Triple oxygen isotopes in meteoric waters
Small variations in the relationship between δ18O and δ17O values of natural waters has become an emerging field ever since Barkan and Luz (2005) demonstrated that such deviations could be measured precisely in waters. These deviations, termed Δ17O, in waters, rocks and plants hold promise to provide new windows into natural systems. As of May 2011, the water extraction line for measuring Δ17O in waters is operational and calibrated to international water standards. See lab website for more details on the extraction line and for recent abstracts. Shuning Li, who recently finished her PhD in the lab, has generated a Δ17O ‘isoscape’ of North American tap waters (see Shuning’s 2015 GCA paper). Shuning has also developed a Δ17O leaf water dataset from Mpala, Kenya and presented those results at the 2013 AGU Fall meeting.
We are now measuring Δ17O in samples from the United States Network for Isotopes in Precipitation (USNIP) in collaboration with Jeff Welker at the University of Alaska Anchorage, from precipitation and river water samples collected by Renée Brooks at the EPA, and from precipitation and river waters collected locally in Baltimore. Preliminary results from this work were presented at the Goldschmidt Conference in Florence, Italy, August 2013 and at the 2014 AGU Fall meeting in San Francisco, CA. This research is funded by the American Chemical Society.
The work on Δ17O in waters is being conducted in parallel with efforts led by Ben Passey to measure Δ17O in carbonates. See list of lab abstracts for the latest on the triple oxygen isotope carbonate work.
Environmental Change in the Southern Kenya Rift
Our work in the southern Kenya Rift involves developing stable isotope records from outcrop and drillcores to reconstruct hydroclimate and ecological change in the region over the last one million years. This work is done as part of efforts led by the Smithsonian Human Origins group. We are currently focusing on outcrop samples from Olorgesailie and drillcore samples from the Olorgesailie Drilling Project. Among our many collaborators on these projects are Rick Potts and Kay Behrensmeyer, who are both at the Smithsonian National Museum of Natural History. Jessica Moerman’s postdoctoral research will focus on developing triple oxygen isotope and clumped isotope records from both outcrop and core carbonates. Stay tuned!
Isotopic Composition of Waters from Eastern Africa
The stable isotopic composition of waters offers an opportunity to use isotopic distributions today as frameworks for interpreting oxygen isotopes archived in the geologic record. Former Blaustein post-doc Zelalem Bedaso is leading the JHU based effort to document isotopic variation in precipitation in Ethiopia and has deployed daily, weekly and monthly precipitation collectors at 4 weather stations in Ethiopia, in collaboration with the National Meteorological Agency of Ethiopia. Zelalem presented the initial results from these collections at the 2013 AGU Fall Meeting and the analysis of samples from the 16-month long sample collection campaign is currently in the works.
This is part of a larger effort by multiple research groups in the Department of Earth and Planetary Sciences to understand the dynamics of African climate.
Woranso-Mille, Afar Region, Ethiopia
Woranso-Mille is a Pliocene paleontological site in the Afar region of Ethiopia known for its fossil record of the hominin Australopithecus. I work on this project with a group of paleontologists and geologists with the aim of reconstructing the sedimentological, tectonic and environmental histories in this area. My work specifically involves generating stable isotopic records from fossil teeth and soil carbonates. Some of this work has been published in a PNAS paper that focuses on diets of hominins and monkeys from the early Pliocene. You can find more publications and more about the project here. This work is in collaboration with Yohannes Haile-Selassie, Beverly Saylor, Mulugeta Alene, Al Deino and Luis Gibert Beotas. The project is funded by the National Science Foundation.
Elandsfontein, Western Cape, South Africa
Work at Elandsfontein, a middle Pleistocene paleontological and archaeological site in the Western Cape of South Africa, is in collaboration with David Braun at George Washington University. My involvement in this project is centered on establishing the stratigraphic and paleoenvironmental context of the fossil and artifact finds at Elandsfontein. Active dune fields that bury the Pleistocene sediments have forced us to make our own outcrop by digging pits and auger holes so that we can actually see the stratigraphy. By taking a look at what’s beneath the modern dunes, we have been able to correlate many of the artifact and fossil localities. See Braun et al. (2013) for a description of the geologic work that we’ve done at Elandsfontein.
The Elandsfontein work also involves isotopic analysis of materials from Elandsfontein (including fossil teeth) with the goal of building detailed isotopic records of mid-Pleistocene environmental and climatic change for the Western Cape.
E&PS graduate student Sophie Lehmann is working on the sedimentological and tooth enamel isotopic records at Elandsfontein. Sophie presented her preliminary results at the 2012 AGU Fall Meeting and will present an update to her work at the 2013 GSA Annual meeting in Denver. David Patterson, PhD at George Washington is taking the lead on the isotopic analysis of micromammals from Elandsfontein. See list of abstracts on the lab website. This work is funded by the National Science Foundation.
Gona, Afar Region, Ethiopia
Gona is best known for archaeological sites that contain the oldest evidence for stone tools in the world, however there is also a rich hominid fossil record that spans the late Miocene through the Pleistocene. In addition to paleoanthropological, archaeological, and paleontological resources, Gona contains an excellent sedimentary archive of >6 million years of environmental change in an active rift basin.
I have worked as geologist on the Gona Research Project since 2001. My work at Gona includes stratigraphy, mapping, and isotopic studies of soil carbonates, fossil teeth and mollusks. These studies are part of an initiative to build a complete paleoenvironmental story at Gona, that provides an environmental context for human evolution and an anchor point for characterizing local terrestrial responses to regional climate change in eastern Africa since the late Miocene. My work at Gona is primarily in collaboration with Sileshi Semaw, Scott Simpson, Dan Peppe, Jay Quade and Stephen Frost, although there are many other scientists who contribute to the research at Gona. All of our work is done with the help of the Afar people. The work was recently funded by the National Geographic Society.
Turkana Basin, Kenya
The Turkana Basin, in northern Kenya and southern Ethiopia, contains extensive exposures of Pliocene and Pleistocene sediments (the Omo Group) that fill a depression where the Main Ethiopian and East African rift systems meet. The Turkana Basin is best known for substantial number of hominid fossil remains that have been recovered from the Omo Group deposits, however the ~5,000 km2 of sediment exposures also provide an excellent opportunity to examine environmental variability in a large basin through time. My work in the Turkana Basin primarily focuses on using carbon and oxygen isotope ratios of pedogenic carbonates and fossil teeth to study this variability and link it to regional and global climate change during the Pliocene and Pleistocene. This isotopic work is in collaboration with Frank Brown, Thure Cerling, John Harris, Meave Leakey, Kay Behrensmeyer, and David Braun.