Times are displayed in (UTC-05:00) Central Time (US & Canada) Change

Carbonates Through Time, Through Time: A Database of Published Carbonate U-Pb Ages From the Last Decade and Beyond

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records (Posters)

Presenting Author:

Sabrina Josephine Kainz

Authors:

Kainz, Sabrina Josephine¹, Jones, Shannon², Gerdes, Axel³, Cantine, Marjorie⁴

(1) Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA, (2) Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA, (3) Goethe-Universitaet Frankfurt, Frankfurt am Main, Hessen, Germany, (4) Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA,

Abstract:

The ability to precisely date geological materials is essential to reconstruct the timing, magnitude, and causal relationships of events in Earth history. Directly dating carbonate minerals allows us to investigate biological, climatic, and tectonic events, especially in systems where other geochronometers (e.g., zircon or apatite) may not be available. Over the past decade, in-situ uranium-lead (U-Pb) geochronology has become widely used. The high spatial resolution of laser ablation ICP-MS allows dating of multiple paragenetic phases that would be otherwise difficult to differentiate with solution-based techniques.

Interpretation of U-Pb carbonate data can be difficult because carbonates are typically low uranium, high common lead-bearing minerals that may exhibit complex open-system behavior. Low-temperature fluid reactions can mobilize U and Pb, mixing or partially resetting the U-Pb system, obscuring primary age information, and making it difficult to recognize geologically meaningful data.

Here, we present a database to understand trends in published carbonate U-Pb dates. Often, measured U-Pb dates are younger than the expected age of the host rock as constrained by biostratigraphy or cross-cutting relationships. We attribute this to post-depositional alteration, which can reset and/or mix age domains, or cause the precipitation of new phases. We examine the initial common Pb composition of carbonates from different environments to compare calculated initial Pb to the Stacey-Kramers model of terrestrial Pb evolution. We also compare global volumes of preserved carbonate stratigraphy, trends in seawater chemistry, and published carbonate U-Pb data across Earth history to identify constraints and opportunities in further application of this technique.