Seismic expression and geological significane of a lacustrine delta in neogene deposits of the western Snake River Plain, Idaho
- Boise State Univ., Boise, ID (United States)
Lacustrine deposits in rift basin environments and groundwater resources in lacustrine sediments have become major petroleum targets and methods are needed to identify facies of permeable strata within thick sections of impermeable mud rocks characteristic of these deposits. High-resolution seismic reflection profiles and well data from the western Snake River plain basin are used to identify a buried lacustrine delta system within Neogene Idaho Group sediments near Caldwell, Idaho. The delta system is detected, 305 m (1000 ft) deep, near the center of the basin by progradational clinoform reflections having dips of 2-5[degrees]. The prodelta slope relief indicates the delta system prograded northwestward into a lake basin 255 m (837 ft) deep. Resistivity logs in the prodelta mud and clay facies show a gradual upward increase in resistivity and grain size over a thickness of about 100 m (300 ft). Lithology of the prodelta is mostly calcareous claystone with several layers of fine sand, some of which fine upward, indicating a density-flow mechanism of transport and deposition. Delta-plain and front sediments are mostly fine-grained, well-sorted sand separated by thin mud layers. These sediments produce up to five cycles of horizontal, high-amplitude reflections with a toplap relationship to prodelta clinoforms. The sands have an abrupt lower contact with prodelta muds and have high resistivity on logs. Permeable lacustrine sands within a predominantly mud and clay section are located by using high-resolution seismic reflection data. Identification of a delta system in the Idaho Group provides insight into the history of Pliocene [open quotes]Lake Idaho.[close quotes] The present depth of the delta/prodelta facies contact of 305 m (1000 ft) is 445 to 575 m (1460-1900 ft) below the lake deposits on the margins. Estimated subsidence from compaction is 220 m (656 ft), and the remaining 225 to 325 m (740-1066 ft) is attributed to tectonic downwarping and faulting.
- OSTI ID:
- 6964684
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 78:1; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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CENOZOIC ERA
COASTAL REGIONS
DEPOSITION
DETECTION
DEVELOPED COUNTRIES
DIMENSIONS
ELECTRIC LOGGING
EXPLORATION
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
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LAKES
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MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
PETROLOGY
RESISTIVITY LOGGING
RESOURCES
RIFT ZONES
RIVER DELTAS
SAND
SEDIMENTARY BASINS
SEDIMENTS
SEISMIC DETECTION
SEISMIC WAVES
SNAKE RIVER PLAIN
STRATIFICATION
SURFACE WATERS
TERTIARY PERIOD
THICKNESS
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WATER
WATER RESOURCES
WELL LOGGING