Luis Ordonez

PhD Student

13 rue des Maraîchers, office 310A

0223796623

 
 
 

Researcher in quaternary geology within the limnogeology and geomicrobiology group at the University of Geneva. In addition to quaternary geology, I have a 6 years background in geochemistry and extensive experience in laboratory techniques and field work acquisition. Very confident with GIS software, data analysis and data curation. Proficient in Spanish, English and French. Sensitive to ecology and conservation of nature.

My Research

My research focuses on Fe-dynamics in lacustrine systems and their relationship with the biogeochemical cycle of other elements such as sulfur and (organic and mineral) carbon. During my PhD I have acquired extensive geochemical skills on the speciation of iron and analysis of Fe- isotopes as tracer for redox processes. In parallel, I have implemented a new approach to interpret Rock-Eval pyrolysis, which is a widely used technique to characterize sedimentary organic matter. Both lines of research are tightly interconnected and have allowed me to understand the cycling of Fe and carbon, and redox sensitive elements in lacustrine environments.

The Lake Towuti drilling project (ICDP)

The Towuti Drilling Project (TDP), co-funded through the International Continental Scientific Drilling Program (ICPD), aims to understand the climatic, biological, and geomicrobiological evolution during the last ca. 1My years of Lake Towuti as part of the Malili lakes system – Indonesia. My goal within this project is to explore authigenic minerals as proxies for climate, considering the potential interferences occasioned by microbial communities.

Lake Towuti is particularly rich in iron owed to the strong flux of Fe-minerals carried by run-off waters eroding the Fe-rich substratum, mainly composed of ultramafic rocks. Additionally, Lake Towuti waters are sulfate-depleted and anoxic below 130 m allowing an enrichment of dissolved reduced iron. Mixing of the entire water column is, however, known to occur occasionally during dry periods. This places iron at the center of a dynamic biogeochemical cycling and, as a redox sensitive element, it will record the redox processes taking place in the Lake Towuti system. Teasing out catchment weathering vs. Fe authigenesis and diagenesis is paramount to the full interpretation of Fe mineralogy and its associated biogeochemical impacts, as is indicated by the changes in Fe/Ti, organic carbon content, and other measurements on previous studies of Towuti sediments.

We used a multiproxy approach to determine whether Fe-phases are authigenic and record paleoclimate signals. Firstly, we performed Fe-speciation following a chemical sequential extraction procedure (Poulton and Canfield, 2005; Henkel et al., 2016) to determine the state of oxidation of iron and how iron is bounded to other elements. After quantification, Fe-isotope ratios were measured in the reactive Fe-pools: siderite, magnetite, Fe-oxihydroxides and Fe-oxides. In addition to iron proxies, organic matter was quantified and analysed as means of fuel for microbial metabolisms, through Rock-Eval pyrolysis. Organic matter proxies encompass Total Organic Carbon (TOC), Mineral Carbon (MinC) and two indexes (HI and OI) discriminating between authigenic and detrital organic matter. Combined with the Fe-speciation dataset this multi-proxy approach will strenght paleoenvironmental interpretations.

Research Interests

  • quaternary geology
  • environmental geochemistry
  • GIS and data analysis

Lecturer Assistant

  • Limnogeology
  • (R)amène ta Science
  • uXRF

Publications

 

Ordoñez L, Vogel H, Sebag D, Ariztegui D, Adatte T, Russell JM, Kallmeyer J, Vuillemin A, Friese A, Crowe SA, Bauer K, Simister R, Henny C, Nomostrayo S, Bijaksana S, the TDP Science Team (in press). Empowering conventional Rock-Eval pyrolysis for organic matter characterization of the siderite-rich sediments of Lake Towuti (Indonesia) using End-Member Analysis. Organic Geochemistry.
 


Morlock M, Vogel H, Nigg V, Ordoñez L, Hasberg A, Melles M, Russell JM, Bijaksana S, the TDP Science Team (2019). Climatic and tectonic controls on source-to-sink processes in the tropical, ultramafic catchment of Lake Towuti, Indonesia. Journal of paleolimnology.
 


Vuillemin A, Wirth R, Kemnitz H, Schleicher A, Friese A, Bauer K, Simister R, Nomostrayo S, Ordoñez L, Ariztegui D, Henny C, Crowe SA, Benning L, Kallmeyer J, Russell JM, Bijaksana S, Vogel H (in press). Formation of authigenic siderite in modern ferruginous sediments. Geology.
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