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1961 The trS atigraphy and Structure of the Parras Basin, Coahuila and Nuevo Leon, Mexico. Alfred Edward Weidie Jr Louisiana State University and Agricultural & Mechanical College
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WEIDIE, Jr., Alfred Edward, 1931- THE STRATIGRAPHY AND STRUCTURE OF THE PARRAS BASIN, COAHUILA AND NUEVO LEON, MEXICO.
Louisiana State University, Ph.D., 1961 Geology
University Microfilms, Inc., Ann Arbor, Michigan
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE STRATIGRAPHY AND STRUCTURE OF THE PARRAS BASIN,
COAHUILA AND NUEVO LEON, MEXICO
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Geology
by Alfred Edward Weidie, Jr. B.A., Vanderbilt University, 1953 M.S., Louisiana State University, 1957 August, 1961
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS
The writer expresses his sincere appreciation to Dr.
Grover E. Murray, Boyd Professor of Geology, Louisiana State
University, for his supervision, aid, and encouragement in the
preparation of this paper; to J. R. Wall, J. A. Wolleben, D.
C. Roberts and B. J. Rawls, geology students, Louisiana State
University, for their aid in field mapping; to R. R. Londot
and Ana Laura Weidie for their assistance in the preparation
of plates and figures; to the various members of the Graduate
Faculty, Louisiana State University, for their many helpful
suggestions and constructive criticisms; and to Dr. H. V.
Howe for his aid and encouragement throughout the writer's
graduate career.
Financial aid was received from a National Science
Foundation Cooperative Fellowship, the Pan American Petroleum
Corporation Fellowship in Geology, and a National Science
Foundation Research Grant (NSF-G5658) for basic stratigraphic
studies in northeastern Mexico, Grover E. Murray, Senior In
vestigator.
Ing. Eduardo J. Guzman, Assistant Mcinager of
ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Exploration, Petroleos Mexicanos, Mexico City, kindly arranged
for the loan of aerial photographs of the areas mapped.
iii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS
PAGE
ACKNOWLEDGMENTS i i
LIST OF FIGURES...... v i
LIST OF PLATES ...... vii
ABSTRACT ...... viii
CHAPTER
I. INTRODUCTION ...... 1
II. REGIONAL GEOLOGY OF NORTHEASTERN MEXICO. .. . 7
Geologic Provinces and Structural Elements . 7 The Rio Grande Embayment ...... 8 The Coahuila Platform...... 12 The Coahuila Marginal Folded Province. . . 13 The Parras Basin ...... 14 The Sabinas Basin...... 15 La Gloria-La Gavia and Burro-Picachos Fold Trends...... 16 The Tamaulipas Platform...... 17 The Burgos Basin ...... 18 The Sierra Madre Oriental...... 18 Regional Stratigraphy...... 20
III. GEOGRAPHY OF THE PARRAS BASIN...... 23
IV. STRATIGRAPHY OF THE PARRAS BASIN ...... 26
Introduction ...... 26 Cretaceous System...... 28
iv
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Gulfian Series ...... 28 Indidura Formation ...... 28 Parras Shale ...... 30 Difunta Group...... 33 Cerro del Pueblo Formation ...... 34 Cerro Huerta Formation ...... 36 Canon del Tule Formation ...... 39 Las Imagenes Formation ...... 41 Cerro Grande Formation ...... 43 Cretaceous and/or Tertiary System(s) .... 46 Gulfian and/or Paleocene Series...... 46 Las Encinas Formation...... 46 Tertiary System...... 47 Paleocene Series ...... 47 Rancho Nuevo Formation ...... 47 Quaternary System...... 48 Mayran Formation and Alluvium...... 48 Crystalline Rocks...... 49 Calcite veins...... 49 Igneous Rocks...... 50 Andesitic(?) Sills and Dikes ...... 50
V. STRUCTURE OF THE PARRAS BASIN...... 51
Introduction ...... 51 Folding...... 58 F a u l t i n g ...... 59 Jointing and Cleavage...... 63
VI. INTERPRETATION OF GEOLOGIC HISTORY ...... 65
SELECTED BIBLIOGRAPHY...... 68
AUTOBIOGRAPHY...... 74
v
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES
FIGURE PAGE
1. Tectonic-Physiographic Map of Mexico ...... 2
2. Index Map of Northeastern Mexico ...... 9
3. Composite Stratigraphic Column, Northeastern Mexico...... 21
4. Correlation Chart, Mesozoic Formations ...... 22
5. Idealized Cross Sections, Parras Basin ...... 25
6 . Wedgeout and Interfingering of Cerro Huerta Formation in the Fraustro and Higueras Areas ...... 38
7. Wedgeout of Las Imagenes and Las Encinas Formations near Zertuche ...... 42
8 . Drag Folding near Rancho Nuevo ...... 60
vi
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF PLATES
PLATE PAGE
I. Geologic Map of the Parras Basin (Four sheets numbered IA, IB, IC, AND ID)...... Pocket
II. Tectonic Map of the Parras Ba s i n ...... Pocket
III. Structure Sections of the Parras Basin...... Pocket
vii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT
The Parras Basin, in southern Coahuila and western
Nuevo Leon, Mexico, contains Upper Cretaceous (Gulfian) and
Tertiary (Midwayan) calcareous-arenaceous-argillaceous sedi
ments whose aggregate thickness exceeds 17,500 feet. These
sediments were deposited in a shallow, subsiding basin between
the Sierra Madre Oriental on the south and the Coahuila Plat
form (or Peninsula) on the north.
The Indidura Formation, the Parras Shale, and the Di-
funta Group comprise the bulk of the Gulfian and Midwayan
sediments in the basin. Detailed stratigraphic measurements
and field mapping disclose that the Difunta consists of two
gross lithic facies, which include (1 ) four gray to brown,
calcareous, shales and siltstone units which intertongue to
the south and west with (2) three red sand, silt, shale, and
mudstone tongues, in part calcareous and fossiliferous. The
seven lithic units have been mapped as formations throughout
the basin, and studies of their stratigraphic characteristics
and areal extent show the gray-brown formations to be marine
and brackish water deposits, while the red formations are
viii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fluviatile and probably lacustrine deposits.
The lower five formations of the Difunta Group contain
fossils of Late Cretaceous age and the upper formation con
tains fossils of Paleocene (Midwayan) age. The intervening
red formation is unfossiliferous and of indeterminable age,
while to the north and east of its wedge-out marine deposition
was continuous from Cretaceous to Tertiary times.
The deformation of the Sierra Madre Oriental orogenic
belt commenced in Paleocene or Eocene times, and the folding
and faulting of the sediments of the Parras Basin was con
comitant. Three areas in the basin with differing deforma-
tional characteristics are discerned: (1) an area of tight,
overturned folds lying between the Sierra Madre Oriental
orogen and the stable Coahuila Platform, (2) an area of elong
ate, open folds lying adjacent to and north of the orogen and
east of the Coahuila Platform, and (3) an area of broad, domal
folds further to the north. These areas illustrate the types
of resultant deformation when an orogenic belt is closely
bordered by a stable platform or the normal diminution of de-
formational intensity away from the orogen with the absence
of a stable platform.
The duration of the Sierra Madre Oriental orogeny is
ix
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. unknown. Subsequent uplift of the basin area has exposed
the deformed sediments to vigorous erosion. Incised and dis
sected bajadas adjacent to the Sierra Madre and the poorly
developed drainage of the basin proper indicate uplift to be
continuous to the present day. This recent uplift is believed
to be a result of broad regional, isostatic adjustment.
x
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I
INTRODUCTION
The Parras Basin (Figures 1 and 2), in western Nuevo
Leon and southern Coahuila, Mexico, is an elongated sedimen
tary basin extending westward from Monterrey, Nuevo Leon, to
the vicinity of Torreon, Coahuila, about 17 5 miles west of
Monterrey. The southern and western limits of the basin are
the front ranges of the Sierra Madre Oriental. The northern
limit is the southern flanks of the Sierra de los Alamitos
(number 14 of Figure 2) and the Sierra de la Paila (number
15 of Figure 2), which are a surface expression of the Coa
huila Platform or Peninsula. The Parras Basin is open to the
east in the vicinity of Monterrey and is separated from the
Sabinas Basin to the northeast by the Sierra de la Gavia
(number 16 of Figure 2) and the Sierra de la Gloria (number
12 of Figure 2), which extend southeasterly from the eastern
side of the Coahuila Platform.
Stratigraphic and structural studies of the Parras
Basin were undertaken with the following primary objectives:
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced
TECTONIC-PHYSIOGRAPHIC MAP OF MEXICO © o ■s. sr£ULfr COASTAL o s H D O OS W
AUtA OWQOWCZU936). *CLUJ*mt»»), VAMATQ(H«»>. ALVAREZOMt), ' ALVARCZ(i99t), NtHIPHHCV(tfO«), (1) differentiation of the Difunta Group into mappable litho-
logic formations; (2) study of the areal extent and facies
relationships of these formations; (3) preparation of a
geologic map of the Parras Basin; and (4) structural studies
of the basin as related to the regional tectonics of north
eastern Mexico.
Previous investigations in or adjacent to the Parras
Basin have been undertaken by many workers. Bose and
Burckhardt made outstanding contributions in the field of
basic stratigraphic research. Diaz, Humphrey, Imlay, Jones,
Kane, Kellum and Kelly studied the stratigraphy and struc
ture, primarily in areas adjacent to the Parras Basin.
Murray and students of Louisiana State University have con
ducted preliminary stratigraphic and structural studies in
northeastern Mexico (see bibliography).
P. D. Lewis, Jr. was the first of the Louisiana State
University students to work in the Saltillo area. With
Saltillo as the southern terminus he worked a strip which
extended approximately 25 miles northward along the Saltillo-
Eagle Pass highway, and about three miles east and west of
the highway. Within this area he described nine (9) "forma
tions." These "formations," which he designated as A, B,
C, etc., are equivalent to the following formations used in
this paper:
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Formation I Cerro Grande Formation
Formation H Las Imagenes Formation
Formation G Canon del Tule Formation
Formation F Cerro Huerta Formation
Formation E Cerro del Pueblo Formation
Formation D Cerro del Pueblo Formation
Formation C Cerro del Pueblo Formation
Formation B Upper portion of Parras Shale
Formation A Upper portion of Parras Shale s Later, a group of students working with G. E. Murray
and C. 0. Durham, Jr. (see for example Boyd, 1959; Forde,
1959; and Murray, et al., 1960) continued Lewis* work an ad
ditional 25 miles northward and also worked along the Sal-
tillo-Monterrey highway. They established seven units,
which with some revisions made by the author, are the forma
tions of the Difunta Group described in this paper. These
formations are to be formally named and described in a forth
coming Bulletin of the American Association of Petroleum
Geologists.
The field work for this report extended over a period
of approximately two years. During this time the units dif
ferentiated by previous investigators were studied in detail
and slightly revised. Areal studies disclosed the continuity
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. of the units over sufficient distances to warrant their being
mapped as formations. The wedge^out or interfingering of the
Cerro Huerta Formation to the north and east as deduced by
earlier investigators was worked out in detail and clarified.
My work has disclosed the wedge-out to the north and east of
the Las Imagenes and Las Encinas Formations and has resulted
in the accumulation of detailed information regarding the
lithology and stratigraphic relationships of the various units.
In addition I have made geologic and tectonic maps of the
entire Parras Basin and also studied the structure and
stratigraphy of areas adjacent to the basin.
The Parras Basin was mapped in the field from aerial
photographs. Various procedures and techniques were used.
Local base maps were constructed by the geometric rectifica
tion of points on aerial photographs. Overlays of individual
aerial photographs were also made. The distribution of the
formations exposed in the basin was plotted on aerial photo
graphs and overlays, then transferred to the base maps. In
some instances the overlays were rectified and joined in a
mosaic pattern. The final map is essentially a construction
from a semi-controlled mosaic. No vertical control was
established due to the large size of the area. It should be
emphasized, however, that the relief shown on structural
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6
cross-sections is relatively correct; i.e., no appreciable
distortion has been introduced into the sections.
Stratigraphic thicknesses were measured by a number of
methods, dependent on the accessibility of the section to be
measured. Plane table and alidade, optical rangefinder, and
pace and compass traverses were used most frequently. In some
areas gross thicknesses were determined by measurement of
horizontal distance across a formation on the aerial photo
graphs and correcting for dip, strike, and slope. The stra
tigraphic terminology and correlations are those established
(Burrows, 1910; Imlay, 1935, 1937, 1938; Kelly, 1936; Murray,
Weidie, Boyd, Forde and Lewis, 1961) in northeastern Mexico.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II
REGIONAL GEOLOGY OF NORTHEASTERN MEXICO
GEOLOGIC PROVINCES AND STRUCTURAL ELEMENTS
Northeastern Mexico (Figures 1 and 2) , as used in
this paper, extends southward from the Rio Grande to the
Sierra San Carlos in Tamaulipas, and westward from the Gulf . • «
of Mexico to the eastern margin of the Mesa Central. This
area embraces parts of two major, regional geologic prov
inces— the Rio Grande Embayment and the Sierra Madre Oriental
The Rio Grande Embayirr- t, a major negative feature projecting
into the continental mass, contains several distinct tectonic
elements which are directly related to the origin and develop
ment of the Parras Basin:
1. The Coahuila Platform or Peninsula
2. The Coahuila Marginal Folded Province
a. The Parras Basin
b. The Sabinas Basin
c. The La Gloria-La Gavia and Burro-Picachos Fold Trends
7
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8
3. The Tamaulipas Platform or Peninsula
4. The Burgos Basin
Humphrey's (1956) geomorphic classification divided
northeastern Mexico into nine physiographic provinces. Mur
ray (1959, 1961) established geologic or tectonic provinces
in the same region. It should be noted, however, that the
physiography of northeastern Mexico rather closely reflects
the structure; thus, there is generally close agreement in
the tectonic and physiographic divisions.
The Rio Grande Embayment
Murray (1961) defined the Rio Grande Embayment (Figure
2) as a structural-stratigraphic segment of the Gulf Coastal
Province extending southward from the San Antonio River (near
San Antonio, Texas) and San Antonio Bay (about 60 miles north
east of Corpus Christi) in Texas to the Sierra Cruillas
(number 26 of Figure 2) and Sierra San Carlos (number 25 of
Figure 2) in Tamaulipas. The embayment extends from the Gulf
of Mexico on the east to the Big Bend Region of Texas and
Coahuila on the west.
The Rio Grande Embayment is the major negative element
of the western Gulf Coastal Province, but includes within its
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9
INDEX MAP OP NORTHEASTERN MEXICO
X
Antonio
Cor pu t C h rnti
t t
2 M o n U rrtv Q4S/A/ Saltillo
Legend — INTERNATIONAL BOUNDARIES — STATE BOUNDARIES C. Victoria !— A N T IC LIN E S • SALT DOMES i - SV N C LIN E S o PROBABLE SALT J— FAULTS DOMESl 1 AREA OF OETAILEO STUDY 0 100 Att*r G. £. Murray, '59 FIGURE 2
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10
FIGURE 2
INDEX MAP OF NORTHEASTERN MEXICO
1. Serranias del Burro 2 . Sierra Hermosa de Santa Rosa 3. Sierra Hermanas or Oballos 4. Sierra de Padilla and Sierra de Capulin 5. Sierra de Salsipuedes 6. Sierra de la Mula 7. Sierra de la Madera 8 . Sierra de las Ovejas 9. Sierra del Lagunilla and Sierra de la Fragua 10. Sierra de San Marcos 11. Sierra de la Purisima 12. Sierra de la Gloria 13. Sierra de Pajaros Azules and Sierra de la Rata 14. Sierra de los Alamitos 15. Sierra de la Paila 16. Sierra de la Gavia 17. Sierra de Minas Viejas 18. Sierra Bustamante or de Palo Blanco 19. Sierra Lampazos-Sabinas or de la Iguana 20. Sierra Picachos 21. Sierra del Fraile 22. Sierra de las Mitras 23. Sierra Papagayos 24. Cerro la Silla 25. Sierra San Carlos 26. Sierra Cruillas 27. Sierra Aldama 28. Sierra de Parras 29. Monterrey Salient of the Sierra Madre Oriental
A. Pearsall fault system B. Luling fault system C. Charlotte fault system D. Mirando-Provident City fault system E. Sam Fordyce-Vanderbilt fault system F. McAllen fault system G. Willamar fault system
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11
boundaries, several positive tectonic units, which because
of their deformation and relief are generally excluded from
the coastal region. Murray (1961) noted that the inner
limit of the coastal element is arbitrary south of the Rio
Grande, and suggested the Sierra Madre Oriental front as the
western and southern limits. He regarded the Coahuila Margin
al Folded Province as an inner belt of the Coastal Province
on the basis of: (1 ) the lack of a definite and recognizable
natural boundary for the inner limits of the coastal region,
(2 ) the importance of the marginal folds in understanding the
geologic history and development of the Coastal Province
proper, (3) the continuity and similarity of the stratigraphic
section, and (4) the similarity of prefolding history.
Structurally, the Rio Grande Embayment (Figure 2) is
bounded on the northeast by the San Marcos Arch, on the north
by the Balcones Fault Zone, on the west and southwest by the
front ranges of the Sierra Madre Oriental, and on the south
east by the uplifts of the Tamaulipas Arch. The embayment is
open to the east to the Gulf Coastal Plain and the Gulf of
Mexico. The boundary is indefinite at the head of the embay
ment but may be drawn through the Big Bend region of Texas
and Coahuila. The northwest-southeast synclinal form of the
embayment is modified by several internal positive features.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12
Sedimentary rocks in the eastern portion of the Rio
Grande Embayment attain thicknesses in excess of 40,000 feet,
Included are evaporites of questionable (Permian to Jurassic)
age, Lower Cretaceous (Coahuilan and Comanchean) calcareous-
argillaceous sediments, and Upper Cretaceous (Gulfian) and
Tertiary argillaceous strata. These deposits thin toward the
head and flanks of the embayment.
The Coahuila Platform or Peninsula
The Coahuila Platform (Figure 1), a pre-Cretaceous
landmass in northeastern Mexico in the states of Coahuila,
Chihuahua, and Durango, projected southward from the Jurassic
North American continent. Bose (1923) was the first to
recognize the presence and significance of this tectonic ele
ment. Numerous other geologists have studied the area and
have documented its existence.
The Coahuila Platform is bounded on the east by the
Sabinas Basin, on the south by the Parras Basin, and on the
west by the folds of the Sierra Madre Oriental. Its northern
extent is indefinite.
Jurassic and Lower Cretaceous sediments adjacent to
the platform contain coarser elastics than equivalent strata
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13
in the nearby basins. The fauna indicates near-shore con
ditions changing to offshore away from the platform. On the
platform itself, Lower Cretaceous sediments lie upon folded,
faulted, and partially metamorphosed pre-Jurassic rocks
(Imlay, 1943).
The Coahuila Platform was uplifted in Late Cretaceous
or Early Tertiary times. The deformation was epeirogenic;
the folds of the platform are broad domal anticlines; and the
dips in the folds rarely exceed 20 degrees. This uplift fur
nished small amounts of sediment to the Parras and Sabinas
Basins near the close of their depositional history.
The Coahuila Marginal Folded Province
Murray (1959) designated the area on the southwestern
flank of the Rio Grande Embayment, between the Sierra Madre
Oriental and the Gulf Coastal Plain, as the Coahuila Marginal
Folded Province. In this province he included the Parras and
Sabinas Basins, the Coahuila and Tamaulipas Peninsulas or
Platforms, and the folds east of the Coahuila Platform and
north of the Tamaulipas Platform. The structural character
and tectonic history of the Coahuila and Tamaulipas Platforms
warrants their being discussed as tectonic elements apart from
the Coahuila Marginal Folded Province, and they are treated
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14
accordingly in this paper.
The Parras Basin
The Parras Basin (Figure 2) , in southern Coahuila and
western Nuevo Leon, extends westward from Monterrey, Nuevo
Leon, to the vicinity of Torreon, Coahuila. It is bounded on
the west and south by the front ranges of the Sierra Madre
Oriental, and on the north by the southern margin of the Coa
huila Platform. The basin is open to the east, but is sepa
rated from the Burgos Basin and Gulf Coastal Plain by a
north-south shelf, extending from the Sierra de los Muertos
(or Monterrey Salient, number 29 of Figure 2) to the Sierra
de Minas Viejas (number 17 of Figure 2) and occupying the
site of the present day Sierra de las Mitras (number 22 of
Figure 2) and Sierra del Fraile (number 21 of Figure 2). The
Parras Basin is separated from the Sabinas Basin to the north
east by a major structural trend of the Coahuila Marginal
Folded Province which extends southeasterly from the eastern
margin of the Coahuila Platform and includes the Sierra de la
Gavia, Sierra de la Gloria, and Sierra de Minas Viejas.
The Parras Basin contains over 18,000 feet of Upper
Cretaceous (Gulfian) and Lower Tertiary (Midwayan) argilla
ceous-arenaceous-calcareous deposits. These sediments were
intensely folded and faulted in Early Tertiary times.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15
The Sabinas Basin
The Sabinas Basin (Figure 2) is a northwesterly trend
ing, sedimentary basin in eastern Coahuila and western Nuevo
Leon. It is bounded on the northeast by the Burro-Picachos
fold trend or geanticline (Figure 1), and on the southwest by
the Coahuila Platform and the La Gavia-La Gloria-Minas Viejas
fold trend, which, as noted above, separates it from the
Parras Basin. The Sabinas Basin is open to the southeast.
Approximately 15,000 feet of Jurassic and Cretaceous
sediments are in the Sabinas Basin. Late Cretaceous (Gulfian)
arenaceous-argillaceous deposits comprise the bulk of the
section.
The Taylor and Navarro strata of the Sabinas Basin are
similar to the sediments of southwest Texas and are quite
different from those of the Parras Basin. In ascending order
these are the Upson clay, the San Miguel consisting of mud
stones grading upwards to siltstones and sandstones, the coal-
bearing shales and sandstones of the Olmos, and the sands and
shales of the Escondido Formation.
The basic synclinal structure of the basin is modified
by northwesterly trending folds that bring Jurassic and Lower
Cretaceous rocks to the surface. The magnitude and intensity
of folding in the Sabinas Basin is much less than in the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Parras Basin and adjacent fold trends.
La Gloria-La Gavia and Burro-Picachos Fold Trends
Two major, northwesterly aligned series of anticlinal
folds form the northeastern and southwestern flanks of the
Sabinas Basin in the states of Coahuila and western Nuevo
Leon. These trends are characterized by numerous, doubly-
plunging, anticlinal folds, which typically form mountains.
The anticlines are commonly breached, exposing Upper Jurassic
carbonate, arenaceous-argillaceous, and evaporitic strata in
the cores, flanked by Lower Cretaceous carbonates.
The folds on the southwestern flank of the Sabinas
Basin, here designated the La Gavia-La Gloria trend, lie im
mediately east of the Coahuila Platform, and extend south
easterly to the Sierra de Minas Viejas. The main folds com
prising this trend are the Sierra Hermosa de Santa Rosa,
Sierra Oballos, Sierra de Pajaros Azules, Sierra de la Rata,
Sierra de la Gloria, Sierra de la Gavia, Sierra Bustamante,
and the Sierra de Minas Viejas (numbers 2, 3, 13, 12, 16, 18,
and 17 of Figure 2).
The La Gavia-La Gloria trend separates the Parras and
Sabinas Basins. That this trend was an effective paleo-
tectonic element is shown by the marked lithic differences
in the Taylor and Navarro sediments of the Parras and
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17
Sabinas Basins (Figure 4 and page 14).
The fold trend on the northeastern flank of the Sabinas
Basin is the Burro-Picachos fold trend. Major folds compris
ing this trend are the Serranias del Burro, the Salado Arch,
Sierra de Lampazos-Sabinas, Sierra de Picachos, and the Sierra
de Papagayos (numbers 1, 19, 20, and 23 of Figure 2).
The Burro-Picachos fold trend is a relatively recent
tectonic feature. It was certainly not a significant tectonic
element in Comanchean and Gulfian times, as is shown by the
marked similarity and sequence of Comanchean and Gulfian
deposits of southern Texas and the Sabinas Basin.
The Tamaulipas Platform
The Tamaulipas Platform, variously termed the Tamauli
pas Arch, Tamaulipas Archipelago, or Tamaulipas Peninsula
(Figures 1 and 2) is a positive tectonic element whose exist
ence in the coastal plain has been documented by many workers
(Carrillo Bravo, 1955; Humphrey, 1956; Kellum, 1937; Imlay,
1937; and others). Murray (1961) designated it a major
positive feature of the Gulf Coastal Province, embracing the
Sierra de Tamaulipas, the Sierra de Cruillas, and the Sierra
San Carlos. The Tamaulipas Platform may extend northward to
the Mexico-Texas border, as predicted by Imlay (1943), and
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18
Humphrey (1956). It should he noted that this inferred
northern extension would coincide with the Burro-Picachos
fold trend. If this is the case, the platform or geanticline
is markedly less positive in the region east of Monterrey.
The Burgos Basin
The Burgos Basin (Figure 1), in western Tamaulipas and
eastern Nuevo reon, contains thick deposits of Upper Cretaceous
and Lower Tertiary sediments. The Basin is bordered on the
south by the Tamaulipas Platform, on the west by the Sierra
Madre Oriental, and merges northward and eastward into the
Rio Grande Embayment proper. The Burgos Basin is separated
from -the Parras Basin to the west by the north-south shelf
from the Sierra de los Muertos to the Sierra de Minas Viejas
(see page 14), and is open to the northwest to the Sabinas
Basin.
THE SIERRA MADRE ORIENTAL
The Sierra Madre Oriental (Figure 1) is a part of the
Rocky Mountain System, which extends from Canada to the Isth
mus of Tehuantepec. It is a distinct tectonic element
characterized by great, doubly-plunging, commonly asymmetri
cal folds developed mainly in Lower Cretaceous carbonates and
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Upper Jurassic carbonates and elastics. The fold belt
trends north-northwesterly from the Isthmus of Tehuantepec
to Monterrey, Nuevo Leon, where it arcs sharply to the west
almost to Ramos Arizpe. West of Ramos Arizpe the folds are
en echelon and plunge steeply to the west and southwest, dis
appearing beneath Gulfian sediments, and receding southwester
ly to the region south of Saltillo. From this area the
tectonic belt trends westward to Torreon, where the folds turn
northwestward, spread out widely, and continue to the United
States border in the vicinity of El Paso.
South of Monterrey the folds are commonly overturned
to the east, and, in places, thrust to the east. West and
southwest of Monterrey the folds are frequently overturned
to the north; at times overturned on both flanks (fanfolding);
but exhibit no conclusive evidence of thrusting. Anticlines
in the Sierra Madre form mountains, and synclines form the
intervening valleys. Some of the anticlines have been
breached and extensive axial valleys now exist in the centers
of some of the folds. Average elevation in the Sierra Madre
is about 7,000 feet, with occasional peaks exceeding 10,000
feet.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20
REGIONAL STRATIGRAPHY
The general stratigraphic sequence in northeastern
Mexico consists chiefly of Upper Jurassic calcareous-argilla
ceous sediments, and Cretaceous and Lower Tertiary arena
ceous-calcareous-argillaceous sediments that have a composite
maximum thickness of about 30,000 feet. Most of the exposed
formations, have been described and defined from localities
in or near the Sierra Madre Oriental. They have been areally
extended on the basis of: (1) lithologic similarity, (2)
stratigraphic position, and (3) faunal content. Additional
detailed stratigraphic work will undoubtedly result in more
precise stratigraphic definition, both spatially and chrono
logically. Figures 3 and 4 are a composite geologic column
of northeastern Mexico and a correlation of these formations
with those of adjacent parts of Mexico and the Gulf Coastal
Plain of the United States.
The nature of the basement rocks in this area is large
ly unknown. Deep wells and a few outcrops disclose the pres
ence of igneous and metamorphic rocks which may be Precambrian,
Paleozoic, or Lower Mesozoic. So little information is avail
able on the basement rocks that extrapolation and interpreta
tion is difficult, if not impossible, at the present time.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 COMPOSITE STRATIGRAPHIC COLUMN OF NORTHEASTERN MEXICO.
" (9) INDIDURA FORMATION w ALTERNATING GRAY TO PINKISH GRAY TO BROWN o FINELY LAMINATED SHALE, ARGILLACEOUS O SILTSTONE, AND LIMESTONE. UNITS AND FACIES w SECTION FROM MURRAY ET AL (1960), SHOWN OCCUR WITHIN ^ ARTEAGA CANYON, COAHUILA, MEXICO. OR ADJACENT TO THE (9A) AGUA NUEVA FORMATION, EASTERN FACIES OF BLACK BITUMINOUS SHALES WITH INTER - COAHUILA MARGINAL BEDS OF DARK, GRAYISH BROWN LIMESTONE. SECTION FROM HUMPHREY AND DlAZ, FOLDED BELT. HUMPHREY (1956)* CERRO LA SILLA, NUEVO LfcON, MEXICO. (8) CUESTA DEL CURA LIMESTONE DIFUNTA GROUP THIN- TO MEDIUM BEODED, DENSE GRAY (11A) CERRO OEl PUEBLO FORMATION (lie) LIMESTONE. WAVY BEDDING GENERALLY ALTERNATING GRAY CALCAREOUS SANDSTONES AND CHARACTERISTIC GRAY, BLACK, AND TAN CALCAR'TOUS SHALES SECTION FROM HUMPHREY AND DlAZ. HUMPHREY (1956)i CERRO LA SILLA, NUEVO (I) CERRO HUERTA FORMAT I*N LCON, MEXICO. ALTERNATING RED, GREEN, GRAY, AND BLACK CALCAREOUS SHALES AND GRAY TO RED CALCA REOUS SANDSTONES WITH RANOOM CONGLOMERA (7) AURORA LIMESTONE TIC STRATA. THICK BEDDED, GRAY, CRYSTALLINE LIME - (118) CANON DEL TULE FORMATION STONE WITH RUDISTIO FRAGMENTS AND CHERT ALTERNATING GRAY CALCAREOUS SANDSTONES AND NODULES. GRAY TO TAN CALCAREOUS SHALES. SECTION FROM SIERRA DEL FRAILE, NUEVO ! LFON, MEXICO. * J (II) LAS IMAGENES FORMATION ALTERNATING RED, GRAY, GREEN, AND BLACK CALCAREOUS SHALES, WITH SILTY SHALES AND (6) LA PEffA FORMATION MUDSTONES, AND CALCAR‘.OUS SILTSTONES AND 7«*>r SANDSTONES. GRAY LAMINATED SHALES ANO SILTY LIME - STONES WITH LENSES OF BLACK CHERT. (IIC) CERRO GRANDE FORMATION SECTION FROM HUMPHREY AND DUZ, ALTERNATING GRAY CALCAREOUS SILTSTONES AND HUMPHREY (1956)* SIERRA OE LA GAVIA, SANDSTONES, AND GRAY, BLACK AND TAN, SILTY COAHUILA, MEXICO. CALCAREOUS SHALES. -in
(III) LAS ENCINAS FORMATION (5) CUPIDO LIMESTONE PREDOMINANTLY RED TO GRAY CALCAREOUS SILT- STONES AND SANDSTONES WITH INTERBEDDED SILTY, CALCAREOUS SHALES. MEDIUM- TO THICK BEDDED, GRAY TO BROWN, DENSE, CRYSTALLINE LIMESTONE. CONTAINS (IID) RANCHO NUtVO FORMATION SOME CHERT NODULES AND MINOR OOLOMITIC TAN, CALCAREOUS SILTSTONE; GRAY CALCAREOUS BEDS. c SHALE; GRAY CALCAREOUS SANDSTONE WITH PEB SECTION FROM SIERRA DEL FRAILE, NUEVO BLY CONGLOMERATE. PROBABLE TERTIARY FOSSILS LCON, MEXICO. SCCTION FROM MURRAY, ET AL (1960), SALTILLO AREA, COAHUILA, MEXICO. BASAL CLASTIC ANO ARKOSIC SECTION (5A) LA MULA SHALE: GRAY TO DARK BROWN, (11E MENDEZ FORMATION: EASTERN EQUIVALENT SILICEOUS SHALES WITH ARENACEOUS, WITH GRAY TO GREEN FISSILE SHALES. BASAL CALCAREOUS, AND OOLITIC BEDS. UNIT WITH CALCAREOUS SHALES AND GRAY LIME STONE. (5B) PATULA ARKOSE: LENTICULAR THIN - TO THICK BEOOEO ARKOSIC SANOSTONE. SECTION EROM HUMPHREY AND DIAZ, SECTIONS FROM HUMPHREY AND OtAZ, HUMPHREY (1956), CERRO LA S ILL A, NUEVO HUMPHREY (1956)* SIERRA DE LA GAVIA, LEON, MEXICO. COAHUILA, MEXICO. C (4) TARAISES FORMATION a IRREGULARLY INTERBEDOED GRAY LfMESTONES AND SHALES; SHALES WITH THIN INTERBEDS OF GRAY LIMESTONE; AND LIMESTONES WITH (HA)‘-“ T s MINOR INTERBEDS OF GRAY FISSILE SHALES. SECTION FROM SIERRA DEL FRAILE, NUEVO L£ON, MEXICO. (4A) BARRIL VIEJO FORMATION, WESTERN FACIES WITH GREENISH GRAY AND BROWN SHALES WITH MINOR INTERBEOS OF SHALY \ LIMESTONE I SECTION FROM HUMPHREY AND OtAZ, HUMPHREY (10) PARRAS SHALE (1956), SIERRA OE LA GAVIA, COAHUILA, fe BLACK TO GRAY AND BROWN, CARBONACEOUS ANQi MEXICO. a CALCAREOUS SHALES WITH THIN, FINE GRAINED CALCAREOUS SANOSTONE. (3) LA CASITA GROUP SECTION FROM MURRAY, ET AL, UNPUBLISHED CHIEFLY SHALES, VARYING IN COLOR AND DATA, PAREO0N AREA, COAHUILA, MEXICO. --ESoti BEDOING. INCLUDES MINOR UNITS OF (10A) SAN FELIPE FORMATION: EASTERN FL-(iO)r_-^ — GENERALLY THIN BEODED LIMESTONES. EQUIVALENT WITH GRAY TO GREENISH GRAY LIMESTONE ALTERNATING WITH LAMINATED SECTION FROM SIERRA DEL FRAILE, NUEVO o GRAY SHALE. LfiON, MEXICO. £ SECTION FROM HUMPHREY ANO DlAZ, (2) ZULOAGA LIMESTONE HUMPHREY (1956), CERRO LA SILLA, NUEVO LEON, MEXICO. THIN- TO THICK BEODED, BLUE, BROWN. PINK, OR GRAY LIMESTONE; GENERALLY MINERALIZED AND FRACTUREO. SECTION FROM SIERRA DEL FRAILE, NUEVO LEON, MEXICO. (1) MINAS VIEJAS GROUP WHITE,GRAY,BROWN,ANO YELLOWISH GYPSUM AND £ ANHYD&ITE| INTERBEDOED SALT AND GYPSUMI „ SALT WITH MINOR INTERBEOS OF SHALE AND LIMESTONE. INTRUSIVE IN PART. PERMIAN and/or TRIASSIC and/or JURASSIC SECTION FROM WELL LOG DATA, PEMEX - LOS RAMONES # 1, NUEVO LEON, MEXICO.
FIGURE 3
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CORRELATION CHART Parras Sabinas Mesozoic Formations Basin Basin
COAHUILA MARGINAL SOUTHWEST TEXAS ARKANSAS ANO LOUISIANA NORTH AMERICAN TAMPICO - TUXPAN SUBSURFACE EUROPEAN STAGE ERA SYSTEM STAGE FOLOEO BEIT / SUBSURFACE
y escondiTx T ESCQNOIOO MACSTRICHTIAN OLMOS
SARATOGA DlFUNTA
02AN
SANTONIAN
NUEVA
LCUER TUSCALOOSA
CUESTA DEL CURA DEL RIO UNDIFFERENTIATED
FREOERICKS- BURG IAN EDWARDS WALNUT
ALB IAN
tO UNDIFFERENTIATED ROOESSA
OTATES
CUP 100 SLIGO
MOSSTON HOSSTON
CALlZA TENE^flPA SCHULER BOSSIER
ZULOAGA f ZULOAGA MINAS ‘v ^IEJa K ______^ N T R U S I V E S
MINAS VIEJAS MINAS VIEJAS GYPSUM
NJ p a l e o z o i c:
(After Murray, 1961) FIGURE 4
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GEOGRAPHY OF THE PARRAS BASIN
The landforras of tne Parras Basin consist basically
of two types, being largely dependent upon the underlying
formation. Outcrops of the Parras Shale form valleys,
large flats, and "Lagunas'1 (large dry playas) . Sediments of
the Difunta Group forms hills of three main types— cuestas,
rounded anticlinal or synclinal hills, and hogbacks. The
larger hills ("cerros") are generally formed by synclines;
the anticlines have been eroded and form the adjacent valleys
Red bed formations of the Difunta Group generally support a
more subdued topography than the intervening formations.
Maximum relief within the Parras Basin is about 2,500
feet in the cerros north of Saltillo. Elsewhere in the basin
the^relief is considerably less, and diminishes virtually to
zero in the region of the Laguna de Mayran, a large, alluvial
covered, dry-lake bed, between Parras and Torreon.
The climate of the Parras Basin is semi-arid, with
rainfall averaging between 12 and 20 centimeters per year,
and coming primarily in the period from June to November.
23
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All streams in the region are intermittent, flowing only
during, and for a few hours after a rain. The virtual absence
of grass permits rapid run-off, and after intense rains, which
infrequently occur, the arroyos become the beds of surging
streams. Upon debouching into valleys and flats the water is
rapidly soaked up by the alluvial cover.
Vegetation is rather sparse, and consists primarily of
cactus and other spine-bearing plants, with occasional patches
of grass and clusters of palms. Rabbits and foxes comprise
the most apparent portion of the indigenous fauna.
The principal towns in the Parras Basin are Saltillo,
Parras, General Cepeda, and Ramos Arizpe. Other large cities
such as Monterrey, Torreon, Gomez Palacio, and Lerdo are on
the periphery of the basin. Agriculture is largely confined
to two main areas, near Torreon and General Cepeda. The two
basic crops are cotton and corn. Viniculture is prominent
in the Parras and Ramos Arizpe areas. The sparse vegetation
of the remainder of the basin supports grazing by a few
cattle and goats.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NJ tn j j C m Parras Sh. Cerro del Pueblo Fm* folos folds
folos
open Cerro Grande Fm. /-Canon del Tule Fa. , , oomal Cerro del Pueblo ftn. , , overturned Parras Sh* , , b r o a d e l o n g a t e
Las Imagenes Pa* t i g h t of of
Eneinas ^ Fm* y Las Imagenes Fm* ^ ^ Corro Huert^ FIGURE 5 of M I LE I M
rea rea Las Las A A rea R a n o h o Nuero Fm. ^ A fta? u o t c IDEALIZED CROSS SECTIONS, PARRAS BASIN SECTIONS, IDEALIZED PARRAS CROSS ^Canan del Tule Pm -Cerro Huerta Pm. Ranoho • • U N ANO VERTICAL SCALE- ANO VERTICAL NOR IZONTAL NOR
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV
STRATIGRAPHY OF THE PARRAS BASIN
INTRODUCTION
The sedimentary rocks ejqposed in the Parras Basin are
of Late Cretaceous (Gulfian) and Early Tertiary (Midwayan)
age. Positive structural features surrounding the basin ex
pose Upper Jurassic and Lower Cretaceous strata, but these
beds do not crop out in the basin proper. It is obvious,
however, that they are present at depth in the basin. The
formations exposed in the basin are:
Quaternary and Recent
Mayran Formation and Alluvium
Tertiary (Midwayan)
Difunta Group
Rancho Nuevo Formation
Cretaceous (Gulfian) and/or Tertiary (Midwayan)
Difunta Group
Las Eneinas Formation
Cretaceous (Gulfian)
26
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Cerro Grande Formation
Las Imagenes Formation
Canon del Tule Formation
Cerro Huerta Formation
Cerro del Pueblo Formation
Parras Shale
Indidura Formation
The Indidura Formation crops out in a narrow band on
the periphery of the basin and adjacent to the marginal
positive elements. It is also present east of Paredon in a
small domal uplift. The Parras Shale, which forms extensive
valleys and flats, is exposed on the margins of the basin,
in anticlinal valleys, and in the large laguna region of the
west, where it is generally covered with alluvium. The Di
funta Group occupies the axial portion of the basin and forms
cuestas and cerros because of its relative resistance to
erosion.
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CRETACEOUS SYSTEM
Gulfian Series
Indidura Formation
Definition and type locality; The Indidura Formation
was described by Kelly (1936) from the region of Las Delicias,
Coahuila. The type locality, the eastern slope of Cerro
Indidura at the southern end of the Sierra de Santa Ana, is
approximately twelve miles west-southwest of Las.Delicias.
There the Indidura is underlain by dense gray■limestones of
the Aurora and overlain by Tertiary conglomerates.
Areal extent: Beds of the Indidura Formation are ex
posed on the periphery of the basin on the northern flank of
the Sierra Madre Oriental, the southern flank of the Coahuila
Platform and the adjacent La Gavia-La Gloria trend. A small
domal uplift east of Paredon exposes Indidura in the core.
Because of its proximity to more resistant, ridge and mountain-
forming strata, and its own weakness to erosion, the Indidura
Formation is generally covered by alluvium and alluvial fan
detritus.
The rocks of the Indidura Formation are widely exposed
in the Sierra Madre Oriental, where they and the Parras Shale
usually form the surface of the synclinal valleys.
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Stratigraphic and lithologic characteristics: The
Indidura Formation consists of thin- to medium-bedded, dark
gray limestones, gray to brown argillaceous limestones, and
brown, calcareous and arenaceous shales. A conglomerate
possibly signifying an erosional discordance is present at
the base of the formation in the Sierra de Mapimx, but else
where it appears concordant with the underlying formation.
In the Sierra de la Pena the middle portion of the Indidura
contains sandy and gypsiferous horizons. Virtually everywhere
the Indidura becomes more shaly or argillaceous towards the
top of the formation. It varies in thickness from 1,500 to
2,500 feet.
Correlation; Jones' (1938) studies of the Indidura
and its fauna indicate that the formation ranges from late
Albian to Turonian age, approximately equivalent to Fredericks
burg, Washita, and Eagleford, in the Sierra de la Pena. Imlay
(1936), based on work in the Sierra de Parras, assigned the
formation to the Cenomanian and Turonian (Washita and Eagle
ford equivalents). Humphrey (1949) considered the Indidura
of the Sierra de ✓los Muertos as Cenomanian and Turonian. Thus,r
the Indidura of the Parras Basin and environs may range in
equivalency from Fredericksburg to Eagleford; and on the basis
of lithic similarity, possibly lower Austin.
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Parras Shale
Definition and type locality: The Parras Shale was
described by Imlay (1936) from the Lomas de San Pablo, about
four miles east of Parras, Coahuila. There the black shales
of the Parras are conformably overlain by the Difunta Group
and conformably overlie the Indidura.
Areal extent; The Parras Shale crops out extensively
in the Parras Basin and adjoining areas. Many synclinal
valleys of the Sierra Madre Oriental are floored by this
formation, and it is widely distributed in the Coahuila
Marginal Fold Trends. Jones (1938) and de Cserna (1956)
state that it is absent due to erosion in the Sierra de la
Pena and de Cserna's cross-sections illustrate the Difunta
Group overlying the Indidura Formation north of the Sierra
de la Pena. This is not the case. The farthest western out
crops of the Difunta in the Cerros Hormigas, between La
Virgen and Bola on the Saltillo-Torreon highway, immediately
north of the Sierra de la Pena, are underlain by Parras
Shale.
Forde (1959) in the area between Saltillo and Monter
rey stated that the Parras Shale was laterally gradational
into the shales of the Mendez Formations to the east. The
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Mendez Formation was described from the Gulf Coastal Plain,
hence I feel that its use should be restricted to the area
east of Monterrey. He also regarded the Parras Shale as
gradational upwards into the Difunta and proposed a "Transi
tion Zone" of the intervening gradational strata.
A "Transition Zone" is a poor concept and only creates
more problems than it solves. My work has shown that the
basal sandstone bed of the Cerro del Pueblo Formation is con
tinuous from Ramos Arizpe westward to Bola and northward
throughout the basin. From Ramos Arizpe to Monterrey the
massive sands begin to occur stratigraphically higher in the
section and the top of the Parras Shale is therefore defined
as the shales immediately below the massive sands.
Stratigraphic and lithologic characteristics: The
Parras Shale at the type locality consists of calcareous, dark
gray to black, fissile to nodular shales with thin beds of
fine-grained, calcareous, gray siltstones. Humphrey (1949)
described the Parras of the Sierra de los Muertos as black or
dark brown, carbonaceous, fissile shales interbedded with
minor units of limestone and gypsum, and noted that some of
the gypsum contained small quartz veins. Everywhere in the
Parras Basin the composition of the formation is fairly uni
form, consisting of black, gray, or brown, nodular or fissile
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shales, with interbeds cf calcareous siltstone, which are # more numerous in the upper part of the section.
The thickness of the Parras Shale varies between 4,000
and 5,000 feet. Imlay (1936) measured 2,300 feet at the type
locality, but estimated its total thickness ,as twice that
magnitude. Humphrey (1949) gives 4,500 feet as the approxi
mate thickness in the Sierra de los Muertos. A measured
section in the domal uplift east of Paredon, Coahuila, has a
thickness of 4,140 feet.
Correlation: Correlation of the Parras Shale is made
difficult by the lack of fossils. Its stratigraphic position
therefore, has most often been determined as the interval
between the Indidura and Difunta, hence, it is usually con
sidered as Austinian.
As noted above, the top of the Indidura Formation is
late Eaglefordian and possibly early Austinian. Therefore,
the basal Parras is early Austinian. Facies changes in the
upper portion of the Parras Shale make correlation more dif
ficult higher in the formation. The Parras is contiguous with
the Mendez Shale to the east which is Tayloran and Navarroan.
Between Parras and Saltillo it is probably equivalent to the
lower Taylor. Near Monterrey Exogyra costata occurs in the
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Parras, indicating a Navarroan (most probably early
Navarroan) age.
Difunta Group
Imlay (1936, 1937b) described the Difunta Formation
from the hills near El Pozo and Boquillas, Coahuila, and
named it for Cuesta Difunta, three miles north of El Pozo.
He correlated it with the Taylor of southwest Texas. Diag
nostic fossils of a Tayloran age occur in the lower Difunta
of the type area. Imlay supposed the entire Difunta to be
Tayloran despite finding fossils indicative of Navarroan
age higher in the section. Murray, Weidie, Boyd, Forde, and
Lewis (1961) raised the Difunta to "Group" rank and differ
entiated seven formations which they named and described.
Of these seven formations, five are of definite Late Cre
taceous (Tayloran and Navarroan) age and one of Tertiary
(Midwayan) age. The intervening Las Eneinas Formation lacks
fossils and may be uppermost Cretaceous, lowermost Tertiary,
or both. Strata of the Difunta Group are restricted to the
Parras Basin and have a maximum thickness of about 12,500
feet.
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Cerro del Pueblo Formation
Definition and type locality: Murray, Weidie, Boyd,
Forde and Lewis (1961) described the Cerro del Pueblo Forma
tion from the small hill just off the Saltillo-Torreon high
way at the northwestern city limits of Saltillo. There the
dark gray shales and siltstones of the Cerro del Pueblo con
formably overlie the Parras Shale and are conformably over- :
lain by the Cerro Huerta Formation. The base of the Cerro
del Pueblo Formation was defined as the base of the massive
siltstone and sandstone which caps the hill. The top was
defined as the top of the massive siltstone, 1,025 feet
stratigraphically higher, immediately below the red and green
shales oi the Cerro Huerta Formation.
Areal extent: The Cerro del Pueblo Formation is re
stricted to the Parras Basin, but crops out extensively within
the basin. It extends eastward from north of the Sierra de
la Pena to the vicinity of Mariposa and Higueras, on the
Saltillo-Monterrey highway. East of the Mariposa-Higueras
area and north and northeast of the Fraustro-Paredon area
the Cerro del Pueblo Formation grades laterally into undif
ferentiated Difunta strata.
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Stratigraphic and lithologic characteristics: In the
type area, the Cerro del Pueblo Formation consists of gray to
black, fissile to nodular, calcareous shales, and calcareous
siltstones and sandstones. Much of the shale and virtually
all of the siltstones and sandstones weather to a buff or
brown color. Throughout the Parras Basin the Cerro del
Pueblo Formation presents a fairly uniform lithology. How
ever, many of the siltstones and sandstones are lenticular,
hence thickening, thinning, and pinch-out are fairly common.
An exception to this is the basal bed, which has a large
areal extent. Glauconite occurs at a few horizons near
Benito Juarez on the Saltillo-Torreon highway. Cross-bedding
and ripple marks are common in the coarser units of the
section.
At the type locality the Cerro del Pueblo has a thick
ness of 1,025 feet. The thickness does not vary appreciably
and virtually everywhere in the basin is between 900 and
1,100 feet.
Correlation: Murray, Weidie, Boyd, Forde, and Lewis
(1961) assigned a late Tayloran and early Navarroan age to the
Cerro del Pueblo Formation. Exogyra ponderosa occurs in the
lower part of the formation, and higher in the section the
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fauna indicates an early Navarroan age. The Cerro del Pueblo
is equivalent to the Mendez Shale of the Burgos Basin and the
San Miguel and Olmos Formations of the Sabinas Basin.
Cerro Huerta Formation
Definition and type locality; The Cerro Huerta Forma
tion was described by Murray, Weidie, Boyd, Forde and Lewis
(1961) from the large hill about 6 miles southwest of Saltillo
on the Concepcion del Oro highway. The redbeds of the Cerro
Huerta Formation are conformably overlain by the Canon del
Tule and conformably overlie the Cerro del Pueblo Formation.
The base of the formation was defined as the red and green
mudstones and siltstones overlying the massive siltstone
which is the top of the Cerro del Pueblo Formation. The top
of the Cerro Huerta Formation was defined as the top of the
red siltstone and sandstone, 3,430 feet stratigraphically
higher, and immediately underlying the basal gray siltstone
of the Canon del Tule Formation.
Areal extent; The Cerro Huerta Formation is restricted
to the Parras Basin. Its areal extent within the basin is
essentially the same as the underlying Cerro del Pueblo Forma
tion. The formation thins to the north and east and is not
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present east of the Mariposa-Higueras area or northeast of
the Fraustro-Paredon area.
Stratigraphic and lithologic characteristics: The
Cerro Huerta Formation is composed of red and green, calcare
ous, mudstones, shales, siltstones, and sandstones, with
occasional interbeds of gray shales and siltstones bearing
marine fossils. Petrified wood, plant remains, charophytes,
and vertebrate fossils are found in the red and green strata.
Ripple marks and cross-bedding are common throughout. The
sediments, flora, and fauna of the Cerro Huerta Formation
indicate deposition in lacustrine and continental environ
ments. Occasional ingress of marine waters (probably brack
ish) is evidenced by the gray fossiliferous strata. The
formation thickens and coarsens to the southwest near General
Cepeda, indicating the source area was to the southwest.
From this locus of maximum deposition the formation thins in
all directions, eventually interfingering and pinching out in
the Mariposa-Higueras and Fraustro areas respectively.
Figure 6 illustrates the interfingering and wedgeout
of the Cerro Huerta Formation in the above two areas. Forde
(1959) noted the interfingering near Mariposa-Higueras but
did not observe the progressive eastward change of the forma
tion. Boyd (1959) concluded that the Cerro Huerta was
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RA I LRGAD H I GHWAY N
Canon del Tule Fm
D ifunta Cerro Huerta Fm UNO IFF*
C erro del Pueblo Fm
FIGURE 6 A N orthern wedgeout of C erro Huerta 5 n i » W of F raustro Ho r izo n ta l s c a l e :1"»4-500' Ve r tic a l scALE:1n»250' W Canon oel Tule Fm
c: C erro D ifunta Huerta Fm und IFF.
Gr
Gr
Gr Gr Gr
I* C erro del pueblo F m~. FIGURE 6 B Eastern interfinger ing of Cerro Huerta 5hi.E of Higueras R= RE D G = GREEN GR=GRAY______—
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absent to the north, but did not determine its northernmost
extent. He contradictorily stated its absence to the north
was due to "wedge-out," "interfingering," "pinch-out," and
"intertonguing."
Correlation: No diagnostic fossils have been encount
ered in the Cerro Huerta Formation, but its stratigraphic
position is clearly defined because of the presence of Navarro
fossils immediately above and below. Murray, Weidie, Boyd,
Forde and Lewis (1961) considered it Navarroan.
Canon del Tule Formation
Definition and type locality: Murray, Weidie, Boyd,
Forde and Lewis (1961) described the Canon del Tule Formation
from the canyon of the same name ten miles north of Saltillo
on the Eagle Pass highway. At the type locality, 1,955 feet
of gray, calcareous, shales, siltstones, and sandstones con
formably overlie the Cerro Huerta Formation and are con
formably overlain by the Las Imagenes Formation. Two massive,
gray, calcareous, silt and sandstone beds form the top and
bottom units of the formation.
Areal extent: The Canon del Tule Formation has es
sentially the same areal extent as the Cerro Huerta and Cerro
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del Pueblo Formations, being restricted to the Parras Basin,
but well-developed everywhere in the basin. East of Paredon
and Zertuche, the formation grades laterally into the undif
ferentiated Difunta Group.
Straticrraphic and lithologic characteristics; The
Canon del Tule Formation consists of gray, calcareous, shales,
siltstones, and fine-grained sandstones. Many horizons are
quite fossiliferous and contain a varied, well-preserved in
vertebrate fauna. Much of the formation consists of rhythmi
cally bedded black calcareous shales and gray calcareous
siltstones. At the type locality it is increasingly arena
ceous upwards. To the southwest, in the vicinity of General
Cepeda, the formation thins to 1,000-1,100 feet, and the
entire sequence is coarser and more arenaceous, ripple marked
and cross-bedded. It thickens slightly farther to the west
near Parras, while to the east of Paredon and Zertuche it
grades laterally into the undifferentiated Difunta Group.
Correlation: Murray, Weidie, Boyd, Forde and Lewis
(1961) on the basis of the molluscan fauna considered the
Canon del Tule as Navarroan. Exocryra costata is found
throughout the section, and the Canon del Tule Formation is
equivalent to the Olmos and Mendez Formations of adjacent
areas.
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Las Imageries Formation
Definition and type locality: Murray, Weidie, Boyd,
Forde and Lewis (1961) described the Las Imagenes Formation
from outcrops exposed near the village of Las Imagenes, 13
miles north of Saltillo on the highway to Eagle Pass, Texas.
Conformably overlying the massive bed which forms the top of
the Canon del Tule Formation are 455 feet of red and green,
calcareous, shales, siltstones, and sandstones of the Las
Imagenes Formation. They are conformably overlain by the
gray shales, silts, and sands of the Cerro Grande Formation.
Areal extent; The Las Imagenes Formation is restrict'
ed to the Parras Basin, extending eastward from the vicinity
of Parras to Zertuche, and northward from General Cepeda to
the area of Paredon. East of Paredon and Zertuche it wedges
out completely. Figure 7A illustrates the eastern wedge-out
of the Las Imagenes 2.5 miles southwest of Zertuche.
Stratigraphic and lithologic characteristics; The
Las Imagenes Formation is predominantly red and green, cal
careous, shale and siltstone with lesser amounts of fine
grained, calcareous, red, green, and gray standstones. At
the type locality the formation is 455 feet thick. It thins
to about 300 feet near Las Encinas, 50 feet northwest of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. D ifunta UNO IFF W
Cerro Grande Fh
Las Imagenes Fm
>
Canon del Tule Fm
FIGURE 7A Eastern wedgeout of Las Imagenes 2.5m»SW of Zertuche
Ho r izo n ta l s c a l e : T i » 4 -5 0 0 '
Ve r t ic a l s c a l e : 1 " » 2 5 0 *
D ifunta UNO f FF.- W 7 r **s.. Rancho Nuevo Fm . < La* EncinaT I Cerro Grande Fm . 1 FIGURE 7B
Eastern wedgeout of Las En c in a s Fm. 1 . 3 m i .3W of Z ertuche
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Paredon, and between San Miguel and Zertuche, and wedges out
completely to the southwest of Zertuche. To the southwest
near General Cepeda the Las Imagenes Formation thickens to
about 800 feet, and further west towards Parras and the
Sierra de la Pena it is 300-500 feet thick. No vertebrate
or invertebrate fossils have found in the sequence, but
charophytes are abundant.
Correlation: Murray, Weidie, Boyd, Forde and Lewis
(1961) noted the absence of direct evidence of the age of the
Las Imagenes Formation, but judged it to be Navarroan on the
basis of its stratigraphic position between two formations
of known age, both of which contain Late Cretaceous (Navar
roan) fossils. Equivalents of the Las Imagenes Formation in
northeastern Mexico are the Mendez and Olmos Formations.
Cerro Grande Formation
Definition and type locality: The Cerro Grande Forma
tion was described by Murray, Weidie, Boyd, Forde and Lewis
(1961) from Cerro Grande, the large hill west of Las
Imagenes, about 13 miles north of Saltillo on the Eagle Pass
highway. The type section, on the east facing slope of Cerro
Grande, consists of 3,285 feet of gray, calcareous arenaceous-
argillaceous strata conformably overlying the Las Imagenes
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Formation, and conformably overlain by the Las Encinas Forma
tion.
Areal extent; The Cerro Grande Formation is present
in the western portion of the basin in the Parras area and
extends eastwards to the vicinity of General Cepeda. It is
also found in the hills north of Saltillo, but east of the
Paredon-Zertuche area the Cerro Grande grades laterally
into the undifferentiated Difunta Group.
Stratigraphic and lithologic characteristics: The
Cerro Grande'Formation is composed of gray, calcareous,
shales, siltstones, and sandstones, with occasional con
glomeratic horizons. The conglomerate layers occur more
frequently than in the Cerro del Pueblo and Canon del Tule
Formations, whose conglomeratic horizons are negligible both
areally and stratigraphically. Glauconite is found at varied
intervals in the Cerro Grande. At the type locality the
formation is 3,285 feet thick, and this probably represents
the maximum thickness of the unit. In most other areas
measured sections show a thickness of 2,100-2,500 feet. The
higher percentage of coarse elastics in the Cerro Grande
probably indicates accelerated epeirogenic uplift in central
Mexico, south and west of the Parras Basin.
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Fossils are abundant in the Cerro Grande, especially
the molluscan forms. Representatives of other phyla are
notably insignificant or lacking.
Correlation: Exoqyra costata occurs throughout the
Cerro Grande Formation. Other less diagnostic fossils are
found in abundance, such as Ostrea spp. Murray, Weidie, Boyd,
Forde and Lewis (1961) designated the Cerro Grande as Late
Cretaceous (Navarroan), and correlated it with the Mendez and
Escondido Formations of northeastern Mexico.
CRETACEOUS AND/OR TERTIARY SYSTEM(S)
Gulfian and/or Paleocene Series
Las Encinas Formation
Definition and type locality: Murray, Weidie, Boyd,
Forde and Lewis (1961) described the Las Encinas Formation
from the north flank of the San Miguel Syncline, 18.5 miles
north of Saltillo on the highway to Eagle Pass. The type
section is well exposed about one-half mile west of the high
way, where the formation is 63 feet thick. The Las Encinas
conformably overlies the Cerro Grande and is conformably over-
lain by the Rancho Nuevo Formation.
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Areal extent: The Las Encinas is present only in the
hills north of Saltillo. It is absent westward because of
erosion or non-deposition. The locus of deposition in the
late Navarro and Early Tertiary was in the San Miguel-Rancho
Nuevo area, hence the Las Encinas and succeeding Rancho
Nuevo Formations are restricted to this region. North and
east of the Paredon-Zertuche area the Las Encinas wedges out.
Figure 7B illustrates the eastern wedge-out of this formation
1..3 miles southwest of Zertuche.
Stratigraphic and lithologic characteristics: The
Las Encinas Formation consists predominantly of red, calcar
eous, shales and siltstones, with lesser amounts of fine
grained, red, calcareous, sandstones, and red and green mud
stones. The maximum exposed thickness is on Cerro Antonio,
immediately west of Cerro Grande, where 430 feet of the
formation crop out. There the upper portion contains coarse
sandstone beds and occasional conglomeratic horizons. The
formation thins rapidly in all directions; is 63 feet thick
at the type locality a few miles north? and wedges out near
Paredon and Zertuche. The western wedge-out of the Las
Encinas has been eroded.
Correlation; No fossils have been found in the Las
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Encinas Formation. Murray, Weidie, Boyd, Forde and Lewis
(1961) correlated it on the basis of its stratigraphic posi
tion between two fossiliferous formations. A definite age
assignment is presently impossible, but the time interval is
small. It may be: (1) uppermost Cretaceous, (2) lowermost
Tertiary, or (3) a gradational Cretaceous-Tertiary sequence.
TERTIARY SYSTEM
Paleocene Series
Rancho Nuevo Formation
Definition and type locality: The Rancho Nuevo Forma
tion was described by Murray, Weidie, Boyd, Forde and Lewis
(1961). The sequence exposed in the San Miguel Syncline, 18.3
miles north of Saltillo (1.4 miles north of San Miguel) on
the Saltillo-Eagle Pass highway, was designated as the type
section. The formation was named for the village of Rancho
Nuevo, 7.6 miles farther to the north, and on the outcrop of
this formation. At the type locality 294 feet of the Rancho
Nuevo sequence conformably overlie the Las Encinas Formation.
Areal extent: The Rancho Nuevo Formation is restricted
to the Las Imagenes and San Miguel Synclines and the Rancho
Nuevo Synclinorium. Its absence throughout the remainder of
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the basin is attributable to erosion or non-deposition.
Stratiqraphic and lithologic characteristics: The
Rancho Nuevo consists of gray, calcareous, shales and silt
stones. Conglomeratic horizons are rare. It conformably
overlies the Las Encinas and is angularly overlain by
Quaternary or Recent gravels. The original thickness of the
formation is impossible to determine; the maximum known thick
ness is about 400 feet. There is no evidence to indicate the
original thickness was appreciably greater, or that later
Tertiary formations were deposited upon it.
Correlation: On the basis of contained fossils, Murray,
et al. (1960a) assigned the Rancho Nuevo Formation an Early
Tertiary (Midwayan) age, and correlated it with the Midway
and Velasco of the Gulf Coastal Plain.
QUATERNARY SYSTEM
Mayran Formation and Alluvium
Definition and type locality: Imlay (1936) defined
the Mayran Formation as follows:
The name Mayran formation is here applied par ticularly to the consolidated conglomerates and tufa deposits capping the mesas along the south side of the Parras Basin, from Parras eastward to
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General Cepeda, and from the Sierra de Parras north ward to the main highway between Saltillo and Tor- reon. The formation should also include all con glomerate deposits in the Parras Basin, or in the surrounding mountains, that were formed at the same time and are due to the same causes as the conglom erates capping the mesas. .
My studies of the Mayran Formation and the alluvium
of the Parras Basin were cursory, the limited time available
not permitting me to undertake detailed studies of these
materials. Their treatment is, therefore, brief and general.
Alluvium is widespread throughout the Parras Basin.
The component materials range from clay to gravel and boulder
size particles. Tufa is a frequent component of the alluvium.
Major alluvial deposits are in the Laguna de Mayran, regional
strike valleys, and large arroyos. The accompanying geologic
map (Plate I) does not depict the true extent of the alluvium.
It is shown diagramatically or not at all, in order that the
underlying geology may be more clearly shown.
CRYSTALLINE ROCKS
Calcite Veins
Calcite veins are common throughout the Parras Basin.
Most are small, having a width of less than 0.5 feet. The
width of the largest vein was 3.0 feet. None of the veins
have an appreciable areal extent, and their attitude is quite
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variable. Over-all, the veins show no significant orienta
tion, but some degree of control is exercised by the local
structure.
Calcite is the predominant vein mineral. Quartz,
gypsum, and siderite are associated minerals. Locally the
veins may be largely composed of a concentration of any of
the above minerals. Quartz commonly occurs in the central
zone of the vein.
IGNEOUS ROCKS
Andesitic(?) Sills and Dikes
Sills and dikes occur in the western portion of the
basin north of the Sierra de la Pena. They are light gray,
weathering to grayish green and grayish brown, and similar
in appearance to the siltstones of the area. The sills and
dikes produce little or no apparent metamorphism, in the
adjacent beds. Imlay (1937b) noted the occurrence of these
sills and dikes and cited plagioclase, calcite, magnetite,
pyrrhotite, limonite, and serpentine as the constituent
minerals, with serpentine and some of the calcite replacing
olivine. He states, "The rock is^ither a basalt or an
andesite depending on the plagioclase present, but the latter
is highly altered and was not determined."
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STRUCTURE OF THE PARRAS BASIN
INTRODUCTION
The Parras Basin is an east-west trending structural
and sedimentary basin. It is surrounded on all sides by
high ranges upheld by the massive Lower Cretaceous limestones.
The structures that form the hills and mountains of Upper
Cretaceous elastics in the basin are parallel to and accord
ant with the Sierra Madre Oriental fold axes.
The strata of the Parras Basin, in general, form a
broad, asymmetrical synclinorium. The structural and de-
positional axes are approximately coincident and are in the
southern half of the basin, nearer the front range of the
Sierra Madre Oriental. The main structural features of the
basin are folds, faults, and joints. The geologic and
tectonic maps (Plates I and II) illustrate the basic struc
tural features. Detailed structure sections are shown on
Plate III. The lines of section are on Plate I.
Three areas with differing deformational
51
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characteristics are delineated. Plate II shows the extent
of these areas, which are termed: (1) area of overturned
folds, (2) area of large, elongate, open folds, and (3) area
of gentle folding and broad domal uplift. These areas show
a diminution of deformational intensity away from the Sierra
Madre Oriental. Figure 5 shows idealized cross-sections of
these areas.
The area of overturned folds is in the western portion
of the Parras Basin. The southern margin of this area is
within 3 to 5 miles of the Sierra de la Pena and the Sierra
de Parras. These small folds, generally 6 to 10 miles in
length and one-half to one and one-half miles in width, are
locally overturned along strike. Basic intrusions, dikes
and sills, occur in the highly fractured axial portions of
some of the anticlines. The close folding and local over
turning is a result of proximity to the Sierra Madre Oriental
on the south and the Coahuila Platform on the north. Thus,
a comparatively narrow belt of sediments was highly deformed
between the active orogenic area to the south and the resist
ant, buttress-like area to the north.
The area of large, elongate, open folds is in the
southeastern portion of the Parras Basin. The southern
margin of this area is within 3 to 6 miles of the Sierra Madre
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Oriental. The large, open folds, 12 to 15 miles long and two
to four miles wide, are predominantly symmetrical and charac
terize this area. To date, no basic intrusions have been
found in this area. Thrust faults occur near the northern
and southern peripheries of this region. In this area the
deformation is less intense than in the Sierra Madres or the
overturned belt to the west. The north and northeasterly
directed compressive forces of the Sierra Madre orogenic belt
did not encounter a resistant region to the north. The lack
of resistance plus the great sedimentary thickness in the
basin caused the sediments to form broad symmetrical folds.
On the western side, where sediments are thinner and adjacent
to the eastern margin of the Coahuila Platform, many small
thrust faults were formed.
The area of gentle folding and broad domal uplift is
/ in the northern and northeastern parts of the Parras Basin.
It is separated from the Sierra Madre fold belt to the south
by the area of large, elongate, open folds. It borders the
eastern margin of the Coahuila Platform and lies many miles
south of the La Gavia-La Gloria trend. The gentle folds and
domal uplift are characterized by low dips, small structural
relief, small size, and subparallel axial alignments, as con
trasted to the parallelism of the above two areas. Thrust
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faults and tear faults are common on the western side near
the Coahuila Platform. The greater distance from the orogen
is clearly shown by the lesser deformation in this area.
The contemporaniety of folding in the Parras Basin and
the Sierra Madre Oriental is indicated by three distinct
lines of evidence. De Cserna (1956a, 1956b) and others
studied the structure and tectonic history of the Sierra
Madre Oriental, and concluded that the deformation is of
Early Tertiary age. Weidie, ert al. (1959) in studies of the
Parras Basin concluded the basinal sediments were folded and
faulted in Early Tertiary times. Evidence indicating this
is:
1. Continuous deposition in the basin from Cretaceous
to Paleocene times.
2. Absence of erosional disconformities or hiatuses
throughout the basin.
3. Accordance of intensity and attitude of folds
vertically through the stratigraphic section.
4. Lack of significantly large coarse elastics in
the section.
5. Uniformly consistent structural alignments and
features vertically through the section.
Studies of adjacent parts of the Parras Basin and the
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Sierra Madre Oriental indicate contemporaniety of deforma
tion. Evidence supporting this is:
1. Marked parallelism of structures.
2. Continuity of direction of structural axes from
the Sierra Madre into the Parras Basin.
3. Continuity of deformational intensity along struc
tures continuous from the basin to the sierras.
The deformation and resultant structure of the Parras
Basin are a function of:
1. The distance of the deformed zone from the orogenic
belt of the Sierra Madre.
2. The spatial relation of the deformed zone to the
active and passive tectonic elements, the Sierra Madre and
Coahuila Platform respectively.
Distance as an operative factor is clearly shown in
the area north of Saltillo. The geologic and tectonic maps
(Plate I and II) illustrate the effect of distance on deforma
tion. The area of large, elongate, open folds yields north
ward to the area of gentle folding and broad domal uplift.
On a large scale the sediments of the Difunta Group may be
said to form a physically homogenous unit.
The generalization of Hooke's Law that "stress is pro
portional to strain" implies that the stress or force to the
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north was less than that in the south. This diminution of
force with distance would result in the progressive decrease
of deformational intensity as outlined above. In many re
gions this relationship is obscured by other factors. How
ever, the region north of Saltillo shows uniform conditions
subject only to a change in distance.
The second factor, that of spatial relation to active
and passive tectonic elements, is demonstrated by the area to
the west. The overturned fold region is between the Sierra
Madre and the Coahuila Platform. The overturning in this
region is a consequence of location. The Sierra Madre Orient
al south of the Difunta overturned belt does not exhibit
greater deformation than that portion of the Sierra Madre
south of the area of large, elongate, open folds in the Di
funta. The explanation of the greater deformation to the
west cannot, therefore, be sought in terms of greater initial
stress.- The presence to the north of the Coahuila Platform,
a passive tectonic element, is the major difference in the
areas. The resistant, buttress effect of the Coahuila Plat
form confined the deformation to a smaller area, hence
deformation was more intense. Eastward the deformation
changes when the southeastern margin of the Coahuila Platform
is reached. Thus, the overturned folds yield to the large,
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elongate, open folds of the east.
Both the literature and field evidence confirm the
validity of regarding the Sierra Madre Oriental and the Coa
huila Platform as active and passive tectonic elements respect
ively. De Cserna (1956a, 1956b) states that the Sierra Madre
was the site of intensive north and northeasterly directed
compressive forces. Wall (1961) noted the greater degree of
deformation in the Sierra Madre as compared to the Coahuila
Marginal Folded Belt. The presence of thick evaporite
sequences below the Lower Cretaceous limestones enabled the
compressive forces to deform the Lower Cretaceous sediments
into folds of the Jura type. This intensity of deformation
certainly warrants the Sierra Madre Oriental being regarded
as an active tectonic element.
The Coahuila Platform exhibits no evidence of severe
deformation. Broad domes characterize the structure of this
area. There is no linearity or parallelism of structures
and dips rarely exceed 10 degrees. It exhibits none of the
mobility of orogenic belts and all post-Cretaceous movements
have been of a broad epeirogenic nature, hence it may be
well regarded as a passive tectonic element.
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FOLDING
As mentioned above, folding of three types is weli-
developed in the Parras Basin. These types have been general
ly described, and only specific or additional information will
be noted here.
The overturned folds trend east-west and the axial
planes usually dip in excess of 60 degrees to the south. The
folds are not overturned throughout their length, but every
where exhibit steep flank dips. Both symmetrical and asym
metrical folds occur; the symmetrical folds are often iso
clinal. Both parallel and similar folds exist; their occur
rence is dependent on the presence or absence of thick,
incompetent, diale or mudstone strata. The plunge of the
axes of the folds is rarely more than 15 degrees.
The large, elongate, open folds also trend east-west
and the axial plane is essentially vertical. The folds are
usually symmetrical and exhibit no evidence of flowage, being
parallel or flexure folds. The axes usually have a plunge of
less than 15 degrees. Maximum dips of the strata in these
folds vary from 30 to 60 degrees.
The gentle folds and domal uplifts trend irregularly.
The axial planes are most often vertical. The folds are
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symmetrical and open, exhibiting no flowage. The plunge of
the axes is usually five to 10 degrees and the maximum dips
rarely exceed 30 degrees. Many of the folds are nearly
circular, and are best described as domes or basins.
Intraformational folding has been observed where the
folding is intense. Shales and mudstones between competent
siltstone and sandstone beds are complexly contorted and
folded. The disordered structure is virtually impossible to
decipher. Drag folding is common adjacent to zones of thrust-
ing. Figure 8 is an example of dragfolds near a thrust fault.
This photograph was taken at the thrust fault approximately
one mile south-southwest of Rancho Nuevo.
FAULTING
Faulting of three types is present in the Parras Basin.
Thrust faults with associated tear faults are fairly common;
normal faulting is less frequent. The geologic and tectonic
maps (Plates I and II) show the distribution and nature of
the faults.
Major thrust faults occur near the northern and south
ern margins of the area of large, elongate, open folds. The
Las Encinas Fault on the north can be traced for over 10
miles. This fault dips southward from five to 20 degrees
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FIGURE 8
DRAG FOLDING NEAR RANCHO NUEVO
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and has an apparent displacement of 500 to 2,000 feet. The
El Meson and Santa Maria Faults in the south have a northward
dip. Displacement along these faults is difficult to ascer
tain, most of the movement being in the Parras Shale.
Numerous thrust faults with negligible displacement
occur near the eastern margin of the Coahuila Platform. All
of these faults dip to the south and die out westward in the
Parras Shale and eastward in the Cerro Grande and Rancho
Nuevo Formations.
The thrust fault zones are marked by intense deforma
tion and secondary mineralization. Gouge and fault breccia
constitute the bulk of the zone, and are cemented by calcite,
quartz, and siderite. The fault zones vary from 1-10 feet
in thickness and the adjacent beds are deformed and con
torted for varying distances away from the fault. Shale beds
near the faults are intensely fractured, jointed, and veined
with calcite, but siltstone and sandstone beds near the
faults show less deformation, and are usually drag folded
(see Figure 8).
In addition to the above criteria, thrust faults have
been recognized by the presence of striations and slicken-
sides, and abnormal stratigraphic sequences. Every thrust
fault on the geologic and tectonic maps has been carefully
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studied in the field. The actual thrust plane or zone has
been observed in at least one or more localities for every
mapped thrust. Apparent displacements have been calculated
by projecting che dips of adjacent strata into the measured
dip of the fault plane.
Tear faulting is frequently associated with thrust
faulting. The displacement along these tear faults is usual
ly slight— rarely exceeding 200 feet. Notable exceptions to
this are known in the Altamira and Zertuche Fault Systems
(see Plate II). The Altamira Fault has a horizontal com
ponent of displacement of about 500 feet. The vertical com
ponent in the southern portion is equally large, but cannot
be as accurately determined. The Zertuche Fault System is a
complex tear fault system associated with the Santa Maria
Fault. The maximum horizontal displacement is 1,300 feet;
the displacement diminishes gradually to each end of the
fault.
Tear fault zones are composed predominantly of calcite.
These zones vary in thickness from one to five feet and are
always within a few degrees of vertical. Horizontal stria-
tions and slickensides are abundant. The predominant north-
south strike of the tear faults is usually at right angles
to the strike of the strata, and in, areas of moderate to
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large dips the offset of the beds is strikingly apparent.
The displacements cited above have been measured in the field
by pacing or tape.
Only one large normal fault has been recognized in the
Parras Basin. It is on the northern flank of the Pico de Vega
Syncline (Plate II). The fault zone dips 75-80 degrees to the
south and the maximum vertical displacement is about 700 feet.
The displacement diminishes to each end of the fault and
eventually dies out. This fault zone is largely composed of
calcite, with little or none of the siderite and quartz com
monly found in thrust fault zones. The fault zone averages
three feet in thickness and has numerous slickensides. In
contrast to thrust fault zones, there is little or no deform
ation in adjacent beds.
Within and near the Zertuche Fault System are small
horsts and grabens of normally faulted blocks. The displace
ment on these is negligible. Similar small fault blocks
occur near the eastern margin of the Coahuila Platform in the
area of small thrust faults.
JOINTING AND CLEAVAGE
Joints are well developed throughout the Parras Basin
and adjacent areas. Most of them are found in one of two
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master sets. One set roughly parallels the structural axes;
the other set is approximately at right angles to it. Of the
two, the right angle or north-south set, is usually better
developed than the parallel or east-west set. Both sets are
generally within five to 10 degrees of vertical. The joints
cut through all types of beds without change in character,
but they are more obvious in the competent beds.
Fracture cleavage is well developed in siltstone and
sandstone beds on and near the crests of anticlines in the
area of tight, overturned folds. Such fracture cleavage is
analogous to closely spaced joints. Most of it trends east-
west and approximates the attitude of the axial planes of
the folds.
Slaty cleavage is quite common in the Parras Shale
and in incompetent strata of the Difunta Group near the
Sierra Madre Oriental. It also occurs in shale and mudstone
strata in the area of tight, overturned folds. It is usually
more or less parallel to the axial planes of the folds.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI
INTERPRETATION OF GEOLOGIC HISTORY
On the basis of the evidence cited in the preceding
pages we may deduce the following geologic history of the
Parras Basin and adjacent areas. Throughout Early Cretaceous
times predominantly calcareous sediments were being deposit
ed in northeastern Mexico. These she^f type carbonates
accumulated slowly under rather uniform environmental condi
tions. Warm, shallow water is indicated by the numerous
reefs present in the section. The vast extent of these
limestones indicates that nearly all of northeastern Mexico
was submerged or slightly above sea level in Coahuilan and
Comanchean times.
The advent of Late Cretaceous times saw slow epeiro-
genic uplift of the land areas. The Indidura, or basal Upper
Cretaceous, is significantly more argillaceous than the under
lying sediments. This slow uplift continued in the Austinian
with the deposition of the predominantly argillaceous Parras
Shale. Greater uplift commenced in central Mexico in the
65
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Tayloran. Larger volumes of coarser sediment were deposited.
The areas of maximal sedimentation began to subside more
rapidly than surrounding areas. The Gulf of Mexico retreated
eastwards and the loci of deposition, the Parras and Sabinas
Basins, became westward extending embayments of the Gulf of
Mexico. Uplift in central Mexico continued; vast areas of
Lower Cretaceous, Jurassic and Permo-Carboniferous sediments
and intrusive igneous rocks were actively eroded. The drain
age system became better developed and channeled large
amounts of coarse elastics from the south and west towards
the Parras Basin. The terrestrial and lacustrine redbeds of
the Difunta Group thicken and coarsen to the south and west.
Conglomerate horizons are larger and more frequent in the
same direction, and the attitude of the great majority of the
cross-bedding indicates derivation from the southwest.
Deposition and subsidence continued unabated into
Tertiary times. During late Paleocene or Eocene times oro-
genic stresses began and the Gulf of Mexico retreated from
the embayment. The basinal sediments were folded and faulted
contemporaneously with the nearby Sierra Madre Oriental oro-
genic belt. The duration of the deformation is unknown, but
it was succeeded by the regional uplift of the folded and
faulted sediments. That regional uplift continues to the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. present day is indicated by the incised and dissected
bajadas adjacent to the Sierra Madre and by the poorly de
veloped drainage in the basin proper.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SELECTED BIBLIOGRAPHY
Alvarez, Manuel, Jr., 1949, Tectonics of Mexico: Am. Assoc. Petrol. Geol. Bull., v. 32, p. 2312-2314.
Baker, C. L., 1941, Brief notes on the higher Cretaceous (Monterrey-Saltillo area): South Texas Geol. Soc. Guide book, 13th Annual Meeting.
______, 1941, Upper Jurassic deposits and structures of the Monterrey-Saltillo area: South Texas Geol. Soc. Guide book, 13th. Annual Meeting.
Bose, Emil, 1906a, Excursion dans les environs de Parras: Internat. Geol. Cong. X, Mexico, Guide Excursion 23.
______, 1906b, Excursion dans les environs de Monterrey et Saltillo: Internat. Geol. Cong. X, Mexico, Guide Ex cursion 29.
______, 1913, Algunas faunas del Cretacico Superior de Coahuila y regiones limitrofes: Boletin Inst. Geolog. de Mexico, num. 30.
______, 1921, On the Permian of northern Coahuila, northern Mexico: Am. Jour. Sci., ser. 5, v. 1, p. 187-194.
______, 1923, Vestiges of an ancient continent in northeast Mexico: Am. Jour. Sci., ser. 5, v. 6, p. 127-136.
______, and Cavins, 0. A., 1927, The Cretaceous and Ter tiary of southern Texas and northern Mexico: Texas Uni versity Bull., no. 2748, p. 7-142.
Boyd, D., 1959, Stratigraphy of the Difunta group in an area north of Saltillo, Coahuila, Mexico: Master of Science Thesis, Louisiana State University.
68
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69
Bridges, L. W., and Deford, R. K., 1961, Pre-Carboniferous Paleozoic rocks discovered in central Chihuahua, Mexico: Am. Assoc. Petrol. Geol. Bull., v. 45, no. 1.
Burckhardt, C. E., 1930, Etude synthetique sur le Mesozoique Mexicain: Soc. Paleon. Suisse Mem., v. 49.
Burrows, R. H., 1910, Geology of northern Mexico: Soc. Geol. Mex. Bol., tomo VII, p. 83-103.
Carrillo Bravo, Jose, 1955, Levantamiento geologico de la Sierra de Tamaulipas, Petroleos Mexicanos, Informe Geologico 487, 46 pp.
De Cserna, Zoltan, 1956a, Tectonica de la Sierra Madre Orien tal de Mexico, entre Torreon y Monterrey, Contr. Inst. Nacional para la investigacion de Recursos Minerales de Mexico, XX Congreso Geologico Internacional.-
______, 1956b, Geologia de la region entre Parral, Chihua hua y Monterrey, N. Leon? XX Congreso Geologico Inter nacional.
Diaz, T., 1954, Geologic compilation and reconnaissance bordering the Monterrey, Nuevo Leon-Saltiilo, Coahuila . highway; in South Texas: Geol. Soc. 21st Field Trip Guidebook.
______, 1956, Generalidades sobre la geologia del norte de Mexico: XX Congreso Geologico Internacional.
Forde, R., 1959, Stratigraphy and petrology of the Difunta Group between Saltillo, Coahuila, and Monterrey, Nuevo Leon, Mexico: Master of Science Thesis, Louisiana State University.
Hill, R. T., 1891, Preliminary notes on the topography and geology of northern Mexico, southeast Texas, and New Mexico: Am. Geologist, v. 8, p. 133-141.
______, 1893, The Cretaceous formations of Mexico and their relations to North American geographic develop ments: Am. Jour. Sci., ser. 3, v. 45, pp. 307-24.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70
Hill, R. T., 1923, Further contributions to the knowledge of the Cretaceous of Texas and New Mexico: (Abs.) Bull. Geol. Soc. Am., v. 34, no. 1, p. 95.
Humphrey, William E., 1941a, Geology of some mountain ranges east of the Saltillo Basin: (Abs.) Bull. Geol. Soc. Am., v. 52, no. 12, pt. 2, p. 1909.
______, 1941b, Stratigraphy of Cortinas Canyon section, Sierra de los Muertos, Coahuila, Mexico: South Texas Geol. Soc., 13th Ann. Meeting, Guidebook.
______, 1949, Geology of the Sierra de los Muertos area, Mexico: Bull. Geol. Soc. Am., v. 60, pp. 89-176.
______, 1954, Stratigraphy of Cortinas Canyon section Sierra de los Muertos, Coahuila, Mexico: South Texas Geol. Soc. Guidebook, 21st Field Trip, pp. 18-26. / 1 i ______, 1956, Tectonic framework of northeast Mexico: Transactions, Gulf Coast Assoc, of Geol. Societies, San-'' Antonio, Texas, vol. 6, pp. 25-35.
______, 1956a, Notes on geology of northeast Mexico: Sup plement to Guidebook, Laredo to Monterrey field trip, Corpus Christi Geol. Soc..Guidebook, 44 pages.
______, and Diaz, Teodoro, 1954, Reconnaissance geology and road log of the Monterrey-Saltillo-Monclova highway: South Texas Geol. Soc. Guidebook, 21st Field Trip.
Hunter, James W., 1931, Geological report of the Paredon area in the states of Coahuila and Nuevo Leon, Mexico: Unpublished report in the files of Petroleos Mexicanos, Monterrey, Nuevo Leon.
______, and Spiers, R. L., 1929, Upper Cretaceous section exposed on Monterrey-Saltillo highway 4.7 miles east of Higueras, Nuevo Leon, Mexico: Unpublished Report.
Imlay, R. W., 1936, Evolution of the Coahuila Peninsula, Mexico: Part IV, Geology of the western part of the Sierra de Parras, Geol. Soc. Am. Bull., v. 47, p. 1091- 1152.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71
Imlay, R. W . , 1937a, Geology of the middle part of the Sierra de Parras: Bull. Geol. Soc. Am., v. 48, pp. 587-630.
______, 1937b, Stratigraphy and paleontology of the Upper Cretaceous beds along the eastern side of the Laguna de Mayran, Coahuila, Mexico: Bull., Geol. Soc. Am., v. 48, pp. 1785-1872.
______, 1938, Studies of the Mexican geosyncline: Bull. Geol. Soc. Am., v. 49, p. 1651-1694.
.______, 1943a, Evidence for Upper Jurassic landmass in eastern Mexico: Am. Assoc. Petrol. Geol. Bull., v. 27, p. 524-529.
, 1943b, Jurassic formations of Gulf region (of North America, including United States, Mexico, and Cuba): Am. Assoc. Petrol. Geol. Bull., v. 27, p. 1407-1533.
______, 1944a, Cretaceous formations of Central America and Mexico: Am. Assoc, of Petrol. Geol. Bull., v. 28, no. 8, pp. 1077-1195.
______, 1944b, Correlation of the Cretaceous of the Greater Antilles, Central America and Mexico: Bull. Geol. Soc. Am., v. 55, no. 8, pp. 1005-1045.
Jones, T. S., 1938, Geology of Sierra de la Pena and paleon tology of the Indidura formation, Coahuila, Mexico: Geol. Soc. Am. Bull., v. 49, p. 69-149.
Kellum, L. B., Imlay, R. W., and Kane, W. G., 1936, Evolution of the Coahuila Peninsula, Mexico: Part I, Relation of structure, stratigraphy, and igneous activity to an early continental margin: Geol. Soc. Am. Bull., v. 47, p. 969- 1008.
Kelly, W. A., 1936, Evolution of the Coahuila Peninsula, Mexico: Part II, Geology of the mountains bordering the valleys of Acatita and Las Delicias: Geol. Soc. Am. Bull., v. 47, p. 1009-1038.
King, P. B., 1947, Carta geologica.de la parte septentrional de la Republica Mexicana: Mexico Universidad Nacional, Inst. Geol., Cartas Geol. y Mineras, no. 3.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72
King, R. E., 1934, The Permian of southwestern Coahuila, Mexico: Am. Jour. Sci., ser. 5, v. 27, p. 98-112.
______/ .et _al., 1944, Geology and paleontology of the Permian area northwest of Las Delicias, southwestern Cca~ huila, Mexico: Geol. Soc. Am., Special Paper 52, 172 p.
Lewis, P. D., Jr., 1955, Strat-paleo study of an area near Saltillo, Coahuila, Mexico: Unpublished Report, Dept, of Geol., L.S.U.
Muir, J. M., 1936, Geology of the Tampico region, Mexico: 280 p., Am. Assoc. Petrol. Geol.
Muller, C. H., 1947, Vegetation and climate of Coahuila, Mexico: Madrono, v. 0, n. 2., p. 33-37.
Murray, G. E., 1961, Geology of the Atlantic and Gulf Coastal Provinces of North America: Harper Brothers, New York, New York.
______, et ail., 1960a, Stratigraphy of Difunta Group, Parras Basin, States of Coahuila and Nuevo Leon, Mexico: Rept. of 21st. session, Internat. Geol. Cong., volume of abstracts, p. 42.
- - - * .et ail., 1960b, Late Cretaceous fossil locality eastern Parras Basin, Coahuila, Mexico: Jour. Paleo, v. 34, n. 2, p. 368-370.
______, Wolleben, J. A., and Boyd, D. R., 1959, Difunta strata of Tertiary age, Coahuila, Mexico: Am. Assoc. Petrol. Geol. Bull., v. 43, n. 10, p. 2493-2495.
______, and Wall, J. R., 1959, Preliminary report on in trusive gypisum, Sierra del Fraile, State of Nuevo Leon, Mexico: Guidebook, 1959 Field Trip, South Texas Geol. Soc., p. DI-D7.
______, Weidie, A. E., Boyd, D. R . , Forde, R . , and Lewis, P. D., Jr., 1961, The stratigraphy of the Parras Basin: Am. Assoc. Petrol. Geol. Bull., (in press).
Stephenson, L. W., 1915, The Cretaceous-Eocene contact in the Atlantic and Gulf Coastal Plains: U.S. Geol. Survey Prof. Paper 90, p. 155-182.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73
Stephenson, L. W . , 1931, Taylor age of San Miguel formation of Maverick County, Texas: Bull. Am. Assoc. Petrol. Geol., v. 15, p. 793-800.
______, 1941, The larger invertebrates of the Navarro Group of Texas: University of Texas Bull. 4101, 641 p.
Tatum, J. L., 1931, General geology of northeast Mexico: Am. Assoc. Petrol. Geol. Bull., v. 15, pp. 867-893.
Weidie, A. E., Wolleben, J. A., and Murray, G. E., 1959, Preliminary report on the structure of the Parras Basin in the vicinity of Saltillo, Coahuila, Mexico: Guide book, 1959 field trip, South Texas Geol. Soc., p. B10- B18.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AUTOBIOGRAPHY
Alfred Edward Weidie, Jr., was born in New Orleans,
Louisiana on July 31, 1931. He attended various elementary
and secondary schools throughout the south and graduated
from Ramsay High School in Birmingham, Alabama, in 1949. He
entered Vanderbilt University, Nashville, Tennessee, in
September, 1949, and received his Bachelor of Arts degree
there in June, 1953.
After receiving his B.A. degree he entered the United
States Marine Corps; was later commissioned; and served
until August, 1955. In September, 1955, he entered the
Graduate School of Louisiana State University, and received
his M.S. degree in geology in August, 1957. He married the
former Miss Ana Laura Torres in September, 1960. He complet
ed the requirements for the Ph.D. degree in geology from
Louisiana State University in June, 1961.
74
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. EXAMINATION AND THESIS REPORT
Candidate: A^ r®d Edward, Weidie, Jr.
Major Field: Geology
Title of Thesis: rhe Stratigraphy and Structure of the Parras Basin, Coahuila and Nuevo Leon, Mexico
Approved:
Maj# Professor and Chai
Dearr of the^Oraduate School
EXAMINING COMMITTEE:
/?
Date of Examination:
May 311 1961
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:: $ M M
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O F T H E PARRAS BASIN
BY
. E. WEIDIE AND G.E. MURRAY
SSISTEO BY R. RAW LS, D. ROBERTS AND J. WOLLEBEN
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of tlie
Parras Basin
b y kL. JL. E. Weidie \ LEGEND
ANTICLINE CCOI.OC I C CONTACT STRIKE *ND OVERTURNED OIP
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rRA ILRQAQ Pa r r a s Sh.
RANCH( SYNCl ^ L ower C r e t a c e o u s ( UNDJFF. H IGHWAY H I GHWAY RAILROAD
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STRUCTURE SECT I
LINES OF SEC
HORIZONTAL AND VERT
Lower C e r r o Hu e r t a Fm Creta C a n o n del r LROAD \ ^HIGHWAY v Tu l e F m . ^G e r r o del u w o 1 Pa r r a s Sh \ Pu e b l o Fm .
RANCHO NUEVO la SYNCLINORIUM
R a n c h o as E n c i n a s Fm N u e v o Fh
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ICTURE SECTIONS OF THE PARRAS BASIN BY A.E.WEIOIE
.INES OF SECTION SHOWN ON PLATE I
AL AND VERTICAL SCALES* MILES
Lower D I FUNTA Cretaceous G r o u p C uwoiff* v * u n o i f f .
•LAS ENCINAS ANTICLINE MAOEN DEL TULE ERRO THRUST MESA Ml RAMOS SYNCL ZP I CL I
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STRUCTURE SECTIONS OF THE PARRAS BASIN BY A* E o WE I 0 I E
LINES OF SECTION SHOWN ON PLATE L-
MILES HORIZONTAL ANO VERTICAL SCALES- q
Lower Cretaceous . UNO i f f * > Cerro del > Pueblo Fm
f LAS ENCINAS
AS IMAGENES F m LAS ENCINAS THRUST rSAN MIGUEL > SYNCLINE S^N MIGUEL > ANTICLINE
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Canon del Tule Fm h IGHWAV erro Grande Fm C erro Huerta F m
EL MESON ^PICO OE VEGA > THRUST V.SYNCLINE
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C erro Hu erta F m .
^ p i c o OE VEGA ‘C erro del rCERRO HUERTA ■Pa r r a s 5 h . V.SYNCLINE I LROAO
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