' knowledge neither abundant nor preserved as crowded trails on a single bedding plane. Likewise, Cylindrichnus is rarely reported from turbidite systems (e.g., Knaust 2017; Hubbard et al 2012), but apparently is not uncommon, particularly in Cenozoic deep-marine turbidite systems (D. Knaust, written communication 2021). However, the record of Helminthopsis, Helminthoidichnites , and Cylindrichnus as elite trace fossils in the Miocene is truly atypical for deep-marine thin-bedded turbidites.…”

Section: Introductionmentioning

confidence: 99%

HELMINTHOPSIS AND CYLINDRICHNUS ICHNOGUILDS FROM MIOCENE THIN-BEDDED TURBIDITES, TIERRA DEL FUEGO, ARGENTINA

OLIVERO,

LÓPEZ CABRERA

2023

Palaios

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Miocene thin-bedded turbidites from Tierra del Fuego record scarce graphoglyptids and two unusual ichnoguilds composed of diminutive elite trace fossils. The first, a monoichnospecific Cylindrichnus ichnoguild, consists of crowded, post-depositional burrows formed in surface sediments during the final phase of turbidite deposition. The second, a pre-depositional Helminthopsis ichnoguild, consists of dense aggregates of simple trails, mainly Helminthopsis and Helminthoidichnites, occupying a very shallow tier in organic-rich mud covering the sea floor prior to turbidite deposition. The trace makers of Cylindrichnus were opportunistic suspension/detritus feeding organisms, probably polychaetes, which bloomed during high flux of labile organic matter brought to internal and external levees by turbidity currents. The trace makers of Helminthopsis and Helminthoidichnites were probably nematodes that grazed on organic-rich muddy sediments with abundant disseminated pyrite associated with Kinneyia-like and other problematic wrinkle structures, suggesting sulfur-cycling chemosynthetic microbial communities originated during interturbidite phases. The rhythmical alternation of the Cylindrichnus and Helminthopsis ichnoguilds clearly differentiate the thin-bedded turbidites of the Viamonte Formation from channel-levee complexes elsewhere, stressing the point that ichnoassemblages reflect sets of environmental parameters and not necessarily particular depositional settings.

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Teichichnus zigzag Frey and Bromley, 1985: a probable echiuran or holothurian burrow from the Jurassic offshore Norway

Knaust

2018

PalZ

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Selected Trace Fossils in Core and Outcrop

Cited by 5 publications

References 342 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

HELMINTHOPSIS AND CYLINDRICHNUS ICHNOGUILDS FROM MIOCENE THIN-BEDDED TURBIDITES, TIERRA DEL FUEGO, ARGENTINA

Teichichnus zigzag Frey and Bromley, 1985: a probable echiuran or holothurian burrow from the Jurassic offshore Norway

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