COMPILATION OF SURFICIAL GEOLOGIC MAPPING IN THE LOUISVILLE METROPOLITAN AREA

The Kentucky Geological Survey recently completed new surficial geologic mapping in the northern, eastern, and southern suburbs of the Louisville Metropolitan Area in west-central Kentucky. A new compilation is being developed to incorporate this new STATEMAP-supported mapping with previous mapping completed by the joint USGS-KGS geologic mapping effort between 1960 and 1978. Louisville is Kentucky’s largest city and metropolitan area, and is a major economic hub, with significant manufacturing, highway transport, air commerce, and river transport activities.

Late Pleistocene outwash fills the Ohio River Valley and underlies a significant portion of the developed area of Louisville Metro. The adjacent floodplain and lower terraces are predominantly used for industrial or recreational space. Tributary streams were temporarily impounded by deposition of the Pleistocene outwash, causing development of slackwater lakes and deposition of lacustrine terraces in many tributaries. A large wide shallow basin in the southeast-central part of the Metro area was also filled with fine-grained lacustrine sediment. This basin apparently overflowed at some point, and a series of fluvial terraces were deposited south of the spillover, leading toward the Salt River to the south. Upland areas are underlain by Lower Paleozoic bedrock. Ridgetops are commonly covered by residual soils, with local layers of preserved Pleistocene loess. Steep hillslopes are mantled by colluvial soils, with accumulations of colluvial sediment and alluvial fans common along toe slopes.

The mapping was completed to support geotechnical decision making, geologic hazards assessment, and environmental management. Digital data products from this effort are being shared with decision makers and local GIS offices. One early derivative product of this geologic mapping effort has been a HAZUS-compatible dataset of seismic properties of regional engineering soils.