The latest SCIPP-Lab paper comes from former SCIPP-lab postdoc Dr. Matt Jones (now at the Smithsonian Institute), publishing the work he did while at UM. Dr. Jones looked at fossil oysters from the Cretaceous Western Interior Seaway and used clumped isotope to reconstruct seaway temperatures during the time they lived.
We found that temperatures during the Cretaceous Thermal Maximum (Cenomanian-Turonian period, ~95 Million years ago) reached upper 20’s to lower 30’s Celsius in what is now modern day Utah and Wyoming. This is very hot! These water temperatures, which occurred in the mid-latitudes during the Cretaceous, are today only found in the warmest areas of the ocean like the Western Pacific Warm Pool. It makes you wonder how hot the tropics were if the mid-latitudes were >30C!! But that’s for another day…
Four members of the SCIPP lab ventured to sunny, hot, humid (sooo humid so hot) Florida to gather shells from the Plio-Pleistocene for geochemical analysis. We spent 5 days in the Florida Shell and Fill quarry near Punta Gorda gathering as many fossils as we could. Graduate students Lucas Gomes, Allison Curley, and Jade Zhang accompanied Professor Sierra Petersen and collaborator Peter Riemersma (Grand Valley State University) for the week. Our local contact Roger Portell from the Florida Museum of Natural History joined the group for the first two days to help us get our bearings. A big shout out to the owners and operators of FL Shell – Joe, Jess, Marilyn, James, Ernesto!! Thank you for giving us access to this awesome site.
During the Plio-Pleistocene interval (around 0.1-3.5 Ma), the southern portion of Florida was underwater much of the time (excluding glacial intervals where seawater was trapped in ice sheets and sea level was lower). Studied formations (Ochape, Caloosahatchee, Bermont, and Fort Thompson) represent marine to shallow marine to beach environments. These formations are SO full of shells, it wasn’t a question of whether we would FIND any fossils, more like could we SAMPLE the right ones and keep track of where we found them. We got very picky about which were the “best” ones by the end of the week.
This site has an amazing diversity of shells. Literally hundreds of species. Some large, some small. We found everything from hand-span-sized scallops (Carolinapecten) to mm-sized micromollusks. Although larger shells appeared caked in mud and sand, when you wash them off, they’re actually filled with even smaller shells!
Whether it was the first real field work, or the first field work in a while, the grad student team did an amazing job with logistics, field sampling, and evening sample organization. Great job everyone! Very excited to see what science comes out of these (many many) samples. 🙂
SCIPP Lab is excited to announce that Sierra has been selected as a 2021 Sloan Research Fellowship.
Paraphrasing from the Sloan website…
The Sloan Research Fellowship seeks to stimulate fundamental research by early-career scientists and scholars of outstanding promise. These two-year, $75,000 fellowships are awarded yearly to 128 researchers in recognition of distinguished performance and a unique potential to make substantial contributions to their field. Their achievements and potential place them among the next generation of scientific leaders in the U.S. and Canada.
Sierra plans to use the funds to push forward our paleo-seasonality projects in the Pliocene and elsewhere.
Julia Kelson (collaborator and now postdoc in the SCIPP group) published a compilation study of all published paleosol clumped isotope data to investigate whether any patterns could emerge regarding seasonal timing of formation or temperature biases. She updated older data using the Brand/IUPAC parameters and culled out early data that didn’t meet current data collection standards.
She found that paleosol carbonates tend to show a warm season bias, and calculated d18Owater values are related to d18Oprecipiation values from the season of carbonate formation.
Our collaborator Benjamin Linzmeier just published a nice paper in Geology looking at calcium isotopes in fossil bivalves spanning the K-Pg boundary. The calcium isotopic composition (44Ca/40Ca) of carbonate is a proxy for carbonate saturation state and can indirectly indicate something about ocean acidification state. Ben analyzed shells from Seymour Island that were previously analyzed for their clumped isotopic composition in the SCIPP lab (Petersen et al., 2016; Nature Communications). We found that the ocean’s carbonate saturation state was highly variable leading into the KPg boundary, which we attribute to CO2 injection into the atmosphere from the massive Deccan Traps volcanic province.
Sierra wrapped up a community-wide effort to reprocess and update clumped isotope calibration data from 11 different laboratories, including over 1200 individual replicates, to bring it into the same framework. This involved updating the fundamental parameters R13_VPDB, R17_VSMOW, R18_VSMOW, and λ used to calculate raw D47, using a consistent and updated set of theoretical equilibrium values (D47_TE) to tie things into the absolute reference frame, and applying a single set of acid fractionation factors (D*90-25) across all studies. We found that agreement is quite good between labs, once all the data processing is done uniformly and the “two-slope” or “multi-slope” problem that plagued the clumped community in the early days has all but disappeared in more recent studies.
As part of this effort, we also developed a data template and began a relationship with the EarthChem database to house future clumped isotope datasets in a long-term storage location. For more information on that, see this page.
We welcomed in the new academic year with the arrival of four new lab members and the return of many others after a summer away. Sierra hosted the whole group at her house for a potluck dinner and the weather cooperated amazingly!
Sierra and Jade spent ~ a week in Bermuda in early May collecting fossil shells and water samples towards Jade’s PhD research, recently funded by NSF! We were joined by Ian Winkelstern, a UM alum and colleague. We visited >10 locations, many undescribed and undated in the literature and brought home ~45 lbs of fossils and rocks (with only a minor customs snafu involving an apple). These fossils will be analyzed for their clumped and stable isotopic composition at bulk and subannual timescales to reconstruct Bermudan mean climate and seasonality during the last interglacial period (and possibly during older interglacials as well, pending dating of some outcrops)!
The highlight of the trip was our last day of field work, which we did via kayak. We visited uninhabited small islands in the Great Bay of Bermuda and found so many fossil bivalves!! We were very excited! It’s amazing that this counts as work!
Sierra was interviewed about life as a (female) academic for the University of Michigan’s Association for Women in Science (AWIS) outreach website. Sierra is the faculty advisor for this amazing campus club that brings together female scientists at all levels to help foster networks, give career advice, organize outreach to local grade schools, and much more.
Earth Scientists of UM gathered today for the annual Michigan Geophysical Union (MGU) Research Symposium. There were over 70 posters presented in two sessions, with 50 from the Earth department. Out of these, 5 posters were from our group – 10% of all Earth department posters! (and an even higher % of the undergraduate poster presenters – wow!).
Jade, Serena, Jon, Becca, and Tianna all did a great job presenting. Our very own Serena won the Best Undergraduate Poster award! Congratulations Serena!
Matt and Sierra contributed too by judging student posters and giving feedback.
Petersen Group | Earth and Environmental Sciences Department | Mailing Address: 2534 North University Building, 1100 N. University Ave., Ann Arbor, MI, 48109, USA