The applicability of modern tidal analogues to pre-vegetation paralic depositional models

Ginny-Marie Bradley, Jonathan Redfern, David Hodgetts, Annette Dale George, Grant Wach

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

In modern siliciclastic environments terrestrial and aquatic vegetation binds substrate, controls weathering and erosion rates, influences run-off, sediment supply and subsequent depositional architecture. This study assesses the applicability of modern depositional models that are impacted by vascular vegetation, as analogues for ancient pre-land plant systems. A review of pre-Devonian published literature demonstrates a paucity of described tidal successions; this is possibly due to the application of modern analogues for interpreting the record when there is a lack of tidal indicators. This paucity suggests a need for revised models of tidal deposition that consider the different environmental conditions prior to land plant evolution. This study examines the Ordovician-Silurian Tumblagooda Sandstone, which is exposed in the gorge of the Murchison River and coastal cliffs near Kalbarri, Western Australia. The Tumblagooda Sandstone comprises stacked sand-rich facies, with well-preserved bedforms and trace fossils. Previous interpretations of the depositional setting have proposed from a mixed sheet-braided fluvial and intertidal flats; to a continental setting dominated by fluvial and aeolian processes. An enigmatic element is the rarity of mud-rich facies preserved in the succession. Outcrop logging, facies and petrographic analysis record dominantly shallow water conditions with episodes of emergence. Abundant ichnotaxa indicate that marine conditions and bi-directional flow structures are evidence for an intertidal and subtidal depositional environment. A macrotidal estuary setting is proposed, with evidence for tidal channels and repeated fluvial incursions. Physical and biogenic sedimentary structures are indicative of tidal conditions. The lack of clay and silt resulted in the absence of flaser or lenticular-bedding. Instead cyclic deposition of thin beds and foreset bioturbation replaced mud drape deposits. Higher energy conditions prevailed in the absence of the binding activity of plants in the terrestrial and marine realm. This is suggestive of different weathering processes and a reduction in the preservation of some sedimentary features. © 2018 International Association of Sedimentologists.
Original languageEnglish
Pages (from-to)2171-2201
Number of pages31
JournalSedimentology
Early online date31 Jan 2018
DOIs
Publication statusPublished - Oct 2018

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vegetation
mud
sandstone
subtidal environment
sedimentary feature
fluvial process
tidal channel
eolian process
weathering rate
terrestrial environment
trace fossil
flow structure
rarity
bedform
sedimentary structure
bioturbation
erosion rate
gorge
cliff
depositional environment

Cite this

Bradley, Ginny-Marie ; Redfern, Jonathan ; Hodgetts, David ; George, Annette Dale ; Wach, Grant. / The applicability of modern tidal analogues to pre-vegetation paralic depositional models. In: Sedimentology. 2018 ; pp. 2171-2201.
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abstract = "In modern siliciclastic environments terrestrial and aquatic vegetation binds substrate, controls weathering and erosion rates, influences run-off, sediment supply and subsequent depositional architecture. This study assesses the applicability of modern depositional models that are impacted by vascular vegetation, as analogues for ancient pre-land plant systems. A review of pre-Devonian published literature demonstrates a paucity of described tidal successions; this is possibly due to the application of modern analogues for interpreting the record when there is a lack of tidal indicators. This paucity suggests a need for revised models of tidal deposition that consider the different environmental conditions prior to land plant evolution. This study examines the Ordovician-Silurian Tumblagooda Sandstone, which is exposed in the gorge of the Murchison River and coastal cliffs near Kalbarri, Western Australia. The Tumblagooda Sandstone comprises stacked sand-rich facies, with well-preserved bedforms and trace fossils. Previous interpretations of the depositional setting have proposed from a mixed sheet-braided fluvial and intertidal flats; to a continental setting dominated by fluvial and aeolian processes. An enigmatic element is the rarity of mud-rich facies preserved in the succession. Outcrop logging, facies and petrographic analysis record dominantly shallow water conditions with episodes of emergence. Abundant ichnotaxa indicate that marine conditions and bi-directional flow structures are evidence for an intertidal and subtidal depositional environment. A macrotidal estuary setting is proposed, with evidence for tidal channels and repeated fluvial incursions. Physical and biogenic sedimentary structures are indicative of tidal conditions. The lack of clay and silt resulted in the absence of flaser or lenticular-bedding. Instead cyclic deposition of thin beds and foreset bioturbation replaced mud drape deposits. Higher energy conditions prevailed in the absence of the binding activity of plants in the terrestrial and marine realm. This is suggestive of different weathering processes and a reduction in the preservation of some sedimentary features. {\circledC} 2018 International Association of Sedimentologists.",
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The applicability of modern tidal analogues to pre-vegetation paralic depositional models. / Bradley, Ginny-Marie; Redfern, Jonathan; Hodgetts, David; George, Annette Dale; Wach, Grant.

In: Sedimentology, 10.2018, p. 2171-2201.

Research output: Contribution to journalArticle

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