RECONSTRUCTING THE MID-CRETACEOUS PALEOCLIMATE AND PALEOENVIRONMENT OF EASTERN NORTH AMERICA USING POTOMAC FORMATION PALEOSOLS

Core holes containing mid-Cretaceous (Aptain/Albian/Cenomanian stages) paleosols of the Potomac Formation were studied to assess climatic and environmental conditions of Eastern North America during this greenhouse world. Soils are a product of interacting climate and environmental conditions during their formation, preserved paleosols therefore offer an excellent proxy to evaluate terrestrial surface conditions that persisted through this interval.

Three cores from New Jersey and Delaware were studied in detail, offering a regional perspective on terrestrial conditions through time. Approximately 106 paleosols were identified in 375.8 m of recovered Potomac Formation sediments across the three cores.

Detailed study on these paleosols includes macro- and micromorphology, xrd and xrf analyses. Five pedotypes were determined, and paleosols included those that were weakly developed forming under poor drainage conditions, to those with increased maturity, forming under moderate to good drainage conditions. Morphology index and trace element analyses were applied to evaluate changing precipitation and drainage conditions at these sites.

The Potomac Formation is informally subdivided into three units, and paleosols within these units from these cores behave comparably, changing through time in a similar manner, suggesting a possible regional control on terrestrial processes. Although these soils all formed under generally humid conditions, there are distinct fluctuations of this humidity within each unit through time.

Analysis of these paleosols from the Potomac Formation indicates that terrestrial conditions during this greenhouse climate did experience noticeable changes in precipitation and environmental conditions through time. This variability is observed across the cores, both between the Potomac Formation units and within each unit itself.