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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.)
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GeoScienceWorld
Date
2019-07-10
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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.
Contents
Subject
avulsion
Cenomanian
channels
clastic rocks
coastal environment
Cretaceous cross-stratification
deltaic environment
depositional environment
fluvial environment
lagoonal environment
Lower Cretaceous
Mesa Rica Sandstone
Mesozoic
New Mexico
North America
planar bedding structures
Quay County New Mexico
ripple drift-cross laminations
sandstone
sedimentary rocks
sedimentary structures
United States
Upper Cretaceous
Western Interior
Western Interior Seaway
Dakota Group
Cenomanian
channels
clastic rocks
coastal environment
Cretaceous cross-stratification
deltaic environment
depositional environment
fluvial environment
lagoonal environment
Lower Cretaceous
Mesa Rica Sandstone
Mesozoic
New Mexico
North America
planar bedding structures
Quay County New Mexico
ripple drift-cross laminations
sandstone
sedimentary rocks
sedimentary structures
United States
Upper Cretaceous
Western Interior
Western Interior Seaway
Dakota Group
Subject(s)
Research Projects
Organizational Units
Journal Issue
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Description
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Department
Geological Sciences