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STRATIGRAPHIC MODELLING OF MIOCENE COMPOUND CLINOFORMS OF THE NEW JERSEY SHALLOW CONTINENTAL SHELF

Abstract : The New Jersey passive margin with well-developed clinoforms has long been a key location for past sea-level reconstructions and an end-member of passive margin sedimentary geometries. Recently, IODP Expedition 313 brings new insights on the facies architecture of Miocene clinothems preserved on the New Jersey shallow continental shelf feeding discussions on their depositional model and stratigraphic organization. This paper uses Dionisos, a process-based numerical modelling software, to reproduce the geometry and the architecture of Miocene clinothems. The objective is two-fold: (1) validate the hypothesis that a depositional model involving compound clinoform geometry (i.e. paired subaerial and subaqueous delta clinoforms) explains the facies architecture of Miocene clinothems, (2) evaluate the amplitude of sea-level fluctuations required to produce such a geometry. Simulations that consider waves and river discharge as equal contributors in the transport of sediment succeed in reproducing most key aspects of the Miocene clinothems: the seismic architecture (dip and geometry of reflectors), the stratigraphic architecture (systems tracts stacking patterns), the facies architecture (spatial distribution of facies), and the scale and geometry of the clinoforms (dip of the shelf, thickness of the sequences and height of the clinoforms). The action of waves exerts the prime control on the geometry of the compound clinoforms, which is characterized by a sandy subaerial delta at the shoreline feeding a muddy subaqueous delta clinoform that progrades on the shelf below wave base. Our results support recent depositional models of subaqueous deltas characterized by deepwater mud-dominated material on the topsets and toesets, and shoreface sand-dominated material on the rollover and foresets. This supposes that topsets muds were emplaced during highstand times, while the rollover sands mark lowstand times in clinothems, which are composed of four systems tracts (TST, HST, FSST, LST) building individual T-R sequences. Major seismic bounding surfaces (i.e. the clinoforms) correspond to Maximum Regressive Surfaces –MRS, which landward of Expedition 313 coreholes, merge with the sequences boundaries –SB– recognized in onshore coreholes. According to this reappraised stratigraphic model and based on Expedition 313 age framework, the New Jersey clinothems arrange in third-order, ~1.2 Myr-long megasequences. Those megasequences likely correspond to obliquity cycles that control the growth and decay of large Antartica ice sheets in the Miocene. A set of simulations was run to test this hypothesis and evaluate the amplitude of sea-level fluctuations. The best-fit simulation corresponds to a sinusoid-like curve characterized by 1.2 Myr-long cycle with amplitude of c.60 m. Even though those values are consistent with astronomical and paleoclimate estimates, such sealevel curve differs from the ones proposed in the literature.
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https://hal-insu.archives-ouvertes.fr/insu-01718055
Contributor : Isabelle Dubigeon <>
Submitted on : Tuesday, February 27, 2018 - 9:47:41 AM
Last modification on : Tuesday, December 3, 2019 - 5:24:09 PM

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  • HAL Id : insu-01718055, version 1

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Hugo Pouderoux, Jean-Noël Proust, Didier Granjeon. STRATIGRAPHIC MODELLING OF MIOCENE COMPOUND CLINOFORMS OF THE NEW JERSEY SHALLOW CONTINENTAL SHELF. International Meeting of Sedimentology 2017, Oct 2017, Toulouse, France. pp.718. ⟨insu-01718055⟩

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