Differences

This shows you the differences between two versions of the page.

--- seqstrat_characterising [20/03/2023 14:04] – mike_gss
+++ seqstrat_characterising [11/05/2023 12:36] (current) – mike_gss
@@ Line 3: / Line 3: @@
 We need to establish characteristic "paleontological signatures" or "fingerprints" for surfaces and components of a sequence. In order to do that we need to know how the fossils – as living organisms – respond to changes in sea level and, to an extent, sediment supply.
-Sequence //surfaces// provide the broad features that separate individual sequences and sequence components and also the mechanism by which sequences are biostratigraphically calibrated and therefore correlated on a well-to-well and eventually regional basis.
+Sequence //surfaces// provide the broad horizons that separate individual sequences and //sequence components// ("systems tracts") and also the mechanism by which sequences are biostratigraphically calibrated and therefore correlated on a well-to-well and eventually regional basis.
+Readers should be familiar with the biostratigraphical principles and applications to (a) Biostratigraphy and Correlation and (b) Paleoenvironments (see [[start|Table of Contents]] on home page). Sequence biostratigraphy brings these two aspects together in a fully integrated way.
 {{:seqstrat01.jpg?nolink|}}
@@ Line 33: / Line 35: @@
 A sequence is formed during a cycle of a sea-level fall and subsequent rise (described on other pages). We can make an educated assumption as to how fossils - both those that dwell on or in the sea floor sediment and those that float or swim above it - might respond to these changes. These responses should be visible in the fossil record within a sequence.
-Often, a sea-level fall will expose the continental shelf and cause erosion and sediment re-deposition (the SB). Marine organisms that inhabited the continental shelf would die out. Erosion/Re-deposition causes fossils that previously inhabited shallower (shelf) environments to be transported downslope into deeper-water (bathyal) sediments. During this period (the LST) water-depths progressively decrease as the basin fills up with sediment, raising the level of the sea-floor. This "shallowing-upwards" trend can be visible in the changing composition of the fossil assemblages.
+Often, a sea-level fall will expose the continental shelf and cause erosion and sediment re-deposition (the SB). Marine organisms that inhabited the continental shelf would die out. Erosion/Re-deposition causes fossils that previously inhabited shallower (shelf) environments to be transported downslope into deeper-water (bathyal) sediments. During this period (the LST) water-depths progressively decrease as the basin fills up with sediment (the sea-level itself is not changing much), raising the level of the sea-floor. This "shallowing-upwards" trend can be visible in the changing composition of the fossil assemblages.
 When sea-levels rise (during a transgression - TST) the exposed shelf is gradually submerged and bottom-living organisms can re-colonise the newly created environmental niches. Planktonic organisms can also be re-introduced as sea-levels rise. During this phase, sea-level rise is often rapid and water-depths get progressively deeper, resulting in a "deepening-upwards" trend in the fossil assemblages.