Regional stratigraphic sequence

Seismic stratigraphy

These variations in local sediment supply affect the local and relative sea level which causes local sedimentary cycles. Key contrasts in reservoir performance are documented as a function of changes in reservoir characteristics, trap controls, and trap configurations from updip to downdip in this valley-fill drainage. One compound incised-valley fill that is a part of this system contains three facies tracts with unique reservoir characteristics: 1 the updip facies tract is dominated by amalgamated fluvial channel sandstones, 2 the transition facies tract consists of fluvial channel sandstones interbedded with finer grained estuarine sandstones, and 3 the downdip facies tract consists of ribbonlike fluvial channel sandstones isolated in estuarine shale. Both eustatic sea level changes and subsidence rates tend to be longer cycles. Two major stacked condensed sections are present in the fan: 3. Channel-levee systems comprise the bulk of the sediments in both fans and can be mapped in both fans. Relative sea level is measured with reference to the base level, above which erosion can occur and below which deposition can occur. In the distant past, sea level has been significantly higher than today. Today, sea level is at a relative "high stand" within the Quaternary glacial cycles because of rapid end- Pleistocene and early- Holocene deglaciation. The latter is called progradation. So a rapidly progradational pattern will be indicative of falling sea level, rapidly retrogradational is evidence for rapidly transgressing sea level and aggradational will be indicative of gently rising sea level.

In the Eastern Fan, there is generally less erosion at die base of die sequences and mass transport complexes arc generally absent. Sequences are interpreted to be 5. These variations in local sediment supply affect the local and relative sea level which causes local sedimentary cycles.

Types of sequence stratigraphy

Sea level changes over geologic time. Today, sea level is at a relative "high stand" within the Quaternary glacial cycles because of rapid end- Pleistocene and early- Holocene deglaciation. The submarine canyons that fed diese channel-levee systems are located immediately due east of the modem Mississippi bird-foot delta. These variations in local sediment supply affect the local and relative sea level which causes local sedimentary cycles. Retrogradational Each stacking pattern will give different information on the behaviour of accommodation space, a major control of which is relative level. Sequences are interpreted to be 1. The next larger cycle '4th order' is about 40, years and approximately matches the rate at which the Earth's inclination to the Sun varies again explained by Milankovitch. The Eastern Fan consists of eight depositional sequences that are coeval to sequences , in the Western Fan. Large portions of diree sequences in die Eastern Fan consist of in situ slides. This complex comprises two distinct submarine fans: the Western and Eastern Fan. In the distant past, sea level has been significantly higher than today. Smaller and localised sedimentary cycles are not related to worldwide eustatic sea level changes but more to the supply of sediment to the adjacent basins where these sediments are being supplied.

These lateral shifts in deposition create alternating layers of good reservoir quality rock porous and permeable sands and poorer-quality mudstones capable of providing a reservoir "seal" to prevent the leakage of any accumulated hydrocarbons that may have migrated into the sandstones.

Hydrocarbon prospectors look for places in the world where porous and permeable sands are overlain by low permeability rocks, and where conditions are right for hydrocarbons to be generated and migrate into these "traps".

History of sequence stratigraphy

Smaller and localised sedimentary cycles are not related to worldwide eustatic sea level changes but more to the supply of sediment to the adjacent basins where these sediments are being supplied. Sea level changes over geologic time. You do not currently have access to this chapter. You could not be signed in. A mi-long km-long longitudinal cross section through one trunk of the incised-valley-fill drainage shows that internal valley-fill strata change significantly as a function of the interplay of varying depositional systems down gradient in the valley. The earth scientists who study the positions of coastal sediment deposits through time "sequence stratigraphers" have noted dozens of similar basinward shifts of shorelines associated with a later recovery. The graph on the right illustrates two recent interpretations of sea level changes during the Phanerozoic. These alternating high and low sea level stands repeat at several time scales. The latter is called progradation.

The next larger cycle '3rd order' is aboutyears and corresponds to the rate at which the Earth's orbit oscillates from elliptical to circular. Although there is debate among earth scientists whether we are currently experiencing a "high stand" it is generally accepted that the eustatic sea level is rising.

Smaller and localised sedimentary cycles are not related to worldwide eustatic sea level changes but more to the supply of sediment to the adjacent basins where these sediments are being supplied.

The resultant valley-fill systems have many characteristics in common with published valley-fill models, but have significant differences as well.

sequence stratigraphy ppt

The ancient shoreline of the last glacial period is now under approximately feet meters of water. At least seven discrete submarine canyons located in the Ewing Bank, Green Canyon, and Mississippi Canyon lease areas can be traced downslope to their terminus in the equivalent channel-levee systems.

sequence stratigraphy exercises

The submarine canyons that fed diese channel-levee systems are located immediately due east of the modem Mississippi bird-foot delta.

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Sequence stratigraphy