Shelf Carbonates of the Paradox Basin San Juan River Field Trip: Bluff to Lake Powell, Utah, July 3-9, 1989

16 Pages·7.225 MB·English

by  Donald L. Baars(auth.)

Tectonic Evolution of
Northent Califontia
Sausalito to Yosemite National Park, California
June 28-July 7, 1989
Field Trip Guidebook T108
Leaders:
M. C. Blake, Jr. D. 5. Harwood
Associate Leaders:
R. J. McLaughlin A. 5. Jayko
W P. Irwin F. C. W Dodge D. L. Jones
M. M. Miller I: Bullen
American Geophysical Union, Washington, D.C.
Published 1989 by American Geophysical Union
2000 Florida Ave., N.W., Washington, D.C. 20009
ISBN: 0-87590-614-1
Printed in the United States of America
COVER: LANDSATimagecenteredonnorthernSacramentoValley, California. CFB=Central
Franciscan belt, EFB=EasternFranciscan belt, KM= Klamath Mountains, GV=GreatValley, K=
Cretaceousoverlap sequence, EC=ElderCreekterrane, SN=SierraNevada, CR=Cascade
Range, C= Chico, R= Redding, RB= Red Bluff, SR= SacramentoRiver,LP=Lassen Peak.
Leaders:
M. C. Blake, Jr. and D. S. Harwood
U.S. Geological Survey
345 Middlefield Road
Menlo Park, CA 94025
Associate Leaders:
R. J. McLaughlin, A. S. Jayko,
W. P. Irwin, and F. C. W. Dodge
U.S. Geological Survey
345 Middlefield Road
Menlo Park, CA 94025
D. L. Jones
Department of Geology and Geophysics
University of California
Berkeley, CA 94720
M. M. Miller
Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA 91125
T. Bullen
Department of Geology
California State University
Hayward, CA 94542
IGC FIELD TRIP T124:
SAN JUAN RIVER CANYONS
SHELF CARBONATES OF THE PARADOX BASIN
D.L. Baars
Kansas Geological Survey, University of Kansas
1930 Constant Avenue, Campus West, Lawrence, KS 66046-2598.
G.M. Stevenson
Consultant, 1721 Bellaire, Denver, CO 80212.
The San Juan River has carved majestic
canyons through a thick sequence of marine
sedimentary rocks of Pennsylvanian (Upper
Carboniferous) age in southeastern Utah. The
superimposed canyons were cut across the huge
Monument Upwarp in late Tertiary to Recent
times, exposing a natural cross section of
the cyclic strata, including algal bioherms,
in unexcelled magnificence. Deepest and
oldest rocks exposed are evaporites and
carbonates of the Paradox Formation (Middle
Pennsylvanian) along the southwestern shelf
of the Paradox evaporite basin. The Paradox
is a pull-apart basin that sagged into
existence during the Ancestral Rockies
orogeny, the American counterpart of the
Hercynian orogeny of Eurasia. Upper canyon
walls are composed of carbonate and clastic
cycles of the Late Pennsylvanian Honaker
Trail Formation.
Red beds of Permian, Triassic, and
Jurassic age express the eroded margins of R I·,?' 0
120km
the Monument Upwarp along either flank of the
20Qmi
Laramide structure. They dip sharply into
the Blanding basin toward the east along the
flanking Comb Ridge monocline, and dip gently
westward into the Henry basin and the course
of the Colorado River, now inundated by Lake FIGURE 1 Regional index map showing major
Powell. Consequently, these younger strata geological features of the Colorado Plateau
are not seen in the deeper canyons. Province, generalized locations of the larger
basement lineaments, and the outline of the
Paradox evaporite basin. The strain
GEOGRAPHIC SETTING ellipsoid is oriented with the Olympic
Wichita Lineament to show the stress field in
Headwaters of the San Juan River are in late Precambrian time. From Baars and
the San Juan Mountains, near Wolf Creek Pass, Stevenson, 1982.
in southwestern Colorado. The alpine stream
flows from there southwestward into Navajo
Reservoir and northern New Mexico before Thus, the San Juan River flows from 14,000
enterinq southeastern Utah. The Animas River foot high peaks of the San Juan Mountains
that flows from Silverton through Durango in southward into the San Juan Basin of northern
southwestern Colorado is the major undammed New Mexico and southern Colorado, and then
tributary to the San Juan, but numerous past the Four Corners into the Blanding Basin
smaller streams, such as the Pine, La Plata, of southeastern Utah. The San Juan was a
Mancos, McElmo, Montezuma, Cottonwood, Comb, major tributary to the Colorado River prior
and Chinle contribute to its flow. The to the construction of the Glen Canyon Dam
common point between Colorado, Utah, Arizona, and the flooding of Lake Powell in the mid
and New Mexico is known as the Four Corners. 1960s.
T124: 1
Major towns and villages of the Four -and beans, and living in relatively large
Corners region include Durango and Cortez in mesa-top villages of greater than 150 rooms.
Colorado, Farmington, Aztec, and Shiprock in During the 1100s and 1200s the Anasazi moved
New Mexico, and Monticello, Blanding, and from their surface dwellings to better
Bluff in Utah. The San Juan River field protection in coves underlying and within the
conference will begin in Farmington and huge sandstone cliffs that typify the
proceed by bus to Bluff via the Four Corners country. They built single dwellings and
and the Aneth Oil Field, then by inflatable condominium-like complexes of stone in every
rafts through Mexican Hat, Utah, and end on well-protected nook and cranny in the myriad
Lake Powell. Lands along the north (right) cliffs, apparently for protection from
bank of the river belong to private marauding bands of nomadic Indians - probably
landowners only in the vicinity of Bluff and the early Utes and Navajos. Sometime after
Mexican Hat, and otherwise are administered A.D. 1250 they abandoned their elaborate
by the Federal Bureau of Land Management and cliff dwellings and left the region, most
the GI~n Canyon National Recreation Area in heading south to the Rio Grande Valley in New
the lower canyon. The San Juan River Mexico and to the Hopi villages of Black Mesa
downstream from Bluff marks the northern in northern Arizona. Evidence of a 30-year
boundary of the Navajo Indian Reservation and drought beginning in A.D. 1270 and
the homelands of the largest Indian tribe in overpopulation probably were contributing
the United States, the Navajo Nation. factors to the mass exodus, and pressure from
The region is a semi-arid, high altitude the nomadic peoples may have been an
desert (Upper Sonoran) on the Colorado important factor. For whatever reason or
Plateau physiographic province; average reasons, the Anasazi had completely departed
elevation is about 5,000 feet above sea the Four Corners region by A.D. 1300.
level. As such, it is suitable only for Ute Indians, and their close relatives,
limited grazing of sheep, goats, and cattle, the Paiutes, arrived in the region by A.D.
with very few small areas used for irrigated 1200. The Navajos are known to have occupied
farming. Mountainous regions, the northern New Mexico by A.D. 1500, but their
laccolithic ranges of the La Plata, Sleeping whereabouts prior to that time is a mystery.
Ute, Carrizo, Abajo, and Henry mountains, are Navajo mythology indicates that there had
utilized for summer grazing and contain been communication with the Anasazi, placing
numerous, now noncommercial, metalliferous them in the region by A.D. 1300. Navajo
mineral deposits. The Four Corners region, legend sheds little light on their origins,
especially the Blanding Basin, is noted for indicating that the ancestral Dineh ("The
its prolific accumulations of petroleum being People," in Navajo) arrived through an
produced from algal bioherms in the Paradox opening in the Earth in the high San Juan
Formation of Pennsylvanian age, occurring at Mountains of southwestern Colorado, with no
depths of 5,000 to 6,000 feet~ prior ancestral roots in this world.
However, linguistics suggest an athapaskan
origin in westernmost Canada at some point in
A BRIEF HISTORY the distant past. The exploring Spaniards
documented the presence of Navajo peoples in
Native Americans 1626 and 1630, naming them for their
agricultural life styles ("navaju" is
The Four Corners region was occupied by believed to mean "area of cultivated lands").
primitive people as early as perhaps 11,000 The various Indian tribes of the Four
to 12,000 years ago, but evidence of their Corners region occupied lands separated
passing is sketchy at best. These earliest largely by the physical geography. Paiutes
inhabitants hunted the woolly mammoth about stayed largely west of the Colorado River,
the time the last Pleistocene glaciers Utes dominated mountainous regions of eastern
retreated, and were still wandering hunters Utah and western Colorado north of the San
and food gatherers in about 6,000 B.C. They Juan River, and Navajo Country was primarily
gradually began to settle down and raise food south of the Sanjuan in southern Utah,
crops, and by A.D. 200 were well established northern Arizona and north-central New
horticulturalists, known as the Anasazi Mexico. The Navajo Nation was centered in
("ancient ones") to the Navajos. north-central New Mexico in "Old Navajoland,"
Anasazi culture is well documented by just east of the present site of Farmington,
their artifacts. Pottery, baskets, stone later spreading westward into Arizona.
tools, and ruins of pit houses and cliff There was always regional overlap, and
dwellings are scattered profusely about the intertribal raiding parties were active
plateaus and mesa tops of the region. By between recognized territories into the late
A.D. 750 they were cultivating corn, squash, 1890s. Each of the tribes had reputations of
T124: 2
being hostile,b oth to neighboringt ribesa nd Dineh. It was left for anothere xpedition
later to Spaniards, Mexicanasn,d invading led by FranciscoA tanasioD ominqueza nd
Americansi n turn. Althought he Navajos FranciscoS ilvestreV elezd e Escalantet o
split from their cousins,t he Apaches,e arly name the river in 1776. Other Spanishp lace
in historyt o becomea griculturalistasn d names in the Four Cornersr egion,s uch as the
pastoralp eoples,t hey obtainedt heir horses, La Plata,A bajo,a nd La Sal mountains,w ere
sheep,a nd goats from Spanishs ettlersb y given by the "SpanishF athers." All Spanish
raids on outpostsi n the Rio GrandeV alley. effortst o establisha northernr oute to
Continuedo pen hostilitiesb y the Navajos Californiaf ailed,a nd it was not until1 830-
eventuallyl ed to their captureb y American 31 that WilliamW olfskilla nd GeorgeC . Yount
militiau nder Kit Carson. They were marched pioneereda wagon trail,t he "Old Spanish
to a reservationa t BosqueR edondoi n Trail,"t hroughs outhwesternC oloradoa nd
southeasterNne w Mexicoa nd held from 1864 to easternU tah.
1868. The experiencew as devastatingt o the
Navajos,b oth economicallayn d spiritually,
and was a total failuret o both cultures. A CanyonT ravel
treatyw as signedi n 1868, establishinag
reservationf or the Navajosn ear their Fur trappersm ay have enteredt he canyons
originalh omelands,b ut not including" Old of the San Juan River in the early 1800s,b ut
Navajoland,a"n d the Dineh returnedh ome. there is no directe videncet o supportt he
The northernb oundaryo f the "Treaty notion. It was not until 1879-80t hat a
Reservationw"a s placeda t the San Juan white man, E.L. Goodridge,t ravelledt he
River,w here it remainst oday with minor river by boat from the presents ite of
variationsr esultingf rom numerous Durango,C oloradot o Lee's Ferry in Arizona,
Congressionaaln d Presidentialla nd prospectingf or gold. He found minuscule
expansionsa nd trades. amountso f flour gold in river sands and
The NavajoN ationi s now largelys elf­ terraceg ravels,a nd a gold rush of sorts
governinga nd self-supportingt,h ankst o followedi n 1882. He also noticedo il seeps
revenuesg ainedf rom oil productionf rom in the canyon wallast the presents ite �f
triball ands since the mid-1950s. Many the Mexican Hat briadngde at SlickhornG uIer.
Navajosh ave left the Reservationa nd taken in the lower canyon. He drilleda shallow
jobs in the outsidec ommunity. Others hole at MexicanH at in 1908 and discovereda
continuel ivinga s their ancestorsd id, "gusher." The resultingM exicanH at
grazings heep,g oats,a nd some cattle, synclinalo il field was never economically
enjoyingt heir priZe possessions- their productiveu ntil the 1970s.
horses,a nd earnings ubsistencef rom the The first geologicals tudiesi n the San
women'ss uperbw eavings killsa nd the men's Juan canyonsw ere conductedb y Hugh D. Miser,
silversmithing.T he NavajoR eservationi s a membero f the government-sponsorTerdi mble
today the largesti n the UnitedS tates, bothE xpeditiono f 1921. Hundredso f geologists
in land area (about 25,00s0q uarem iles)a nd have since studiedt he importanto il-bearing
in population (motrhea n 150,000). In spite stratao f Pennsylvaniaang e in the canyons.
of what we might considert o be a stark and
inhospitablhea bitat,D ineh and the Navajo
Nationh ave prospereda s have no other Native The Mormons
Americans.
Memberso f the Churcho f Jesus Christo f
LatterD ay Saints,c ommonlyk nowna s the
Spanish Exploration "Mormons,"w ere rejectedf rom their homes in
Nebraskab y otherr eligiouss ects and forced
Long after the Anasazil eft the cliffsa nd to migratew est. They settledi n the Salt
mesas of the Four Cornersr egiona nd the Lake Valleyo f centralU tah in 1847, and
Navajoso ccupiedt he lands,S panishe xplorers quicklyb egan colonizingt he region. By 1880
venturedn orthwardf rom Santa Fe, New Mexico they had establishedn umerousv illagesw est
in searcho f a safe route tto heir California of the mountainso f centrala nd southern
missions. Althought hey did not enter the Utah. Memberso f the churchl ivingn ear
canyonso f the San Juan River,a party led by Cedar City in southernU tah received" the
FranciscanF atherS an Maria AntonioR ivera caB" by their leader,B righamY oung,t o
crossedt he river near present-dayA ztec,N ew settlet he San Juan River valleys in
Mexicoi n the summero f 1765. They were southeasterUnt ah and to begin" civilizing"
aware of the presenceo f the Navajos,a s the Indians. The followinga ccounti s from
reportsw rittenb y Arate Salmeroni n 1626 and Powell (1983).
Father Benavidasi n 1630 describingt he A well-known,r elativelye asy wagon trail,
T124:3
generally the Old Spanish Trail, would have GEOLOGY
led northward to Provo and cross the
mountains at Soldiers Summit, then southward The course of the San Juan River generally
through Moab, Monticello, and Blanding to the approximates the southern shelf of the
Bluff area, a distance of about 300 miles. Paradox basin. The elongate, faulted,
The appointed leader of the colonizing party, evaporite basin of Pennsylvanian (Upper
Silas S. Smith, was told of another route, Carboniferous) age extends from near
although not an established trail, almost Farmington, New Mexico northwestward to near
directly eastward toward the San Juan Price, utah. Rocks deposited on the shelves
country. He did not relish the normal month of the basin are exposed only in the San Juan
long journey and decided instead to take the Mountains and in deep canyons of the San Juan
"shortcut." Consequently, a group of 236 and Colorado rivers where they dissect the
pioneers loaded their possessions into Monument Upwarp. Otherwise 3,000 to 5,000 ft
wagons, gathered their livestock, and set out (1 to 2 km) of Permian and Mesozoic strata
on the "mission" in September 1879. blanket the Pennsylvanian System.
They traveled an established trail
eastward to the community of Escalante, but Basement Tectonics
from there they had only a general
description of a route to the Colorado River. To appreciate the Paradox basin one must
The country is rugged to say the least. understand the tectonic setting from
Wooded valleys changed abruptly to barren Proterozoic time to the present. Beginning
slickrock desert, laced with precipitous sometime around 1.7 Ga and extending to about
canyons. Rocks and canyons everywhere! They 1.6 Ga, continental-scale wrench faults
were forced to literally chip a trail for the trending NW-SE and NE-SW crossed the region.
wagons from bare rock buttes and canyon walls The NW-SE set, the Olympic-Wichita Lineament,
for much of the way. When they finally had a right-lateral sense of displacement,
reached the Colorado River, they were and displacement on the NE-SW set, the
confronted with a thousand-foot-high cliff Colorado Lineament of Warner (1978), was
leading down to the river and an equally left-lateral, indicating N-S compression
difficult exit from Glen Canyon beyond. (Baars, 1976). The magnitude of lateral
Instead of turning back, the party chipped displacement is unknown, but it was probably
and blasted a route through a natural break considerable. A 10,000 ft (3 km) thick
in the cliff by which they could lower the sequence of Proterozoic quartzite and slate
wagons and teams of horses on ropes. The was faulted into juxtaposition with
resulting edifice is now known as "Hole-in crystalline basement rocks in the San Juan
the-Rock," and is still visible from Lake Mountains. The faults were reactivated
Powell. It took a month of back-breaking during Late Cambrian, Late Devonian, and
labor to make the crossing, but no one was Early Mississippian (Lower Carboniferous)
killed or seriously injured during the times, but displacement was then only minor.
ordeal, although a baby was born in the Reactivation of the wrench fault system
process. The route ahead was nearly as occurred on a major scale in Middle
difficult, as they had to cross the Monument Pennsylvanian (Atokan) time. Kluth and Coney
Upwarp and Comb Ridge before reaching (1981) suggested that continental collision
tillable lands along the San Juan River. between North America and South America-
They arrived in what was to be Bluff in Africa was responsible for readjusting the
March 1880, six long and difficult months basement fabric. Whatever the cause, the NW
after leaving Cedar City. The "Hole-in-the SE set was rejuvenated in a right-lateral
Rock party" decided to settle the little sense, causing the opening of a large-scale
valley in utter exhaustion. And it was not pull-apart basin along the NE-SW set of
easy. There were hostilities with both Utes preexisting faults. The Uncompahgre Uplift
and Navajos, and the river flooded the valley was raised to become a major source for
each spring. Some gave up in despair after a clastic sediments, while the Paradox basin
short time and moved farther east to Cortez, was subsiding. Thus the Paradox is a
others headed north to settle Blanding, while Pennsylvanian age pull-apart basin of major
a few hardy souls remained in Bluff and went proportions (Stevenson and Baars, 1987).
into the communal cattle-grazing business. Existing structures were rejuvenated in
Although the trip across miles of rugged, Late Cretaceous-Early Tertiary time (Laramide
rocky desert and the crossing of Glen Canyon Orogeny), forming the present-day structure
was a tribute to the perseverance and of the Colorado Plateau Province. Principal
dedication of the hardy pioneers, it was also stress was now directed from west to east,
one of the most foolhardy events in Mormon generally uplifting and overturning
history. structures toward the east. Thus the major
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Each of the systems reflects rejuvenation of
the basement structural fabric on a minor
scale. Otherwise, the rocks represent
relatively stable conditions in regionally
widespread, shallow seas.
Pennsylvanian (Upper Carboniferous). As
the Paradox basin subsided along major
VIRGIL
basement faults in Middle Pennsylvanian time,
normal marine waters entered the basin where
MISSOURI
circulation was greatly restricted. Marine
water crossing the shallow shelves of the
z basin was optimal for carbonate
<
z
sedimentation, and thick cyclical sequences
<
> of limestones resulted. In the deeper,
.>.J restricted water of the central basin,
en
z
z evaporites of the Paradox Formation were
0W.. deposited. Some 29 cycles of anhydrite and
salt were deposited during Middle
Pennsylvanian time, accumulating to a total
thickness of more than 4,000 ft (1,500 m).
; ~KERTONTRALFM.
ATOKA MOlASFM. Depositional thickness cannot be accurately
?
MORROW determined, as salt flowage above the
basement faults formed large elongate salt
CHESTER
diapirs in the deeper basin. Meanwhile,
en MERAMEC
course-grained arkosic clastics were shed
en
~ from the Uncompahgre highlands immediately
OSAOE
east of the basin, filling the adjacent,
KINO£RHOOK deepest graben of the basin with 12-18,000 ft
OURAYL».ESTONE
(4-6,000 m) of sediments.
upperEl:Jertmember __--
Z Normal marine circulation returned to the
<z E ; McCRACKENas MBA. Paradox basin by Late Pennsylvanian time.
0
> Resulting cyclical sequences of marine
W
C MIOOl.E limestones, alternating with shales and
AND
LOWER sandstones, constitute the Honaker Trail
SILURIAN Formation, and form the ledgy, gray cliffs
along the deep canyons of the San Juan River.
ORDOVICIAN
They were named for the trail leading from
! UPPER the canyon rim to the river down stream from
MlDOLE
~ the Goosenecks (Wengerd and Matheny, 1958).
"'--L-OW-E-R--1
Here the formation is of Late Middle (upper
PRECAMBRIAN
Desmoinesian) and Late Pennsylvanian
(Missourian) age; no rocks of latest
"FIGURE 3 Correlation chart of Paleozoic Pennsylvanian (Virgil) age are recognized in
rocks of the Paradox basin. Oil (solid the region. The Honaker Trail Formation
circles) and gas (barbed circles) indicate averages about 1,000 ft (300 m) in thickness.
productive intervals. From Baars and
stevenson, 1982. Permian. Rocks of Lower Permian age, the
Cutler Group, rest disconformably on the
monoclines, such as the Comb Ridge monocline Honaker Trail Formation (latest Pennsylvanian
crossed by the San Juan River, are Laramide rocks are missing). The term "Rico
contortions of basement structure. formation" referred to in some literature is
a misnomer and should not be applied, at
Stratigraphy least in this area.
The Permian System of the Monument Upwarp,
Early Paleozoic. Sedimentary rocks of consists of the basal Halgaito Shale, Cedar
Late Cambrian, Late Devonian, and Early Mesa Sandstone, Organ Rock Shale, and
Mississippian age underlie Pennsylvanian DeChelly Sandstone in ascending order (Baars,
rocks throughout the Paradox basin, but are 1962). All except the Cedar Mesa Sandstone
nowhere exposed except in Grand Canyon and in were ultimately derived from the Uncompahgre
the San Juan Mountains (Baars, 1966; Baars Uplift that was still high and shedding vast
and See, 1968; Baars and Stevenson, 1982). quantities of clastic sediments in Early
T124: 5
I
WYOMING
UINTAUPLIFT
UINTABASIN
HIGH
PLATEAUS
CAPITOL
REEF"
UTAH COLORADO
ARIZONA
NEWMEXICO
Holbrook
Basin
o 30 60miles
o 20 40kilometers
FIGURE 2 Major structural subprovinces of the Colorado Plateau.
T124: 6