Geomorphology and pedostratigraphy in the Mayan Lowlands, Tabasco-Chiapas: an approach to the alluvial history of the Usumacinta river
Por:
Solís-Castillo B., Ortiz-Pe´rez M.A., Solleiro-Rebolledo E.
Publicada:
1 ene 2014
Categoría:
Earth and Planetary Sciences (miscellaneous)
Resumen:
This work presents the reconstruction of the fluvial processes that have
modified the alluvial landscape in the Maya Lowlands, based on the
identification of geomorphologic-environmental units, and their temporal
relation from the Pliocene to the late Holocene. The unit identification
has been made according to the following criteria: a) genesis of the
geoforms; b) configuration and arrangement of the geoforms, c) processes
of the terrain modelling, and d) the temporality (ages of the structures
and forms), using a pedostratigraphic analysis. Eight units are
proposed, labeled from 1 to 8, four of them (1, 2, 3, 5) are present in
the south area, in the Sierra of Chiapas. These units are the oldest in
the study area and are controlled by: erosion, following the original
tectonic structures (unit 1); dissolution of calcareous rocks
(karstic-unit 2); erosion of the sedimentary clastic rocks (unit 3); and
colluvial accumulation in the foothills (unit 5). The soils
characterizing these units are variable, from poorly developed at higher
elevations (rendzic Leptosols), to highly developed in the valley
bottoms (Luvisols). On the other hand, the units in the alluvial plain
(4, 6, 7, 8) are younger (Pleistocene-late Holocene) and have developed
a terrace system. The soils of the Pleistocenic terraces (TP3, TP2, TP1,
from the oldest to the youngest), from unit 4, show strong weathering.
Soils with gleyic properties are found especially in TP1. Optical
luminescence (OSL) dating of material from the base of the terrace
reveals an age of 122000 years, which constrains its temporal
development. Unit 6 corresponds to the depressions and wetlands in the
alluvial plain. Unit 8 is restricted to the Chacamax River, which has an
autochthonous sediment source. Unit 7 presents a series of terraces
developed during the Holocene (TH2, TH1). An age date of 9000 years in
sediment from terrace TH2 gives evidence of environmental changes in the
Usumacinta system. The pedogenesis of soils in terrace TH1 is
characterized by vertic features and processes of accumulation of
organic matter and carbonates, which are related to drier conditions.
The development of these soils occurs during the middle Holocene, a
period when regional climatic changes are documented. The soils of the
late Holocene, also present in TH1, are less developed, and evidence of
impact by human activities in the area is high since the Early
Formative.
Filiaciones:
Ortiz-Pe´rez M.A.:
Instituto de Geologi´a, Universidad Nacional Auto´noma de Me´xico, Circuito de la Investigacio´n Cienti´fica s/n, Me´xico, D.F, 04510, Mexico
Solleiro-Rebolledo E.:
Instituto de Geologi´a, Universidad Nacional Auto´noma de Me´xico, Circuito de la Investigacio´n Cienti´fica s/n, Me´xico, D.F, 04510, Mexico
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