Differences

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--- seqstrat_tst [20/03/2023 14:53] – mike_gss
+++ seqstrat_tst [20/03/2023 14:55] (current) – mike_gss
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 //Retrograde sediments of the TST which onlap the MRS/TS and (on the shelf) the SB.//
-Organisms respond to this change generally in a positive way. The returning marine waters to the (previously exposed) continental shelf opens up a huge variety of new environmental niches which are colonised at first by "pioneer" species of high numbers but low diversity, then these are eventually - as conditions stabilise - replaced by better adapted organisms and diversity increases.
+Organisms respond to this change generally in a positive way. As transgression occurs and the shelf is resubmerged, marine fossil assemblages progressively overlie marginal or non-marine assemblages that existed when the shelf was exposed. The returning marine waters to the (previously exposed) continental shelf opens up a huge variety of new environmental niches which are colonised at first by "pioneer" species of high numbers but low diversity, then these are eventually - as conditions stabilise - replaced by better adapted organisms and diversity increases.
 The rate of sea-level rise during the TST is at its highest and water-depths show a gradual net increase as sedimentation and the rate of rise in the sea-floor cannot match that of the sea-level. This is reflected in fossil assemblages by "deepening upwards" trends (e.g., a gradual increase in the % of planktonic microfossils compared with benthic ones) vertically through the sediments of the TST.