Guide to the Development and Application 

of Geographic Information Systems for 

Sedimentary Basin Analysis-Case Study for 

the San Juan Basin, New Mexico and Colorado 

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Guide to the Development and Application 

of Geographic Information Systems for 

Sedimentary Basin Analysis-Case Study for 

the San juan Basin, New Mexico and Colorado 

By BETTY M. MILLER 

An evaluation of the feasibility of applying geographic 

information systems technology to the development of a 

prototype computer-based system that provides the framework 

for three-dimensional analysis of sedimentary basins. The San 

juan Basin, New Mexico and Colorado, is used as the pilot 

study for the development of a geographic information system 

data base 

U.S. GEOLOGICAL SURVEY BULLETIN 2025 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 

For sale by 

Book and Open-File Report Sales 

U.S. Geological Survey 

Federal Center, Box 25286 

Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Miller, Betty M. 

Guide !o the development and application of geographic information systems 

for sedimentary basin analysis : case study for the San juan Basin, New 

Mexico and Colorado I by Betty M. Miller. 

p. em. - (U.S. Geological Survey bulletin ;2025) 

Includes bibliographical references. 

Supt. of Docs. no.:l19.3:2025 

1. Sedimentary basins-San juan Basin (N.M. and Colo.)-Data processingCase studies. 2. San Juan Basin (N.M. and Colo.) 3. Geographic information systems. 4 Geological modeling. I Title. II. Series. 

QE75.B9 no. 2025 

[QE144.S24] 

557.3 s-dc20 

[025.06'5514'1] 92-8528 

CIP 
CONTENTS 

Abstract 1 

Introduction 2 

Basin Analysis-A Review of the Literature 2 

Computer Mapping 4 

Mapping Systems Versus Geographic Information Systems 4 

Geographic Information Systems 4 

The Role of GIS in Subsurface Characterization for Basin Analysis 6 

Developing the GIS for Basin Analysis 7 

Determining the Objectives 7 

Building the Data Base 7 

Performing the Geographic Analysis 8 

Presenting the Results 9 

A GIS for the San Juan Basin 9 

San Juan Basin, New Mexico and Colorado-The Pilot Study Area 10 

Regional Geology of the San Juan Basin 10 

Stratigraphy and Petroleum Geology 11 

Dakota Sandstone 13 

Gallup Sandstone 13 

Point Lookout Sandstone 15 

Pictured Cliffs Sandstone 16 

Map Coverages for the San Juan Basin 16 

Surface Map Coverages 16 

Area Map 16 

Base Map 16 

Landownership Map 17 

Surficial Geology Maps 17 

Outcrop Maps 18 

Well-Location Maps 18 

Subsurface Map Coverages 19 

Stratigraphic Section 19 

Structural Maps 19 

Isopach Maps 20 

Performing a Geographic Analysis in the San Juan Basin 23 

San Juan Basin Data Base 23 

Using the GIS for San Juan Basin Analysis 24 

Additional Map and Data Coverages 26 

Further Applications of GIS for the San Juan Basin 27 

Summary 28 

Acknowledgments 30 

References Cited 30 

Appendix A. ARC/INFO Geographic Information System 36 

Appendix B. TIN Mapping Programs for ARC/INFO 37 

Contents Ill 
IV Contents 

FIGURES 

1. Diagram showing map features organized into sets of data layers or themes of 

information 5 

2. Chart showing major steps in conducting a GIS project by using the 

ARC/INFO method 7 

3. Diagrams showing (A) intersection of buffer zones within 2 mi of gas wells 

producing from the Pictured Cliffs Formation and buffer zones within 1 ,500 ft 

of existing streams and (B) topological overlay joining polygons from three 

coverages 10, 11 

4. Map showing structural elements of the San Juan Basin and adjacent areas 12 

5. Stratigraphic correlation chart of the San Juan Basin 14 

6. Map of the Four Comers area showing the location of the San Juan structural 

basin and the study area 17 

7. Computer graphic of the San Juan Basin study area taken from the more 

detailed base map coverage for the San Juan Basin illustrating a highly simplified base map clipped to the study area boundaries 18 

8-10. Digital map coverage displays showing: 

8. Landownership in the San Juan Basin study area 19 

9. One combination of identified geologic units of the surficial geology in 

the San Juan Basin study area 20 

10. Selected outcrops of some of the Cretaceous oil- and gas-bearing formations within the San Juan Basin study area 21 

11. Composite computer-generated map coverage showing ( 1) the locations of all 

oil, gas, and nonproductive (dry hole) wells that either produce from or penetrate the Dakota Sandstone, (2) Dakota Sandstone outcrops, and (3) the 

Dakota Sandstone subcrop extent 22 

12. Digital map coverage showing structure contours for the top of the Dakota 

Sandstone within the Dakota Sandstone subcrop extent 23 

13. Composite digital map coverage for the Dakota Sandstone, including oil- and 

gas-producing wells, structure contours for the top of the Dakota, Dakota 

Sandstone outcrops in the San Juan Basin study area, and Dakota Sandstone 

subcrop extent 24 

14. Digital map coverage showing the subcrop extent of and isopach contours for 

the Pictured Cliffs Sandstone in the San Juan Basin study area 25 

15-18. Composite digital map coverages showing: 

TABLE 

15. The structure contour coverage, outcrop and subcrop extent, and oil and 

gas wells producing from the Pictured Cliffs Sandstone 26 

16. The isopach contour coverage, outcrop and subcrop extent, and oil and 

gas wells producing from the Pictured Cliffs Sandstone 27 

17. The oil and gas wells producing from the Pictured Cliffs Sandstone and 

from the Gallup Sandstone 28 

18. An overlay of the subcrop extent and isopach contours for the Pictured 

Cliffs Sandstone onto map coverages for subcrop extent and isopach contours for the Point Lookout Sandstone to determine if patterns of deposition are similar or different for the two formations 29 

1. Map coverages for locations of oil, gas, and nonproductive wells listed by formation in the San Juan Basin GIS data base 22 
Guide to the Development and Application of 

Geographic Information Systems for Sedimentary 

Basin Analysis-Case Study for the San juan Basin, 

New Mexico and Colorado 

By Betty M. Miller 

Abstract 

Analysis of sedimentary basins 

requires a multidisciplinary approach 

drawing on many areas of geologic 

expertise supported by the integration and analysis of large volumes of 

multivariate spatial data. Such an 

extensive data base requires computer technology to make the most 

effective use of all the available information and to analyze the data within 

a three-dimensional framework. One 

such method being investigated for 

analyzing sedimentary basins is the 

application of geographic information systems (GIS). GIS technology 

involves the integration of mapping 

and data base functions so that a 

geologist can combine complex geographic, geologic, and geophysical 

data sets into overlay and composite 

maps. The technology allows a geologist to conduct multivariate spatial 

data analysis and to access a variety of 

options for analyzing these basin data 

bases. GIS technology when applied 

to sedimentary basin analysis is used 

to establish a three-dimensional perspective of a basin's fundamental 

stratigraphic and structural framework and to aid in the identification 

of its temporal and tectonic relationships relative to origin, subsequent 

development, and occurrence of its 

natural resources. 

A GIS program can be organized 

into a series of four logical steps, each 

Manuscript approved for publication February 26, 1992. 

of which builds upon the previous 

one. The four steps are determining 

the objectives, building the data base, 

performing the analysis, and presenting the results of the analysis. Determining the objectives defines the 

scope and purpose of the project, 

which in turn dictate the design and 

content of the data base. Building the 

data base is the most critical and the 

most time-consuming part of the 

project. The completeness and accuracy of the data base determine the 

quality of the analysis and final products. The principal value of the GIS, 

however, is its ability to analyze a data 

base by developing and applying 

models to reveal underlying trends in 

the geographic data and making new 

information available. The GIS provides new data coverages that can be 

combined in meaningful sequences 

to develop new models. Results of 

geographic analysis can be presented 

by creating customized maps to display geographic relationships and by 

preparing reports for summarizing 

tabular data and documenting any 

calculated values. 

The San Juan Basin in northwestern New Mexico and southwestern Colorado is used as the pilot 

study area to demonstrate the feasibility of applying GIS techniques to a 

basin analysis and to develop a prototype to assess the GIS data base for 

the basin. The GIS study focuses on 

those formations in the Upper Cretaceous that are recognized as the 

major oil and gas producers within 

the basin. The four formations studied are the Dakota, Gallup, Point 

Lookout, and Pictured Cliffs Sandstones. 

Data bases for surface coverages 

within the San Juan Basin include digital base maps; hydrography, landownership, and surficial geology 

data; well-location maps of more than 

26,000 oil, gas, and nonproductive 

wells; and information on well status 

and oil and gas fields. Data bases 

created for subsurface mapping and 

analysis include geologic information, such as structure-contour, isopach, and lithology maps for the four 

major oil- and gas-producing formations; stratigraphic information for 

cross sections and fence diagrams; 

and composited map products. 

GIS analysis techniques successfully applied in the San juan Basin are 

designed to address the basin's fundamental geologic, stratigraphic, and 

structural +ramework with particular 

emphasis on the petroleum geology 

of the basin. Some of the GIS applications used in this basin study are 

analyzing (1) composite map coverages for structural configurations relative to the basin tectonics, (2) depositional patterns by using isopach 

maps relative to production trends 

within the producing formations, (3) 

spatial relationships depicting geologic conditions favorable for the 

occurrence of oil and gas trends 

within productive formations, and (4) 

spatial geometries of transgressive 

and regressive cycles of deposition 

for productive sandstones. 

Abstract 
GIS technology is demonstrated to be an important 

new tool for the earth scientist for geological interpretation of three-dimensional, multivariate spatial data in 

conducting an integrated analysis of sedimentary basins. 

GIS technology can contribute to innovative research in 

geological interpretation, to updating and documenting 

information data bases, and to developing new concepts 

in basin analysis and resource appraisal methodology. 

INTRODUCTION 

Most of the world's energy resources and many of its 

metallic and mineral resources are derived from sedimentary rocks. Exploration and assessment of these resources 

require an understanding of their relation to the host strata 

within sedimentary basins, whether the resources are primary or postsedimentation deposits. The most important 

result of a study of these host strata is a basin analysis that 

documents the geologic and paleogeographic evolution of 

the sedimentary basin and its related resource occurrences 

(Miall, 1984). Such a comprehensive basin analysis requires an understanding of data from many diverse components, including sedimentology, stratigraphy, structural 

geology, geophysics, and geochemistry, and the ability to 

assess the interrelations of many types of multivariate 

spatial data. 

The concepts and methods for conducting sedimentary basin analysis have evolved from fairly simplistic 

geological studies that employed primarily qualitative and 

semiquantitative techniques, to studies of ever-increasing 

complexity that employ quantitative evaluations from total 

basin systems. Two of the major guiding principles of basin 

analysis are the importance of an integrated approach and 

the consideration of the sedimentary basin as a whole 

(Potter and Pettijohn, 1963). This complex quantitative 

approach requires enormous amounts of multivariate spatial 

data to quantify the geologic, geophysical, geochemical, 

and hydrologic processes reacting over time throughout the 

history of a sedimentary basin. 

Such an integrated analysis of a sedimentary basin is 

difficult to accomplish without computer assistance. The 

analysis requires a multidisciplinary approach that draws on 

many areas of geologic expertise supported by the integration and analysis of large volumes of multivariate spatial 

data. However, new applications of knowledge-based computer mapping techniques (geographic information systems) 

can provide the tools needed to define new strategies and 

technologies for conducting and automating the complex 

tasks common to sedimentary basin analysis, particularly 

for extending two-dimensional mapping techniques to 

three-dimensional basin analysis. Geographic information 

system (GIS) technology involves the integration of digital 

mapping techniques and data base functions so that a 

geologist can combine complex geographic, geologic, and 

geophysical data sets into overlay and composite maps. It 

also allows a geologist to conduct multivariate exploratory 

data analysis and to access a variety of options for analyzing 

these basin data bases. 

In 1986, the Director of the U.S. Geological Survey 

(USGS) established a research fund designated the "GIS 

Sweepstakes." The objectives of this funding were to (1) 

develop and provide GIS capabilities to the traditional 

USGS geologic missions and (2) promote interdivisional 

research. One project supported by this fund, and headed by 

the author, is entitled "Three-Dimensional Analysis of 

Sedimentary Basins Using Knowledge-Based Geographic 

Information Systems (KB-GIS) and Artificial Intelligence 

(AI)-Expert Systems." 

The major objectives of this project are to explore the 

feasibility of applying ( 1) GIS digital mapping techniques to 

integrate and manipulate spatial and attribute data, to 

combine complex data sets (geographic, geologic, and 

geophysical) into overlay maps, and to conduct exploratory 

data analysis and (2) AI-expert systems techniques to 

simulate the logic of basin experts to model geologic 

concepts, to document and analyze geologic attributes, and 

to characterize the history of a sedimentary basin. 

This report is written for the geologist as an introduction to GIS development and its application to geologic 

basin studies. The report is limited to a discussion of GIS 

techniques and applications used to conduct a sedimentary 

basin analysis. The San Juan Basin is used as the pilot study 

area to test the feasibility of applying GIS techniques to a 

basin study and of developing a GIS data base. This report 

is not intended to serve as a complete geologic analysis of 

the San Juan Basin. The work on applying AI-expert 

systems techniques to classification and analysis is covered 

in separate reports and will continue to be developed 

(Miller, 1987, 1989a). 

BASIN ANALYSIS-A REVIEW OF THE 

LITERATURE 

The geologic literature reflects a considerable difference of opinion among geologists over the last three to four 

decades as to what constitutes a basin analysis. The expression "basin analysis" was first introduced by Potter and 

Pettijohn (1963) in their well-known textbook "Paleocurrents and Basin Analysis." The objective of basin analysis 

in the 1960's was essentially paleogeographic, with emphasis on the mode of the sediments filling the basin. Basins 

were analyzed by using a combination of paleocurrent 

measurements and facies distributions. Basin analysis, or 

the paleogeographic reconstruction of a sedimentary basin 

as it evolved, was simply a tool, along with isopach and 

lithofacies maps, for understanding the relationships 

between sedimentation and tectonics, with the major 

emphasis placed on tectonics (Krynine, 1942, 1948; Kay, 

1951; Pettijohn, 1957; Krumbein and Sloss, 1963; Potter 

and Pettijohn, 1963; Aubouin, 1965; Reading, 1988). 

2 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
Sedimentologists of the 1960's, however, were 

highly critical of the direct correlation of sedimentary suites 

with tectonic regimes and stressed the hydrodynamics of 

clastic sediments and the monitoring of modem sedimentary 

processes. They contended that sedimentary facies, 

sequences, and cycles should be interpreted as responses to 

observable sedimentary processes rather than to tectonic 

movements (Reading, 1988). 

Much of basin analysis has changed with the development of the concept of tectonics. Most sedimentary 

basins now can be explained in terms of plate-margin or 

plate-interior processes, and their structure and stratigraphy 

can be described with more comprehension. The importance of plate tectonics to basin analysis is now nearly 

universally recognized. 

After the advancement of plate-tectonic models, near 

the end of the 1960's, three lines of study emerged in basin 

analysis. Sedimentologists continued to concentrate on 

more detailed sedimentary processes, without major concern for the wider geologic implications. Two other schools 

of thought reflected both tectonics and sedimentation. One 

emphasized the dominant role of tectonics in controlling 

sandstone composition and was a continuation of the 

Krynine tradition (Krynine, 1942, 1948). The second 

school focused more on sedimentary facies than on composition and attempted to understand sedimentation in terms of 

structural tectonic patterns and the magmatic and metamorphic background (Reading, 1988). 

Toward the end of the 1970's, the interrelationship of 

tectonics, sedimentology, and basin analysis was firmly 

established. An important factor added to this integration of 

specialties was the research of petroleum geologists in their 

analysis of sedimentary basins to establish the hydrocarbon 

potential of petroleum source rocks. The study of tectonics 

and sedimentation for basin analysis is approached by 

theoretical geophysical and sedimentological modeling, by 

classical global tectonic modeling, and by detailed field 

studies (Reading, 1988). Many of these techniques have 

been made possible or enhanced by the availability of 

computers and computer techniques that can manipulate the 

large and diverse data bases necessary for basin analysis. 

Current geologic textbooks, however, still consider 

basin analysis from somewhat differing viewpoints on 

specific, as well as general, approaches. The textbook 

"New Perspectives in Basin Analysis" (Kleinspehn and 

Paola, 1988) emphasizes two major areas of sedimentological research: (1) source-area characterization and lithostratigraphy (McBride, 1988; Van Houten, 1988) and (2) 

tectonics and sedimentation (Reading, 1988). 

Miall ( 1984), in his textbook "Principles of Sedimentary Basin Analysis," emphasizes five new developments in 

sedimentary geology: the evolution of sedimentology in 

terms of explaining the origin of sedimentary rocks through 

facies studies and facies models, the study of depositional 

systems relative to their complete package of environments 

and sedimentary products, the evolution of modem seismic 

stratigraphic techniques, the developments in plate-tectonic 

theory and its impact on understanding basin evolution and 

sedimentary styles, and the evolutionary refinements in 

chronostratigraphy through developments in radiometric 

dating techniques. The first two steps for basin analysis, as 

proposed by Miall ( 1984), are ( 1) establishment of the 

framework of major sequences through seismic methods 

and detailed lithostratigraphic correlation and biostratigraphic zonation and (2) interpretation of each sequence in 

terms of its component depositional systems, using sedimentological data, the principles of facies analysis, and 

basin mapping methods. 

Lerche (1990), in his textbook "Basin Analysis: 

Quantitative Methods," addresses the problem of quantitative basin analysis in relation to oil accumulations. His book 

is devoted to examining the quantitative methods of reconstructing the burial history of sediments in basins; the 

problem of quantitative reconstruction of the thermal histories of sedimentary basins, based on model-derived heat 

fluxes and an inversion of present-day thermal indicator 

data; and the integration of the hydrocarbon generation, 

migration, and accumulation modeling aspects with the 

burial history and thermal history as the basic foundation for 

the basin studies. Lerche examines the quantitative aspects 

of basin analysis viewed as an integrated picture, unlike 

many other authors who address only the qualitative application of basin analysis methods (Hunt, 1979). 

This review of some of the more recent literature 

demonstrates the complexity of basin analyses, the value of 

older tectonic and sedimentological techniques, and some 

updated approaches. Because of the enormous amounts of 

data required to describe complex basin systems, quantification of these processes was not feasible in past studies. 

Thus, until recently, only qualitative or semiquantitative 

basin studies were made and presented as case studies. The 

increasing capacity and speed of computers, however, 

should support the initiation and development of quantitative basin studies. 

Two examples of such quantitative studies are those 

of Green (1987) and Welte and Yukler (1981). Green's 

study is an integrated sedimentary basin analysis that 

involves the construction of a geologic model documenting 

how a basin formed, filled with sediments, compacted, and 

matured within the natural system of the Earth's 

geochemical-geologic cycle (Green, 1987). Welte and Yukler's (1981) study is a construction of a three-dimensional 

deterministic dynamic basin model and the quantification of 

complex dynamic processes of petroleum formation and 

occurrence in a given sedimentary basin. The study 

describes a basin system in which the generation, migration, and accumulation of petroleum occur within the 

three-dimensional dynamic geologic framework. 

Basin Analysis-A Review of the Literature 3 
COMPUTER MAPPING 

Geologists routinely perform three-dimensional analyses and employ three-dimensional concepts to understand 

and describe spatial relationships. In contrast, the typical 

mode of display, such as maps and cross sections, is two 

dimensional. As a result, geologists have used twodimensional tools (such as graphic displays that involve 

specialized maps, cross sections, fence diagrams, and 

geometrical constructions such as stereonets) to project 

information from three-dimensional space to a more manageable, but less accurate, two-dimensional space. 

Computers, and modem software programs, offer 

important advantages in ( 1) manipulating large quantities of 

data, (2) speed, (3) manipulating maps and map data, (4) 

updating and documenting, (5) ensuring objectivity and 

consistency, and ( 6) incorporating geological interpretations (Jones and others, 1986). This paper does not discuss 

the various computer mapping techniques available to the 

geologist interested in spatial analysis and using the computer for data preparation and processing, methods, applications, and interpretations. The reader interested in the 

techniques for two-dimensional geological coverages, concentrating on mapping structural surfaces and thickness 

intervals, is referred to "Contouring Geologic Surfaces with 

the Computer" by Jones and others (1986). 

Mapping Systems Versus Geographic 

Information Systems 

Two principal types of computer mapping have 

evolved-mapping systems and geographic information 

systems. The two types offer similar kinds of data capture, 

edit, and display capabilities, and both can be applied to 

some of the same tasks. However, mapping systems and 

GIS' s have different philosophies, data structures, and 

preferred coordinate systems (Aanstoos, 1989). 

Mapping systems focus mainly on boundaries and so 

generally are best for data base management and highquality cartographic map output. Two kinds of mapping 

systems are available: those used for map drafting and those 

used for facilities mapping. Most mapping systems store 

data in Cartesian, or x, y, coordinates. 

GIS is intended primarily for geographic data analysis 

and thematic mapping. GIS focuses on areas or polygons 

and so is stronger in spatial data analysis (Lang, 1988; 

Aanstoos, 1989). The basic data structure is topological; that 

is, each map element is treated as a point, line, or polygon. 

Like flat maps, GIS uses various planar coordinate systems 

to map the Earth's surface. Each coordinate system used is 

based on a particular map projection, such as the Universal 

Transverse Mercator (UTM), the Albers Equal-Area Conic, 

or the Polar Stereographic Coordinate system. The functions of mapping systems and GIS' s, however, are evolving 

slowly toward each other. In the future, there may be little 

distinction between them. 

Geographic Information Systems 

One definition of GIS is "a computer based technology composed of hardware, software, and data used to 

capture, edit, display, and, most importantly, analyze 

geographic information.... The key distinction between 

mapping software and GIS software lies in its [GIS] ability 

to analyze spatial data" (Lang, 1989, p. 17). According to 

Dangermond (1989, p. 25), "A GIS is, first of all, an 

automated information system. A GIS brings information 

together, it unifies and integrates that information. It makes 

available information to which no one had access before, 

and places old information in a new context. It often brings 

together information which either was not or could not be 

brought together previously." 

GIS' s originally were designed and developed nearly 

20 years ago as a method to overlay and combine diverse 

kinds of data into a single map to summarize geographic, 

cultural, and scientific attributes. Since that time, these 

systems have evolved to serve many different applications, 

such as inventory mapping of forests, water, and other 

natural resources; lease management; topographic mapping; 

exploration; marketing and facility information; municipality planning; land use planning; military applications; teaching; and scientific research. 

With the growing interest in three-dimensional geologic modeling and the need for subsurface geologic analysis, new applications of GIS are being investigated that 

provide data integration to link surface and subsurface 

geology with associated rock attributes such as geochemical 

and geophysical data (Loudon, 1986). A GIS typically links 

different data sets and allows many different types of data to 

be spatially and statistically analyzed (Robinove, 1986). 

Figure 1 shows the linking of a number of related data 

layers that can be extracted from various surface and 

subsurface geographic and geologic data bases. 

A GIS data model, such as the commercial product 

ARC/INFO, involves storage of tabular data (attributes) in 

association with simple cartographic features, such as 

points, lines, and polygons. Cartographic data are stored in 

tables recording spatial location in relation to other descriptive attributes and not as graphic primitives or symbols. (A 

brief description of the ARC/INFO software system is 

presented in appendix A.) Because of this data structure, 

GIS's can analyze geographic (and geologic) data and 

provide a geologist with the ability to view and analyze 

spatial data relationships, as well as to map, query, and 

manipulate spatial information (Chrisman, 1987). GIS's 

also can be used for entry, editing, and maintaining digital 

maps. 

4 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
__ _.L _________________ _ 

/ 

I --~/ 

I 

~----------------

/ 

I 

Surficial geology 

Subsurface geology 

Geochemistry 

Figure 1. Map features organized into sets of data layers or themes of 

information. Linking of surface and subsurface geographic data bases 

is represented by a number of related data layers or coverages in 

geographic information systems. 

Computer Mapping 5 
THE ROLE OF GIS IN SUBSURFACE 

CHARACTERIZATION FOR BASIN ANALYSIS 

Early GIS applications involved mapping essentially 

two-dimensional land-surface phenomena such as land use, 

landownership, hydrographic features, vegetation, and 

soils. Most commercially available GIS products cannot 

represent true three-dimensional data, although they can 

represent topographic data, usually as a digital elevation 

model (DEM), and can display isometric views, contour 

maps, and so on. Most DEM's use either gridded elevation 

matrices or triangular meshes to allow these terrain representations. In these cases, the elevation, or z coordinate, is 

treated as a dependent variable. Some systems also allow 

the draping of another mapped feature, such as soils or land 

cover data, onto an isometric view of a topographic elevation surface, thereby creating the illusion of a threedimensional model (Turner, 1989). 

Some geological applications using a GIS can be 

accomplished by reducing the three-dimensional data to a 

quasi-three-dimensional mode by using individual surfaces 

or stacked subsurface layers. These surfaces, which can 

represent bedding planes or formation boundaries for example, then can be contoured or displayed as isometric views. 

In these cases, however, the elevation of the surface is not 

a truly independent variable, and so these systems are best 

defined as quasi-three-dimensional, or 2.5-dimensional systems. Many regional geological studies operate in a 2.5-

dimensional mode because the geographic dimensions (x 

andy) are several orders of magnitude larger than the depth 

dimension (z) (Turner, 1989). 

Detailed three-dimensional subsurface data are especially crucial in applications such as petroleum reservoir 

characterization (Jones, 1988), ground water contamination modeling, and geotechnical site characterization 

for increasingly complex construction projects. Threedimensional subsurface data characterization is also crucial 

for conducting studies on basin evolution and basin analysis 

and for the exploration, evaluation, and management of 

natural resources (Bak and Mill, 1989). All of these 

applications have one thing in common; they require 

increasingly quantitative and accurate rock-property characterizations within the three-dimensional subsurface environment (Unger and others, 1989; VanDriel, 1989; Youngmann, 1989). Subsurface studies require a true threedimensional data framework because the geographic 

dimensions (x and y) are of the same general order of 

magnitude as the depth dimension (z) and because the 

accurate depiction of spatial relations is essential for basin 

analysis (Turner, 1989). This study investigates the application of GIS technology to subsurface data and subsurface 

mapping, whereas previously it has been applied only to 

surface data and surface mapping (Miller, 1988, 1989b, 

1991). Major problems, however, occur when working with 

subsurface data in geological applications, and these problems differ considerably from those encountered in other 

fields of study. Some examples follow: 

1. Geologists deal with information that is frequently 

incomplete, inferred or interpretive, often uncertain, and 

sometimes unreliable. They must extrapolate and interpolate to construct a complete subsurface model. The 

quality and accuracy of three-dimensional geologic 

models are severely constrained by the availability of 

subsurface information about depths, boundaries, or 

geometries and the variable nature of the rock properties, ranging from microscopic to megascopic, being 

recorded. 

2. The natural subsurface geology or basin configuration 

can be characterized by extremely complex spatial 

relations, such as intricate faulting and folding, or by 

complicated and frequently discontinuous boundaries or 

geometries for depositional facies. 

3. The irregularly spaced or clustered location of wells and 

well data or the lack of seismic data frequently results in 

insufficient sampling. As a result, less than adequate 

subsurface information is available to resolve all uncertainties in mapping and geologic interpretation. 

4. The relationships of sampled rock properties derived 

from geological and engineering data developed from 

exploration procedures (such as well tests and core data, 

seismic exploration, and stratigraphic or sedimentological descriptions of depositional systems) to the threedimensional or volumetric distribution of the rock units 

are usually unknown and must be treated as interpretive 

in nature. 

True three-dimensional GIS products could greatly 

aid the resolution of these difficulties by enabling the 

visualization of spatial relations and by providing datamanagement capabilities. Unfortunately, true threedimensional GIS is unavailable at this time. "By 'true 3-D' 

we mean manipulation of solid, volumetric cubes of the real 

world" (Davis and Williams, 1989, p. 51). To date, the 

inability to visualize these three-dimensional features has 

been a major constraint. By making true three-dimensional 

visualization possible in realtime, three-dimensional GIS 

could substantially improve existing analytical capabilities 

(Turner, 1989). Recently announced commercial systems, 

such as the Dynamic Graphics Interactive Volume Modeling (IVM), are attempting to address these visualization 

needs (Smith and Paradis, 1989; Paradis and Belcher, 

1990). 

Future three-dimensional GIS technology must strike 

a balance between its dual roles of spatial visualization and 

data management. Recent speculations concerning the 

merging of GIS and computer-aided· drafting and mapping 

technologies emphasize the shortcomings of the current 

systems for many geoscience applications (Lang, 1988). 

Geological applications of GIS currently form a very 

small part of the total GIS market. The inclusion of the third 

coordinate (z) and the conversion from planar to solid 

6 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
BUILDING THE DATA BASE ANALYSIS PRESENTATION 

DESIGN DATA AUTOMATION 

Managing Performing Presenting the 

Starting the Getting Making Getting the geographic results of the 

attribute data base design analysis ARC/INFO spatial data spatial data data into project into ARC/INFO usable ARC/INFO 

Identify required Prepare map Create Create Convert Evaluate Create final maps 

layers and manuscript coverages data file coverages to and interpret Create reports 

attributes Digitize Display and and add UTM coordinate spatial data 

manuscript correct errors attributes system 

Collect existing Reformat 

data digital data 

Join data Join map sheets 

Create master Construct Reconstruct to attribute 

tic file topology topology table 

Figure 2. Major steps in conducting a GIS project by using the ARC/INFO method. Modified from Environmental Systems 

Research Institute, Inc. (1990). 

geometry add storage and computational costs to the GIS 

software. Thus, until very recently, developers and vendors 

of GIS software have not pursued the three-dimensional 

GIS market. This situation is rapidly changing, due largely 

to the increasing interest in three-dimensional graphics 

systems for many uses and the development of new hardware that can support the generation of three-dimensional 

graphical displays. However, the lack of affordable, fully 

functional, three-dimensional GIS products to date has had 

ramifications for many geological applications. This report, 

therefore, is basically restricted to the applications of the 

quasi-three-dimensional or 2.5-dimensional systems to subsurface characterization for support of geological basin 

studies. 

DEVELOPING THE GIS FOR BASIN ANALYSIS 

The following section is a brief overview of the basic 

steps used in developing a typical GIS project. The four 

major steps are determining the objectives, building the data 

base, performing the analysis, and presenting the results of 

the analysis. Each of these steps is briefly discussed below 

as it relates to the design and development of the San Juan 

Basin GIS. Most GIS projects will follow a similar 

sequence. Figure 2 summarizes the basic steps in conducting a GIS project by using ARC/INFO. For a more detailed 

account of how to start an ARC/INFO project, refer to 

"Understanding GIS-The ARC/INFO Method" (Environmental Systems Research Institute, Inc. (ESRI), 1990, 

chap. 3). 

Determining the Objectives 

Determining the objectives of a GIS study is important to define the scope of the project and its implementation. The purpose and objectives of the project dictate the 

design and contents of the data base. The nature of 

the geologic problems to be resolved and the final products of the project (that is, reports, working maps, and 

presentation-quality maps) determine the types of coverages 

needed in the data base to perform the various analyses. 

In the San Juan Basin pilot study, the basic objectives 

are (1) to explore the feasibility of applying GIS technology 

to the analysis of the basin's fundamental geologic, stratigraphic, and structural framework and (2) to develop a 

working prototype system that will provide a model for 

conducting three-dimensional analysis of sedimentary 

basins. New lines of inquiry relative to geological interpretations and spatial relationships emerged during the course 

of the pilot study as the feasibility of applying these GIS 

techniques successfully to a basin study became evident. 

Building the Data Base 

The most important and frequently the most timeconsuming part of the GIS project is building the data base. 

The steps involved in building an ARC/INFO data base are 

designing the data base, automating the data by entering the 

spatial data and the attribute data in the data base, and 

managing the data base by transforming the coordinate 

system for all map coverages to a common planar coordinate system (fig. 2). 

The first step in designing any data base is determining what data are to be included by identifying the geographic features and their attributes, organizing the data 

layers, and identifying the map coverages to be automated. 

Some of the decisions to be made about the coverages are 

determining the study area boundary, the map coordinate 

system to be used, the data layers (or map coverages) 

required, the features to be included in each coverage, the 

attributes needed for each feature type, and the attribute 

Developing the GIS for Basin Analysis 7 
coding scheme and organization to be used. The coverages 

and their associated feature-attribute tables are the basic 

building blocks of the data base. 

Automation of the data involves getting the spatial 

and attribute data for the map coverages into the data base. 

Spatial data can be captured directly from a map by entering 

the data manually, by digitizing, or by using an electronic 

scanner and putting the data into a computer file. Another 

method involves reformatting existing digital data and 

converting the data into an ARC/INFO format. Map coverages are composed of sets of features where each feature 

has a location defined by coordinates and topological 

"pointers" to other features, as well as attributes defined by 

a set of fields or as items in a feature-attribute table. There 

are a number of important aspects in coverage creation, in 

addition to digitizing coordinates, such as creating feature 

topology , building feature-attribute tables, and connecting 

feature attributes to a corresponding coverage feature. For a 

more detailed account of building coverages for the data 

base, refer to an ARC/INFO user's manual (for example, 

ESRI, 1990). 

After designing and automating the basic coverages 

for the study area, the geologist must ensure that each 

coverage is topologically correct, that the feature-attribute 

tables are present, that the accuracy of all feature locations 

and feature attribute values has been verified, and that a 

system of tics or ground control points exists. Additionally, 

to manage the data base, all geographic features and map 

coverages must be converted into real-world coordinates, 

and the features of each coverage must be spatially referenced against features in associated coverages (see fig. 2). 

For example, when the maps were digitized for the San Juan 

Basin study, the x andy coordinates used for the geographic 

features, tics, and Petroleum Information-Well History 

Control System (PI-WHCS) data (Petroleum Information 

Corp.) were in latitude and longitude coordinates, a geographic reference system-not a two-dimensional (planar) 

coordinate system. Because GIS' s use planar coordinate 

systems to map the Earth's surface, the latitude and longitude coordinates were transformed into planar (UTM) 

projection units. 

Performing the Geographic Analysis 

The ability to perform geographic analysis sets geographic information systems apart from digital mapping 

systems and is where the true value of a GIS becomes 

evident. Analytical tasks that are otherwise extremely time 

consuming, or even impossible, if done manually can be 

performed efficiently by using a GIS. 

Geographic analysis helps the geologist to study 

real-world processes, such as three-dimensional analysis of 

sedimentary basins, by developing and applying models. 

Such models can reveal underlying trends in the geographic 

(geologic) data and thus make new interpretations or concepts possible. A GIS enhances this process by providing 

tools that can be used to combine map coverages in 

meaningful sequences to develop new models. These models may reveal new or previously unidentified relationships 

within and between data sets or coverages, thus increasing 

our understanding of the three-dimensional framework and 

processes within a sedimentary basin. Alternative scenarios 

also can be tested by making minor revisions in the 

analytical method. 

Three types of spatial operations can be performed on 

the coverages for a geographic analysis. The first is the 

generation of buffer zones within a given distance of an 

identified region where the analysis requires interpreting the 

attributes in an area surrounding a specified set of geographic features. A buffer zone generates one or more 

polygons surrounding existing specified geographic features 

identified by the user and creates a new polygon coverage. 

The second type of spatial operation creates new coverages 

by either removing or adding features to a coverage; that is, 

manipulating spatial features by selecting, erasing, and (or) 

adding features. The third type of operation is polygon 

overlay, which lays one or more polygon coverages over 

another and thereby creates new polygon coverages. The 

spatial locations of each set of polygons and their polygon 

attributes are joined to derive new data relations. Joining 

polygons enables the user to perform operations that require 

new polygon combinations; thus, existing coverages can be 

combined to remove, replace, or merge geographic features. 

The following example of an analysis procedure 

illustrates the three types of spatial operations that can be 

performed on the coverages for a basin data base. The 

problem to be analyzed is locating sites favorable for 

productive gas wells in the San Juan Basin. Selection 

criteria for the proposed well sites follow: 

1. Site must be in San Juan County, N. Mex. 

2. Site must be on privately owned lands (not on Federal or 

State lands). 

3. Preferred target formation is the Pictured Cliffs Sandstone (PCSS). 

4. Preferred depth to top of the PCSS formation is between 

3,500 and 4,500 ft. 

5. Preferred thickness of the PCSS formation is between 50 

and 120 ft. 

6. Preferred porosity of PCSS formation is greater than 10 

percent. 

7. Site must be beyond 1,500 ft of existing streams. 

8. Site must be within 2 mi of gas wells currently producing more than 200 million cubic feet of gas per day 

(MCFGD) from the PCSS formation. 

First, new coverages must be created from the existing data base coverages by selecting, erasing, and adding 

features that address the selection criteria needed to solve 

the problem. For example, the following selections would 

8 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
be made: (1) from the digital line graphs (DLG) base-map 

coverage, only San Juan County and all streams in that 

county; (2) from the landownership coverage, only the 

private lands within the county; and (3) from the welllocation coverages, the gas wells producing more than 200 

MCFGD within the county. New coverages also must 

address the Pictured Cliffs Sandstone attributes as follows: 

(1) from the structure-contour map coverage, those polygons covering areas that have depths ranging from 3,500 to 

4,500 ft to the top of the PCSS formation; (2) from the 

isopach map coverage, those polygons covering areas 

where the PCSS formation ranges in thickness from 50 to 

120ft; and (3) from the porosity distribution map coverage, 

those polygons covering areas having porosities greater than 

10 percent. Two buffer-zone coverages must be generated: 

(1) one from the newly created producing-gas-well coverage by identifying the buffer zones within 2 mi of each gas 

well that meets the production criteria and (2) one from the 

new DLG coverage for the existing streams in San Juan 

County by identifying the buffer zones within 1 ,500 ft of 

each stream. 

Additionally, to meet all the selection criteria for the 

proposed favorable well-site locations, all of the above data 

coverages, a minimum of 10, must be combined to identify 

the polygons that meet all 8 criteria. The final coverage will 

include only those polygons that meet the preferred criteria 

for the well-site locations that are considered favorable for 

prospective gas wells in San Juan County. 

The combination of more than 10 data coverages is 

too complex to illustrate here. However, an example of 

generating the buffer zones to identify the gas-producing 

areas within 2 mi of the designated gas wells and the buffer 

zones identifying the areas within 1 ,500 ft of existing 

streams is shown in figure 3A. If all of the other selection 

criteria are met, wells can be drilled within the areas of the 

buffer zones 2 mi around the producing gas wells but not 

within 1 ,500 ft of an existing stream. Figure 3B shows a 

very simple example of performing polygon overlays to 

create a new polygon coverage. In the figure, the landownership polygon coverage is overlain with the polygon 

coverages of the preferred depths to the top of the PCSS 

formation and the preferred porosities of the PCSS formation. The three sets of coverages (landownership, preferred 

depths, and preferred porosities) are combined to create 14 

new polygons. 

Performing geographic analysis in basin studies.-

Each of the data layers or map coverages in the data base 

contains specific information required for the basin analysis. To identify new associations between the data layers, 

geologic information within the GIS must be manipulated. 

Geographic analysis allows a geologist to manipulate the 

data and investigate the relationships between the data 

layers by developing and applying different models or by 

changing the values of the attributes in the selection criteria. 

These models may reveal underlying trends in the geographic and geologic data and thus make new information 

available that will aid in geologic interpretations. 

Presenting the Results 

Results of geographic analysis can be communicated 

by computer-generated maps, reports, or both. A GIS offers 

many options for creating customized maps and reports. 

The maps are best used to visualize and (or) display 

geographic or spatial relations, whereas reports are more 

appropriate for summarizing tabular data and documenting 

any calculated values. 

A GIS FOR THE SAN JUAN BASIN 

GIS technology applied to the San Juan Basin pilot 

study initially was directed to the development and integration of a multivariate spatial data base needed for the basin 

analysis. This technology when applied to sedimentary 

basins is used to establish a three-dimensional perspective 

of the basin's fundamental geologic, stratigraphic, and 

structural framework based on subsurface data. The San 

Juan Basin GIS integrates mapping and data base functions 

that not only allow a geologist to generate various maps but 

also provide a variety of options for analyzing and manipulating geographic information. The GIS, through its ability 

to carry out spatial operations, typically links the different 

data sets (surface and subsurface) by using the geographic 

location as the common key. In this pilot study, subsurface 

geologic data representing geological surfaces and attributes 

were designed as a part of the geographically referenced 

information (fig. 1). Surface data were used for data bases 

pertinent to the project, such as landownership, surficial 

geology, topography, hydrography, and the location and 

status of all oil and gas wells. 

Data bases created for subsurface mapping include 

structure contour, isopach, and facies information for the 

major oil- and gas-producing formations; cross sections and 

fence diagrams; input for paleogeographic reconstructions; 

and composited map products. The PI-WHCS data base 

(Petroleum Information Corp.) is one of the major sources 

of well, depth, and thickness information for identified 

formations within the basin and a variety of data on 

productive reservoirs. 

Among the cartographic data bases investigated for 

surface mapping in the San Juan Basin are (1) the US 

GeoData system from the USGS's National Mapping Program, including Digital Elevation Models (DEM) for terrain 

elevations; (2) Digital Line Graphs (DLG) for planimetric 

information on boundaries, transportation, and hydrography; (3) the U.S. Public Land Survey System; and (4) Land 

Use and Land Cover (LULC) data. Additional data bases 

investigated for surface mapping include surficial geology, 

locations of oil and gas wells, dry holes, well status, and oil 

and gas fields. 

A GIS for the San Juan Basin 9 
Current GIS technology and mapping software being 

used in this project for the three-dimensional analysis of the A 

San Juan Basin include ESRI's ARC/INFO GIS software 

(Environmental Systems Research Institute, Inc., 1987, 

1990) and the Interactive Surface Modeling (ISM) mapping 

software package (Dynamic Graphics, Inc., 1984). Both 

programs run on the USGS PRIME computer system. 

SAN JUAN BASIN, NEW MEXICO AND 

COLORADO-THE PILOT STUDY AREA 

The San Juan Basin, located in northwestern New 

Mexico and southwestern Colorado, was chosen for the GIS 

pilot study for several reasons. First, and foremost, the 

basin contains major economic deposits of natural gas, oil, 

coal, and uranium; thus, it is a prime candidate for a study 

in the applications of GIS techniques to evaluate its energy 

resources for natural resource management. The basin is 

moderately to well explored and has a greater than 80-year 

history of development; more than 26,000 wells have been 

drilled in the area. The abundant well data and the results of 

many studies conducted in this basin by industry, government, and academic geologists using geophysical logs, well 

cuttings, core, and other subsurface data provide a major 

source of information for building the basin data base. The 

San Juan Basin is also one of the selected areas of study for 

the USGS Evolution of Sedimentary Basins Program. This 

program was created in 1985 to provide a mechanism for 

conducting multidisciplinary geological research for 

regional studies on the evolution of ancient and modem 

sedimentary basins (Dean and others, 1990; Ridgley and 

Huffman, 1990). 

Using the San Juan Basin for the pilot study also 

capitalizes on the experience and expertise of the USGS in 

GIS projects that were already underway. These projects 

include ( 1) the development of a new digital map base for 

the basin and improved methods for moving digital data into 

the ARC/INFO GIS system and (2) the implementation of 

the ARC/INFO system and the application of mapping 

software for digital mapping of aquifer systems in the San 

Juan Basin. The work on the San Juan Basin aquifer system 

was conducted as part of the USGS Regional AquiferSystem Analysis Program (Sun, 1986; Welder, 1986). As 

part of a hydrogeology atlas series for the San Juan Basin, 

maps of the following formations have been published to 

date: Dakota Sandstone (Craigg and others, 1989), Gallup 

Sandstone (Kernodle and others, 1989), Morrison Sandstone (Dam and others, 1990), Point Lookout Sandstone 

(Craigg and others, 1990), Cliff House Sandstone (Thorn 

and others, 1990), Kirtland Shale and Fruitland Formation 

(Kernodle and others, 1990), San Jose, Nacimiento, and 

Animas Formations (Levings and others, 1990a), and the 

Menefee Formation (Levings and others, 1990b). 

EXPLANATION 

Gas well -¢- Dry hole 

2-mi buffer zone around well 

Stream and buffer zone within 1,500 ft of stream 

Figure 3A. Intersection of buffer zones within 2 mi of gas 

wells producing from the Pictured Cliffs Formation and 

buffer zones within 1,500 ft of existing streams. 

Regional Geology of the San Juan Basin 

The San Juan Basin occupies the southeastern part of 

the Colorado Plateaus physiographic province. The 14,000-

mi2 Laramide structural basin, slightly elongated north to 

south, is more than 150 mi long and 100 mi wide. It is 

strongly asymmetrical; the axial trace forms an arcuate belt 

paralleling its northern and northeastern boundaries, where 

the deepest part of the basin to the top of the Precambrian is 

in excess of 7,500 ft below sea level (Woodward and 

Callender, 1977, p. 209). Structural relief between the 

uplift and the deepest part of the basin is more than 15,000 

ft (Ridgley, 1989). 

The basin is bounded on the north and northwest by 

the San Juan-La Plata Mountains and the Hogback monocline of the Colorado Plateaus; on the northeast, east, and 

southeast, by the Archuleta-Nacimiento uplifts and the 

Puerco fault zone; on the south, by the Zuni uplift and the 

Chaco slope (a broad structural shelf sloping gently northeastward into the main part of the basin); and on the west 

and southwest, by the Defiance uplift. Structures of the San 

Juan Basin and adjacent uplifts developed primarily during 

the Laramide orogeny (Late Cretaceous and early Tertiary). 

Figure 4 shows the structural elements of the San Juan 

Basin and adjacent areas. 

10 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
B 

32 

.J.J 

5% 

I 

I I 1/ 

! 

I 

5% 

-Landownership 

-Preferred depths to 

top of Pictured Cliffs 

Sandstone, in feet 

-Preferred porosity 

of Pictured Cliffs 

Sandstone, in percent 

-Combined polygon 

coverage 

Figure 38. Topological overlay joining polygons from three coverages to establish the spatial 

relationships among landownership, preferred depths to the top of the Pictured Cliffs Formation, 

and preferred porosities of the Pictured Cliffs Formation. Three sets of coverages are combined to 

create 14 new polygons. 

The San Juan structural basin contains a thick 

sequence of sedimentary rocks ranging in age from Cambrian through Tertiary. The maximum thickness is about 

15,000 ft in the northern part of the basin, and in this area 

the sequence is composed mostly of Pennsylvanian through 

Tertiary age rocks. The older sedimentary rocks crop out 

around the basin margins and are successively overlain by 

younger rocks toward the northern part of the basin. 

Stratigraphy and Petroleum Geology 

This report is not intended to be a complete and 

detailed geologic discussion of the San Juan Basin. The 

reader is referred to other publications for details on the 

tectonic and stratigraphic framework for the basin. 

This pilot study applies GIS techniques to those 

formations in the Upper Cretaceous that are recognized as 

San Juan Basin, New Mexico and Colorado-The Pilot Study Area 11 
38° 

3T 

36° 

35° 

110° 

eCtl 

~ Q. 

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c 

Q) 

E 

:J 

c 

0 

Moab e 

109° 

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0 La Sal 

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l 

l 

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Uncompaghre 

uplift 

Abajo 

dome 

Paradox fold and fault belt 

Blanding 

basin 

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platform ~,<:-0 

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San Juan Basin 

Black Mesa 

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50 MILES 

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Chaco slope 

Zuni uplift 

Gunnison 

uplift 

San Juan 

sag 

Sawatch 

uplift 

106° 

Rio Grande 

trough 

Sandia 

uplift 

Alamosa • 

Figure 4. Structural elements of the San Juan Basin and adjacent areas. Compiled by Finch and others (1989); modified 

from Kelley and Clinton (1960), Grose (1972), and Woodward (1974). 

12 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
the major oil and gas producers in the San Juan Basin. The 

four formations discussed in this report are the Dakota, 

Gallup, Point Lookout, and Pictured Cliffs Sandstones. The 

Gallup represents the only major oil producer; the remaining three formations are primarily natural gas producers. 

The San Juan Basin stratigraphic correlation chart is shown 

in figure 5. 

The Cretaceous stratigraphy of northwestern New 

Mexico and southwestern Colorado represents numerous 

transgressions and regressions depositing intertonguing 

sequences of shale, sandstone, and lesser amounts of 

limestone and coal in marine, nearshore marine, coastalbarrier, deltaic, and fluvial environments. The interbedded 

marine and continental deposits range in thickness from 

4,000 to more than 6,000 ft. The total sediment thickness 

for the Cretaceous is relatively uniform despite the abrupt 

transgressive and regressive facies changes across the basin 

and the recognized unconformity within the Gallup 

sequence. 

Due to limited exposures, little is known about the 

Early Cretaceous in the San Juan Basin. The Burro Canyon 

Formation in the northern and northeastern parts of the 

basin is considered by most geologists to be Early Cretaceous in age (Saucier, 1974; Aubrey, 1988). Tschudy and 

others ( 1984, p. 1) report that the upper parts of the Cedar 

Mountain and Burro Canyon Formations yield palynomorphs that are palynologically of Early Cretaceous age. 

Upper Cretaceous rocks of continental origin are the 

lower part of the Dakota Sandstone, most of the Crevasse 

Canyon Formation, the Menefee Formation, the Fruitland 

Formation, and the Kirtland Shale. The major transgressive 

and regressive Upper Cretaceous marine sandstones in the 

basin are the Gallup Sandstone; Tocito Sandstone Lentil of 

the Mancos Shale; and Point Lookout, Cliff House, and 

Pictured Cliffs Sandstones (Condon and Huffman, 1989). 

These sandstones are important reservoirs for oil and gas 

resources. The stratigraphy of the four Upper Cretaceous 

formations included in this GIS pilot study is discussed in 

the following sections. 

Dakota Sandstone 

The Dakota Sandstone, deposited on a regional erosion surface, rests unconformably on sandstone and shale of 

the Morrison (Upper Jurassic) or Burro Canyon (Lower 

Cretaceous) Formations (fig. 5). The upper contact of the 

Dakota is conformable with the Graneros Member of the 

Mancos Shale (Upper Cretaceous), and intertonguing of 

these two units is common near the contact. The strata 

represent a transition from continental alluvial-plain deposition in the lower part of the formation to marine coastal 

deposition in the upper part. The stratigraphy of the Dakota 

Sandstone is complex and consists of four major members-

(in ascending order) the Oak Canyon Member, Cubero 

Tongue, Paguate Tongue, and Twowells Tongue (Landis 

and others, 1973; Owen, 1973). The two upper sandstone 

members intertongue with the Graneros Member of the 

Mancos Shale. 

The Dakota Sandstone consists of fine-grained 

quartzose sandstones, carbonaceous shales, and occasional 

conglomerates and coals generally in the basal section 

(Deischl, 1973). Because of correlation problems concerning the location of the top and bottom of the Dakota 

Sandstone in many areas of the basin, the thickness of the 

Dakota is reported as ranging from a few tens of feet to 

about 500ft. Stone and others (1983) report that 200 to 300 

ft probably is a more common range. Depth to the top of the 

Dakota Sandstone ranges from 0 ft in areas of outcrop to 

about 8,500 ft in the northeastern part of the study area. 

Data used in this study to compute the depths to the 

top of the Dakota Sandstone were taken from the PI-WHCS 

data base (Petroleum Information Corp.). Supplemental 

information was taken from existing water-well records in 

the USGS national Water-Data Storage and Retrieval System (WATSTORE) data base (Craigg and others, 1989) and 

from outcrop elevations. 

The Dakota Sandstone produces both gas and oil in 

the San Juan Basin. Most of the gas produced from the 

Dakota is from the Basin Dakota field, which was discovered in 1947 and covers an area of approximately 1,500 

mi2 • Dakota production is not continuous, however, across 

the productive trend due both to lack of continuity of the 

reservoir sandstones and to areas of little or no porosity. 

The trapping mechanism for the gas accumulation is considered to be stratigraphic and hydrodynamic rather than 

structural. Oil production from the Dakota Sandstone 

occurs toward the more shallow margins of the basin and is 

mostly structurally controlled, with some stratigraphic production. No satisfactory explanation of this juxtaposition of 

oil and gas has yet been given (Fassett and others, 1978). 

Total cumulative production from seven Dakota gas 

fields in New Mexico, as of December 31, 1989, was more 

than 4.4 trillion cubic feet (TCF) and 37 million barrels of 

oil. The total cumulative production from 16 oil pools and 

undesignated wells, as of December 31 , 1989, was more 

than 20 million barrels of oil and more than 13 billion cubic 

feet (BCF) of casinghead gas (New Mexico Oil and Gas 

Engineering Committee, 1989). 

Gallup Sandstone 

The Gallup Sandstone is the first major regressive 

sequence in the San Juan Basin and lies approximately 400 

to 700ft above the Dakota. The New Mexico Oil Conservation Commission defines the Gallup producing interval as 

that stratigraphic interval between the top of the Greenhorn 

Limestone Member of the Mancos Shale and the base of the 

overlying Mesaverde Group (Fassett and others, 1983). 

San Juan Basin, New Mexico and Colorado-The Pilot Study Area 13 
SOUTH 

ZUNI UPLIFT OUTCROPS SAN JUAN BASIN SUBSURFACE 

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= MIDDLE 

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'v~ ~ .!r _______ H~E~~NI:!_O _!IE~T~I:!! ~ED_~ _ _ _ 

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' 

GALLUP SS 

--- SEMILLA SS MBR (SE) 

TOCITO SS LENTIL / EL VADO SS MBR (NEJ $ 

~~-~ 

~ l Illfll.Jll 11 OPE MBA 15- 0 m 

BRIDGE CREEK GREENH RN LS M~R 12-20 m 

GRANEROS MBA 18-90 m 

r 

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-~ WESTWATER CANYON MBR 

RECAPTURE MBR 

COW SPRINGS SS 0 7 5 m 

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-

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+---LOW_ER ?~r11.J,...l).r 11.J,...LJ.~1.J..J.).r 1 1..J...L.Lr ll..J...L.L! 1 1.J-L:I:r r ~rr ~l -1+.¥r J...L..lr..J..J,..I.r l..J..J,..I.l J.J..J.r )..!.J.l ~~o~,L..J..J.~ pt~1 JB'R,..I...J.J..\u,l.j..J,l IDJJ1W~!:.::k;:? ~ W~WlNGA~TiE SS~(Nr=t-i, -

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= = SONSELA SS BED = = PETRIFIED FOREST M6R 150 _500 m 

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1

·? 

LEONARDIAN J--.,Y~E~SO~F~M~O 7.::12~0~m~------___;::..:::::::A~-u_f LIJ llllJJ LIJUJ LIJ lll l IJ 11 

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~:::::::::::~~~~~~:~==-~M~O~N~IT~O~R~B~U~T=T~E~M BR~-------T--------------------7 

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en _MERAMECIAN 

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::E !KINDERHOOK. 

::. UPPER 

:=: t-----MI D_D_L_E--t 

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SILURIAN 

ORDOVICIAN 

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6 0-910 m GROUP ( NWl _.:,.P:..:.A:.:.RA:..::D::.O::.X:..:....:.F..:.:M:....:.:.( N;:.:W.:.:l~!"' 

r-- :--r- ...- PINKERTON TRAIL FM ~ 

fl 1 l 

Jl]]JJ ]JlliD 

MOLAS FM 0 30 m -

IJLIJllJll fl I I l :- L ADVILLE LS 0 50 m 

J lli.JlUl[ J[ OJRAY LS (NWl 0-25 m 

ELBERT FM 0-100 m 

r 11 r 1 J 

PER MBR 

McCRA• ~KEN SS M8R 

Figure 5. San juan Basin stratigraphic correlation chart. Compiled by Molenaar (1977a,b); revised by Molenaar (1989). 

LS, limestone; SS, sandstone; SH, shale; II II, disconformity. 

14 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
(This definition includes other named stratigraphic units. 1

) 

The Gallup producing interval can be divided into two 

stratigraphic parts in the San Juan Basin. The first or lower 

stratigraphic part, containing a series of marine and fluvial 

sandstones and shales, represents a major regression of the 

sea across the basin toward the northeast and has been 

called the regressive or true Gallup Sandstone. The uppermost section of this regressive unit has been named the 

Torrivio Sandstone Member of the Gallup Sandstone by 

Molenaar (1973). 

The second or upper stratigraphic interval commonly 

contains a series of sandstone lenses at its base, which have 

been assigned to several different formations. These elongate bodies occur above and seaward from the regressive 

Gallup in a band of discontinuous, northwest-trending 

sandstone lenses in the northwestern part of the basin and lie 

northeast of the edge of the regressive Gallup unit. These 

upper Gallup sandstones have been referred to as the 

transgressive Gallup and basal Niobrara transgressive sandstone (Molenaar, 1973, 1974) and as the Tocito Sandstone 

Lentil in the Mancos, as used by Reeside ( 1924), Lamb 

(1968), Molenaar (1977a), and Fassett and Jentgen (1983). 

As shown on Molenaar's 1989 San Juan Basin stratigraphic 

correlation chart (fig. 5), an unconformity separates the 

regressive Gallup unit from the transgressive Gallup in the 

northern part of the basin (Molenaar, 1989). 

The transgressive Gallup sandstones (Tocito Sandstone Lentil) are the major oil-producing rocks of the San 

Juan Basin. Most of the 33 oil fields in the basin are 

stratigraphic traps consisting of sandstone lenses enclosed 

by the marine Mancos Shale (Fassett and others, 1978; 

Fassett, 1983). A few of the fields also may be structurally 

controlled. The origin of these long, narrow, northwesttrending sandstone lenses, commonly less than 50ft thick, 

is still poorly understood, but some may be associated with 

topography on the underlying Niobrara unconformity that 

represents Niobrara time (McCubbin, 1969; Huffman, 

1989). Oil has been produced from the transgressive Gallup 

interval at depths ranging from about 400 to 7, 700 ft. The 

northwestern trend of sandstone lenses (Tocito Sandstone 

Lentil) produces from about 1 ,500-ft depth on the Four 

Comers Platform and from about 4,500- to 5,500-ft depth to 

the southeast in the south-central part of the basin. The 

largest oil fields in the transgressive Gallup are the Horseshoe and the Lower Bisti fields, which had a cumulative 

production of more than 38.5 million barrels and 37 million 

barrels, respectively, as of December 31, 1989. 

The regressive Gallup in the southern part of the basin 

produces oil from about 1 ,500-ft depth at the Hospah field, 

1 This definition was applied by the New Mexico Oil Conservation 

Commission for convenience in describing an oil and gas productive 

interval. The defmition is used in this report and includes the identification 

of the Gallup Sandstone tops in the PI-WHCS well data files (Petroleum 

Information Corp.). 

which is the only known field producing from the regressive 

Gallup. The field appears to be structurally controlled and 

produces from the "Hospah Sandstone," which is equivalent 

to the Torrivio Sandstone Member of the Gallup (Molenaar, 

1973). It has produced nearly 20 million barrels of oil, as of 

December 31, 1989. 

The Gallup producing interval in northwestern New 

Mexico, as of 1989, had a total cumulative production of 

more than 170 million barrels of oil, 520 thousand barrels of 

condensate, 88 BCF of dry gas, and 350 BCF of casinghead 

gas (New Mexico Oil and Gas Engineering Committee, 

1989). 

Data used in this study to compute the depths to the 

top of the Gallup were taken from the PI-WHCS well data 

file (Petroleum Information Corp.). Because most of the 

transgressive Gallup or Tocito Sandstone Lentil tops are 

identified in this well data file as Gallup, the productive 

Gallup interval in this study includes both the regressive and 

transgressive Gallup sandstones. Supplemental information 

taken from the USGS W A TSTORE data base was restricted 

to the regressive Gallup Sandstone, as used by Kernodle 

and others (1989). 

Point Lookout Sandstone 

The Upper Cretaceous Mesaverde Group is the major 

gas-producing interval in the San Juan Basin. It consists of 

three formations-(in ascending order) the regressive 

marine Point Lookout Sandstone, the nonmarine Menefee 

Formation (consisting of sandstone, shale, and coal beds), 

and the transgressive marine Cliff House Sandstone (Peterson and others, 1965; Huffman, 1989). 

The Point Lookout Sandstone, probably the largest 

gas-producing formation in the Mesaverde Group, was 

chosen as one of the four petroleum-productive formations 

used in this study. It is the most extensive regressive 

coastal-barrier sandstone in the San Juan Basin and represents a regional regression throughout the area of the 

Western Interior. The Point Lookout Sandstone consists of 

very fine to medium-grained, light- to medium-gray, wellcemented sandstones having laminations of light- to darkgray carbonaceous shale and ranges in thickness from 140 

to 250 ft (Peterson and others, 1965; Pritchard, 1973). It 

merges with the transgressive Cliff House Sandstone on the 

northern side of the basin (Molenaar, 1977a). 

Because most of the gas production from wells 

completed in the Mesaverde section is comingled, knowing 

exactly how much gas has been produced from the Point 

Lookout, Menefee, or Cliff House units individually is 

impossible. However, the Point Lookout Sandstone is 

thought to be the largest gas producer as it is thicker and has 

greater continuity than the Cliff House Sandstone. A small 

amount of dry nonassociated gas has been produced from 

thin lenticular channel sandstone bodies and thin coal beds 

of the Menefee. The total production from all Mesaverde 

San Juan Basin, New Mexico and Colorado-The Pilot Study Area 15 
Group pools, as of December 31, 1989, was more than 7.2 

TCF of gas and nearly 32 million barrels of oil. 

The trapping mechanism for Mesaverde gas is not 

fully understood and is as much of an enigma as that of the 

Dakota Sandstone gas; that is, huge reserves of natural gas 

in the deeper central part of the basin have no apparent seal 

to prevent the gas from migrating updip and escaping. It is 

believed that swelling clays or hydrodynamic pressures may 

be sufficient to contain the gas within the traps, but such an 

explanation has its problems, and more studies are needed. 

Data used in this study to compute the depths to the 

top of the Point Lookout Sandstone were taken from the 

PI-WHCS well data file (Petroleum Information Corp.). In 

some cases, the tops for the Mesaverde Group in the 

well-data file were not differentiated as to Point Lookout, 

Menefee, or Cliff House but reported only as the Mesaverde 

Group. These undifferentiated wells were not included in 

the data base coverages for the structural and isopach maps 

for the Point Lookout Sandstone. Supplemental information 

from the USGS W ATSTORE data base also was used, 

when available. 

Pictured Cliffs Sandstone 

The Pictured Cliffs Sandstone, a regressive coastalbarrier sandstone, is the youngest marine rock unit in the 

San Juan Basin and represents the final regression of the 

Late Cretaceous Western Interior sea from the area. The 

Pictured Cliffs Sandstone, like the Point Lookout Sandstone, was deposited during regression of the Cretaceous 

sea (Fassett, 1977). The configuration of the Pictured Cliffs 

Sandstone is remarkably similar to that of the Point Lookout 

Sandstone; that is, both units rise to the northeast in a series 

of steplike stillstands, but the younger Pictured Cliffs 

extends farther to the northeast. 

The Pictured Cliffs Sandstone occurs above the 

marine Lewis Shale and below a prominent basal coal 

interval of the Fruitland Formation. Stillstands or brief 

reversals in the regression of the seas to the northeast 

produced the thick Pictured Cliffs shoreline sandstones, 

which are locally as much as 400ft thick (Molenaar, 1977a) 

and have been the most gas productive. The average 

thickness of these sandstones, however, is much less, but 

exact thickness is difficult to measure because of intertonguing with the underlying Lewis Shale. Pay thicknesses 

range from 5 to 150 ft but are typically less than 40 ft. 

The Pictured Cliffs Sandstone is made up of very fine 

to fine-grained, fairly well sorted quartz grains and a small 

amount of darker grains including glauconite, mica, and 

carbonaceous shale, cemented by authigenic clay. Gas is 

produced from stratigraphic traps in the elongate northwesttrending beach or nearshore sandstone beds enclosed in 

shale or coal at the top of the unit. The producing area for 

the Pictured Cliffs trends northwest across the central part 

of the San Juan basin, is about 80 mi long by 20 mi wide, 

and covers nearly 1,600 mi2 (Brown, 1973). 

Total cumulative production through 1989 from pools 

in the Pictured Cliffs Sandstone was about 716,000 barrels 

of oil, more than 3 TCF of gas, and more than 500,000 

barrels of condensate. 

Data used in this study to compute the depths to the 

top of the Pictured Cliffs Sandstone were taken from the 

PI-WHCS well data file (Petroleum Information Corp.). 

Supplemental information from the USGS W ATSTORE 

data base also was used, when available. 

MAP COVERAGES FOR THE SAN JUAN BASIN 

Each of the digitized map coverages or data layers 

that are in the San Juan Basin data base contains specific 

information required for the basin analysis. Separate coverages must be created for each data layer that may be 

needed in the project. To identify new associations between 

the map coverages, or to visualize combinations of data 

layers, map overlays, or composite map products, the 

geographic and geologic information must be manipulated. 

Geographic analysis techniques allow a geologist to visualize, manipulate, and investigate the relationships among the 

data layers by developing and applying different models. 

The models may reveal underlying trends in the related 

surface and subsurface data and thus provide new information or insight that will aid in the geologic interpretation. 

This section briefly describes some of the specific 

surface and subsurface digital map and data coverages that 

were developed for the San Juan Basin data base. In 

addition, the section discusses some examples of composite 

map coverages that were generated by using the GIS for the 

automated geographic analysis of the basin data base. 

Surface Map Coverages 

Area Map 

A simplified map coverage, shown in figure 6, of the 

Utah, Colorado, New Mexico, and Arizona State boundaries was derived from scanned USGS base maps and from 

digitized map boundaries (Craigg and others, 1989). Digitized outlines are shown on figure 6 for the San Juan Basin 

boundary, the study area boundary, the Colorado Plateaus 

boundary, and the State boundaries. 

Base Map 

Figure 7 is a simplified computer graphic taken from 

the more detailed base map coverage of the San Juan Basin 

study area showing State and county lines, some cities, and 

latitude and longitude. Information was derived from DLG 

16 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
r -----, 1020 

I I 109' _______ ---\ 

40, !-UTAH - -l-,t~ COLORADO l 

I I I 

I Colorado I 1\ 

Plateau San Juan 

3rl"'"---:---------

l 

("-J Study area 

ARIZONA 

.......__ ____ II_ 

structural basin I 

I -----r 

NEW MEXICO 

r---

0 

I 

I 

\ 

I 

I 

l 

I 

I 

___ j 

200 MILES 

0 200 KILOMETERS 

Figure 6. Map coverage of the Four Corners area showing. the loca~ion of the Sa~ 

juan structural basin and the study area. The study area 1s approx1mately 150 m1 

long by 100 mi wide. 

format, scale 1:100,000. The base map was clipped2 to the 

study area boundary as shown. 

When certain map features appear in more than one 

coverage, such as the study area boundary or base map data, 

a template coverage is made with all these features included 

on it. New map coverages can be created more rapidly by 

using this template. New features specific to each coverage 

are then added. A template coverage of the study area 

boundary combined with a simplified base map was used 

repeatedly in this study in combination with many of the 

following map coverages. 

2

Clipping is the process of extracting data from a coverage that 

resides entirely within the boundary of features in another coverage (called 

the clip coverage). 

Landownership Map 

A digital map was generated showing landownership 

in the San Juan Basin, principally in northwestern New 

Mexico, covering private, Indian, Federal, and State lands. 

The landownership polygon coverage shown in figure 8 was 

derived from data in MOSS (Mapping Overlay and Statistical System) format provided by the Bureau of Land 

Management. Landownership maps, when combined with 

producing-well data and oil and gas field information, can 

pinpoint the occurrence of petroleum resources on private, 

Federal, State, or Indian lands. 

Surficial Geology Maps 

Map coverages were generated showing the surficial 

geology of the San Juan Basin, with each of the major 

Map Coverages for the San Juan Basin 17 
Durango 1 

( Pagosa Springs 

~L_O~~~- -

- - NEW MEXICO r36° 

l Shiprock .I 

I 0 Farmington I ~~~ I 

~ ~ I ~~~ IZ L-------

Chaco Culture National l 

Historical Park Cuba 

-------, 

I 

I Window Rock Crownpoint \ 

I I 

___I .... -~ \ 

0 50 MILES 

0 50 KILOMETERS 

Figure 7. Computer graphic of the San juan Basin study 

area taken from the more detailed base map coverage for 

the San juan Basin illustrating a highly simplified base 

map clipped to the study area boundaries. Political 

boundaries are derived from data in digital line graph 

format. 

formations identified and in color. The GIS allows the user 

to select from a list of 43 identified geologic units that were 

digitized from geologic map sources (Dane and Bachman, 

1965; Wilson and others, 1969; Tweto, 1979; Hintze, 1980) 

at a scale of 1:500,000 and are in the San Juan Basin data 

base. Composite map coverages of the surficial geology can 

be generated by selecting various geologic units or groupings (categories) of geologic units to be identified on the 

map (limitations are set by ARC/INFO on the total number 

of units to be displayed at one time). For example, by using 

geographic analysis techniques, one such composite surficial geology map was generated with emphasis on the 

maximum extent for the Dakota Sandstone within the study 

area. Figure 9 shows the composite geology map identifying the following 10 geologic categories: 

l. Surface deposits (includes alluvium, terrace deposits, 

dune sand, valley-fill, glacial, bolson, and other surface deposits). 

2. Paleocene and younger rocks (includes the Chuska, 

San Jose, Nacimiento, and Ojo Alamo Formations). 

3. Igneous rocks (includes Tertiary extrusive and intrusive 

rocks, volcanic rocks, basalts, and other intrusive 

rocks). 

4. Kirtland and Fruitland Formations. 

5. Pictured Cliffs Sandstone. 

6. Shale formations (includes Mancos Shale, Lewis 

Shale, and other Cretaceous shale members). 

7. Mesaverde Group (includes Mesaverde Group undifferentiated, La Ventana Tongue of Cliff House Sandstone, Cliff House Sandstone, Hosta Tongue of Point 

Lookout Sandstone, and the Point Lookout Sandstone). 

8. Gallup Sandstone. 

9. Dakota Sandstone. 

10. Jurassic and older rocks (includes the Morrison Formation, San Rafael Group, and Triassic age rocks). 

Outcrop Maps 

Map coverages were generated showing selected 

outcrops for oil- and gas-bearing formations within the San 

Juan Basin study area. The outcrop coverages are derived 

from the digitized surficial geology coverages. The GIS 

allows a geologist to select any one or more of the geologic 

units from the list of identified geologic units in the data 

base for display on an outcrop map coverage. For example, 

figure 10 shows one composite outcrop map generated for 

this study that includes the following seven geologic units: 

the Pictured Cliffs Sandstone, the Cliff House Sandstone, 

the undifferentiated Mesaverde Group, the Menefee Formation, the Point Lookout Sandstone, the Gallup Sandstone, 

and the Dakota Sandstone. 

Well-Location Maps 

A series of map coverages was prepared showing the 

well locations in the San Juan Basin by using the location 

coordinates and other information taken from the PI-WHCS 

data base (Petroleum Information Corp.). These map files, 

built in INFO, were created by using data from PI-WHCS 

cards 10002, 10010, 103, and 104 containing the following 

items: a unique well number, latitude and longitude in 

decimal degrees, the producing formation and zone codes, 

general well classification (56 well categories), specific 

final well status, operator, commercial well elevation, 

elevation reference datum, and log total depth or driller's 

total depth for the well. Point coverages were generated by 

selecting a formation and all the wells by well class or status 

that either produced from or penetrated that formation (that 

is, oil, gas, or nonproductive (dry hole) wells). Then a 

series of map coverages showing the location of all oil, gas, 

and nonproductive wells was generated for each of the 

formations. Figure 11 shows a composite computergenerated map with the point coverages for all wells that 

-either produce from or penetrate the Dakota Sandstone, for 

the Dakota Sandstone outcrops, and for the Dakota Sandstone subcrop extent. Well coverages, organized by 

18 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
EXPLANATION 

D Unavailable 

D Private 

D Indian 

D Federal 

• State 

D Water 

Figure 8. Map coverage display of landownership in the San Juan Basin study area, showing 

private, Indian, Federal, and State lands. The landownership polygon coverage was derived 

from data provided by the Bureau of Land Management. 

formation and well status, can be combined with any other 

associated map coverages, such as structure or isopach 

contours for each of the formations, to create additional 

composite maps. 

Subsurface Map Coverages 

Stratigraphic Section 

A time-stratigraphic correlation chart (fig. 5) was 

digitized and generated to provide a stratigraphic section 

and nomenclature chart in the data base for the San Juan 

Basin. The features for the stratigraphic section were 

digitized from published sources (Molenaar, 1977a,b, 

1989). The stratigraphic section can be manipulated, 

revised, and updated, just as the other digitized coverages in 

the data base can. 

Structural Maps 

A series of structural maps, such as those shown for 

the Dakota Sandstone in figures 12 and 13, was generated 

for each of the producing formations by using depth to tops 

of formations as taken from the PI-WHCS well data file 

(Petroleum Information Corp.). Locations for all well data 

points and the calculated depths to the tops of the formations were stored in the data base. All of the structure 

contours in this study represent the depths to the top of the 

formations corrected to sea level. Figure 12 shows a 

structure contour map for the top of the Dakota Sandstone 

within the Dakota Sandstone subcrop extent. Figure 13 

shows composite map coverage for the Dakota Sandstone, 

including productive wells, structure contours for the top of 

the Dakota, the Dakota Sandstone outcrops within the study 

area, and the Dakota Sandstone subcrop extent. 

Map Coverages for the San Juan Basin 19 
EXPLANATION 

• Paleocene and younger 

D Kirtland/Fruitland Formations 

D Cretaceous shales 

D Mesaverde Group 

D Surface deposits 

D Pictured Cliffs Sandstone 

• Gallup Sandstone 

D Igneous rocks 

Dakota Sandstone 

• Jurassic and older 

Figure 9. Map coverage showing one combination of identified geologic units of the surficial geology in the 

San juan Basin study area. This map is based on 43 detailed geologic-unit codes stored as attributes for the 

digital data. 

Isopach Maps 

A series of isopach maps, such as the one shown in 

figure 14 for the Pictured Cliffs Sandstone, was generated 

for each of the producing formations by using thickness data 

taken from the PI-WHCS well data files (Petroleum Information Corp.). Locations for all well data points and 

thickness measurements for the producing formations were 

stored in the data base. Thickness data represent the 

calculated differences between depths to the top of a 

formation and to the top of the underlying formation in most 

cases. 

All of the digitized structure and isopach contour 

maps for each of the producing formations were created for 

the basin data base by using the Interactive Surface Modeling (ISM) mapping software program. ISM mapping 

techniques were substituted for ARC/INFO's mapping software program, TIN (Triangulated Irregular Network; 

appendix B). The file of well data locations (point data) and 

depths to formation tops and thickness data was used as 

input data for the ISM mapping software package. The ISM 

mapping program calculates a grid from the scattered well 

data from which can be plotted base maps, contour (structure and isopach) maps, cross sections, fence diagrams, and 

perspective views or block diagrams. The structural and 

isopach line data are saved in ASCII format in ISM and 

imported back to the ARC/INFO system where a line 

coverage is generated. For a detailed accounting of the use 

of ISM mapping software, refer to "ISM Interactive Surface 

Modeling User's Guide" (Dynamic Graphics, 1984). 

Composite structural or isopach maps showing associated map coverages can be generated automatically by 

using the GIS. For example, to produce a composite 

structural map for the Pictured Cliffs Sandstone, ( 1) the 

study area boundaries, (2) the outcrops and subcrops 

recording the extent of the Pictured Cliffs Sandstone, and 

20 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
• • 

D 

D 

D 

D 

EXPLANATION 

Pictured Cliffs Sandstone 

Cliff House Sandstone 

Undifferentiated Mesaverde 

Group 

Menefee Formation 

Point Lookout Sandstone 

Gallup Sandstone 

Dakota Sandstone 

Figure 10. Map coverage showing selected outcrops of some of the Cretaceous oil- and gas-bearing formations 

within the San juan Basin study area. 

(3) the structure contour map using the depths to the top of 

the Pictured Cliffs are combined. Then all coverages for the 

oil and gas wells producing from the formation and for the 

nonproductive (dry hole) wells that penetrate this formation 

are added. To produce a similar composite map by using an 

isopach contour coverage, the same sequence of selections 

is repeated, but coverage for the structure contour map is 

replaced with coverage for the isopach contour map. 

Figure 15 shows a composite map of the Pictured 

Cliffs Sandstone combining the coverages for the outcrops 

and subcrops, the structure contour map, and the locations 

of the 13 oil and 5,047 gas wells producing from the 

formation. This composite structural map shows the spatial 

relationships of the productive trends for the oil and gas 

wells within the Pictured Cliffs Sandstone relative to the 

structural configuration of the formation within the basin. 

The nonproductive wells (dry holes) penetrating the Pictured Cliffs were omitted from figure 15 because there are 

nearly 10,000 and their depiction would completely clutter 

the map at this scale. Figure 16 shows a composite map of 

the Pictured Cliffs Sandstone combining the isopach contour coverage in place of the structure contour coverage 

with the same associated map coverages as shown in figure 

15. This composite map shows the spatial relationships for 

the productive trends for the oil and gas wells within the 

formation relative to the thickness configuration of the 

producing sandstones. The nonproductive well coverage 

was omitted from figure 16 also. 

These composite map coverages may reveal new 

spatial data patterns or previously unidentified spatial relationships that can be recognized by a geologist as pertinent 

to new interpretations for the geological data. The San Juan 

Basin data base contains 21 point coverages that map the 

location of oil, gas, and nonproductive wells by the formations that they produce from or, in the case of dry holes, by 

the formations that they penetrate (table 1). Figure 17 shows 

Map Coverages for the San juan Basin 21 
·~ . • • _.·II:. ,:..· :' .... :· , .. : 

EXPLANATION 

Dakota Sandstone outcrop 

Producing gas wells (3, 168) 

Producing oil wells (443) 

D Dry holes (3, 116) 

Dakota Sandstone 

subcrop extent 

Figure 11. Composite computer-generated map coverage showing (1) the locations of all oil, gas, and 

nonproductive (dry hole) wells that either produce from or penetrate the Dakota Sandstone, (2) Dakota 

Sandstone outcrops, and (3) the Dakota Sandstone subcrop extent. 

Table 1. Map (point) coverages for locations of oil, gas, 

and nonproductive wells (dry holes) listed by formation in 

the San Juan Basin GIS data base 

Number of wells 

Nonproductive 

Formations (older to younger) Oil Gas (dry holes) 1 

Dakota Sandstone ................ 443 3,168 3,116 

Gallup Sandstone ................ 2,554 250 5,430 

Undifferentiated Mesaverde Group. 63 3,583 2,633 

Menefee Member of the Mesaverde 

Group ........................ 41 56 6,047 

Cliff House Member of the 

Mesaverde Group ............. 63 109 7,256 

Point Lookout Member of the 

Mesaverde Group ............. 17 276 9,837 

Pictured Cliffs Sandstone ......... 13 5,047 9,907 

1 The nonproductive wells (dry holes) either reach total depth (TD) 

within the respective formation or penetrate the formation to reach TD in 

an underlying formation. 

an example of the composite map coverage for the oil and 

gas wells producing from the Pictured Cliffs Sandstone and 

from the productive interval in the transgressive Gallup 

Sandstone. The spatial relationships for the producing 

trends within the two formations are strikingly different and 

reflect ( 1) the timing of the geologic conditions controlling 

the location of shorelines and subsequent reservoir occurrences and (2) the juxtaposition of the older oil-producing 

trend in the Gallup Sandstone and the younger gasproducing trend of the Pictured Cliffs. The San Juan Basin 

data base lists 13 oil wells and 5,047 gas wells producing 

from the Pictured Cliffs Sandstone and 2,554 oil wells and 

250 gas wells producing from the Gallup Sandstone. There 

are more than 5,430 non producing wells penetrating the 

Gallup Sandstone, and nearly 10,000 nonproducing wells 

penetrating the Pictured Cliffs Sandstone. 

22 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
I I 

11 1 I I 1 ',, 

I I I, 

I 

I / / 

I 

/I 

'I, 1,, 

',, ,,,, 

EXPLANATION 

-6ooo- Structure contours at 

500-ft intervals representing the top of the 

Dakota Sandstone 

relative to sea level 

--- Dakota Sandstone 

subcrop extent 

Figure 12. Map coverage showing structure contours for the top of the Dakota Sandstone within the Dakota 

Sandstone subcrop extent. 

PERFORMING A GEOGRAPHIC ANALYSIS IN 

THE SAN JUAN BASIN 

San Juan Basin Data Base 

The current San Juan Basin data base includes all of 

the mapped data layers or coverages discussed in this report 

and all of the accompanying feature-attribute tables, lookup 

tables, and annotation coverages. It requires approximately 

30,000 physical records of storage on a PRIME 50 series 

minicomputer, located in Reston, Va. This coverage does 

not include the PI-WHCS well-data file (Petroleum Information Corp.) for more than 24,000 wells in the San Juan 

Basin. 

Several teaching tools were prepared as a part of this 

project to demonstrate some of the features of a GIS using 

ARC/INFO and the potential for using GIS techniques in 

the analysis of sedimentary basins. Information from the 

San Juan Basin data base was used for the demonstrated 

applications. The first tool, the San Juan Basin Demonstration System, runs on a PRIME 50 series minicomputer and 

is available on magnetic tape. The San Juan Basin Demonstration System requires approximately 15,000 physical 

records, or 30,720,000 bytes of storage (Person, 1989). The 

second teaching tool is a videocassette demonstrating the 

applications of geographic information systems techniques 

to basin characterization by using the San Juan Basin as a 

case study. The techniques demonstrated include the 

ARC/INFO software system and the ISM automated mapping software package, as well as well information taken 

from the PI-WHCS data base (Petroleum Information 

Corp.). The video tape demonstration is designed for the 

geologist or earth scientist unfamiliar with GIS technology, 

who is interested in adapting new computer techniques to 

analyzing spatial data used in sedimentary basin analysis or 

for petroleum exploration studies (Miller and others, 

1990a,b). 

Performing a Geographic Analysis in the San Juan Basin 23 
EXPLANATION 

Producing gas wells (3,168) 

• Producing oil wells (443) 

• Dakota Sandstone outcrop 

Dakota Sandstone 

subcrop extent 

-6ooo- Structure contours at 500-ft 

intervals representing the top 

of the Dakota Sandstone 

relative to sea level 

Figure 13. Composite map coverage for the Dakota Sandstone, including oil- and gas-producing wells, 

structure contours for the top of the Dakota, Dakota Sandstone outcrops in the San juan Basin study area, and 

Dakota Sandstone subcrop extent. 

Using the GIS for San Juan Basin Analysis 

The following two scenarios taken from the San Juan 

Basin pilot study illustrate how a geologist can use the 

GIS' s ability to interpret and display geographic information by generating geographic (geologic) models and performing geographic analysis. Addressing these geologic 

problems by using composite map coverages is best shown 

in an automated on screen display using the computer. 

However, the reader will need to visualize these procedures 

through the following descriptions, which identify a 

sequence of spatial and attribute manipulations, and through 

the two-dimensional computer-generated graphics, which 

illustrate the spatial relationships onscreen. 

The first scenario involves the Point Lookout and the 

Pictured Cliffs Sandstones, which have both been identified 

as major regressive cycles in the San Juan Basin. The map 

coverages containing information for these sandstone formations can be combined for direct onscreen visualization 

and comparison in various sequences to determine whether 

any meaningful relationships exist within and between data 

sets from the two formations. Comparisons can be made 

automatically and rapidly for the geologic relationships 

being investigated, without resorting to time-consuming 

manual procedures that use transparent overlay maps to 

explore the probable spatial relationships within and 

between these data coverages. The following stages 

describe some of the geologic comparisons and analyses 

that can be made by using onscreen visualization: 

1. Develop a composite coverage showing an overlay of 

the structure contour maps for the two formations to 

determine if the surfaces are conformable. 

2. Develop a composite coverage showing an overlay of 

the isopach contour maps to determine if patterns of 

24 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
EXPLANATION 

Pictured Cliffs 

subcrop extent 

-240- Isopach contour 

lines at 20-ft 

intervals 

Figure 14. Map coverage showing the subcrop extent of and isopach contours for the Pictured Cliffs Sandstone in the 

San juan Basin study area. 

sediment thicknesses and deposition are similar or different for the two formations (see example in fig. 18). 

3. Add the gas-producing wells from each of the two 

formations (in different colors) to each of the composite 

maps described above to determine if there are significant spatial patterns of occurrence for the producing 

trends relative to each other and relative to the structure 

and thickness patterns within each formation. 

4. Develop a composite coverage showing an overlay of 

the isopach map onto the structure contour map for each 

formation separately to determine if structural highs or 

lows coincide with depositional patterns of sand thicknesses; then add oil and gas wells to determine if there 

are any structural or thickness patterns relative to the 

occurrence of the productive zones. 

The number and combinations of realistic composite map 

coverages that can be generated are dependent only upon 

the availability of the required data in the GIS data base and 

the nature of the geologic problems to be resolved. 

A second scenario describes the process of addressing 

a problem by using composite surface and subsurface map 

coverages. A geologist, wanting to see all the gas wells that 

produce from the Dakota Sandstone drilled on Indian lands, 

can generate a composite map showing the features necessary to respond to this question. This computer-generated 

map will include a clip showing the extent of the Dakota 

Sandstone both as an outcrop and subcrop map, an overlay 

of the Indian lands within the Dakota clip, and an additional 

overlay of the location of all the gas wells producing from 

the Dakota Sandstone. By zooming in and enlarging various 

land tracts by using the data manipulation features of the 

GIS, the individual gas wells producing on Indian lands can 

be identified, and well information can be retrieved from 

the PI-WHCS well data base (Petroleum Information 

Corp.). Additional coverages, such as the location of all the 

oil wells producing from the Dakota or the structure 

contours from the top of the Dakota, can be added. The 

major limitation to such an exercise is the amount of clutter 

Performing a Geographic Analysis in the San juan Basin 25 
EXPLANATION 

Pictured Cliffs 

outcrop 

Producing gas 

wells (5,047) 

Producing oil 

wells (13) 

Pictured Cliffs 

Sandstone subcrop 

extent 

Structure contour 

lines at 250-ft 

intervals 

Figure 15. Composite map coverage for the Pictured Cliffs Sandstone showing structure contour coverage, outcrop and 

subcrop extent, and oil and gas wells producing from the formation. 

building up on the display screen and eventually making 

viewing impossible. This buildup is especially evident 

when visualizing the maps of the entire basin at a smaller 

scale, rather than smaller areas in the basin viewed at a 

larger scale. 

Additional Map and Data Coverages 

A geologist, by using the joint capabilities of the ISM 

mapping software and the ARC/INFO system, can generate 

a variety of subsurface map coverages, depending on the 

geological data that have been added to the GIS data base. 

The number and types of geological data that can be entered 

into a data base for sedimentary basin analysis are endless. 

Theoretically, the only limitations on such a data base, 

assuming access to the necessary computer facilities, are the 

availability of the respective geological data needed to 

complete the study and the creativity and ingenuity of the 

geologist for investigating the relationships that may exist in 

and among the multivariate spatial data sets. 

In addition to structural and isopach data that are 

essential to understanding the basin framework and stratigraphy for interpreting basin history, there are many other 

types of geological information that can be added to a basin 

data base. Selection of data types to be incorporated into the 

data base is dependent upon the objectives of the study and 

availability of the data. A few of the more typical data sets 

that can be added are lithologic data for facies analysis and 

depositional environment studies; engineering data (such as 

porosity, permeability, water saturation, bottom-hole and 

formation temperatures and pressures) for reservoir characterization; stratigraphic data and deposition, compaction, 

and subsidence information for stratigraphic analysis and 

burial history of the basin; organic data for hydrocarbon 

generation and thermal history; and petrographic and geochemical data for analysis. 

26 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
EXPLANATION 

Pictured Cliffs 

outcrop 

Producing gas 

wells (5,047) 

Producing oil 

wells (13) 

Pictured Cliffs 

Sandstone subcrop 

extent 

Isopach contour 

lines at 20-ft 

intervals 

Figure 16. Composite map coverage for the Pictured Cliffs Sandstone showing isopach contour coverage, outcrop and 

subcrop extent, and oil and gas wells producing from the formation. 

Further Applications of GIS for the San Juan 

Basin 

During the review of the stratigraphy and petroleum 

geology for the San Juan Basin, a number of interesting and 

complex spatial geometries were revealed in the subsurface 

framework of the basin. If the data needed to address the 

geological problems were available in the basin's GIS data 

base, then the following situations would lend themselves to 

additional studies for a three-dimensional geologic analysis 

using GIS. 

1. Dakota gas is present in the deeper parts of the interior 

basin, whereas most Dakota oil is located near the rim of 

the basin. No satisfactory explanation of this juxtaposition of shallow oil and deep gas has yet been given 

(Fassett and others, 1978). Investigations using GIS 

techniques of the spatial relationships for oil and gas 

occurrence within the Dakota Sandstone may be useful 

for the three-dimensional geological analysis of these 

conditions. 

2. The spatial relationships represented between the regressive and transgressive Gallup sandstones and the Niobrara unconformity lend themselves to future correlation 

studies using GIS within the three-dimensional basin 

framework. 

3. The trapping mechanism for Mesaverde gas is not fully 

understood and is as much of an enigma as that of the 

Dakota Sandstone gas. The spatial relationships represented by the deep-basin gas reservoirs and the structural 

and trapping configuration within the Point Lookout 

Sandstone are appropriate studies for a threedimensional investigation using GIS computer mapping 

techniques. 

Performing a Geographic Analysis in the San juan Basin 27 
EXPLANATION 

D Gallup Sandstone 

oil wells (2,554), and 

gas wells (250) 

D Pictured Cliffs Sandstone 

oil wells (13) and 

gas wells (5,047) 

Gallup Sandstone 

subcrop extent 

Figure 17. Composite map coverage for oil and gas wells producing from the Pictured Cliffs Sandstone and 

from the Gallup Sandstone. The spatial relationships for the producing trends within the two formations are 

strikingly different and reflect the geologic conditions controlling the reservoir occurrences within each 

formation. 

4. The spatial relationships represented by the remarkably 

similar isopach configurations of the regressive Point 

Lookout and Pictured Cliffs Sandstones and the occurrence of their respective gas fields provide additional 

opportunities for a three-dimensional geological analysis 

using GIS computer mapping techniques, especially for 

exploration. 

SUMMARY 

Modern sedimentary basin analysis requires an understanding of many diverse geological specialties, vast quantities of multivariate spatial data, and the application of 

sophisticated computer technology to make the most effective analyses of the available data within the threedimensional basin framework. One method being investigated for analyzing basins is the application of a geographic 

information system. 

This report provides an introduction to geographic 

information systems and is a guide to the planning, development, and applications of a GIS data base to be used in 

the analysis of a sedimentary basin. The report demonstrates the application of GIS' s and their potential for 

providing the tools needed to define new strategies and 

technologies for conducting and automating the complex 

tasks common to sedimentary basin analysis and particularly for extending two-dimensional computer mapping 

techniques to three-dimensional basin analysis. 

GIS technology, involving the integration of computer mapping and data base functions, enables a geologist 

not only to query large data bases but also to integrate and 

manipulate spatial (coordinate) data with attribute (thematic) data. As a result, complex geographic and geological 

data sets can be combined to develop and apply new models 

and generate new composite maps. But more importantly, 

28 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
Figure 18. Composite map coverage showing an 

overlay of the subcrop extent (blue boundary) 

and isopach contours for the Pictured Cliffs Sandstone onto map coverages for subcrop extent (black 

GIS allows a user to conduct multivariate spatial data 

analysis and to have access to a variety of options for 

analyzing these data bases. 

The San Juan Basin was used as a pilot study area to 

test the feasibility of applying GIS techniques to a basin 

analysis and for the development of a GIS data base. 

Specific GIS applications were designed to address the San 

Juan Basin's fundamental geologic, stratigraphic, and structural framework. These applications include the analysis of 

composite coverages for structural configurations relative to 

tectonics, depositional patterns using isopach contour maps 

relative to production trends, spatial relationships depicting 

geologic conditions favorable for the occurrence of oil and 

gas trends within productive formations, oil- and gas-field 

locations relative to their spatial occurrences within and 

between the producing formations, spatial geometries of 

transgressive and regressive cycles of deposition for proEXPLANATION 

Point Lookout 

Sandstone isopach 

contour lines at 

20-ft intervals 

Pictured Clifffs 

Sandstone isopach 

contour lines at 

20- ft intervals 

boundary) and isopach contours for the Point Lookout Sandstone to determine if patterns of deposition 

are similar or different for the two formations. 

ductive sandstones, and landownership relative to the locations of favorable producing and perspective trends. 

The relationships that may occur in and among the 

multivariate spatial data sets to be investigated are nearly 

unlimited, depending upon the number and types of geological, geophysical, and engineering data that can be 

entered into a data base for a sedimentary basin. The 

number of relational investigations that can be conducted 

for a basin study is, in tum, determined by the availability 

of the required data, the objectives of the study, and the 

interpretive ingenuity of the researcher. 

GIS is an important new tool for the geologist, 

particularly for geological interpretation of threedimensional multivariate spatial data in conducting basin 

analysis. As the advantages of a GIS become more obvious, 

the greater will be the versatility and scope of these basin 

studies. The nature of the additional map coverages needed 

Summary 29 
to conduct these analyses will change and become more 

specialized as the objectives for new studies focus upon 

more specific geologic problems. Along with these changes 

will come geological applications that require new solutions 

to data base access and three-dimensional representation 

due to the range of data types, irregular data distribution, 

and the complex spatial geometries of the subsurface 

environment. Much research remains to be done in threedimensional GIS, particularly for geoscientific modeling 

and basin studies. 

ACKNOWLEDGMENTS 

The work described in this paper was funded for the 

most part by an award to the writer in 1988 from USGS 

research funds, designated the Director's "GIS Sweepstakes," to support GIS research for geological applications. 

Grateful acknowledgment is made to Darcy Person, J. Mike 

Kernodle, and other Regional Aquifer-System Analysis 

personnel in the U.S. Geological Survey, Albuquerque, N. 

Mex., for some of the initial work completed on the data 

base for the San Juan Basin. The writer thanks Patricia C. 

Latzke (USGS) for her technical assistance in this project 

and for continuing to develop the digital data base for the 

San Juan Basin. Special thanks goes to Brian R. Schachte, 

computer specialist (USGS), for his assistance in using 

ARC/INFO and computer graphics. 

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References Cited 33 

APPENDIXES 

A. ARC/INFO GEOGRAPHIC INFORMATION SYSTEM 

B. TIN MAPPING PROGRAMS FOR ARC/INFO 
APPENDIX A. ARC/INFO GEOGRAPHIC INFORMATION SYSTEM 

The following is an introduction to the ARC/INFO 

GIS and a very brief description of the ARC/INFO GIS 

method. For detailed instructions on the operation of the 

ARC/INFO system, the reader is referred to the 

"ARC/INFO Users Guide," volume 1 (Environmental Systems Research Institute, Inc. (ESRI), 1987), "Understanding GIS-The ARC/INFO Method" (ESRI, 1990), "Basic 

Readings in Geographic Information Systems" (Marble and 

others, 1984), and "ARC/INFO: A Geo-Relational Model 

for Spatial Information" (Morehouse, 1985). 

ARC/INFO is a GIS cartographic system built around 

a hybrid data model and designed to provide a tool box of 

general purpose GIS programs for creating, analyzing, 

displaying, and managing computerized maps in a vector 

format. It organizes geographic data by using a relational 

and topological model. This format facilitates the handling 

of the two generic classes of spatial data: ( 1) location data 

describing the location and topology of point, line, and 

polygon-area features and (2) attribute data describing the 

characteristics of these features. ARC/INFO represents map 

features by sets of lines (arcs) and label points and as 

relationships between connected or adjacent lines and 

points. The relationships used to represent the connectivity 

and contiguity of these features are referred to as topology. 

Topology is a mathematical procedure for explicitly defining these spatial relationships. It is used to store three 

spatial relationships for each map feature: area definition, 

contiguity (the identification of polygons that touch each 

other or connect), and connectivity (the identification of 

interconnected arcs). 

ARC/INFO is composed of two subsystems: ARC 

and INFO. ARC, the x, y coordinate-handling software, is 

the main program environment in ARC/INFO and provides 

the extensive capabilities of the GIS system. ARC is used to 

automate, update, and edit spatial data and to manipulate 

the data through analytical operations such as buffering, 

map overlay, transformation, and coordinate projection. 

ARC handles the display of the map information. INFO is 

a complete Relational Data Base Management System for 

managing map attribute (thematic) data associated with 

geographic features in map coverages. All ARC/INFO 

attribute files are stored in INFO-readable formats. This 

format allows INFO to be employed for processing a 

coverage's thematic data. 

In ARC/INFO, a coverage is the basic unit of 

information, and it represents a single map or theme of 

geographically referenced information. It is analogous to a 

digital version of a single map-sheet layer, or map separate, 

in conventional cartography and generally describes only 

one type of map feature, such as roads, streams, geologic 

rock units, or landownership tracts. A coverage defines the 

locational data (defined by coordinates and topological 

relationships with others) and includes thematic attributes 

(defined as a set of named variables or items) for map 

features in a geographic area. By varying the types of 

features contained in a coverage and the thematic items 

associated with the features, the coverage can be used to 

represent many types of map information. The coverage 

serves as a unified framework for the representation of 

geographic information in ARC/INFO. 

36 Development and Application of Geographic Information Systems for Sedimentary Basin Analysis 
APPENDIX B. TIN MAPPING PROGRAMS FOR ARC/INFO 

TIN is the set of software programs used to store, 

manage, and analyze three-dimensional surfaces for 

ARC/INFO. TIN stands for Triangulated Irregular Network-a set of adjacent, nonoverlapping triangles used to 

represent the facets of the Earth's surface. A TIN structure 

is created from a set of irregularly spaced points having x, 

y coordinates and z values such as elevation or subsurface 

depth. Because the TIN data structure includes topological 

relationships between points and their close neighbors (that 

is, which points define each triangle and which triangles are 

adjacent), it allows the user to generate surface models. 

TIN is integrated with the rest of the ARC/INFO 

system. It provides data conversion, modeling, and display 

capabilities for terrain and other types of surfaces, as well as 

conversions to and from standard ARC/INFO coverages. 

Appendix B. TIN Mapping Programs for ARC/INFO 37 



SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS 

Periodicals 

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly). 

Technical Books and Reports 

Professional Papers are mainly comprehensive scientific reports 

of wide and lasting interest and importance to professional scientists 

and engineers. Included are reports on the results of resource studies 

and of topographic, hydrologic, and geologic investigations. They also 

include collections of related papers addressing different aspects of a 

single scientific topic. 

Bulletins contain significant data and interpretations that are of 

lasting scientific interest but are generally more limited in scope or 

geographic coverage than Professional Papers. They include the results 

of resource studies and of geologic and topographic investigations, as 

well as collections of short papers related to a specific topic. 

Water-Supply Papers are comprehensive reports that present 

significant interpretive results of hydrologic investigations of wide 

interest to professional geologists, hydrologists, and engineers. The 

series covers investigations in all phases of hydrology, including 

hydrogeology, availability of water, quality of water, and use of water. 

Circulars present administrative information or important 

scientific information of wide popular interest in a format designed for 

distribution at no cost to the public. Information is usually of short-term 

interest. 

Wate1·-Resources Investigations Reports are papers of an 

interpretive nature made available to the public outside the formal 

USGS publications series. Copies are reproduced on request unlike 

formal USGS publications, and they are also available for public 

inspection at depositories indicated in USGS catalogs. 

Open--File Reports include unpublished manuscript reports, 

maps, arid other material that are made available for public consultation 

at depositories. They are a nonpermanent form of publication that may 

be cited in other publications as sources of information. 

Maps 

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 7.5- or 15-minute quadrangle formats (scales 

mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or 

engineering geology. Maps generally include brief texts; some maps 

include structure and columnar sections only. 

Geophysical Investigations Maps are on topographic or planimetric bases at various scales; they show results of surveys using 

geophysical techniques, such as gravity, magnetic, seismic, or 

radioactivity, which reflect subsurface structures that are of economic 

or geologic significance. Many maps include correlations with the 

geology. 

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also 

includes 7 .5-minute quadrangle photogeologic maps on planimetric 

bases that show geology as interpreted from aerial photographs. Series 

also includes maps of Mars and the Moon. 

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at var:1ous scales showing bedrock or surficial 

geology, stratigraphy, and structural relations in certain coal-resource 

areas. 

Oil and Gas Investigations Charts show stratigraphic 

information for certain oil and gas fields and other areas having 

petroleum potential. 

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topograpbc or planimetric bases for quadrangle or 

irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations. 

Hydrologic Investi:~ations Atlases are multicolored or blackand-white maps on topographic or planimetric bases presenting a wide 

range of geohydrologic data of both regular and irregular areas; 

principal scale is 1:24,000, and regional studies are at 1:250,000 scale 

or smaller. 

Catalogs 

Permanent catalogs, as well as some others, gtvmg 

comprehensive listings of U.S. Geological Survey publications are 

available under the conditions indicated below from the U.S. 

Geological Survey, Book and Open-File Report Sales, Federal Center, 

Box 25425, Denver, CO 80225. (See latest Price and Availability List.) 

"Publications of the Geological Survey, 1879-1961" may be 

purchased by mail and over the counter in paperback book form and as 

a set of microfiche. 

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volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982, 1983, 1984, 1985, 1986, and for 

subsequent years since the last permanent catalog may be purchased by 

mail and over the counter in paperback book form. 

State catalogs, "Li~;t of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by 

mail and over the counter in paperback booklet form only. 

"Price and Availability List of U.S. Geological Survey 

Publications," issued annually, is available free of charge in paperback 

booklet form only. 

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" are available free of charge by mail or may 

be obtained over the counter in paperback booklet form only. Those 

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Note.-Prices of Government publications listed in older 

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Therefore, the prices charged may differ from the prices in catalogs, 

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