GCG Online

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004–3143

December 2004

Gulf Coast Geology (GCG) Online

Printed on recycled paper

A large percentage of the present 

and future energy resources of 

the United States resides in the 

Gulf of Mexico Basin, one of the major 

hydrocarbon-producing areas of the 

world. Recent conceptual and technological advances have resulted in important 

new discoveries and have led to new or 

renewed exploration in large areas of 

the basin. The U.S. Geological Survey’s 

(USGS) Framework Studies and Assessment of the Gulf Coast Project was 

established in 1999 to conduct essential 

geologic, geophysical, and geochemical 

studies that will aid in a reassessment of 

energy commodities (coal, gas, and oil) in 

the Gulf Coast region. The project targets 

those stratigraphic intervals identified 

during previous oil, gas, and coal assessments as requiring additional study. Goals 

of the project are to (1) define the petroleum systems of the region; (2) conduct 

specific geologic framework studies and 

petroleum-system analyses on selected 

priority intervals; (3) study coal-bearing 

intervals to evaluate coal distribution and 

quality, coal-bed gas, and source-rock 

potential; (4) work in cooperation with 

the National Oil and Gas Assessment 

(NOGA) Project of the USGS to conduct a focused assessment of the Gulf 

Coast Region; and (5) contribute to the 

next phase of the USGS’s National Coal 

Resource Assessment.

Gulf Coast Geology (GCG) Online is 

a Geographic Information System (GIS) 

database developed using map service 

technologies. It serves three primary 

needs of the project: (1) efficient, centralized data management and visualization; 

(2) development and sharing of data and 

interpretations by project personnel; and 

(3) dissemination of information and 

products to customers in a readily usable 

format. Currently, all USGS oil and gas 

assessments are petroleum-system based 

and require large amounts of geologic, 

geophysical, geochemical, and paleontologic data in addition to well and oil- and 

gas-field databases. In well-explored and 

developed regions and provinces, such 

as the Gulf Coast, these data sets can be 

Figure 1. Example of GCG 

online Internet Mapping 

System and customized 

map output.

http://energy.cr.usgs.gov/oilgas/gulf/gcgonline
BAYOU LONG

DARROW

WHITE CASTLE

NAPOLEONVILLE

OAKLEY

DELIA

LAKE VERRET, EAST

GRAND BAYOU

MYSTIC BAYOU

BAYOU PIGEON

BAYOU ST VINCENT

PIERRE PASS

LAUREL RIDGE

BAYOU PIGEON, EAST

RATCLIFF

BAYOU POSTILLION

SULLIVANS LAKE

BAYOU GROSBEC

BAY NATCHEZ

BAYOU POSTILLION, EAST

OAKLEY, NORTHWEST

BAYOU PIGEON, NORTH

LAKE VERRET

BIG BAYOU PIGEON

MYSTIC BAYOU, WEST

WILDCAT-SO LA HOUMA DIST

-9000

-9500

-8500

-10000

-10500

-11500

-11000

-12000

-12500

-13000

-9000

-11500

-11000

-12000

-11500

-10000

-8500

-9500

Louisiana

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Figure 2. Example 

showing structure contours, 

control wells 

for structure 

contours (white 

dots), salt 

diapers (areas 

enclosed by 

purple lines), and 

lower Miocene 

hydrocarbon 

producing areas 

(gray areas) 

overlain on isopach map (warm 

colors = thicker) 

of lower Miocene 

of south-central 

Louisiana

large and require comprehensive data 

management. For example, the Miocene 

of southern Louisiana database alone 

currently consists of nearly 100 layers in addition to 25 layers of general 

geographic and geologic information. 

It is desirable for the large number of 

USGS project personnel working under 

tight deadlines on a wide variety of topics 

to have simultaneous and ready access 

to these data as well as to the data and 

interpretations most recently developed 

by other project scientists. An additional 

requirement is that the output be in a format that is easily used by project personnel or customers (such as administrators, 

other scientists, and the general public) 

who may or may not have GIS expertise 

or software. This requirement is particularly important for government agencies, 

such as the USGS, that place a strong 

emphasis on providing the best and most 

current information possible to decision 

makers and the public.

GCG Online is accessed via an Internet Mapping System (IMS) which can be 

used by anyone with an internet connection and web browser. The IMS allows 

users to interact with spatial information directly online in many ways. It has 

tools that can overlay the many different 

thematic layers, zoom in and out, make 

measurements, or perform basic queries by simply clicking on a feature of 

interest. Some advanced features include 

the ability to hyperlink directly to well 

information supplied by the State of 

Louisiana, and the ability to create custom, high-quality maps directly online for 

immediate download and for hardcopy 

printing (fig. 1). 

The USGS will publish Data Series 

90 (DS 90) in a series of releases that 

will be made available online as they 

are completed. DS 90-A will pertain to 

the Miocene only, whereas DS 90-B, 

90-C, and so on, will pertain to other 

parts of the stratigraphic section. Each 

release will have a version number so that 

updates may be tracked and referenced. 

DS 90-A, version 1.0, for example, deals 

almost exclusively with the Miocene of 

southern Louisiana. Sources of data specific to each individual layer within the 

database are documented in the metadata 

for that layer. In most cases, data from 

outside sources such as private industry 

are assumed to be sufficiently reliable 

for purposes of regional compilation, but 

the user is cautioned in the use of these 

data at prospect and smaller scales. All 

data are in the form of shapefiles and 

ArcSDE (Spatial Data Engine) layers 

that are maintained on the USGS Central 

Energy Resources Team (CERT) server 

along with the applications software. An 

updated version, DS 90-A, version 2.0, 

may combine data on the Miocene of 

Texas with the previously published data 

and will be published later. All versions 

of each release will be available through 

the CERT Web site. 

Version 1.0 of the Miocene deals 

almost entirely with southern Louisiana, 

primarily because of the availability of 

data, especially biostratigraphic data. 

Publicly available data have been used 

wherever possible. However, in the case 

of proprietary data, such as the Tenroc Regional Geologic Database, only 

derivative products are made available. 

For example, the isopach and structure 

contour maps show the locations of wells 

used to construct the contours but do not 

reveal the precise depths of the micropaleontologic identifications in that well 

(fig. 2). In addition to the data specific to 

southern Louisiana, a number of regional 

geologic and geographic layers that will 

be applicable to all versions are included 

in version 1.0 for reference.

For further information:

GCG Online is available at the USGS 

Central Energy Team Web site:

http://energy.cr.usgs.gov/oilgas/gulf/

gcgonline

Geology:

A. Curtis Huffman, Jr.

achuffman@usgs.gov

303.236.1543

GIS:

Laura R.H. Biewick

lbiewick@usgs.gov

303.236.7773

Web Application:

Gregory L. Gunther

ggunther@usgs.gov

303.236.5884

Acknowledgments:

Scott A. Kinney: GIS

Heather R. Mitchell: GIS

Chris C. Skinner: Database Management

GCG Online http://energy.cr.usgs.gov/oilgas/gulf/gcgonline