Analytical and supplemental data from: Ammonites as paleothermometers: Isotopically reconstructed temperatures of the Western Interior Seaway track global records

Ammonites are externally shelled cephalopods that were common in the North American Western Interior Seaway (WIS), and as they grew their aragonitic shells via accretion, they recorded aspects of their environment in the stable isotopic composition of their shells. While the mobility of ammonites may complicate efforts to reconstruct temperatures from their shells, they remain a valuable potential target for paleothermometry. In this study, we reconstruct the spatial and temporal variability of WIS temperatures using a suite of ammonites (n=113) covering the last 25 million years of the Cretaceous and spanning from the Canadian WIS to the Mississippi Embayment. We present a temporally high-resolution (~0.6 Ma) oxygen isotope record from these ammonites that indicates cooling temperatures in the WIS (of comparable magnitude (~18°C +/- 4°) to the temperature change seen in global studies, most notably cooling from the Cretaceous Thermal Maximum in the Turonian until the Late Maastrichtian..., , , # Analytical and supplemental data from: Ammonites as paleothermometers: Isotopically reconstructed temperatures of the Western Interior Seaway track global records

[https://doi.org/10.5061/dryad.msbcc2g60](https://doi.org/10.5061/dryad.msbcc2g60)

## Description of the data and file structure

This repository is associated with McCraw et al., (2024) Ammonites as paleothermometers: Isotopically reconstructed temperatures of the Western Interior Seaway track global records. Paleogeography, Paleoclimatology, Paleoecology.

In this study, 113 ammonite fossils were sampled multiple times for stable oxygen isotopic analyses. The raw data are averaged into a specimen mean value, which can be averaged into a locality mean in which all specimens in a given locality are combined, and then an Ammonite Zone or Compiled Zone average, in which all specimens in a given time period are averaged. The dataset contains associated data described below.

This repository contains the scripts and raw data n...