Interaction between sea-level changes and the development of littoral herbaceous vegetation and autotrophic dinoflagellates

摘要

In addition to sedimentological studies, palynological analyses provide specific criteria for the recognition of sea-level changes according to geographical situation. During periods of rapid rise in sea level, marine clastic sedimentation progrades towards the land and marine waters penetrate into estuaries bringing in assemblages of dinoflagellate cysts dominated by Spiniferites bentorii. In addition, in coastal lowlands, this progradation causes the formation of coastal barriers in front of the troughs closest to the shoreline. The impounding of fresh water leads to an increase in the development of aquatic plants. During phases of slower rise in sea level, on the other hand, the marshes extend out towards the sea over the clastic marine sediments. Chenopodiaceae are established at the base of the vegetation sequence, followed by Poaceae and then Cyperaceae. In coastal peat land, the development of Ericaceae and Sphagnum characterizes the maximum deceleration of sea-level rise. In estuaries, dinoflagellates are adapted to less renewed water, which are richer in nutrients supplied by continental runoff. Under these conditions, the assemblages tend to be almost monospecific containing Lingulodinium machaerophorum.