Detailed Sections from Auger Holes in the Roanoke Rapids 1:100,000 Map Sheet, North Carolina

Introduction

The Roanoke Rapids 1:100,000 map sheet straddles the Coastal Plain / Piedmont boundary in northernmost North Carolina (Figure 1). Sediments of the Coastal Plain underlie the eastern three-fourths of this area, and patchy outliers of Coastal Plain units cap many of the higher hills in the western one-fourth of the area. Sediments dip gently to the east and reach a maximum known thickness in the extreme southeast part of the map area (Figure 2). The gentle eastward dip is disrupted in several areas due to faulting.

The U.S. Geological Survey recovered one core and augered 97 research test holes within the Roanoke Rapids 1:100,000 map sheet to supplement sparse outcrop data available from the Coastal Plain portion of the map area. The recovered sediments were studied and data from them recorded to determine the lithologic characteristics, spatial distribution, and temporal framework of the represented Coastal Plain stratigraphic units. These test holes were critical for accurately determining the distribution of major geologic units and the position of unit boundaries that will be shown on the forthcoming Roanoke Rapids geologic map, but much of the detailed subsurface data cannot be shown readily through this map product. Therefore, detailed descriptions have been collected in this open-file report for geologists, hydrologists, engineers, and community planners to provide a detailed shallow-subsurface stratigraphic framework for much of the Roanoke Rapids map region.