The Bessemer 7.5-minute quadrangle lies within the Birmingham metropolitan area, much of which is being mapped as part of the National Geologic Mapping Program. Strata from Late Cambrian to Early Pennsylvanian form a sequence that was extensively thrust-faulted during the Alleghanian orogeny and now forms part of the Valley and Ridge physiographic province. Quaternary alluvium is also present. The map and accompanying report describe the geologic formations and structures, with a brief discussion of the timing of deformation. Once one of the nation's chief iron- and coal-mining districts, the Birmingham area is now undergoing rapid development as a financial and medical center, and geologic maps such as this are useful in urban planning.
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 Bessemer 7.5-minute quadrangle for use by the public, industry, and government of Alabama.
Map and report can 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 this dataset, 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 ArcGIS. 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.
Feature geometry.
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Internal feature number.
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Area of feature in internal units squared.
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Stratigraphic Unit
Author
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 interbeds of coal and underclay.
Light-pinkish-gray quartzose sandstone containing intervals of quartz pebble conglomerate and intervals of dark-gray silty shale.
Alternating units dominated by yellowish-olive to reddish-brown weathered shale and very thin to medium-bedded, medium-gray to olive-brown to reddish-brown, laminated, fine- to medium-grained lithic sandstone, in part interbedded; sandstone locally contains muscovite, mud intraclasts, or fossil molds.
Black, dark-gray, and medium-greenish-olive shale with minor thin-bedded siltstone, sandstone, and fossiliferous clayey limestone to chert.
Grayish-black, evenly bedded, very clayey limestone to chert in lower part; light yellowish-gray, fossiliferous, bioturbated chert alternating with reddish-brown partings to interbeds in upper part.
Very light gray, thin- to thick-bedded quartzose sandstone with minor interbeds of pale-gray and purple shale.
Black to dark-bluish-gray to pale-gray clay shale and minor sandstone.
Dark-gray, medium- to thick-bedded, fossiliferous, sparry limestone (silicified near surface) with minor shale and chert (Tuscumbia); light-gray, thin- to medium-bedded, variably fossiliferous chert with partings and interbeds of shale (Fort Payne); dark-brown to greenish-gray and purplish-red, phosphatic(?) clay shale to mudstone (Maury).
Light-gray, fine- to very coarse grained quartzose sandstone and interbedded variably colored clay (Frog Mountain); dark-purplish-red, dark-reddish-brown, olive-gray, and light-gray, variably ferruginous and fossiliferous, fine- to medium-grained sandstone interbedded with siltstone and shale, with minor pebbly sandstone and fossiliferous limestone to oolitic ironstone (Red Mountain).
Dark-purplish-red, dark-reddish-brown, olive-gray, and light-gray, variably ferruginous and fossiliferous, fine- to medium-grained sandstone interbedded with siltstone and shale, with minor pebbly sandstone and fossiliferous limestone to oolitic ironstone.
Light-gray, laminated to bioturbated, variably fossiliferous limestone, calcareous siltstone, calcareous shale, and minor greenish-gray bentonite.
Light- to medium-gray, laminated to stromatolitic to brecciated, finely crystalline cherty dolomite; produces abundant dense, stromatolitic chert residuum.
Light- to medium-gray, thick-bedded, finely to coarsely crystalline dolomite.
Lower part interbedded dark-gray shale and micritic limestone; middle and upper parts include dark-gray stylonodular, bioclastic, and oolitic limestone; upper part dolomitic.
Length of feature in internal units.
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Map Unit Abbreviation
Author
Alluvium
Pottsville Formation undifferentiated (exclamation point is used for Pennsylvanian symbol in map annotation, Ppv)
Boyles Sandstone Member of Pottsville Formation (exclamation point is used for Pennsylvanian symbol in map annotation, Ppvb)
Parkwood Formation (exclamation point is used for Pennsylvanian symbol in map annotation, PMpw)
Floyd Shale
Bangor Limestone
Hartselle Sandstone
Pride Mountain Formation
Tuscumbia Limestone, Fort Payne Chert, and Maury Formation undifferentiated
Frog Mountain Sandstone and Red Mountain Formation undifferentiated
Red Mountain Formation
Chickamauga Limestone
Copper Ridge Dolomite (backslash is used for Cambrian symbol in map annotation, Ccr)
Ketona Dolomite (backslash is used for Cambrian symbol in map annotation, Ck)
Conasauga Formation (backslash is used for Cambrian symbol in map annotation, Cc)
Internal feature number.
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Feature geometry.
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Contact or fault line type description
Author
Contact not physically located, approximate location based on field observations
Contact concealed by overlying units
Extent of this 1:24,000 study
Fault not physically located, approximate location based on field observations, higher confidence of location than "normal fault, very approximately located"
Fault not physically located, approximate location based on field observations, higher confidence of location than "normal fault, very approximately located." Marker on left side of line, denoting downthrown side.
Fault not physically located, approximate location based on field observations, higher confidence of location than "normal fault, very approximately located." Marker on right side of line, denoting downthrown side.
Fault not physically located, approximate location based on field observations
Fault not physically located, approximate location based on field observations. Marker on left side of line, denoting downthrown side.
Fault not physically located, approximate location based on field observations. Marker on right side of line, denoting downthrown side.
Trace of thrust fault not physically located, approximate location based on field observations
Thrust fault concealed by overlying units
Name of selected features, see detailed descriptions in map report
Author
Length of feature in internal units.
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Internal feature number.
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Feature geometry.
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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
Synclinal axis located approximately
Synclinal axis located approximately with character marker for symbolization purposes
Name of selected features, see detailed descriptions in map report.
Author
Length of feature in internal units.
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Internal feature number.
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Feature geometry.
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Cross Section
Author
Cross Section Label
Author
Length of feature in internal units.
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Internal feature number.
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Feature geometry.
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Type of bedding measurement
Author
Strike and dip of inclined beds
Location of horizontal bedding
Strike and dip of overturned beds
Strike of vertical beds
Angle between reference orientation and strike of planar surface using 0-360 azimuth and right hand rule.
Author
Slope of planar surface relative to horizontal.
Author
Internal feature number.
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Feature geometry.
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Internal feature number.
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Feature geometry.
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Length of feature in internal units.
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Area of feature in internal units squared.
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Internal feature number.
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Feature geometry.
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Length of feature in internal units.
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Area of feature in internal units squared.
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Internal feature number.
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Feature geometry.
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Length of feature in internal units.
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Area of feature in internal units squared.
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Internal feature number.
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Feature geometry.
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Length of feature in internal units.
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Area of feature in internal units squared.
ESRI
Publications Sales Office
Geological Survey of Alabama
PO Box 869999
420 Hackberry Lane
Map and report can 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 will not be held liable for any damages resulting from its authorized or unauthorized use.
P.O. Box 869999
420 Hackberry Lane