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Tectonics, neotectonics and sedimentation in active fault zones: example of Plio-Pleistocene deposits in the northern Andes of Central Colombia

English title sedimentation in active fault zones: example of Plio-Pleistocene deposits in the northern Andes of Central Colombia
Applicant Gorin Georges
Number 107866
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geology
Start/End 01.04.2005 - 31.03.2008
Approved amount 148'136.00
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Keywords (6)

ACTIVE FAULTS; CONTINENTAL SEDIMENTATION; CAUCA-PATIA; FLUVIO-VOLCANIC MASSFLOWS; MORPHOTECTONICS; ROMERAL FAULT SYSTEM

Lay Summary (English)

Lead
Lay summary
This project addresses two aspects of sedimentary basin research:

A)Sedimentary organic matter as high-resolution palaeoecological tool:
A1) Amorphous organic matter (OM) in anoxic environments and present-day analogs In the sedimentary record, sedimentary organic matter is an important constituent that can be used for the evaluation of paleoenvironments. In particular, understanding the occurrence of “amorphous” OM (AOM) in sedimentary rocks is quite relevant, because this type of OM constitutes the most prolific petroleum source rocks in the world. Nevertheless, the origin of AOM is still heavily debated. Using high-resolution microscopical and geochemical approaches in fossil anoxic sediments and comparing these observations with present-day analogs, this project demonstrates that AOM contains lots of indications of a high degree of OM preservation. In particular, these results shed a new light on the role of microbial activity in AOM accumulation: bacteria seem to contribute to OM preservation, whereas they have been so far considered only as a degradation agent. Results support the hypothesis of existing fossil bacterial DNA in ancient sediments and the exceptional OM preservation in some fossil anoxic environments.
A2) High-resolution palynology in the Holocene of Colombia This project aims at studying the vegetation and climate changes in the last 14’000 years in tropical Colombia, using high-resolution palynology as the main proxy. Data are obtained from cores taken from a high-altitude peat bog in the northern part of the Colombian Andes, where the vegetation is practically undisturbed. The steep slope gradients that surround this location make it very sensitive to register past vegetation changes linked to vertical species migration and resulting from climate change. Core data can be calibrated with 14C datings and high-resolution sampling will make it possible to obtain a time resolution of less than 50 years. This project will test the climate variability in the Holocene, for which high-quality data are missing in the tropics. Because the studied zone is close to the Pacific where climate variability influences the migration of the Intertropical Convergence Zone (ITCZ), the identification of dry/humid and warm/cold cycles might be looked at in relation with the ITCZ and ENSO-type variations.

B)Past glacial processes derived from high-resolution seismic and elevation models in a perialpine setting
This project sheds new light onto past subglacial processes in the Swiss Alpine foreland. Geomorphology and seismic stratigraphy have been used: the analysis of digital elevation models (DEM) on the Swiss Plateau evidences landforms inherited from glaciations, whereas high-resolution seismic stratigraphy in the Western Lake Geneva (Petit-Lac) highlights the subglacial sedimentary sequence accumulated in glacial valleys.
Results from DEM analysis provide the first global study of drumlins at the scale of Switzerland and the first record of rib moraines under the former Alpine and Jura ice caps. The association of subglacial landforms such as tunnel-valleys, rock drumlins, drumlins, ribbed moraines and eskers have so far been reported only under larger ice sheets. Seismic stratigraphy in the Petit-Lac illustrates the up to 220 m-thick sequence of glacial, glacio-lacustrine and lacustrine sediments infilling the Petit-Lac glacial valley. This sequence can be subdivided in 14 seismic units. The retreat of the Rhône glacier is particularly well illustrated in the Petit-Lac valley by two stages of readvance, which produced large push moraines and proglacial debris flows.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
67080 Tectonics, neotectonics and sedimentation in active fault zones: example of the Qindío Departement (Colombia) in the northern Andes 01.04.2002 Project funding

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