Changes

==Interpretation of stratal patterns example==

==Interpretation of stratal patterns example==

Relative changes in sea level can also be inferred from detailed analysis of local depositional geometries on seismic reflection profiles. On the seismic reflection profile schematic below.<ref name=ch04r6>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref> clinoforms 1-5 pinch out with toplap against a common horizon, suggesting oblique clinoforms.<ref name=ch04r68>Mitchum, R., M., Jr., 1977, Seismic stratigraphy and global changes in sea level, II: [[Glossary]] of terms used in seismic stratigraphy, in Seismic Stratigraphy—Applications in Hydrocarbon Exploration: AAPG Memoir 26, p. 205–212.</ref> These oblique clinoforms can be interpreted as forming when sediment supply exceeds the accommodation space and causes shelf-margin progradation; sea level falls at the same rate as subsidence, completely bypassing the shelf with no accumulation of seismic-scale topset beds. Clinoforms 6 and 7 are sigmoidal<ref name=ch04r68 /> These can be interpreted as sediment supply exceeding accommodation space, forcing progradation but with subsidence exceeding the relative change in sea level and consequent accumulation of topset beds. The change from no topset beds to aggradational topset beds indicates a turnaround from apparent still-stand to apparent rise in sea level at the site of deposition.

Relative changes in sea level can also be inferred from detailed analysis of local depositional geometries on seismic reflection profiles. On the seismic reflection profile schematic in [[:file:sedimentary-basin-analysis_fig4-27.png|Figure 8]]<ref name=ch04r6>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref> clinoforms 1-5 pinch out with toplap against a common horizon, suggesting oblique clinoforms.<ref name=ch04r68>Mitchum, R., M., Jr., 1977, Seismic stratigraphy and global changes in sea level, II: [[Glossary]] of terms used in seismic stratigraphy, in Seismic Stratigraphy—Applications in Hydrocarbon Exploration: AAPG Memoir 26, p. 205–212.</ref> These oblique clinoforms can be interpreted as forming when sediment supply exceeds the accommodation space and causes shelf-margin progradation; sea level falls at the same rate as subsidence, completely bypassing the shelf with no accumulation of seismic-scale topset beds. Clinoforms 6 and 7 are sigmoidal<ref name=ch04r68 /> These can be interpreted as sediment supply exceeding accommodation space, forcing progradation but with subsidence exceeding the relative change in sea level and consequent accumulation of topset beds. The change from no topset beds to aggradational topset beds indicates a turnaround from apparent still-stand to apparent rise in sea level at the site of deposition.

==Time significance of seismic reflections==

==Time significance of seismic reflections==