Mathieu Richaud

Paleoceanography in the Eastern Equatorial Pacific

Numerous studies have highlighted the importance of pCO2 as an amplifier and/or primary driver of the glacial/interglacial cycles, though the scientific community remains ignorant of the exact mechanisms causing these cycles. A leading hypothesis for the cause of glacial/interglacial atmospheric CO2 change involves the extraction of carbon from the surface ocean by biological production, either at low or high latitudes, coupled with changes in the marine calcium carbonate and silica budgets (Archer et al., 2000; Sigman and Boyle, 2000; Brzezinski et al., 2002). The central theme of my research is the glacial/interglacial variations of biogenic fluxes (CaCO3 , OrgC and Si) across the equatorial Pacific (Richaud et al., 2007).

Coastal geology of California's Central Coast

Several undergraduate and graduate students work with me on coastal marine geology, focusing our efforts on the Morro Bay sand spit along the Central Coast of California. The central coast of California is hit every three to seven years by intense El Niño-Southern Oscillation (ENSO) events that damage the coastline in several different ways (Storlazzi et al, 1999). Elevated sea levels, increased wave height, and higher precipitation characterize ENSO events and are largely to blame in erosion of the coastline (Allan and Komar, 2006). We postulate that ENSO events accelerates beach sand erosion. The project uses a LiDAR mounted on a UAV to provide high-resolution imagery to more accurately analyze, calculate and model erosion rates along the Morro Bay sandspit.

Sedimentology of the Canterbury Basin, New Zealand

In 2010, I was a shipboard participant onboard the R/V JOIDES Resolution during IODP Expedition 317. Several graduate students work with me to reconstruct high-resolution paleodepth estimates via benthic foraminifera assemblages and a sequence-stratigraphy model of foraminiferal assemblages, combined with detailed facies and lithology analyses, over a complete Late Quaternary transgressive-regressive sequence. Sites U1353 and U1354 provide a stratigraphic record of depositional cycles through the Holocene and late Quaternary across the shallow-water environment most directly affected by relative sea level change. Both cores are suitable for high-resolution study of recent glacial cycles in a continental shelf setting, allowing to estimate the timing and amplitude of global sea level change and to document the sedimentary processes that operate during sequence formation (Exp. 317 Scientists, 2010). If the vertical movements of a basin floor can be reconstructed from the sedimentary record, these movements can be more accurately constrained when information from the sedimentary history is combined with paleodepth estimates derived from fauna (Hayward, 1986; Murray, 1991; van Hinshergen et al., 2005).

Foraminifera ecology of the North Atlantic Ocean (Svalbard)

I am interested in the structure of benthic environments and the paleochemical record of foraminifera, small marine organisms pervasive throughout the oceans. I am part of a group of researchers that maintained a seabed sampling program from 2007 to 2010 on the western European margin of the Fram Straits extending into the fjords of Svalbard in the northern North Atlantic. We are interested in assessing how benthic foraminiferal shell geochemistry is sensitive to the geochemical conditions of the microhabitats selected by particular foraminiferal species. Understanding these microhabitats is essential for the proper interpretation of the proxies, mainly of which have been extensively used to develop paleoceanographic tracers (Loubere et al., 2011).