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Coalesced delta-front sheet-like sandstone bodies from highly avulsive distributary channels; the low-accommodation Mesa Rica Sandstone (Dakota Group, New Mexico, U.S.A.)

Anna E. Van Yperen, John M. Holbrook, Miquel Poyatos-More and Ivar Midtkandal
Coalesced delta-front sheet-like sandstone bodies from highly avulsive distributary channels; the low-accommodation Mesa Rica Sandstone (Dakota Group, New Mexico, U.S.A.)
Journal of Sedimentary Research (July 2019) 89 (7): 654-678

Abstract

Low-accommodation deltaic systems are often challenging to interpret due to their condensed, low-gradient nature, which often results in extensive, sheet-like sandstone bodies. As a result, detailed studies of such systems are scarce, and their internal depositional architecture is still poorly understood. We analyze one such system, the Cenomanian deltaic Mesa Rica Sandstone (Dakota Group), which was deposited in the Western Interior Seaway, in east-central New Mexico, USA. A > 20-km-long escarpment, subparallel to the main delta progradation direction, allows a detailed analysis of facies distribution, depositional architecture, and the spatial extent of stratigraphic surfaces. Results reveal an arrangement of laterally variable shallowing-upward facies successions with three depositional cycles preserved. The first cycle is characterized by deltaic sheet-like sandstone bodies that are consistently overlain by sand-filled amalgamated distributary-channel deposits. The two successive cycles record a progressive reduction of sediment supply into the basin. Vertical and lateral relationships between facies associations and architectural geometries allow the recognition of regional key stratal surfaces, incised-valley fills, and the presence of lagoonal deposits at a sub-regional scale. The Mesa Rica deltaic system represents a river-dominated delta with multiple distributary channels. The sheet-like delta-front sandstone bodies are interpreted as the result of the combined effect of high sandy-sediment supply and low accommodation. The latter acted as an accelerator for autogenic depositional mechanisms such as mouth-bar deposition and abandonment, and for the highly avulsive character of distributary channels. After deposition, minor wave reworking facilitated lateral sand redistribution and favored bioturbation. This study demonstrates that sheet-like delta-front sandstone geometries from low-accommodation systems can be formed without the dominance of wave redistribution processes. This cautions against interpretations of amalgamated shoreline systems based solely on apparent sandstone geometries, without taking into account the preservation potential and postdepositional modification of primary deltaic characteristics.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 89
Serial Issue: 7
Title: Coalesced delta-front sheet-like sandstone bodies from highly avulsive distributary channels; the low-accommodation Mesa Rica Sandstone (Dakota Group, New Mexico, U.S.A.)
Affiliation: University of Oslo, Department of Geosciences, Oslo, Norway
Pages: 654-678
Published: 201907
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 91
Accession Number: 2019-065668
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 2 tables, sketch maps
N34°56'33" - N34°56'33", W103°28'17" - W103°28'17"
N34°52'30" - N34°52'30", W103°29'38" - W103°29'38"
Secondary Affiliation: Texas Christian University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 2019
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