seqstrat_sb
Differences
This shows you the differences between two versions of the page.
| Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
| seqstrat_sb [20/03/2023 14:16] – mike_gss | seqstrat_sb [20/03/2023 14:27] (current) – mike_gss | ||
|---|---|---|---|
| Line 2: | Line 2: | ||
| The SB is formed when sea levels fall and the coastline moves distally across the continental shelf, usually as far as the continental shelf edge. Naturally, countless organisms which previously lived on or in the waters above the continental shelf – one of Earth’s most productive environments – have literally been left high and dry if they weren’t (as species rather than individuals) able to follow the receding waters quickly enough. Even if species could adapt quickly enough, the subsequent “new” coastal belt is considerably narrower than the submerged shelf that existed before and increased competition between species for the remaining available niches results in even more extinctions. Consequently the SB, as expressed in shelf settings, represents a major disruption to organic life with major extinction (or at least, temporary removal) of different species. | The SB is formed when sea levels fall and the coastline moves distally across the continental shelf, usually as far as the continental shelf edge. Naturally, countless organisms which previously lived on or in the waters above the continental shelf – one of Earth’s most productive environments – have literally been left high and dry if they weren’t (as species rather than individuals) able to follow the receding waters quickly enough. Even if species could adapt quickly enough, the subsequent “new” coastal belt is considerably narrower than the submerged shelf that existed before and increased competition between species for the remaining available niches results in even more extinctions. Consequently the SB, as expressed in shelf settings, represents a major disruption to organic life with major extinction (or at least, temporary removal) of different species. | ||
| + | |||
| + | {{: | ||
| + | {{: | ||
| + | |||
| + | //A major sea-level fall between the end of one sequence (during the highstand phase above) and the beginning of a new one (the lowstand phase bellow) resulting in a new Sequence Boundary (SB: red line) in the lower image.// | ||
| When the next cycle of sea level change begins to cause sea levels to rise (the Transgressive Systems Tract - TST), the returning (submerged) continental shelf environment will contain suites of organisms made up of those species who were able to survive the disruption, together with a set of new species that may have arisen and can now exploit the new niches that are becoming available. | When the next cycle of sea level change begins to cause sea levels to rise (the Transgressive Systems Tract - TST), the returning (submerged) continental shelf environment will contain suites of organisms made up of those species who were able to survive the disruption, together with a set of new species that may have arisen and can now exploit the new niches that are becoming available. | ||
| Line 11: | Line 16: | ||
| However, in distal parts of the basin, where water depths are perhaps in the order of hundreds or thousands of metres deep, even a global eustatic sea-level fall (at most probably a fall of around 150-200 metres) would not cause much disruption to marine benthic or planktonic life, and sedimentary deposition (albeit at very slow rates) would continue. The surface that represents the SB here is termed a " | However, in distal parts of the basin, where water depths are perhaps in the order of hundreds or thousands of metres deep, even a global eustatic sea-level fall (at most probably a fall of around 150-200 metres) would not cause much disruption to marine benthic or planktonic life, and sedimentary deposition (albeit at very slow rates) would continue. The surface that represents the SB here is termed a " | ||
| + | {{: | ||
| The story is somewhat different on continental slope and ocean floor settings. In these environments a global fall in sea level by around 150 metres do not have such an appreciable effect and the vast majority of slope environments, | The story is somewhat different on continental slope and ocean floor settings. In these environments a global fall in sea level by around 150 metres do not have such an appreciable effect and the vast majority of slope environments, | ||
seqstrat_sb.1679321766.txt.gz · Last modified: 20/03/2023 14:16 by mike_gss