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Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey

D. M. Hodgson, J. V. Browning, Kenneth G. Miller, S. P. Hesselbo, M. Poyatos-More, G. S. Mountain and J. N. Proust
Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey
Geosphere (Boulder, CO) (February 2018) 14 (1): 95-114


Drilling of intrashelf Miocene clinothems onshore and offshore New Jersey has provided better understanding of their topset and foreset deposits, but the sedimentology and stratigraphy of their bottomset deposits have not been documented in detail. Three coreholes (Sites M27-M29), collected during Integrated Ocean Drilling Program (IODP) Expedition 313, intersect multiple bottomset deposits, and their analysis helps to refine sequence stratigraphic interpretations and process response models for intrashelf clinothems. At Site M29, the most downdip location, chronostratigraphically well-constrained bottomset deposits follow a repeated stratigraphic motif. Coarse-grained glauconitic quartz sand packages abruptly overlie deeply burrowed surfaces. Typically, these packages coarsen then fine upwards and pass upward into bioturbated siltstones. These coarse sand beds are amalgamated and poorly sorted and contain thin-walled shells, benthic foraminifera, and extrabasinal clasts, consistent with an interpretation of debrites. The sedimentology and mounded seismic character of these packages support interpretation as debrite-dominated lobe complexes. Farther updip, at Site M28, the same chronostratigraphic units are amalgamated, with the absence of bioturbated silts pointing to more erosion in proximal locations. Graded sandstones and dune-scale cross-bedding in the younger sequences in Site M28 indicate deposition from turbidity currents and channelization. The sharp base of each package is interpreted as a sequence boundary, with a period of erosion and sediment bypass evidenced by the burrowed surface, and the coarse-grained debritic and turbiditic deposits representing the lowstand systems tract. The overlying fine-grained deposits are interpreted as the combined transgressive and highstand systems tract deposits and contain the deepwater equivalent of the maximum flooding surface. The variety in thickness and grain-size trends in the coarse-grained bottomset packages point to an autogenic control, through compensational stacking of lobes and lobe complexes. However, the large-scale stratigraphic organization of the bottomset deposits and the coarse-grained immature extrabasinal and reworked glauconitic detritus point to external controls, likely a combination of relative sea-level fall and waxing-and-waning cycles of sediment supply. This study demonstrates that large amounts of sediment gravity-flow deposits can be generated in relatively shallow ( approximately 100-200 m deep) and low-gradient ( approximately 1 degrees -4 degrees ) clinothems that prograded across a deep continental shelf. This physiography likely led to the dominance of debris flow deposits due to the short transport distance limiting transformation to low-concentration turbidity currents.

EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 14
Serial Issue: 1
Title: Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey
Affiliation: University of Leeds, School of Earth and Environment, Leeds, United Kingdom
Pages: 95-114
Published: 201802
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 98
Accession Number: 2018-036962
Categories: StratigraphyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., sketch map
N39°38'03" - N39°38'03", W73°37'18" - W73°37'18"
N39°33'57" - N39°33'57", W73°29'50" - W73°29'50"
N39°31'10" - N39°31'10", W73°24'48" - W73°24'48"
Secondary Affiliation: Rutgers University, USA, United StatesUniversity of Exeter, GBR, United KingdomUniversity of Oslo, NOR, NorwayUniversite de Rennes, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201809
Program Name: IODPIntegrated Ocean Drilling Program
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