Ongoing Research

 Key interests (as of today)

  • What drives the oxygenation of marine basins over decadal, centennial and multimillenial timescales? (How: applying productivity and redox proxies to a collection of high-resolution sediment cores from oxygen-deficient marine settings)
  • What is the fate of modern Oxygen Minimum Zones as they start responding to climate change? (How: finding past analogs for quick reoxygenation and deoxygenation in the sedimentary and rock record)
  • What redox processes occur during the settling of marine snow before it reaches the sea bottom? (How: comparing the geochemistry of sediment trap material with recently-deposited marine sediments)
  • What novel proxy toolboxes can we use to track past changes in productivity and redox? (How: refining the δ238U proxy in modern anoxic settings)

 Detailed topics (current and past)

The biogeochemical cycling of major, minor and trace elements and their isotopes is key for understanding important questions on the oceans of our planet: how they function, how they evolved and what will their fate be with exponentially increasing human presence. This research, only made possible with the help and ideas of numerous friends/collaborators from a broad range of institutions (CICIMAR-IPN, UNAM, UABCS, UABC, CICESE, UCR, UCSC, UCSD, UCLA, USC, UCI, UCB, FURG, ICBM, CEREGE, Russian Academy of Sciences, University of Leeds, Cardiff University and Utrecht University), countries (Mexico, United States, Brazil, France, United Kingdom, Netherlands, Germany, Russia) and funding agencies (CONACYT, UC MEXUS, COFAA, NSF, NASA, IODP, IAEA), is what keeps me up late at night responding to emails and definitely what makes me wake up in the morning (late morning, of course) for long oceanic expeditions and lab sessions.

Current Collaborating Institutions: 

         Image result for ucr riverside Image result for asu logo  Image result for USC  Image result for UC irvine logo

          Image result for UNAM logo geofisica   Image result for UABC  Image result for IPN Image result for cicese

        logo   Prifysgol Caerdydd

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The major Oxygen Minimum Zones (OMZs) of the World Ocean are known to fluctuate due to productivity, climatic and sea-level factors. Despite many studies, the key drivers of such variability remain relatively unknown. In my research, I try to separate the main causes of short and long scale changes of oxygen, nutrients, and micronutrients (including bio-available Fe) in the three biggest and economically important OMZs: Eastern Tropical North Pacific (ETNP), Eastern Tropical South Pacific (ETSP) and the Arabian Sea. I focus on various timescales subject to El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), orbital forcing (Milankovitch cycles) and glacial-interglacial conditions. My broad interests range from interannual variability of anthropogenically-influenced eutrophication to Heinrich perturbations of oceanic biogeochemical cycles during the Last Glacial period.

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Location of the sediment core material from the three major Oxygen Minimum Zones: ETNP, ETSP and the Arabian Sea, collected by me during oceanographic campaigns or obtained through collaboration with other institutions

Click here for a detailed map with sediment core locations


I use various types of geochemical proxies (carbon, sulfur and redox-sensitive trace element concentrations and isotopes, Fe and S relationships) to constrain past trends in suboxia, anoxia and euxinia of the Gulf of California and Eastern Pacific. Differences of restriction of marine basins and water column depth are determining factors in whether a basin is at all able to preserve paleoceanographic signal, or such record is forever lost. One of the elements that attract my particular interest due to its relationship not only with redox but also with productivity is uranium. We found prominent enrichments not only in anoxic and suboxic sediments of Santa Rosalia, La Paz, Pescadero but also in settling particles of Alfonso Basin (Choumiline, 2011; Shumilin et al., 2012). I am extremely lucky to be given the opportunity to apply the geochemical tools and redox framework used in Tim Lyons Biogeochemistry Lab (Alternative Earths Astrobiology Center, part of NASA NAI at UCR) at the Department of Earth Sciences of the University of California Riverside to extensively work on various kinds of restricted and non-restricted basins of the southern Gulf of California (Alfonso, La Paz, and Pescadero). It is becoming more evident that for this region (and beyond) sea level is not the only driver of redox shifts, which are also often enhanced by productivity, orbital forcing and anthropogenic activity (Choumiline, 2011; Shumilin et al., 2012; Choumiline et al., 2019; Choumiline et al., in prep). Besides the latter, my particular interest in this is to promote the need for a broad multiproxy approach involving various types of biological, sedimentological and geochemical (inorganic and organic) proxy datasets, that will finally allow fine-tuning known and novel redox proxies. Proper understanding of redox proxies will allow better reconstruction of the evolution of oxygenation in the oceans of Planet Earth.


Uranium concentrations in sediment core tops from basins of the Gulf of California and Eastern Tropical North Pacific with contrasting levels of oxygenation and primary productivity, based on previously published (colored circles) and our own (white circles) data (Choumiline et al., 2019; Choumiline et al., in prep)

Current project collaborators:

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Ligia Perez Cruz (UNAM)


Jose D. Carriquiry (UABC)

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Robert Raiswell (University of Leeds)



After recent improvements in isotopic geochemistry and the increasing availability of Multicollector ICP-MS equipment in several labs across the world, the potential for novel isotopic systems just started to unravel. Besides more established isotopic relationships such as δ13C, δ18O, δ34S, δ15N, I focus my research on novel isotopic approaches involving δ238U – promising toolbox for high-resolution paleoredox and paleoproductivity reconstructions. I test these proxies on a whole range of sedimentary material from various open marine and coastal settings with diverse levels of basin restriction, productivity, and oxygenation. One of my main career goals is to provide new insights on how these proxies work in the modern ocean for a better interpretation of Holocene-Pleistocene and deep time past oxygenation (preserved in the geological rock record).

Current project collaborators:

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Morten Andersen (Cardiff University)

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Steve Romaniello (ASU)

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Geoff Gilleaudeau (George Mason University)



The IODP-ICDP Expedition 364 drilled the Chicxulub Impact Crater site M0077 and recovered a sequence from 505.7 to 1334.7 mbsf. I am collaborating on the post-impact Paleogene sequence. Our preliminary results not only show the hyperthermals such as PETM and ETM2, but also several organic-carbon-rich events potentially associated with enhanced anoxia (Perez-Cruz et al., 2017; Lowery et al., submitted; Perez-Cruz, in prep). Stay tuned for more updates over the next few months.

Current project collaborators:

Expedition 364 Science Party

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Sandra Kirtland Turner (UCR)

Allison Keller

Allison Keller (UCR)

Andrey Bekker (UCR)



Emphasizing high-resolution records of settling particles (sediment trap material), as well as box, gravity, piston and CALYPSO core archives from Alfonso, La Paz, Pescadero and Carmen basins it was possible to trace and reconstruct trends in climate changes across a wide range of spatiotemporal timescales. With the finest resolution logistically possible (7-15 day between each sample), it was possible to detect the immediate effect of hurricanes on the terrigenous sedimentation of coastal anoxic marine basins of the Gulf of California (Alfonso Basin), providing another mechanism for varve formation in marine sediments, adding the possibility of a dark laminae to represent high flux event during seasons of high biological productivity, otherwise erroneously interpreted (Choumiline, 2011; Choumiline et al., 2011). The clear effect of  the North American Monsoon, has not only been evident for dramatic shifts in wind direction, established by our 10-year sediment trap record from Alfonso Basin (Silverberg et al., 2007; Silverberg et al., 2014; Choumiline, 2011; Choumiline, in prep), but also sediment core archives for the Holocene. On a longer scale, the latitudinal migration of the Intertropical Convergence Zone (ITCZ) is the main driver of changeability across the Holocene and Pleistocene (Perez-Cruz, 2013; Perez-Cruz et al., submitted; Choumiline et al., in prep), found for Ti, Al and Sc as terrigenous indicators, analogue to the famous Cariaco Basin paleoclimate story and implications for human civilizations (Haug et al., 2003, Peterson and Haug, 2005).

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Variations in the terrigenous indicator element scandium in settling particulate matter collected with a sediment trap in Alfonso Basin, Gulf of California, showing the influence of hurricanes and wind reversal patterns as drivers of fluvial and aeolian sedimentation in the basin (Choumiline, 2011; Choumiline et al., in prep) 


Current project collaborators:

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Norman Silverberg (CICIMAR)

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Fernando Aguirre Bahena (CICIMAR)


Despite being a semi-desertic region with severe conditions for agriculture, the natural beauties of the southern Baja California peninsula made it particularly attractive for tourists from all over the world. Even the Spanish explorer and conquistador Hernan Cortes, after being greeted by the indigenous tribes that populated the region,  described the peninsula as “Calida Fornax” or hot furnace, referring to the hot and dry climate of Baja.  A relatively unknown fact by the majority of visitors is that Baja is extremely rich in various types of natural resources. Besides the phosphorite mines of San Juan de la Costa (ROFOMEX enterprise) and saltworks of Guerrero Negro (ESSA company – biggest marine salt exporter of the world), the igneous and metamorphic geologic past of Baja left a patrimony of precious metals (copper, silver, gold, among many others) found in mineral deposits throughout the peninsula. This, of course, was the main driver of development, which gave rise to the major mining regions of Santa Rosalia and El Triunfo – San Antonio. Despite the short-term economic prosperity, these activities left long-lasting aftermath of pollution with potentially-toxic trace elements. While doing my M.S. thesis at CICIMAR-IPN (La Paz, Mexico) and part of short collaborative projects I participated in various attempts to evaluate the impact of copper, silver and gold mining and smelting activities on the composition of sediments from dry stream and marine systems of southern Baja California with extreme levels of geochemically mobile potentially-toxic trace elements such as arsenic and anthropogenic uranium (Shumilin et al., 2011Shumilin et al., 2012).

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Geochemical mobility (e.g. potential toxicity) of arsenic in sediments from an arroyo stream system  of San Antonio mining region (Shumilin et al., 2015)


For my Bachelor’s Degree thesis I used heavy minerals to infer the contribution sources of detrital material through dry streams into a coastal lagoon of the Gulf of California – La Paz Lagoon. With the help of ArcGIS and multiple geostatistic multivariate approaches, I distinguished a dramatic zonation in superficial marine sediments, due to the differential influence of surrounding drainage basins with contrasting rock formations and marine redistribution processes such as coastal currents and inflow/outflow dynamics (Choumiline et al., 2009; Choumiline, 2009).

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Spatial distribution of the heavy mineral hornblende in La Paz Lagoon – a coastal marine system of southern Baja California (Choumiline et al., 2009

Konstantin Choumiline