THE MAAH DAAH HEY GEOSOL: A NEW STRATIGRAPHIC UNIT SPANNING THE PALEOCENE/EOCENE THERMAL MAXIMUM IN THE WILLISTON BASIN, ND STRATA

A new pedostratigraphic unit has been recognized in the Paleogene strata of western North Dakota. We have named it the Maah Daah Hey geosol, and it is contained within the lower member of the Golden Valley Formation, the Bear Den Member. The Maah Daah Hey geosol is named for the trail of the same appellation that runs through the Little Badlands of North Dakota. The name translates to "grandfather" or "long lasting," as related to certain ancient landscapes that command respect (www.americantrails.org/nationalrecreationtrails). The Bear Den Member was formally recognized as a stratigraphic unit in 1977, albeit simply as fluvial accumulations. Few authors since then have studied this unit, but those who have largely recognize it as an ancient weathering profile. The Bear Den Member has been broadly dated to the Paleocene/Eocene Thermal Maximum (PETM) interval by rare paleobotanical evidence, as well as by some correlations with known regional strata. Because the PETM is recognized as our best geological analogue for modern global greenhouse conditions, recognition of a new stratigraphic unit is an important addition to the paleoclimatic and geological literature. The basin-wide paleosol, here named the Maah Daah Hey geosol, exhibits morphologies and chemical signatures specific to soils found in modern tropical regions. As such, the full characterization of the Maah Daah Hey geosol has important implications for better understanding greenhouse climatic regimes. The latest revision to the North American Stratigraphic Code, published in late 2005, recognizes the geosol as the lone formal pedostratigraphic classification. It contains more specific language pertaining to proper classification than did the prior iteration of the Code. Using a wide range of paleopedological methods and interpretations, I have shown the Maah Daah Hey geosol fits the requirements for classification as such.