New insight into the sedimentology and stratigraphy of the Dur At Talah tidal-fluvial transition sequence (Eocene–Oligocene, Sirt Basin, Libya)

Abouessa, Ashour; Pelletier, Jonathan; Duringer, Philippe; Schuster, Mathieu; Schaeffer, Philippe; Métais, Eddy; Benammi, Mouloud; Salem, Mustapha; Hlal, Osama; Brunet, Michel; Jaeger, Jean‐Jacques; Rubino, Jean‐Loup

doi:10.1016/j.jafrearsci.2012.02.004

Cited by 29 publications

(27 citation statements)

References 35 publications

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“…9). Mouth bars with similar angles are described in marine deltas (Catuneanu 2006;Fielding 2010;Abouessa et al 2012) and lacustrine deltas (Coleman and Prior 1982;Schomacker et al 2010) and are possibly associated with river load with a density in the same range as the density of the water of the receiving basin (Mulder et al 2003). Foreset dips are oriented parallel to cross-stratification paleoflow, indicating forward accretion and progradation.…”

Section: Architecturementioning

confidence: 66%

Stratigraphic Record of River-Dominated Crevasse Subdeltas With Tidal Influence (Lajas Formation, Argentina)

Gugliotta¹,

Flint²,

Hodgson³

et al. 2015

Journal of Sedimentary Research

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Crevasse subdeltas develop on modern river-dominated delta plains, and may be affected by the interaction of river currents and marine processes. However, their sedimentology and stratigraphic architecture is poorly constrained, leading to simplistic depositional models of delta-plain systems in the ancient record. Extensive exposures of the Middle Jurassic Lajas Formation permit the architecture, main stratigraphic surfaces, and lateral and vertical facies variations of crevasse subdelta deposits to be constrained. Lower-delta-plain successions studied in the Lajas Formation consist of up to 5-m-thick distributary channels and interdistributary-bay deposits, interpreted as crevasse subdeltas. Crevasse subdelta deposits consist of small-scale lenticular units (, 1-2 m thick) interpreted as crevasse channels and upward-coarsening and upward-thickening packages (, 2 m thick) with clinothems interpreted as crevasse mouth bars. These deposits preserve interbedding of coarser and finer sediments that are interpreted as river flood and interflood couplets associated with variations in river discharge. River flood beds are commonly structureless and erosionally based, and show little evidence of tidal action and brackish-water conditions. Interflood deposits show rhythmically distributed mudstone drapes, bimodality, and brackish trace fossils. This study highlights an important but largely undocumented component of interdistributary deposits consisting of tide-influenced, but strongly riverdominated, prograding depositional bodies. An implication is that some coarsening-upward, forward-accreting units previously interpreted from the rock record as interchannel ''tidal bars'' may instead represent minor mouth bars of tide-influenced crevasse subdeltas. Furthermore, present-day crevasse subdeltas are restricted to river-dominated delta systems that flow into semi-enclosed or enclosed seas and lakes with microtidal conditions and limited wave action, which is comparable to paleogeographic reconstructions for the Neuquén Basin during the Middle Jurassic.

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Section: Architecturementioning

confidence: 66%

Stratigraphic Record of River-Dominated Crevasse Subdeltas With Tidal Influence (Lajas Formation, Argentina)

Gugliotta¹,

Flint²,

Hodgson³

et al. 2015

Journal of Sedimentary Research

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“…The Dur At-Talah escarpment, located in the southern part of the Sirt Basin, consists of 150 m of mainly clastic rocks divided into two stratigraphic units: the New Idam Unit at the base composed of fine sand/claystone alternations and the Sarir Unit at the top dominated by sandstones. Abouessa et al (2012) provided a recent synthesis of the stratigraphy, sedimentology, and depositional environments of Eocene rocks comprising the Dur At-Talah escarpment. The New Idam Unit has yielded one of the richest Paleogene faunas known from North Africa including both lower vertebrates and placental mammals (Savage and White, 1965;Savage, 1969;Court, 1995;Delmer, 2009;Jaeger et al, 2010a,b;Grohé et al, 2012;Tabuce et al, 2012).…”

Section: Geological Context and Specimensmentioning

confidence: 99%

New fossils from the Paleogene of central Libya illuminate the evolutionary history of endemic African anomaluroid rodents

et al. 2015

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“…), which are characterized by the simultaneous presence of fluvial and marine processes (Dalrymple & Choi, ; Dashtgard et al ., ; La Croix & Dashtgard, ). In the study of ancient deposits, the fluvial to marine transition zone or similar terms have been used to describe stratigraphic changes from interpreted marine or tidal to fluvial deposits (Simpson et al ., ; Makhlouf, ; Eriksson et al ., ; Abouessa et al ., ). The term has rarely been applied to interpret down dip changes in time‐equivalent deposits that formed within a well‐defined zone with mixed fluvial and marine energy (van den Berg et al ., ; Martinius & Gowland, ; Martinius & Van den Berg, ; Martinius et al ., ) or to describe the interaction of fluvial and marine processes during deposition (Ghosh et al ., ; Dalrymple et al ., ; Gugliotta et al ., ; Jablonski & Dalrymple, ).…”

Section: Introductionmentioning

confidence: 99%

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

et al. 2016

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The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes, a tract known as the fluvial to marine transition zone, which varies between systems due to the relative strength of these processes. To understand how fluvial and tidal process interactions and the fluvial to marine transition zone are preserved in the rock record, large‐scale outcrops of deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated. Fluvial–tidal indicators consist of cyclically distributed carbonaceous drapes in unidirectional, seaward‐oriented cross‐stratifications, which are interpreted as the result of tidal modulation of the fluvial current in the inner part of the fluvial to marine transition zone. Heterolithic deposits with decimetre‐scale interbedding of coarser‐grained and finer‐grained facies with mixed fluvial and tidal affinities are interpreted to indicate fluvial discharge fluctuations (seasonality) and subordinate tidal influence. Many other potential tidal indicators are argued to be the result of fluvial–tidal interactions with overall fluvial dominance or of purely fluvial processes. No purely tidal or tide‐dominated facies were recognized in the studied deposits. Moreover, fluvial–tidal features are found mainly in deposits interpreted as interflood (forming during low river stage) in distal (delta front) or off‐axis (interdistributary) parts of the system. Along major channel axes, the interpreted fluvial to marine transition zone is mainly represented by the fluvial‐dominated section, whereas little or no tide‐dominated section is identified. The system is interpreted to have been hyposynchronous with a poorly developed turbidity maximum. These conditions and the architectural elements described, including major and minor distributary channels, terminal distributary channels, mouth bars and crevasse mouth bars, are consistent with an interpretation of a fluvial‐dominated, tide‐influenced delta system and with an estimated short backwater length and inferred microtidal conditions. The improved identification of process interactions, and their preservation in ancient fluvial to marine transition zones, is fundamental to refining interpretations of ancient deltaic successions.

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New insight into the sedimentology and stratigraphy of the Dur At Talah tidal-fluvial transition sequence (Eocene–Oligocene, Sirt Basin, Libya)

Cited by 29 publications

References 35 publications

Stratigraphic Record of River-Dominated Crevasse Subdeltas With Tidal Influence (Lajas Formation, Argentina)

Stratigraphic Record of River-Dominated Crevasse Subdeltas With Tidal Influence (Lajas Formation, Argentina)

New fossils from the Paleogene of central Libya illuminate the evolutionary history of endemic African anomaluroid rodents

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

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