Florida Field Work – May 2022

SCIPP Lab members measuring section and collecting Plio-Pleistocene fossil shells

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.

Grad Student Lucas Gomes describing the upper portion of the section.
Grad student Jade Zhang points to an in-place coral we hope to date.

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!

Fast growing scallop, Carolinapecten.
Micromollusks washed out of a larger gastropod shell, inside a yogurt container for scale.
Grad students Jade Zhang, Allison Curley, and Lucas Gomes organizing samples in the garage of our AirBNB in the evening. Great teamwork, great organization!

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. 🙂

New Paper Update: Subannual D47 reconstructs Last Interglacial climate and d18Owater variability in Bermuda

Sliced Cittarium pica, showing location of high resolution d18Ocarb drilling (green) and seasonally-targetted D47 drilling (red)

Jade’s first paper is now published in the journal Paleooceanography and Paleoclimatology. Congrats Jade! In this work, Jade analyzed fossil shells of the species Cittarium pica, a large gastropod known as the Indian Top Shell. She sampled these shells along their spiral growth direction to reconstruct ocean temperatures and oxygen isotopic compositions (seawater d18O) throughout a few years of their lifetime. These shells date from the Last Interglacial (LIG) interval (~125,000 years ago), a period when global climate was 1-2 degrees warmer and sea levels were 6-9m higher. Despite overall global warmth, we found Bermuda was actually slightly cooler during the LIG, consistent with other records from the region. We also found unexpectedly high variability in d18Oseawater, which we linked to freshwater discharge from an underground aquifer into the near coastal areas.

LINK TO PAPER: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020PA004145

New Paper Update: Tropical Seasonality in the Miocene

Serena’s first paper was just published in Geology! She measured the oxygen isotopic composition of modern and fossil gastropod shells of the genus Turritella at high (subannual) resolution. In tropical settings, temperature doesn’t vary too much throughout the year, so the large seasonal variations in d18Ocarbonate were therefore attributable to changes in d18Oseawater, which she linked to on-shore precipitation. This indicated that there was a high seasonality of precipitation at the sample site (Guajira Peninsula, Colombia), which is today an extremely arid environment. She suggested that the Intertropical Convergence Zone (ICTZ), a band of high precipiation, could have extended to a more northerly position during the warm Miocene and been the source of this increased precipitation seasonality.

Congrats Serena on your first paper!

 

Link to Paper

New Paper Update: High-Resolution climate records from Cretaceous oysters

Our collaborator Niels de Winter just had his (our) paper come out in Climate of the Past. Link to Paper here.

Niels used many proxy methods to assess the preservation of climate information in Cretaceous oysters from the Nequen Basin (Argentina). He found that the umbo/hinge region where calcite is densest is the best place to sample to reveal climate information. Porous zones of “honeycomb” carbonate had been replaced with secondary calcite with divergent isotopic compositions.