journal article Jul 26, 2017

Integrated sedimentology and ichnology of Late Jurassic fluvial point‐bars – facies architecture and colonization styles (Lourinhã Formation, Lusitanian Basin, western Portugal)

Sedimentology Vol. 65 No. 2 pp. 400-430 · Wiley
View at Publisher Save 10.1111/sed.12385
Abstract
AbstractIntegrated sedimentological and ichnological case studies of ancient meandering river systems have, for the most part, focused on the deposits of the fluvial–tidal transition zone; much less emphasis has been placed on the purely fluvial realm above the landward limit of tidal effects. This problem needs to be addressed so that in future the defining sedimentological and ichnological criteria assigned to ancient fluvial reaches are sufficiently well‐established to enable their separation from the down‐dip fluvial–tidal transition zone. Accordingly, a case study has been carried out on a well‐exposed meander belt deposit from the Late Jurassic Lourinhã Formation of the Lusitanian Basin, western Portugal (Praia Do Valmitão, Ribamar). Analysis indicates that the meander belt here comprised mixed‐load fluvial channels traversing a vegetated floodplain subject to a seasonal winter wet/summer dry palaeoclimate. This setting facilitated the development of both calcic palaeosols and shallow lakes on the adjacent floodplain. Critically, there is no evidence of the effects of tidal modulation on bedding structures, thereby establishing purely fluvial conditions. Heterolithic point‐bar deposits generated in this setting are bioturbated extensively by a trace fossil assemblage dominated by the meniscate traceTaenidium barretti, withSkolithos linearis,Planolites beverleyensisandCylindricumisp. also recognized. A number of factors suggest that theTaenidium barrettiproducer in this case was a subaquatic organism living in an active fluvial channel setting (i.e. not colonizing subaerially exposed channel‐margin/floodplain deposits). Accordingly, there are some implications for current ichnofabric/ichnofacies models in the continental realm. Firstly,Taenidium‐dominated ichnofabrics need not necessarily be confined to colonization beneath subaerially exposed surfaces; they might also be produced within submerged substrates. Secondly, there is scope to extend the range of theScoyeniaichnofacies to include active fluvial channels and not simply those channels that were inactive or abandoned.
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References
83
[1]
Abbink O.A.(1998)Palynological investigations in the Jurassic of the North Sea region. Laboratory of Palaeobotany and Palynology Contributions Series 8 Utrecht 192pp.
[4]
Allen J.R.L. "Studies in fluviatile sedimentation: a comparison of fining‐upwards cyclothems with special reference to coarse‐member composition and interpretation" J. Sed. Petrol. (1965)
[5]
Allen G.P. (1991)
[6]
Alpert S.P. "Systematic review of the genus Skolithos" J. Paleontol. (1974)
[9]
Alves T.M. "Mesozoic‐Cenozoic evolution of North Atlantic continental‐slope basins: the Peniche basin, western Iberian margin" AAPG Bull. (2006) 10.1306/08110504138
[10]
[12]
Billings E. (1862)
[14]
Brady L.F. "Invertebrate tracks from the Coconina Sandstone of northern Arizona" J. Paleontol. (1947)
[15]
Bridge J.S. (2003)
[16]
Bridge J.S. "Interpreting the dimensions of ancient fluvial channel bars, channels, and channel belts from wireline‐logs and cores" AAPG Bull. (2000)
[17]
Bromley R.G. (1990)
[18]
Buatois L.A. (2004)
[21]
Buatois L.A. (2007)
[22]
Collinson J.D. (1996)
[23]
D'Alessandro A. "Meniscate trace fossils and the Muensteria‐Taenidium problem" Palaeontology (1987)
[30]
Gabinete Para a Pesquisa e Exploração (GPEP)(1993)The petroleum potential of Portugal. Data package.Instituto Geológico E Mineiro Portugal.
[31]
Genise J.F. (2004)
[32]
Ghinassi M. "Inferring fluvial morphodynamics and overbank flow control from 3D outcrop sections of a Pleistocene point bar, Dandiero Basin, Eritrea" J. Sed. Res. (2013)
[34]
S.S. Haldeman 1840 Privately printed Philadelphia 3
[42]
Jackson R.G. "Depositional model of point bars in the lower Wabash river" J. Sed. Petrol. (1976)
[43]
Keighley D.G. "The ichnogenus Beaconites and its distinction from Ancorichnus and Taenidium" Palaeontology (1994)
[48]
Linck O.(1949)Lebens‐Spuren aus dem Schilfsandstein (Mittl. Keuper km 2) NW‐Württembergs und ihre Bedeutung für die Bildungs‐Geschichte der Stufe.Jh. Ver. Vaterl. Naturkd. Wurttemberg Jahresh 97–101 1–100.
[49]
Water escape structures in coarse‐grained sediments

DONALD R. LOWE

Sedimentology 10.1111/j.1365-3091.1975.tb00290.x

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Published
Jul 26, 2017
Vol/Issue
65(2)
Pages
400-430
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Cite This Article
Stuart Gowland, Andrew M. Taylor, Allard W. Martinius (2017). Integrated sedimentology and ichnology of Late Jurassic fluvial point‐bars – facies architecture and colonization styles (Lourinhã Formation, Lusitanian Basin, western Portugal). Sedimentology, 65(2), 400-430. https://doi.org/10.1111/sed.12385
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