Daniel Stolper, Professor

Closed (1) Reconstructing past summer temperatures for the glacial and interglacial past using fossilized carbonate minerals

Applications for fall 2021 are now closed for this project.

About 11,000 years ago, the last glacial period ended. The melting of glaciers was related to a change in Earth's surface temperatures. Humans were alive during this time, and likely changed their habits and habitats during this changing climate. Throughout this time, they consumed hackberries, fruits produced by the Celtis tree that are unique because they surround an inorganic (e.g., mineral) shell, made of aragonite — such plants are found on campus. This aragonitic shell, or endocarp, can persist through long periods of time, and therefore can give us insight into the past.
We have compared carbonate endocarps from these fruits to a series of environmental variables and determined that their stable isotopic compositions reflect growing season temperatures and thus measurements of this can be used as a 'paleothermometer' to reconstruct temperatures in the past.
The student selected for this project will work to examine how growing season temperatures change throughout a series of cave deposits from the glacial and interglacial transitions.

•Learn aspects of laboratory organic and inorganic geochemistry, including how to remove organic matter from carbonates, clean these carbonates, and prepare samples for analysis

•Learn about mass spectrometry including how to measure the stable isotopic composition of carbonates.

•Learn about the climatic history of the past 20,000 years where deposits are from.

Day-to-day supervisor for this project: Dr. Rebekah Stein, Post-Doc

Qualifications: •Sophomore, Junior, or Senior •Completed introductory science course work.

Weekly Hours: to be negotiated

Related website: https://eps.berkeley.edu/people/daniel-stolper

Closed (2) How do limestones form? An isotopic perspective.

Applications for fall 2021 are now closed for this project.

Carbonate limestones are one of the major sedimentary rock types on Earth. They are generally made up of mineralized shells of organisms that during burial convert from soft sediments to rock. These rocks represent one of the primary archives of Earth's past climatic states. Indeed, the stable isotopic composition of these carbonates (e.g., 13C and 18O contents), can be used to reconstruct past temperatures of the ocean, amount of ice on continents, and local salinities. A fundamental question is how the process of conversion from soft sediments to a rocks modifies the isotopic composition of the originally deposited shell. Such could change what these important samples reflect about the past of Earth's climate.

The student will help study the process of conversion of sediments to rocks by studying the isotopic composition of carbonates from deep-ocean sediment cores that go from ooze, to chalk, to limestone. They will reconstruct how the isotopic composition of sediments changes during burial and rock formation. Based on this, the student will help reconstruct both past climatic conditions and how to 'see through' burial processes.

Day-to-day supervisor for this project: Andrew Turner, Graduate Student

Qualifications: Roles: •preparation of samples for isotopic measurements •use of a mass spectrometer for isotopic measurements •application of models to reconstruct burial conditions during rock formation Qualifications: •Sophomore, Junior, or Senior •introductory science coursework

Weekly Hours: to be negotiated

Related website: https://eps.berkeley.edu/people/daniel-stolper