Understanding the Pliocene-Pleistocene Transition in the Southwestern US Through a New, Novel Proxy: Paleosol Nitrate Δ17O
Abstract
The Pliocene-Pleistocene transition's global climate change went from a relatively warm, wet global climate state with no ice sheets in the northern hemisphere, to a cooler and drier climate with greater pole-equator temperature gradient and cyclical glaciation in both hemispheres. To evaluate the changes in precipitation in Death Valley, CA between 1.6 and 2.4 million years ago using paleo-lake deposits in the Confidence Hills Formation, a new precipitation proxy, nitrate 17O anomalies (Δ17O), was developed. To address the question of precipitation change in the southwestern US, as future water resources may be limited due to the Earth warming from anthropogenic greenhouse gas emissions, geochemical and isotopic proxies in the deposits were analyzed. Samples were collected in an exposed drainage and soluble ions were extracted, mineralogy determined, and isotopic analyses of nitrate were performed. The study of changes in ion content (NO3-, Cl-, SO42-) and isotopic ratios (δ15N, δ 18O, and Δ17O) over time suggest changes in local precipitation including shifts in erosional regimes. Changes in δ15N, δ 18O, and Δ17O suggest a changing nitrogen cycle connected to water availability.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMPP35E1006B