June 2000 The Value Of Public Information Series No.3 Geologic Maps

urvey INTRODUCTION people’s counterparts, with whom they interact, in the S A geologic map is one that depicts the distributions

of rock types, formations, and geologic features such as agency that funds the work. faults, according to their particular characteristics and With time, newer and more detailed mapping may geologic ages. The making of geologic maps involves reveal areas with potential for improvement. Some the gathering of information about the properties of years after an area was originally mapped, it may be ripe different rock and sediment occurrences—especially for revisitation and complete remapping for improve- their composition and texture—and rendering their ment of detail and of consistency with more recent configurations, strata, and structure in map format, as mapping done in surrounding areas. illustrated by Figure 1. Geologists produce these geologic maps in order to portray the geology re- SOCIOECONOMIC BENEFITS searched in different areas and to reconstruct and better The effort and expense required to make geologic understand the areas’ geologic histories. But, because of maps are justified by their socioeconomic value, which their numerous derivative applications, the maps, once derives from their multiple uses and applications in a made, can have far-reaching value to many other variety of contexts. The distribution of geologic map people. units may be important to assessing coastal erosion and Geologic mapping makes use of topographic land loss, flood hazards, unstable-soil hazards, ground- information, aerial photography and other types of water resource development and contamination

eological imagery, soil survey information, and observations and potential; protection strategies for aquifer-recharge documentation made in the course of field work. The areas and for regions susceptible to ground-water field work may target specific aspects of previous pollution and soil erosion; and suitability of areas for mapping, if such exists, that is subsequently identified waste disposal, aggregate-and mineral-resource poten-

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as having interpretive problems. Previous work covering tial, and location of residential areas. the area is, in any case, reviewed and evaluated and used Thus accurate, up-to-date geologic maps are as a framework within which to conduct the new essential for planning by a host of agencies and investigation where appropriate. industries concerned with such issues. The socioeco- Support investigations may also be conducted. For nomic value of new geologic maps relative to their example, interpretive problems in selected areas may be predecessors derives in part from the added detail that addressed by drilling boreholes or by subjecting provides clearer delineation of map units in these types borehole and surface samples to various specialized of derivative applications. Figure 2 shows where tests. Information thus gathered in the study area is detailed geologic mapping of Louisiana parishes has fitted to the published topographic maps covering it, been done since the Louisiana Geological Survey’s which are used as a base. The work often also includes founding in 1934. consultation with other geologists who have experience and expertise germane to the problems encountered in COMMERCIAL VALUE the study area. Geologic maps not only lend themselves to a

ouisiana Ultimately, the geologic mapping effort is a joint multitude of timely uses but are an essential starting one involving geologists, cartographers, geographic point for a host of other, more specialized investiga- information systems (GIS) specialists, and other tions. Impressive financial returns on the investments L technical personnel, as well as the necessary administra- tive support personnel—plus potentially all these www.lgs.lsu.edu

THE VALUE OF GEOLOGIC MAPS 1 which is the principal source of ground water for 13 parishes in southwestern Louisiana. The investigation and mapping of the geology in a particular area can have important implications if it is a large urban center. For example, socioeconomic value of geologic mapping in the Baton Rouge area, which includes the capital seat of the state and is impacted by active faults, Figure 1. Portion of a derives from the implications of geology geologic map of the Fort Polk for urban development (environmental- area where sediments of geologic applications), for ground-water Eocene, Oligocene, Miocene, protection (containment of potential Plio-Pleistocene, and contaminants), and for developing Holocene age crop out. The strategies for fault-hazard risk assessment sediments shown range from and damage reduction. Middle Miocene through The surface faults, though they do not Holocene, spanning a time produce detectable earthquakes, are known interval of approximately 15 to be active because of the cumulative million years. (Geology by damage done to structures built on and David J. Hinds [1998], near certain fault segments over periods of cartography Mary Lee years and decades. Detailed mapping of Eggart). the faults provides a framework useful for formulating and evaluating such strategies made in geologic mapping have been coastal land loss; geologic maps provide for constructing structures within areas 1 documented in other states through both basic information applicable to the that overlap the fault-line scarps. present economic benefits and avoidance of guidance of development in Louisiana's In summary, geologic mapping has future financial loss. Direct benefits include coastal zone. Detailed mapping in the myriad applications specific to timely oil and gas field discoveries, as well as coastal zone and the lower Mississippi needs in Louisiana, including: development of nonfuel mineral and River flood plain can provide information ✥ ground-water resources. Avoidance of future about the distributions of permeable and A variety of uses in conjunction with costs is derived from the early identification impermeable sediments and of surface the assessment of the quality, of natural hazards, and the optimal site faults, which is crucial in the effort to quantity, and distribution of ground location and design of structures and rationally plan the permitting of activities water and surface water, and the facilities based on such knowledge. in the coastal zone in ways that minimize prevention and mitigation of their The National Cooperative Geologic the threat of land loss. contamination. Mapping Program was authorized by Geologic mapping can, in places, ✥ Safe and optimal location of industrial Congress in 1992 to support the goal of resolve sediment and landform combina- and commercial facilities, including eventually mapping the geology of the tions characteristic of different environ- waste repositories. entire United States at the scale of 7.5- ments of deposition—such as former ✥ Monitoring and assessment of coastal minute quadrangles. In Kentucky, the first stream courses, meander belts, natural land loss. state to completely map its geology at this levees, and backswamps—with characteris- ✥ scale, benefits were estimated to exceed tic physical properties that have important Assessment and mitigation of natural costs by 50 to 1 on a $21 million invest- consequences in engineering applications. hazards (in Louisiana, principally 2 flooding and landslides). ment over the life of the program (1960 Knowledge of the distribution of such to 1978). characteristics is essential to the determina- ✥ A variety of uses relating to mineral tion of constraints for optimally locating resources—specifically to their POTENTIAL APPLICATIONS industrial facilities. This includes the exploration, the mapping of their The geologic mapping applications conscientious location of waste-treatment distribution, the economics of their mentioned above have value for addressing facilities relative to the recharge zones of exploitation and development, and needs specific to many current problems in aquifers that are important sources of their management. Louisiana. A critical problem in our state is drinking water, such as the Chicot aquifer,

1 The best documented example is Kentucky, the state that is most comprehensively mapped at 1:24,000, which is the scale of 7.5-minute quadrangles. 2 Smath (1988)

2 THE VALUE OF GEOLOGIC MAPS JUNE 2000 ROLE OF THE LOUISIANA that supports its population, and on its McCulloh, R. P. 1992. Surface geologic ability to safeguard its populace against mapping in Louisiana: history, present GEOLOGICAL SURVEY status, and future prospects. Open-file known hazards; hence, accurate and up-to- series no. 92-01. Baton Rouge: Louisi- The Louisiana Geological Survey is date geologic maps are essential to that ana Geological Survey. 20 pp. responsible for investigating the geology of well-being. Smath, M.L. 1988. Kentucky Survey’s the state and disseminating the knowledge history and challenges. Geotimes acquired through its investigations via REFERENCES 33(10):23 25. published reports and maps. Aspects of the Cressman, E.R., and M.C. Noger 1981. geology mentioned above in connection Geologic mapping of Kentucky a CONTACTS history and evaluation of the Kentucky with the manifest derivative applications of Geological Survey. U.S. Geological For more information on geologic geologic maps relate primarily to the Survey mapping program, 1960 1978. maps, contact Rick McCulloh geologic occurrence of energy and mineral U.S. Geological Survey Circular 801, ([email protected]), resources and of natural hazards. 22 p. Paul Heinrich ([email protected]) Hinds, D. J. 1998. Geologic map of the or John Snead ([email protected]) or reach Nonrenewable resources largely Fort Polk area, Vernon Parish, Louisi- comprise minerals in the broadest sense of ana. Geologic quadrangle map no. them by phone at (225) 388-5320. the term. Identification, exploitation, and GQ-1. Baton Rouge: Louisiana management of such resources, and Geological Survey. Produced in identification and mitigation of natural cooperation with U.S. Geological Survey, EDMAP program, under hazards, depend on geologic maps. The assistance award no. 1434-HQ-96-AG- Additional well-being of any state is based to a 01535. Scale 1:24,000. considerable degree on the resource base Web Sites:

WEBSTER BOSSIER CADDO http://www.usgs.gov/ CLAIBORNE UNION MOREHOUSE WEST 1960 CARROLL Louisiana http://ngmdb.usgs.gov/ EAST 1954 LINCOLN 1970 CARROLL http://ncgmp.usgs.gov/homepage.html 1952 RICHLAND OUACHITA 1970 MADISON 2000 JACKSON http://ncgmp.usgs.gov/ngmdbproject/ BIENVILLE Cumulative Map Production standards/metadata/metaWG.html 1948 FRANKLIN by Parish 1948 RED 1939 RIVER TENSAS CALDWELL at Scales of 1:62,500 and Greater DE SOTO 1939 http://www.fgdc.gov/metadata/ CATAHOULA WINN metadata.html 1992 Published with year of publication 1938 1936 1960 1938 LA SALLE NATCHITOCHES 1936 GRANT SABINE Unpublished with year of release

CONCORDIA Unmapped in parish format 1942 1940 RAPIDES 1940

VERNON AVOYELLES 1974 EAST WEST FELICIANA 1969 FELICIANA 1972 WASHINGTON 1957 ST. 1952 HELENA 1952 EVANGELINE POINTE 1957 COUPEE 1991 1972 BEAUREGARD ALLEN EAST ST. LANDRY BATON TANGIPAHOA WEST ROUGE 1969 BATON LIVINGSTON ROUGE ST. TAMMANY

JEFFERSON ACADIA DAVIS CALCASIEU ST. MARTIN IBERVILLE ASCENSION LAFAYETTE

N T H IS O T S P N . J A A T E S B L E R H O T ST. JAMES ST. CHARLES S ASSUMPTION IBERIA T CAMERON . M VERMILION A R ST. BERNARD T IN

J E ST. MARY F F E R S O LAFOURCHE N

PLAQUEMINES

TERREBONNE Written by Richard P. McCulloh, LGS. Reviewed by James M. Coleman, Coastal Studies Institute, LSU; and James E. Rogers (consultant, Figure 2. Parishes in Louisiana for which detailed geologic maps (those done at scales hydrology), Chacko J. John, LGS. of 1:62,500 or larger) have been made, with dates (redrawn and adapted from McCulloh 1992). Those in the unpublished category comprise portions of masters’ Graphic design by Ed Koch theses, doctoral dissertations, and open-file reports. Of a total of 64 parishes, 28 have Edited by Margo Olinde, LGS. been geologically mapped in detail.

THE VALUE OF GEOLOGIC MAPS 3 Louisiana Geological Survey 208 Howe-Russell Geoscience Complex Baton Rouge, Louisiana 70893 225•388•5320 Fax 225•388•3662 www.lgs.lsu.edu

This public information document is part of a series published periodically by the Louisiana Geological Survey, whose offices are located at Louisiana State University, Room 208 Howe-Russell Geoscience complex, Baton Rouge, La. 70803-4101. This information is distributed free of charge. Contact the LGS business office at (225) 388-5320 for extra copies or for more information, or visit the web site at http://www.lgs.lsu.edu.

This public document was published at a total cost of $861.31. One thousand copies of this document were published in this first printing at a cost of $861.31. This document was published by the Louisiana Geological Survey, Box G, Baton Rouge, La. 70893, to aid in public understanding of the geology of Louisiana under the authority of R.S. 30:206. This material was printed in accordance with standards for printing by state agencies established pursuant to R.S. 43:31. 4 THE VALUE OF GEOLOGIC MAPS JUNE 2000