PUBLICATIONS

• Publications by topic
  • Groundwater
  • Surface Water
  • Water Quality
  • Water Use

• Publications by date
  • Recent publications

Annual Water Data Report

USGS Publications Warehouse

USGS IN YOUR STATE

USGS Water Science Centers are located in each state.

Structural and stratigraphic framework, and spatial distribution of permeability of the Atlantic Coastal Plain, North Carolina to New York

Professional Paper 796
By P.M. Brown, J.A. Miller, and F.M. Swain

Abstract

This report describes and interprets the results of a detailed subsurface mapping program undertaken in that part of the Atlantic Coastal Plain which extends from the South Carolina and North Carolina border through Long Island, N.Y. Data obtained from more than 2,200 wells are analyzed. Seventeen chronostratigraphic units are mapped in the subsurface. They range in age from Jurassic(?) to post-Miocene. The purpose of the mapping program was to determine the external and internal geometry of mappable chronostratigraphic units and to derive and construct a permeability-distribution network for each unit based upon contrasts in the textures and compositions of its contained sediments.

The report contains a structure map and a combined isopach, lithofacies, and permeability-distribution map for each of the chronostratigraphic units delineated in the subsurface. In addition, it contains a map of the top of the basement surface. These maps, together with 36 stratigraphic cross sections, present a three-dimensional view of the regional subsurface hydrogeology. They provide focal points of reference for a discussion of regional tectonics, structure, stratigraphy, and permeability distribution. Taken together and in chronologic sequence, the maps constitute a detailed sedimentary model, the first such model to be constructed for the middle Atlantic Coastal Plain.

The chronostratigraphic units mapped record a structural history dominated by lateral and vertical movement along a system of intersecting hinge zones. Taphrogeny, related to transcurrent faulting, is the dominant type of deformation that controlled the geometry of the sedimentary model.

Twelve of the seventeen chronostratigraphic units mapped have depositional alinements and thickening trends that are independent of the present-day configuration of the underlying basement surface. These 12 units, classified as genetically unrooted units, are assigned to a first-order tectonic stage. A structural model is proposed whose alinements of positive and negative structural features are accordant with the depositional geometry of the chronostratigraphic units assigned to this tectonic stage. The dominant features of the structural model are northeast-plunging half grabens arranged en echelon and bordered by northeast-plunging fault-block anticlines. Tension-type hinge zones that strike north lie athwart the half grabens.

Five of the seventeen chronostratigraphic units mapped have depositional alinements and thickening trends that are accordant with the present-day configuration of the underlying basement surface. These five units, classified as genetically rooted units, are assigned to a second-order tectonic stage. A structural model is proposed whose alinements of positive and negative features are accordant with the depositional geometry of the chronostratigraphic units assigned to this tectonic stage. The dominant feature of this model is a graben that stands tangential to southeast-plunging asymmetrical anticlines. Tension-type hinge zones that strike northeast lie athwart the graben.

To account for the semiperiodic realinement of structural features that has characterized the history of the region and as a working hypothesis, we propose that the dominant tectonic element, which is present in the area between north Florida and Long Island, N.Y., is a unit-structural block, a "basement" block, bounded by wrench-fault zones. We propose that forces derived principally from the rotation and precession of the earth act on the unit-structural block and deform it. Two tectonic models are proposed. One model is compatible with the structural and sedimentary geometries that are associated with chronostratigraphic units assigned to a first-order tectonic stage. It features tension-type hinge zones that strike north and shear-type hinge zones that strike northeast. The other model is compatible with the structural and sedimentary geometries associated with chronostratigraphic units assigned to a second-order tectonic stage. It features tension-type hinge zones that strike northeast and shear-type hinge zones that strike north.

Using a working concept of a fixed system of intersecting hinge zones, we conclude that the geometry of the regional structural-sedimentary system is associated predominantly with the action of lateral compressive forces, and that vertical forces operative in the region are chiefly the resultants of compressional stress. A geographic distribution of sedimentary troughs in the region studied is discussed, together with the nature of their boundaries and cross structures during each of the two tectonic stages.

The correlation framework established in this report utilizes both formally designated stratigraphic units and informally designated working units. The latter are identified by letter symbols (A-I). For each chronostratigraphic unit mapped, we include lithologic and biostratigraphic descriptions. Paleontologic data, chiefly the occurrence and distribution of Ostracoda recovered from well cuttings and cores, were used in the subsurface mapping. Ostracoda and Foraminifera that are characteristic of the units mapped in the subsurface are listed in the text and are identified on the stratigraphic cross sections. Type reference sections in the subsurface are designated for each of the chronostratigraphic units mapped.

The measured combined thickness for beds of sand, shale, and carbonate are computed as percentages of the total thickness of the chronostratigraphic interval in which they occur. Using these data, seven lithologic percentage categories (lithofacies), based upon textural and chemical composition, are established. These categories encompass the observed percentage variability in the vertical occurrence of sand, shale, and carbonate in the sediment mass within the report area. The delineation of the different categories by means of boundary lines and patterns drawn on an isopach map is used to construct a lithofacies map for each of the 17 chronostratigraphic units mapped.

Each lithofacies is assigned a number, ranging from 1 to 7, indicative of its comparative position on a scale of relative intrinsic-permeability lithology. The number 1 is assigned to a very high intrinsic-permeability lithology, whereas the number 7 is assigned to a very low intrinsic-permeability lithology. The numbers, together with the areal distribution of a lithofacies to which each number is assigned, constitute a permeability-distribution map for each of the 17 chronostratigraphic units mapped.

The series of combined isopach, lithofacies, and permeability-distribution maps, together with the series of structure-contour maps, illustrate the distribution of intrinsic permeability in that part of the Atlantic Coastal Plain which extends from the South Carolina and North Carolina border through Long Island, N.Y.

Brown, P.M., Miller, J.A., and Swain, F.M., 1972, Structural and stratigraphic framework and spatial distribution of permeability of the Atlantic Coastal Plain, North Carolina to New York: U.S. Geological Survey Professional Paper 796, 79 p.