The Chelsea 7.5-minute quadrangle is located in north-central Shelby County, Alabama. The quadrangle is located in the Alabama Valley and Ridge physiographic section. Geologically, the Chelsea quadrangle is located within the foreland thrust belt of the southern Appalachian orogen. Appalachian structures within the quadrangle include the Helena fault, Cahaba Valley fault, New Hope anticline and syncline, Shackleford Gap fault, Dunavant syncline, Big Narrows anticline, Vandiver anticline, Yellowleaf fault, Yellowleaf syncline, and Camp Branch anticline. The Chelsea quadrangle is underlain by Paleozoic rocks ranging in age from Middle to Late Cambrian through Pennsylvanian The "Geologic map of the Chelsea 7.5-minute quadrangle, Shelby County, Alabama," was compiled from newly collected field data as part of the STATEMAP program (http://ncgmp.usgs.gov/ncgmpabout/statemap). This dataset represents the distribution of geologic formations at the surface of the earth within the Chelsea 7.5-minute quadrangle. Data used to generate this map are archived in the unpublished field notes and maps of the Geological Survey of Alabama. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.
The Geological Survey of Alabama is an independent state agency whose mission is to survey and investigate the mineral, energy, water, and biological resources of the state; to maintain adequate geologic, topographic, hydrologic, and biologic databases; and to prepare maps and reports on the state's natural resources to encourage the safe and prudent development of the natural resources while providing for the safety, health, and well-being of all Alabamians. The purpose of this map is to provide basic geologic data in the area represented by the Chelsea 7.5-minute quadrangle for use by the public, industry, and government of Alabama.
Map and report may be ordered through mail. Online order forms are available at http://www.gsa.state.al.us/publications.aspx. Map report is not included in this digital database.
publication date
Reproduction or redistribution of digital datasets or products derived therefrom to a third party organization or entity is expressly forbidden. None of these data shall be electronically duplicated on magnetic or optical media for use by others, in whole or in part, without permission of the Geological Survey of Alabama. Any hardcopies utilizing these datasets shall clearly indicate their source. If the data are modified in any way by the user, the user is obligated to describe the types of modifications performed on the hardcopy map. User specifically agrees not to misrepresent these datasets, nor to imply that any changes made by the user were approved by the Geological Survey of Alabama. The Geological Survey of Alabama should be acknowledged as the originator of the data. This dataset is to be used as a primary reference source. This is public information and may be interpreted by organizations or others based on needs; however, users are responsible for the appropriate application. Federal, state, or local regulatory bodies are not to reassign to the originators any authority for decisions they make. Photographic or digital enlargement of these maps to scales greater than that at which they were originally delineated can cause misrepresentation of the data. Uses of this digital geologic map should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was edited for a scale of 1:24,000 means that higher resolution information is not present in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, where this database is used in combination with other data of higher resolution, the resolution of the combined output will be limited by the lower resolution of these data. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.
420 Hackberry Lane
Attribute accuracy is tested by manual inspection/comparison of the source with hardcopy printouts and/or symbolized display of the digital contacts/faults and structural locations on an interactive computer graphic system. Attribute information is collected and recorded in the field by the Geological Survey of Alabama mapping staff. Attribute tables are created in Microsoft Excel, converted into text files, and joined to coverages using ESRI ArcInfo software. The Geological Survey of Alabama checks all entities and their attribute data for compliance with FDGC data standards. These checks do not ensure that data accurately reflect conditions in the field, only that the attributes meet database design specifications.
Data for contact, fault, and geologic formation locations are represented by a set of digitized arcs and polygons for each geologic unit. Geologic structural data are represented by a set of digitized points for each location. The Geological Survey of Alabama is responsible for ensuring 1) that all geospatial data are complete and correctly projected to the proper geodetic datum, and 2) that the attribute data are compliant with the GSA data standards. However, inconsistencies could exist in data collected by professional geologists working on this project. Logical consistency of Geological Survey of Alabama data cannot be guaranteed.
Horizontal accuracy of point data is only as good as the locations submitted by the field geologists who collected the data. Some locations were determined using hand-held global positioning systems units, and the accuracy of these data is typically better than +/- 35 feet. Other data were determined from conventional field techniques such as triangulation and pacing, with accuracy generally better than +/- 50 feet.
Data used to generate this dataset were obtained from field measurements and observations by professionals working for the Geological Survey of Alabama. This information includes location data and other important attribute information.
Geological Survey of Alabama geologists record locational data points for structural measurements in a Universal Transverse Mercator (UTM) projection. These locational data points are plotted on scale-stable media and digitized using a high-resolution digitizer table. Attributes are recorded using Microsoft Excel and converted into text files. These text files are then joined with the locational datasets. Contacts and faults are transferred from field maps to scale-stable material. The line work is then scanned, registered, and vectorized using ArcInfo. Line attributes are then linked to the datasets. Polygons are created using the digitized data from the contacts and faults dataset. All datasets are projected into a UTM coordinate system.
Dataset copied.
Metadata imported.
Metadata imported.
Feature geometry.
ESRI
Internal feature number.
ESRI
Stratigraphic Unit
Author
Alluvium. Unconsolidated quartz silt, sand, and gravel containing clasts of local bedrock.
Dark-gray silty shale containing intervals of light- to medium-gray lithic sandstone and minor interbeds of coal and underclay; predominantly dark-gray shale between lower quartzose sandstone members. Includes intervals of grayish-red mudstone.
Predominantly light-brownish-gray to grayish-orange quartzose sandstone weathered reddish-orange.
White to very pale-orange quartzose sandstone.
Very light gray quartzose sandstone containing scattered quartz pebbles and quartz pebble conglomerate. Wavy-bedded sandstone and mudstone common near top.
Very light gray quartzose sandstone containing scattered quartz pebbles and quartz pebble conglomerate. Includes a middle interval of dark-gray shale.
Medium-gray to black partly sideritic shale containing intervals of light- to medium-gray lithic sandstone.
Medium- to dark-gray shale containing intervals of light- to medium-gray lithic sandstone.
Dark-gray to black shale containing siderite nodules; locally containing very minor sandstone.
Grayish-orange bedded fossiliferous chert.
Moderate-yellowish-brown slightly feldspathic sandstone.
Dark-gray partly fossiliferous stylonodular limestone locally containing chert nodules; medium- to dark-gray fenestral limestone at base (Mosheim Limestone Member of Lenoir Limestone); upper part relatively argillaceous, bioturbated, and fossiliferous (Little Oak Limestone).
Dark-gray, mottled dolomitic limestone overlain by dark-gray fossiliferous stylonodular limestone, locally containing chert nodules.
Light- to medium-bluish-gray chert-free micritic limestone containing minor interbeds of light- to light-bluish-gray dolomite and medium- to dark-gray bioturbated dolomitic limestone.
Interbedded light-medium-gray micritic and partly sandy limestone and light-gray dolomite; commonly contains thin interbeds and nodules of chert.
Light- to dark-gray dolomite containing intervals of interbedded light- to medium-bluish-gray limestone; produces abundant predominantly cavernous chert.
Light- to medium-gray dolomite producing abundant predominantly dense chert containing common stromatolites.
Light-gray, dense, small chert fragments.
Light- to dark-gray chert-free dolomite.
Length of feature in internal units.
ESRI
Area of feature in internal units squared.
ESRI
Map Unit Abbreviation
Author
Alluvium
Pottsville Formation undifferentiated
Straight Ridge Sandstone Member of the Pottsville Formation
Wolf Ridge Sandstone Member of the Pottsville Formation
Pine Sandstone Member of Pottsville Formation
Shades Sandstone Member of Pottsville Formation
Parkwood Formation and Floyd Shale undifferentiated
Parkwood Formation
Floyd Shale
Fort Payne Chert
Little Oak Limestone and Lenoir Limestone undifferentiated
Odenville Limestone
Newala Limestone
Longview Limestone
Chepultepec Dolomite
Copper Ridge Dolomite
Knox Group undifferentiated
Ketona Dolomite
Geologic Age
Author
Feature geometry.
ESRI
Length of feature in internal units.
ESRI
Internal feature number.
ESRI
Contact or fault line type description
Author
contact not physically located, approximate location based on field observations
contact concealed by overlying units
trace of thrust fault not physically located, approximate location based on field observations
thrust fault concealed by overlying units
extent of this 1:24,000 study
Internal feature number.
ESRI
Feature geometry.
ESRI
Type of structural feature
Author
anticlinal axis located approximately
anticlinal axis located approximately with character marker for symbolization purposes
anticlinal axis located approximately with arrow marker showing a plunge in an easterly direction
anticlinal axis located approximately with arrow marker showing a plunge in a westerly direction
overturned anticlinal axis located approximately
overturned anticlinal axis located approximately with character marker for symbolization purposes
synclinal axis located approximately
synclinal axis located approximately with character marker for symbolization purposes
synclinal axis located approximately with arrow marker showing a plunge in an easterly direction
synclinal axis located approximately with arrow marker showing a plunge in a westerly direction
Length of feature in internal units.
ESRI
Slope of planar surface relative to horizontal.
Author
Feature geometry.
ESRI
Internal feature number.
ESRI
Angle between reference orientation and strike of planar surface using 0-360 azimuth and right hand rule.
Author
Type of bedding measurement
Author
Strike and dip of inclined beds
strike of vertical beds
strike and dip of overturned beds
Angle between reference orientation and strike of planar surface.
Author
Internal feature number.
ESRI
Feature geometry.
ESRI
Cross Section
Author
Cross Section Label
Author
Length of feature in internal units.
ESRI
Internal feature number.
ESRI
Feature geometry.
ESRI
Length of feature in internal units.
ESRI
Area of feature in internal units squared.
ESRI
Internal feature number.
ESRI
Feature geometry.
ESRI
Length of feature in internal units.
ESRI
Area of feature in internal units squared.
ESRI
Internal feature number.
ESRI
Feature geometry.
ESRI
Length of feature in internal units.
ESRI
Area of feature in internal units squared.
ESRI
Attributes are used to identify the location and extent of the boundary for the "Geologic Map of the Chelsea 7.5-Minute Quadrangle, Shelby County, Alabama". Attribute information is obtained from data collected by geologists working for the Geological Survey of Alabama.
Attributes are used to identify the location and extent of the boundary for the "Geologic Map of the Chelsea 7.5-Minute Quadrangle, Shelby County, Alabama." Attribute information is obtained from data collected by geologists working for the Geological Survey of Alabama.
Publications Sales Office
Geological Survey of Alabama
PO Box 869999
420 Hackberry Lane
Map and report may be ordered through mail. Online order forms are available at http://www.gsa.state.al.us/publications.aspx.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the Geological Survey of Alabama. Although this publication has been subjected to rigorous review and is substantially complete, the Geological Survey of Alabama reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that the Geological Survey of Alabama may not be held liable for any damages resulting from its authorized or unauthorized use.
P.O. Box 869999
420 Hackberry Lane