LANDFORMS AND SEQUENCE STRATIGRAPHY: USE OF COMPREHENSIVE LANDSCAPE ANALYSIS TO CREATE MAPS OF SURFICIAL DEPOSITS AND THEIR HYDROLOGIC ATTRIBUTES, COASTAL PLAIN SECTOR, NEUSE RIVER BASIN, NORTH CAROLINA, USA

The Atlantic Coastal Plain of eastern North Carolina is an area where relict Plio-Pleistocene topography reflects a falling stage systems tract (after Plint and Nummedal, 2000). This landscape, including the Neuse River Basin, is characterized by a series of progressively younger (highstand and falling stage) paleoshorelines and intervening terraces that step down in elevation and age towards the coast and into drainages. Each highstand shoreline was abandoned during a subsequent regression, or fall in relative sea level.

This paper explains how to subdivide this type of relict landscape into a series of progressively younger depositional systems and their landform elements, using Brierley's constructivist approach. A stratigraphically complex terrain is simplified through an iterative process that defines the relationship between relict landforms, stratigraphy, soils, and the shallow aquifer system. Assumptions for the geomorphic analysis are based on widely circulating concepts (e.g.: Oaks et al, 1974; Johnson, 1976; Soller, 1988; Mixon et al, 1989; Owens, 1989), and some new ideas. Data shown was acquired from the Little Contentnea Creek Watershed, including a 3D subsurface analysis at the Lizzie Research Station (km2). Map units were defined from electronic databases (digital elevation models, lidar, 7.5 minute digital raster graphics, and soils and wetland coverages).

A set of rules or assumptions for defining the geomorphic elements of a relict falling stage systems tract (FSST) is proposed. Systematic application of these rules subdivides and redefines the landscape in the context of a geologic conceptual model that explains the relative age, position, and geometry of each landform. Facies and significant bounding surfaces identified at detailed study sites such as Lizzie provide bases for defining unconformity bounded units that are regionally extrapolated using geomorphology. Within each sequence, 3D facies geometries such as those observed at Lizzie provide a template for understanding groundwater pathways in shallow aquifers systems. Integrating the results of this geomorphic analysis with the landscape units defined by Mew (2003, this meeting) from soils coverages, will enable assignment of attribute data such as recharge, to surficial geologic map units.