The Yorktown Formation: Improved Stratigraphy, Chronology, and Paleoclimate Interpretations from the U.S. Mid-Atlantic Coastal Plain

Harry J Dowsett,Marci M Robinson,Kevin M Foley,Timothy D Herbert

doi:10.3390/geosciences11120486

Harry J Dowsett, Marci M Robinson + Show 2 more

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https://doi.org/10.3390/geosciences11120486

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Abstract

The Yorktown Formation records paleoclimate conditions along the mid-Atlantic Coastal Plain during the mid-Piacenzian Warm Period (3.264 to 3.025 Ma), a climate interval of the Pliocene in some ways analogous to near future climate projections. To gain insight into potential near future changes, we investigated Yorktown Formation outcrops and cores in southeastern Virginia, refining the stratigraphic framework. We analyzed 485 samples for alkenone-based sea surface temperature (SST) and productivity estimates from the Holland and Dory cores, an outcrop at Morgarts Beach, Virginia, and the lectostratotype of the Yorktown Formation at Rushmere, Virginia, and analyzed planktonic foraminferal assemblage data from the type section. Using the structure of the SST record, we improved the chronology of the Yorktown Formation by establishing the maximum age ranges of the Rushmere (3.3–3.2 Ma) and Morgarts Beach (3.2–3.15 Ma) Members. SST values for these members average ~26 °C, corroborating existing sclerochronological data. Increasing planktonic foraminifer abundance, productivity, and species diversity parallel increasing SST over the MIS M2/M1 transition. These records constitute the greatest temporal concentration of paleoecological estimates within the Yorktown Formation, aiding our understanding of western North Atlantic temperature patterns, seasonality and ocean circulation during this interval. We provide a chronologic framework for future studies analyzing ecological responses to profound climate change.

Highlights

The Earth’s changing climate is an existential threat to the environment, public health, and infrastructure, often dominating political, economic, and cultural dialogues
Paleotemperatures were estimated for 485 Yorktown Formation samples at the RushK 0 index, mere and Farm Road localities and in the Holland and Dory cores [44], using the U37 which is based on the temperature dependence of double and triple carbon bonds in the alkenones produced by haptophyte algae [45,46,47,48]
Still exposed is the lectostratoype for the Yorktown Formation at Rushmere, Virginia [9], where the Rushmere, Morgarts Beach, and Moore House Members are exposed above beach level, and the Sunken Meadow Member can be accessed by digging

Summary

Introduction

The Earth’s changing climate is an existential threat to the environment, public health, and infrastructure, often dominating political, economic, and cultural dialogues. The latest climate models project conditions for the end of this century that are generally outside of the human experience [1,2,3]. Deep-time records of paleoclimate provide insight into the climate system over millions of years, sampling conditions different from the present day, and in some cases similar to model projections for the future. The Pliocene (5.33–2.59 Ma) has often been used to investigate how the climate system works under different boundary conditions and to gain insight into the potential magnitude of changes that might occur by the end of the 21st century [4]. One popular target for paleoclimate research within the Pliocene Epoch is the mid-Piacenzian Warm Period (MPWP), 3.264 to 3.025 Ma [5]. The MPWP is the most recent interval of the past with

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