Facies and stratal patterns in incised valley complexes: Examples from the recent Gironde estuary (France), and the Cretaceous Viking Formation (Canada)
- Total Exploration Lab., Saint-Remy-Les-Chevreuse (France)
- Esso Resources, Calgary, Alberta (Canada)
Incised valleys form during a relative fall in sea level and fill during lowstand and relative rise. They constitute favorable exploration targets, forming regionally continuous sand ribbons up to 20-50 m thick and 10-25 km wide, sealed by transgressive marine muds. Modern estuaries furnish analogs to study facies and stratal patterns within incised valleys. Studies in the Gironde estuary indicate that they are filled with a tripartite upward transgressive section comprising basal fluid sands, overlain by estuarine sands and muds, blanketed by marine muds. The fluvial sands in the valley thalweg accumulate by aggradation of the fluvial profile during lowstand time, and represent the updip equivalent of the lowstand prograding wedge. During transgression, fluvial aggradation ceases, and the backstepping transgressive tract onlaps the fluvial profile. In a vertical section, the lowstand-transgressive tract contact is recognizable by a major fluvial-estuarine facies boundary associated with the landward migration of the bayline over the fluvial plain. These estuarine deposits are usually truncated by a wave ravinement surface, overlain by nearshore sand and shelf muds. In high tide settings, a tidal ravinement surface also forms, resulting in an increased thickness of estuarine sand. These characteristic facies and stratal patterns have been recognized in incised valleys of the Cretaceous Viking Formation. These valleys formed during third order (1-3 Ma) eustatic cycles, punctuated by higher frequency eustatic cycles (<1 Ma), with short-lived base level falls accompanied by renewed stream incision and fluvial sand deposition. This has resulted in complex multistory valley fills comprising several superposed sharp-based upward transgressive units.
- OSTI ID:
- 5788104
- Report Number(s):
- CONF-910403-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
Similar Records
Sequence stratigraphy and facies model of an incised valley fill: The Gironde estuary, France
GREYBULL SANDSTONE PETROLEUM POTENTIAL ON THE CROW INDIAN RESERVATION, SOUTH-CENTRAL MONTANA
Related Subjects
03 NATURAL GAS
CANADA
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
FRANCE
EXPLORATION
RESERVOIR ROCK
STRATIGRAPHY
CRETACEOUS PERIOD
ESTUARIES
GEOLOGIC FORMATIONS
GEOLOGIC MODELS
LITHOLOGY
QUATERNARY PERIOD
SEA LEVEL
CENOZOIC ERA
DEVELOPED COUNTRIES
EUROPE
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
LEVELS
MESOZOIC ERA
MINERAL RESOURCES
NORTH AMERICA
RESOURCES
SURFACE WATERS
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration