Normally graded laminae - common link between storm-generated facies of progradational nearshore marine strata

Conference · Fri Jul 01 04:00:00 EDT 1988 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6179750

Gustason, E R

Tabular sandstone beds, hummocky cross-stratified sandstone (HCS), and trough and planar tabular cross-stratified sandstone (St/Sp) are characteristic facies of coarsening- and thickening-upward Cretaceous marine strata in the Rocky Mountain region. All contain sharp and/or erosional basal surfaces and consist of normally graded, planar, parallel and/or concordant laminae, indicating episodic erosion and deposition from suspension, with very little or no bed-load deposition. Sharp-based tabular sandstone beds are normally graded overall (sandstone-to-mudstone) and contain normally graded planar parallel laminae. Similarly, HCS sets consist of normally graded concordant to slightly asymptotic laminae that overlie hummocky and swaley erosional basal surfaces. Sets of St/Sp are composed of unidirectional dip-oriented cross-strata bound by reactivation surfaces, which commonly have a sigmoidal shape. Internally, these cross strata consist of normally graded concordant to asymptotic laminae. Normally graded laminae of all three facies typically fine upward from sand to silt or clay with abundant carbonaceous trash and/or mica flakes, indicating deposition from suspension. Tabular sandstone beds record punctuated deposition from suspension below storm wave base, but HCS records erosion and deposition from suspension within storm wave base. St/Sp record erosion and deposition from suspension within storm wave base and under the influence of a unidirectional current, perhaps reflecting longshore drift in the upper shoreface zone. Dip-oriented outcrops reveal that sharp-based tabular sandstone beds can be traced up depositional dip into the erosional bases of HCS. St/Sp commonly build downcurrent from hummocks of HCS. These features suggest that erosion and deposition of all three facies are genetically related to the same erosional and depositional event.

• Research Organization: RPI International Inc., Boulder, CO (USA)
• OSTI ID: 6179750
• Report Number(s): CONF-8808223-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 72:7
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CARBONACEOUS MATERIALS
CRETACEOUS PERIOD
DEPOSITION
GEOLOGIC AGES
GEOLOGY
MATERIALS
MESOZOIC ERA
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
STRATIGRAPHY