Development and geomorphological evolution of palm swamp system in the northernmost Amazon

Abstract

Palm swamp phytophysiognomy in the northernmost Amazon is evident by small valleys settled in deficit-drained areas in a region dominated by savannas. The limited number of studies on this ecological system has led to the assumption that groundwater exudation, conditioned by the subsurface and surface hydrological regimes, results in their establishment. The aim of the research was to investigate the evolution of palm swamp areas in the Amazon region. Thus, we hypothesized that the palm swamps are the product of the variability of the accumulated pulses in the region, represented by the alternation of allochthonous sedimentation processes originating from slope erosion with autochthonous conditions of pedological and climatic stability that allowed the bioconstruction of the bogs. To investigate palm swamp evolution, this study was based on a survey of images from remote sensors and fieldwork integrated into chronological data (OSL/SAR) and textural analyses of the sediment. The integration of field data and remote sensors indicated that palm swamps occurred mainly in the accumulation models, with predominantly sandy geo-covers, corresponding to the material sandstone resulting from the pedogenization of a pre-weathered mantle from the Boa Vista Formation. The absolute dating results indicated that palm swamps developed in different phases during the Late Holocene, between OSL/SAR = 2160 years before the present (BP) and OSL/SAR = 520 years BP, which correlated with wet regional events. The rise of palm swamps would be in response to the new conditions of the spatial arrangement imposed by the relief setting and the increase in humidity conditions that allowed the formation of peat bogs during periods of biostasis.