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Climatic versus tectonic control on facies and composition of the Andean Amazon basin-Fill in Ecuador

English title Climatic versus tectonic control on facies and composition of the Andean Amazon basin-Fill in Ecuador
Applicant Martin-Gombojav Nergui
Number 106175
Funding scheme Marie Heim-Voegtlin grants
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.10.2004 - 30.09.2005
Approved amount 91'759.00
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Keywords (6)

provenance analysis; heavy minerals; clay minerals; palaeoclimate; sedimentary facies; basin analysis

Lay Summary (English)

Lead
Lay summary
The Ecuadorian Andean Amazon Basin (AAB) occupies the tectonic position ofa transpressive retro-arc foreland basin with respect of thedouble-vergent Andean orogen in Ecuador.
The project includes research topics (sedimentology, sedimentarypetrography, palaeoclimatology, orogenesis and basin analysis), which arecurrently pursued in the Ecuadorian AAB at the Department of Earth Scienceof ETH-Zürich. The present project will extend these studies by focussingalso on the palaeoclimatic aspect, that was not invoked earlier byresearchers of the Ecuadorian Andes.

The present project is aimed at:
1.a regionally and stratigraphically advanced provenance analysis of thedetrital material in the Subandean Zone and Oriente Basin to reconstructthe response of sedimentation in the AAB to variations in the history oftectonic uplift and erosional exhumation in the supplying Andeancordilleras and shield areas,
2.subsidence analyses (back-stripping method) in the AAB,
3.the analysis of the bearing of palaeoclimate on variations in thecomposition of the detrital material and sedimentary facies in the AABsedimentary series in particular, and of the impact of changing climate onthe Andean orogen in general.

The sediment dispersal pattern repeatedly changed from orogenperpendicular to orogen parallel directions in the AAB. We hypothesizethat variations in tectonic shortening and uplift in the cordilleras mayhave driven changes in orogenic load on the South American plate andaccommodation in the AAB (or destruction of sedimentation space when loadis removed). The advanced (XR microprobe analysis-aided) heavy mineral andsandstone framework grain analyses proposed here will provide an improvedpicture of the sediment dispersal in the AAB.
Clay minerals in clastic sediment series primarily document the lithologiccomposition of the source terranes, but also reflect climatic and tectoniccontrols on exhumation and transport of the detrital material. Inparticular, the maturation stage of the clay minerals under variableclimates and exhumation rates (the latter controls the topographic relief)can be measured by semi-quantitative analyses of the clay fraction. Aseries of samples will be analysed for palynological content (the qualityof preservation of organic material) in order to calibrate the claymineral data.
It also will be possible to test if variations in clay mineral contentsare driven by changing or increasing elevation of the source terranes ordue to general climate variations at low latitude.
A meaningful discrimination of tectonic from climatic controls can beachieved only by combining the results of the provenance and claymineral/palynological methods. The palaeoclimatic analyses therefore willstrongly add to the understanding of the orogenic development of theAndes.
Direct link to Lay Summary Last update: 21.02.2013

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