Changes

* variations in well log response

* variations in well log response

* biostratigraphic data such as microfossil abundance patterns and biofacies distribution

* biostratigraphic data such as microfossil abundance patterns and [[Fossil assemblage|biofacies]] distribution

Armentrout<ref name=ch04r9>Armentrout, J., M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio–Pleistocene, in Howell, J., Aiken, J., eds., High Resolution [[Sequence stratigraphy]]: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65–86.</ref> discusses integration of these data sets.

Armentrout<ref name=ch04r9>Armentrout, J., M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio–Pleistocene, in Howell, J., Aiken, J., eds., High Resolution [[Sequence stratigraphy]]: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65–86.</ref> discusses integration of these data sets.

==GOM basin example==

==GOM basin example==

In the GOM basin, variations in well-log response and biofacies distribution are analyzed for recognition of stacked depositional sequences. The [[Basic open hole tools#Gamma ray|gamma-ray]] log display provides a measure of sediment type, with curve deflections to the left suggesting increased sand content while high values to the right indicate increases in clay content. Use of multiple logs, especially [[Basic open hole tools#Spontaneous potential|spontaneous potential]], [[Basic open hole tools#Resistivity|resistivity]], density, and velocity logs calibrated by well-cutting descriptions and formation microscanner displays, provides a data set for reliable rock type identification. The figure below illustrates an interpretation template for log motif analysis.

In the GOM basin, variations in well-log response and [[Fossil assemblage|biofacies]] distribution are analyzed for recognition of stacked depositional sequences. The [[Basic open hole tools#Gamma ray|gamma-ray]] log display provides a measure of sediment type, with curve deflections to the left suggesting increased sand content while high values to the right indicate increases in clay content. Use of multiple logs, especially [[Basic open hole tools#Spontaneous potential|spontaneous potential]], [[Basic open hole tools#Resistivity|resistivity]], density, and velocity logs calibrated by well-cutting descriptions and formation microscanner displays, provides a data set for reliable rock type identification. The figure below illustrates an interpretation template for log motif analysis.

Patterns of forestepping vs. backstepping log-motif funnels can define transgressive vs. regressive depositional trends and candidate systems tracts and sequences. Vail and Wornardt<ref name=ch04r101>Vail, P., R., Wornardt, W., W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> and Armentrout et al.<ref name=ch04r8>Armentrout, J. M., S. J. Malacek, L. B. Fearn, C. E. Sheppard, P. H. Naylor, A. W. Miles, R. J. Desmarais, and R. E. Dunay, 1993, Log-motive analysis of Paleogene depositional systems tracts, central and northern North Sea: Defined by sequence stratigraphic analysis ''in'' J. R. Parker, ed., Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, The Geological Society of London, p. 45-57.</ref> detail the process.

Patterns of forestepping vs. backstepping log-motif funnels can define transgressive vs. regressive depositional trends and candidate systems tracts and sequences. Vail and Wornardt<ref name=ch04r101>Vail, P., R., Wornardt, W., W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> and Armentrout et al.<ref name=ch04r8>Armentrout, J. M., S. J. Malacek, L. B. Fearn, C. E. Sheppard, P. H. Naylor, A. W. Miles, R. J. Desmarais, and R. E. Dunay, 1993, Log-motive analysis of Paleogene depositional systems tracts, central and northern North Sea: Defined by sequence stratigraphic analysis ''in'' J. R. Parker, ed., Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, The Geological Society of London, p. 45-57.</ref> detail the process.

</gallery>

</gallery>

The histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well are shown in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The histogram is based on a detailed checklist of the relative abundance of each species of fossil in each well-cutting sample.<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref> Display of this data in two-way time facilitates integration with seismic reflection profiles using the [[synthetic seismogram]] to match the well data with the seismic reflection profile at the well site. Patterns of shallow vs. deep biofacies and fossil abundance (i.e., concentration vs. dilution) can be correlated with progradation of sandstone vs. mudstone interpreted from wireline log patterns. Bioevents (abbreviated acronyms such as 2B and SG) and faunal discontinuity events (abbreviated FDA-3 and FDA-4) provide correlation horizons between which the abundance patterns provide additional events for correlation.<ref name=ch04r7 />

The histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well are shown in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The histogram is based on a detailed checklist of the relative abundance of each species of fossil in each well-cutting sample.<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref> Display of this data in two-way time facilitates integration with seismic reflection profiles using the [[synthetic seismogram]] to match the well data with the seismic reflection profile at the well site. Patterns of shallow vs. deep [[Fossil assemblage|biofacies]] and fossil abundance (i.e., concentration vs. dilution) can be correlated with progradation of sandstone vs. mudstone interpreted from wireline log patterns. Bioevents (abbreviated acronyms such as 2B and SG) and faunal discontinuity events (abbreviated FDA-3 and FDA-4) provide correlation horizons between which the abundance patterns provide additional events for correlation.<ref name=ch04r7 />

In the histogram in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]] (see [[:file:sedimentary-basin-analysis_fig4-17.png|Figure 1]] for well location), the foraminiferal abundance scale is 0-1000 specimens and the nannoplankton abundance scale is 0-800 specimens. Biofacies include inner neritic (IN, 0-50 m), middle neritic (MN, 50-100 m), outer neritic (ON, 100-200 m), upper bathyal (UPPB, 200-500 m), middle bathyal (MDLB, 500-1000 m), and lower bathyal (LOWB, 1000–2000 m). This figure is the leftmost (southern) well panel in [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]]. The wireline log (gamma ray) motif patterns ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 2]]), biostratigraphic abundance events, and extinction datums provide correlation events.

In the histogram in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]] (see [[:file:sedimentary-basin-analysis_fig4-17.png|Figure 1]] for well location), the foraminiferal abundance scale is 0-1000 specimens and the nannoplankton abundance scale is 0-800 specimens. Biofacies include inner neritic (IN, 0-50 m), middle neritic (MN, 50-100 m), outer neritic (ON, 100-200 m), upper bathyal (UPPB, 200-500 m), middle bathyal (MDLB, 500-1000 m), and lower bathyal (LOWB, 1000–2000 m). This figure is the leftmost (southern) well panel in [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]]. The wireline log (gamma ray) motif patterns ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 2]]), biostratigraphic abundance events, and extinction datums provide correlation events.

The four wells in the [[cross section]] are in a depositionally dip-oriented transect.<ref name=ch04r9 /> The correlation horizons, based on seven chronostratigraphically significant bioevents (mostly extinction events), partition the strata into age-correlative intervals.<ref name=ch04r10 /> Most of the chronostratigraphically significant bioevents occur in association with maximum fossil abundance, resulting in the interpretation of these correlation horizons as maximum flooding surface-condensed section data.<ref name=ch04r34 /><ref name=ch04r35 /><ref name=ch04r10 /><ref name=Shaffer1987a>Schaffer, B. L., 1987a, The potential of calcareous nannofossils for recognizing Plio-Pleistocene climactic cycles and sequence boundaries on the shelf: Proceedings, Gulf Section SEPM 8th Annual Research Conference, p. 142-145.</ref><ref name=Shaffer1987b>Schaffer, B. L., 1987b, The nature and significance of condensed sections in Gulf Coast late Neogene sequence stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 186-195.</ref><ref name=ch04r72>Pacht, J., A., Bowen, B., E., Bearn, J., H., Schaffer, B., L., 1990, [[Sequence stratigraphy]] of Plio–Pleistocene depositional facies in the offshore Louisiana south additions: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 1–18.</ref><ref name=ch04r9 />

The four wells in the [[cross section]] are in a depositionally dip-oriented transect.<ref name=ch04r9 /> The correlation horizons, based on seven chronostratigraphically significant bioevents (mostly extinction events), partition the strata into age-correlative intervals.<ref name=ch04r10 /> Most of the chronostratigraphically significant bioevents occur in association with maximum fossil abundance, resulting in the interpretation of these correlation horizons as maximum flooding surface-condensed section data.<ref name=ch04r34 /><ref name=ch04r35 /><ref name=ch04r10 /><ref name=Shaffer1987a>Schaffer, B. L., 1987a, The potential of calcareous nannofossils for recognizing Plio-Pleistocene climactic cycles and sequence boundaries on the shelf: Proceedings, Gulf Section SEPM 8th Annual Research Conference, p. 142-145.</ref><ref name=Shaffer1987b>Schaffer, B. L., 1987b, The nature and significance of condensed sections in Gulf Coast late Neogene sequence stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 186-195.</ref><ref name=ch04r72>Pacht, J., A., Bowen, B., E., Bearn, J., H., Schaffer, B., L., 1990, [[Sequence stratigraphy]] of Plio–Pleistocene depositional facies in the offshore Louisiana south additions: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 1–18.</ref><ref name=ch04r9 />

Each well panel is formatted the same as [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The foraminiferal (left histogram) and calcareous nannoplankton (right histogram) abundance patterns of each well are very similar. Biostratigraphic correlation horizons (horizontal lines) provide ties between the wells, facilitating comparison between the abundance patterns and biofacies variations within each chronostratigraphic interval. Each correlation was checked against correlations independently constructed using a regional grid of seismic reflection profiles.

Each well panel is formatted the same as [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The foraminiferal (left histogram) and calcareous nannoplankton (right histogram) abundance patterns of each well are very similar. Biostratigraphic correlation horizons (horizontal lines) provide ties between the wells, facilitating comparison between the abundance patterns and [[Fossil assemblage|biofacies]] variations within each chronostratigraphic interval. Each correlation was checked against correlations independently constructed using a regional grid of seismic reflection profiles.

==Identifying sequence in the GOB basin example==

==Identifying sequence in the GOB basin example==