The eastern Amazonian region is dominated and shaped by a macrotidal regime, harboring
environments such as muddy plains colonized by mangroves, estuaries associated with tidal
channels, floodplains, and macrotidal beaches, among others. To understand the vegetation
dynamics and carry out the paleoenvironmental reconstitution in an Amazonian floodplain,
palynological, sedimentary, and C-14 dating data were integrated based on a subsurface
sedimentary profile collected in the region of the Taperaçu’s herbaceous fields, in the Bragança
peninsula (PA), on the Amazon coast. The present study identified three fácies associations and
four pollen zones that occurred during the Late Pleistocene and Holocene. The first facies
association is defined as an alluvial deposit, which presented pelite facies, flaser heterolithic
bedding with a coarsening upward sequence. The vegetation was predominantly typical of trees
and shrubs, marked by the presence of Rubiaceae, Agavaceae, and Annonaceae families and
with low herbaceous vegetation dominated by the Araceae family developed around 41,200-
39,975 cal years BP. The second facies association identified showed typical characteristics of
a tidal channel, with a well-delimited erosive surface, which marks a transition in the processes
operating over this environment; it comprises gravel, massive sand, and wavy-marked mud
facies. Toward the Taperaçu’s tidal channel, herbaceous vegetation was developed, represented
by Cyperaceae and Ulmaceae, and the presence of trees and shrubs, such as Arecaceae,
Malphighiaceae, and Rubiaceae. During the early and mid-Holocene (6000-5915 cal years BP),
at a depth of 6.45 m from the surface, the results revealed the formation of a tidal flat. The main
pollen result during this phase was the establishment of mangroves, colonized by Rhizophora
and Avicennia, in addition to the presence of herbaceous vegetation, which currently occupies
the studied region, marking the late Holocene.
|
