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Margareta Johansson

Researcher

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Reconstructing cold climate paleoenvironments from micromorphological analysis of relict slope deposits (Serra da Estrela, Central Portugal)

Author

  • Alexandre Nieuwendam
  • Goncalo Vieira
  • Carlos Schaefer
  • Barbara Woronko
  • Margareta Johansson

Summary, in English

The paper focuses on analysis of macro‐ and micromorphological characteristics of relict slope deposits in Serra da Estrela (Portugal) to understand the significance of different slope processes and paleoenvironmental settings. Micromorphology is a useful sedimentology technique allowing significant advances compared to macroscopic techniques. Results show that different processes are involved in the development of the slope deposits, reflecting different environmental conditions. The main processes responsible for the emplacement of the relict slope deposits are solifluction, debris‐flow and runoff, but postdepositional changes are also present. Solifluction was identified in slope deposits between 650 and 1500 m a.s.l. The common microfeatures identified are circular arrangement of grains with a core grain, rounded vesicles, vertical grains, matrix deformations and fine‐grained deposits. Slope deposits above 1300 m a.s.l have a platy microstructure and coincide with the altitudinal range of the relict rock glaciers, indicating the elevation limit of permafrost. Below this altitude platy microstructures are less frequent. Slope deposits in north‐facing slopes were affected by frost‐induced processes in a seasonal frost regime, followed by a postdeposition illuvial phase. Debris‐flow and runoff were identified in slope deposits between 680 and 1260 m a.s.l. The common microfeatures are oblique grains, grain dumps, and coarse and fine grain lineations, and banded microstructures were identified in runoff processes. Debris‐flow deposits have a circular arrangement of grains without a core grain, identified in sediments in paraglacial and periglacial environments. The slope deposits show evidence of past periods of enhanced periglacial activity since the last glaciation until the Younger Dryas.

Department/s

  • Dept of Physical Geography and Ecosystem Science
  • MERGE - ModElling the Regional and Global Earth system
  • BECC - Biodiversity and Ecosystem services in a Changing Climate

Publishing year

2020-05-26

Language

English

Pages

567-586

Publication/Series

Permafrost and Periglacial Processes

Volume

31

Issue

4

Document type

Journal article

Publisher

John Wiley and Sons Inc.

Topic

  • Geology

Status

Published

ISBN/ISSN/Other

  • ISSN: 1099-1530