Paleomapping: Creating testable visual hypotheses of ancient worlds

The story of the Earth's changing landscapes is often told through paleogeographic maps. These images are some of the most accessible and widely used illustrations in the Earth sciences. However, no formal procedure for the creation of photorealistic paleomaps (i.e., paleosatellite images) exists. Using an example from the Late Jurassic of the Rocky Mountain region, we present a method for making paleoenvironmental and paleosatellite maps that is scalable, reproducible, testable, and incorporates peer review. The process includes a literature review followed by data-visualization, paleoenvironmental interpretation, peer-review, iterative revisions, and the creation of a false contour map and color gradient used to render a paleosatellite image. Paleosatellite images are photorealistic versions of paleoenvironmental maps that incorporate global climatic and tectonic information as well as principles of actualism; they can be made through comparison to analogous modern landscapes. An important component of this process is that the data maps that ground this paleomapping process allow evaluation of where paleoenvironmental interpretations are well-supported by outcrop and subsurface data, and where such visualization is highly interpretive – often because of lack of available rocks or studies in a given area. As such, our paleoenvironmental maps and paleosatellite images are testable pictorial hypotheses. By outlining a procedure that produces referenced, data-rich, and visually realistic maps, we hope to demystify the paleoenvironmental map-making process and improve accessibility of paleomaps for the broader geoscience community. Where resources and complementary data are available, such maps also have potential for georeferencing and integration with larger continent-scale paleogeographic maps.