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Geomorphological indicators of large-scale climatic changes in the Eastern Bolivian lowlands

  • May J
Geographica Helvetica (2006) 61(2) 120-134
DOI: 10.5194/gh-61-120-2006
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Abstract

Abstract. This study provides an inventory of geomorphological landforms in Eastern Bolivia at different spatial scales. Landforms and associated processes are interpreted and discussed regarding landscape evolution and paleoclimatic significance. Thereby, preliminary conclusions about past climate changes and the geomorphic evolution in Eastern Bolivia can be provided. Fluvial and aeolian processes are presently restricted to a few locations in the study area. A much more active landscape has been inferred from large-scale Channel shifts and extensive paleodune Systems. Mobilization. transport and deposition of Sediments are thought to be the result of climatic conditions drier than today. However. there are also indications of formerly wetter conditions such as fluvial erosion and paleolake basins. In conclusion, the documentation and interpretation of the manifold landforms has shown to contain a considerable amount of paleoecological information, which might serve as the base for further paleoclimatic research in the central part of tropical South America.

Figures

  • Fig. 1: Macro-scale geomorphological units in the study area as deduced from digital elevation data (black boxes refer to location of figures) Geomorphologische Grosseinheiten im Untersuchungsgebiet, abgeleitet von digitalen Höhendaten (schwarze Kästchen beziehen sich auf die Lage der Abbildungen) Unites geomorphologiques de la zone d'etude ä grande echelle, issues eles donnees nutneriques d'altitude (les rectangles noirs indiquenl la localisalion des images) Source: SRTM 90-m data, Global Land Cover Facility http://www.landcover.org.
  • Fig. 2: Paleodunes (1) and largely inactive drainage Channels (white dashed lines, 2) are the most characteristic features on the piedmont between the erosional scarp (3) of the Rio Grande and the uplifted and dissected Sub¬ andean foothills (4) (arrow paleowind direction). Paläodünen (1) und grösstenteils inaktive Gerinnebellen (weisse gestrichelte Linien, 2) sind die charakteristischen Formen auf dem Piedmont zwischen Erosionsterrasse des Rio Grande (3) und den gehobenen, zerschnittenen Subandinen Vorbergen (4) (Pfeil Paläo-Windrichumg).
  • Fig. 3: Incised drainage Channels (1), floodouts (2) and area of paleo-floodouts (3) along the southern piedmont Eingeschnittene Gerinne (1), «floodouts» (2) und Zone der Paläo-«floodouts» (3) entlang des südlichen Pied¬ mont Chenaux de drainage incises (1), zones de debordement («floodouts») (2) et paleozones de debordement (3) le long du piemont sud Source: Landsat TM 230-74, Band combination 3-2-1, Global Land Cover Facility http://www.landcover.org.
  • Fig. 4: Paleodune field of the Lomas de Guanacos with oldest dune generation (1), younger formations (2) and active dunes (3) (arrow paleowind direction) Paläodünenfeld Lomas de Guanacos mit ältester Dünengeneration (I), jüngeren Formationen (2) und aktiven Dünen (3) (Pfeil Paläo-Windrichtung) Champ de paleodunes de Lomas de Guanacos montrant la generation la plus ancienne (1), les formations plus jeunes (2) et les dunes actives (3) (lafleche indique la direction du paleovenl) Source: Landsat ETM 230-73, Band combination 5-3-3, Global Land Cover Facility http://www.landcover.org.
  • Fig. 5: Paleodunes (dotted, 1) and active dunes within the Lomas de Arena dune field; deflation on restricted floodplain areas (3) (arrow paleowind direction) Paläodiinen (gepunktet, 1) und aktive Dünen im Dünenfeld Lomas de Arena; Deflation in kleinen Teilen des Flussbettes (3) (Pfeil Paläo-Windrichtung) Paleodunes (pointilles, 1) et dunes actives du champ dunaire de Lomas de Arena; deflation dans certaines parties de la plaine alluviale (3) (lafleche indique la direction du paleovent) Source: ASTER VNIR 231-72, L1B.003:2003834450, Band combination 2-3-1, EROS Data Center http://eros.
  • Fig. 6: Overview of the Rio Grande megafan and the associated paleodune fields (1), the paleochannels (shaded, 2), antecedent Quimome gap (3), mapped caiiadas (black dashed lines), fluvial ridges (FR-I to FR-V) based on topographic transect (4) and northward propagation of the avulsion point (white dashed arrow, A-I to A-IV) (arrow paleowind direction) Überblick über den Rio Grande «megafan» und die damit assoziierten Paläodiinenfelder (1), Paläoflussläufe (schattiert, 2), der antezedente Quimome Flussdurchbruch (3), die kartierten «canadas» (schwarze gestrichelte Linien), Dammufer (FR-I bis FR-V) auf der Basis eines topographischen Transektes (4) und die Verlagerung des «avulsion point» (weisser gestrichelter Pfeil, A-I to A-IV) (Pfeil Paläo-Windrichlung) Vue d'ensemble du megaeventail du Rio Grande et des champs de paleodunes qui lui sont associes (1), paleochenaux (ombre, 2), fosse ancien de Quimome (3), «canadas» cartographiees (lignes noires discontinues), levees fluviatiles (FR-I ä FR-V) basees sur le transect topographique (4) et propagation septentrionale du «point d'avulsion» (fliehe discontinue blanche, A-I a A-IV) (la fliehe indique la direction du paleovent) Source: SRTM 90-m data. Global Land Cover Facility http://www.landcover.org.
  • Fig. 8: Sequential landscape evolution as observed for the geomorphological units of the study area and the tentative correlation to paleoclimatic phases (grey shades and black dots) Sequentielle Landschaftsgeschichle für die geomorphologischen Grosseinheiten im Untersuchungsgebiet und die vorläufige Korrelation mit Paläoklimaphasen (grau schattiert und gepunktet) Evolution sequentielle des unites geomorphologiques de la zone d'etude et correlation possible avec les phases paleoclimatiques (ombre grise et pointilles)

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APA

May, J. (2006). Geomorphological indicators of large-scale climatic changes in the Eastern Bolivian lowlands. Geographica Helvetica, 61(2), 120–134. https://doi.org/10.5194/gh-61-120-2006

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