Abstract

As a part of a general project that aims to reconstruct the paleosuccession of Paleogene mangroves of the Maracaibo Basin, this paper deals with the quantitative reconstruction of Middle Eocene mangrove communities, and their relation to potential forcing factors. Four palynological assemblages were found. These represent, respectively, inland forests (A1), back-mangrove herbaceous swamps (B1), mangroves (B2), and an unknown plant community dominated by the extinct Echitriporites trianguliformis. Mangroves were dominated by Pelliciera and Nypa; Brevitricolpites variabilis, which has been considered the dominant taxon of the early and middle Eocene mangroves in nearby areas, has not been found in this study. The succession of coastal vegetation, linked to sea-level changes, could be reconstructed from these assemblages. The trends constitute a palyno-cycle which began and ended with a low sea-level plant community dominated by unknown stands represented by E. trianguliformis and interpreted low paleosalinities; intermediate high sea-level vegetation is represented by mangroves and interpreted high paleosalinities. This cycle is correlated chronologically with the global eustatic cycle TEJAS A 3.4, extending from 44 to 42.5 Ma (Lutetian). The floristic composition of middle Eocene mangroves was very different from those of the Oligocene to Recent. An important, probably worldwide, evolutionary change occurred during the late middle Eocene and the late Eocene in these communities. Pollen taxa botanically related to known and extant mangrove elements seem scarce for this time span.

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