i
i"
NEW
MEXICO
GEOLOGICAL
SOCIETY
"
|
E
i--
---t-
/"
"i
,
’,
!
Guidebook
i
OF THE
|
South and West Sides
i
OF THE
SAN
!
NEW
JUAN
MEXICO
BASIN
AND
ARIZONA
!
!
SECOND
FIELD
CONFERENCE
I1’:
October 12-13-14, 1951
!
.
NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE
EDUCATIONAL
* SAN JUAN BASIN
INSTITUTIONS
New Mexico Institute of Mining & Technology
University of New Mexico
Albuquerque
Socorro
Welc:ometo the University:
New Mexico Instituteof Mining and Technology
extendsits heartiestwelcometo they"participants
in the second Field Conferenceof. the New Mexico
GeologicalSociety.
The University of New Mexico hopes that you
will make yourselvesat ¯home on the campus during registrationfor the Field Conferenceof the
New Mexico Geological Society.
This institution
in all of its threedivisions;
namely, the College Division, the State Bureau
of Mines and Mineral Resources, and the Research
and DevelopmentDivision has a very strong interest in the geologyof the state as well as the various
industrieswhich are concernedwith the development of the mineral resources of the state. The
facultyand the professional
staff of the three divisions of the institutionare activelyengagedin research on various problemsof interest to the
petroleum industry and other mineral industries.
Staff members of the Department of Geology
especiallyhave been active in geologicresearch
in the San Juan Basin and elsewherein the state.
The campus is situated on an eminence in the
eastern part of Albuquerque,almost within the
shadow of the toweringSandia Mountainsto the east,
and overlooksthe historicRio Grande to the west.
The campus is a mile above sea level,
it is our hope that you may find time to visit
around the campus and see the modified Indian
pueblo style of architecturewhich has been incorporateduniformlyinto its buildings.
The scope of the institution’s
educationalprogram is wide and therefore many departments
serve the petroleum industryin one way or another.
The departments of chemical engineering, mechanical engineering,electricalengineering,and civil
engineering,all within the Collegeof Engineering,
train men who take active parts in the various
phases of the petroleum industry. The large Fuels
Sectionof the U. S. GeologicalSurvey is located
at the Universityof New Mexico.
Studentsare graduatedwith a bachelor’sdegree in geology, geophysics, petroleum engineering, mining engineering,metallurgicalengineering,
and in the relatedbasic fields of chemistry,mathematics, and physics. In addition, graduate work
leading to the master’s degree is performedin
geology and geophysics.
The Petroleum Section of New Mexico Bureau
of Mines and Mineral Resources is very active in
its services to the petroleumindustry. Oil-well
sample cuttings, sample descriptionsand plotted
log strips on many of the wells drilled in New Mexico are availablefor referenceuse at the Bureau.
Copies of 6, 000 drillers’logs for most of the
wells drilled in New Mexico may be obtained from
the Bureau of Mines. The Bureau publishes bulletins, many of which are on subjectsof interestto
petroleum geologists.Maps and bulletins of the
United States GeologicalSurvey that pertain to New
Mexico may be obtained from the Bureau at the
regularsale price.
The Universityhas a very fine libraryand its
facilitiesare made availableto industryand the
public. The geology library has proved especially
useful to the petroleumgeologistsin this part of
the State.
The Departmentof Geology is located on the
second floor, west wing of the buildingin which
registrationis held. They have a fine museum in
which are exhibitsof minerals,fossils, and rocks,
In additionto their"regularexhibits,thereare
specialdisplaysfor this occasion,includingmaps,
charts, and cross sections of the San Juan Basin
region.
The Bureau of Mines and Mineral Resources
is also activelysponsoringand cooperatingin
several geologicalmapping projects ia New Mexico.
Members of the staff of the Bureau of Mines are
availablefor regularconsultationserviceto representativesof the industry.
The faculty of the Departmentof Geology has
had a long and wide interestin the geologyof New
Mexico, and its members are very active in geologicalresearchin and near the San Juan Basin.
The department graduates students with bachelor’s
and master’s degrees specializedin stratigraphy,
paleontology,sedimentation,mineralogy, petrography, or mining geology,
I extend my best wishes to you for an enjoyable
and successful Conference.
Sincerelyyours,
It is my hope that you will ha~e a most.enjoyable and successfulField Conference.
Sincerelyyours,
¯
~~To
L.
~m
4~,
E. ~
President
~
/7
Presidel~f ~ . v
2
~k
man
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NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE
* SAN JUAN BASIN
I
CONTENTS
Page
5
Foreword .......................................................................................
Officers
of
the
New
Mexico
Geological
Society
.......
.........
5
Acknowledgements...............................................................................
5
ConferenceCommittee ...............................................................
¯. ..........6
Schedule ......................................................................................
7
Instructions....................................................................................
8
Introduction...................................................................................
9
I
Road Logs .......................................................................................
II
FirstDay, Albuquerque
to Grants,Friday,October12 ........
. .............................
II
Index Map First Day’s trip ..................................................
12
Nomenclature
Chartfor termsused in road logs ..............................................
13
Second Day, Grantsto Gallup,Saturday,October13 .......................................
33
Index map Second Day’s trip .................................................
34
ThirdDay~ Gallupto Shiprock,Sunday,October14 ......... ............................ 58
Index Map Third Day’s trip ...................................................
59
i
Stratigraphy
of the Outcropping
PermianRacksAroundthe San Juan Basin
By Charles B. Read ....................................................................
80
TriassicRocksof the Arizona-New
MexicoBorderArea
By E. D. McKee ......................................................................
85
I
JurassicFormations
of the Southand WestSidesof the San Juan Basin
By L. C. Craig C. N. Holmes,John W. I-larshbarger,
R. L. Jackson,CharlesRepenning,
and Clay T. Smith .....................................................
...............93
facing..........
96
Index Map of Navajo Reservation........................................
facing.........98
Isometric
FenceDiagramof Jurassicrocksin NavajoReservation
...............
facing.........100
IsopachMaps of Chinleformationand Glen CanyonGroup ...................
102
IsopachMap of San RafaelGroupand FaciesDistribution
formation
....~ facing..
I Map of Morrison
Appendix-Measured
section,Cow Springssandstone,Cow Springs,Arizona....................
103
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NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN
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Page
Cretaceous
Stratigraphy
of theSanJuanBasin
By Casweli
Silver...................
. ................................................
104
I
Stratlgraphic
Correlation
fromSanJuanCounty,
NewMexico:
to Archuleta
County
Colorado...............................
..........
facing...
104
I
Tertiary
andlaterIgneous
Rocksof theSanJuanBasin
119
By EugeneCallaghar~
..................................................................
Tectonics
of theSanJuanBasin
124
By VincentC. Kelley.................
. ...............................................
Proved
andPotential
OilandGasTrapsof theSanJuanBasin
By FrankC. BarnesandEmeryArnold.......................................... 132
I
I
140
Stratigraphic
Production
Chartof :theSanJuanBasin.......................................
I
facing...
140
Structure
ContourMap of HospahOilField........................................
Mineral
Resources
of theSanJuanBasin
I
By RobertA. Bieberman
..................................................................
141
Preliminary
Reporton theGround-Water
Resources
of theNayaj0
andHopiIndianReservations,
Arizona,
New Mexico,and Utah.
By L. C. HaJpenny.
.......................................................
: ..........I,$7
IndexMap of the NavajoReservation
...........................................
facing...
148
History
of Development
andProduction
of OilandGasin theSanJuanBasin
By FrankC. Barnes.................................................
....................
155
Landsof theSanJuanBasin
By A. L. Duff, Jr. and J. V. Fritts...............
I
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161
I
Business
and Professional
Directory
...................................................
..............
164
Geologic
Mapof theSanJuanBasin
By CaswellSilverand W. B. Hoover..........................................
... in back
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INEW MEXICO GEOLOGICAL SOCIETY* SECOND FIELD CONFERENCE * SAN JUAN BASIN
I
FOREWORD
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The NewMexicoGeological
Societywelcomes
you to its SecondField
Conference.
We hopeby meansof
thisconference
to roundoutthestudyof theSanJuanBasinundertaken
at theFirstFieldConference
in November
1950.Muchof thesection
youwillseeis highly
controversial
andit ishopedthatnewideasandconclusions
maybe developed
understimulus
of discussion
andgoodfellowship.
Weregret
thenecessity
forsomuchtravel
overgravel
orothernon-surfaced
roads;
the,areaswhichwewill
traverse
comprise
someof thefinest
combinations
of colorful
vistas
andperfect
outcrops
knownanywhere
and
perhaps
thescenery
andgeology
willcompensate
in a smallwayfortheinconveniences.
I
OFFICERS OF THE SOCIETY
President
i
Charles
B. Read
I
William
B. Hoover
U.S.Geological
Survey
FirstVice-President
HumbleOilandRefining
Company
SecondVice-President
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JohnE. Allen
NewMexicoInstitute
of Mining
and Technology
Secretary-Treasurer
EugeneCallaghan
I
New MexicoBureauof Minesand
Mineral
Resources
Counci
Iors
i
E.J.Foley
Threeyearterm
HumbleOil and RefiningCompany
JosephL. Borden
Twoyearterm
PureOil Company
I
ShermanA. Wengerd
Oneyearterm
University
of New Mexico
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ACKNOWLEDGMENTS
:: TheConference
Committee
gratefully
thankseachpersonandorganization
contributing
to thefieldconference
andguidebook.
TheCommittee
is especially
indebted
to theUniversity
ofNewMexico
forproviding
facilities
forregistration;
to theUnited
States
Geological
Survey
forthePolaroid
LandCamera
usedto illustrate
theroadlogs;andto the
NewMexicoBureau
of MinesandMineral
Resources
forproviding
office
facilltles
andpersonnel
forthepreparation
of theguidebook.
TheHumbleOilandRefining
Company
through
itsAlbuquerque
andRoswell
offices
contributed
markedly
to thepreparatibn
oftheguidebook.
TheStateGeologists
at SantaFe contributed
a greatdealof statisticalinformation
as wellasmaps.Manyof themapsandplatesin theguidebook
werepossible
onlythrough
the
cooperation
of theCartographic
Office
of theU. S. SoilConservation
Service
whichprovided
thereproductions
forprinting.
NEW MEXICO GEOLOGICAL SOCIETY * SECONDFIELD CONFERENCE* SAN JUAN BASIN
CONFERENCE COMMITTEE
General
Chairman
.....
ClayT. Smith...........................................
.....~ ....New MexicoInstitute
of Mining
and Technology :
Advisory
..
Eugene
Callaghan
..................
. .......
..............
~........
New MexicoBureauof Minesand
Mineral
Resources
U.S.Geological
Survey
JohnW. Harshbarger
..............................................
HumbleOil andRefining
Company
WilliamB. Hoover................................................
¯
University
of New Mexico
Vincent
C. Kelley...........................
.. .............................
............
U.S.Geological
Survey
Charles
B.Read....
Geologist
. ....
:...... Consulting
Caswell
Silver.
........
Guidebo0k
NewMexicoInstitute
of Mining
: .....
ClayT. Smith(Compiler
andEditor)
.............................
andTechnology
............
ConsUlting
Geologist
; .............
Caswell
Silver
(MapEditor)
..............
New MexicoGeological
Society
Margaret
Pickett
(Assembling)
............................
~ ........
;.......... New MexicoBureauof Minesand
JeanBurand(Assembling)
................................
Mineral
Resources
..
U.S.Geological
Survey
DianaBaltz(Drafting).
.:.~...
........
.
~
.........
U.S.
Geological
Survey
MarianJo Cowan(Drafting)
................
. ..
New MexicoBureauof Minesand
HildaKalish(Drafting).
~ ......................................
Mineral
Resources
RoadLog
of Mining
. ~ .........
....................NewMexicoInstitute
JohnE. Allen(Editor)
..............
:
and Technology
Survey
EdwardC. Beaumont
...........
.......
¯ .........
¯ ................ U.S.Geological
U.S.Geological
Survey
JohnW. Harshbarger.
..
HumbleOil and Refining
Company
WilliamB. Hoover...............................................
University
of NewMexico:
Vincent
C. Kelley...~....:
.................
L .........
~ ~ ........
. ......... U.S.Geological
Survey
Charles
B. Read...................
U.S.Geological
Survey
GordonWood.
TripArrangements
....:................
Consulting
Geologist
....:
.....
SamuelJohnson
(Chairman)
............
Eugene
Collaghan
(Reservations)
............
.....................
~....
New MexicoBureauof Minesand
:
Mineral
Resources
:
"
NewMexicoInstitute
of Mining
Stewart
M. Jones(Caravan).
:
and Technology
EdwardC. Beaumont
..........
.
U.S.Geological
Survey
William
B. Hoover...................
........
÷ ...............
.;.....
HumbleOil and Refining
Company
ShermanA. Wengerd.......................
University
of
New
Mexico
~i::.-:
.....
.......
- .....
MarkWhelan...............................................
:-....
:Independent
Registration
Survey
:. ......................
-~..... U.S.Geological
GordonWood(Chairman)
.............
;.
University
of New Mexico
J. PaulFitzslmmons
..................
............................
6
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NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN
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...
SCHEDULE
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Thursday,
OctoberII
I
, ;.,2:00p.m.
Registration.
Administration
Building,
UniverSity
of New Mexico.
Friday
, October12.
7:00a.m.
Caravanassembles
on northeast
corner0f University
Campus.
i
7:30 a.m.
Caravanleaves Albuquerque,
:New Mexico.
5:30 p.m.
CaravanarrivesGrants,New Mexico.
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7:00 p.m.
Informaldinnerand programarrangedby the GrantsChamberof Commerce.
Saturday,October13. Grants, New Mexico to Gallup, New Mexico.
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6:00 a.m.
Breakfastin Grants,New Mexico
7:30 a.m.
CaravanleavesGrants
, New Mexicoassemblingat west end of town.
6:00 p.m.
CaravanarrivesGallup,New Mexico.
7:30 p.m.
Informaldinnerwith Kodachrome
slidesof secondand thirddays trip by W. B. Hoover,
HumbleOil and RefiningCompany.
Sunday,October14. Gallup, New Mexico to near Shlprock,New Mexico.
I
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6:00 a.m.
Breakfastin Gallup,New Mexico.
7:30 a.m.
CaravanleavesGallup,New Mexico assemblingat west "Y".
6:00 p.m.
Caravandisbandsnear Shiprock,New Mexico.
ConferenceEnds.
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NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUANBASIN
GENERAL INSTRUCTIONS
It is essential
thatthecaravan
starteachmorning
at theannounced
t~me.Yourcooperation
willbe appreciated.
Youwillbe seated
in a different
careachday(except
drivers).
Yourcarassignments
arelisted
on theslips
whichgiveyourroomassignments
andyourtotalcharges
forthetrip.!fyouwishto ridein somespecial
carpleasenotifysomememberof theArrangements
committee
thenightbeforeyoumakethechange.
3.
Youwillbe assigned
to yourlodging
reservations
at thetlme
of registration.
Please
do notmakeanysubsequent
changeof roomwithout
notifying
somememberof theArrangements
Committee.
4. Please
payyourlodging
billin advance
or before
you go tobreakfast
so as tonotdelaythedeparture
timeof
thecaravan.
5. Thethirddayof theConference
isalmostexclus!vely
within
theconfines
of theNavajo
Indian
Reservation;
roadsarepoorlymarked
andin manycasesimpassible.
Pleasedo notleavethecaravan
beforethecompletion
of theConference
without
notifying
somememberof theArrangements
Committee.
plck-up
trucks
in thecaravan
andifyouhaveluggage’which
willnotfitinthecar
6. Therewillbeseveral
in whichyouareridingnotifya memberof theArrangements
Committee
andyouwillbe provided
withspace
foryourluggage
in someothercarinthecaravan.
7.
Theperson
sitting
inthefrontseatwiththedriver
should
keephiminformed
of stops,
points
ofdanger~
points
of interest,
etc.,notedintheroadlog,andheshould
readthegeologic
roadlogtothedriver.
SPECIAL INSTRUCTIONSTO CAR DRIVERS
I. DO NOT DISREGARD THE WARNINGS IN THE ROAD LOGS CONCERNING ROAD CONDITIONS,
THEY ARE FOR YOUR PROTECTION.
2. Youwillbe givena numbered
placard
forattachment
to yourrearwindow.
Thisnumberdesignates
your
positlonin
thecaravan.
3. If foranyreason
youhavedroppe
yourposition
at anysubsequent
stop.A space
d outof llne,youmayresume
willbeleftforyoubythedriver
inyourrearatallstops
until
youreturn.
4. Neverpassanother
Conference
carwhilethecaravan
is in motion
unless
thatcarhasdropped
outof line.
please
stopat thesideof theroadandallowthecaravan
tOpass. Ifyouneedhelp,
5,. If youhavecartrouble,
flagdownthetow.’da~’~vhlch
willbeat.thereafof thecaravan.
6.
Ple0se
service
yourcarat nightto insure
prompt
departure
thefollowing
morning.
7.
Gasoline
cannotbe pu?chased
on theNavajorese-rvatlon
on Sunday.
As notedelsewhere
in theroadlog,the
Society
is making
arrangements
fora tanktruck
to bringgastothelaststopon thethirddayoftheconference;
thegaswillbe soldina strictly
cashtransaction
because
ofthelimitations
of time.Youarerequested
todetermine
carefully
howmuchyouwillneedto returnto Gallupor wherever
youmaybe heading
beforethetruckis ready
toservice
you.Useas little
as possible
inOrderthateveryonemaybeserved
intheshortest
possible
time.Oil
mayalsobe purchased
at thissameStop.
8. Wateris veryscarceandif yourcarhasa tendency
to overheat
youshould
carrywaterwithyouon boththe
second
andthirddaysof thetrip.ThegradeovertheChuska
Mountains
attheendofthethirddayof thetrip
isexceedingly
steepandthegreatmajority
ofcarsboiltraversing
thispass.Thereis a spring
aboutone-thlrd
of thewayup thehillwhichwillprovide
plenty
of waterbutin orderto-keep
thecaravan
moving,
onlythose
whicharein especial
needshould
stop.
9. At stopswhendouble
parking
in morethanoneline~driveas closeas possible
to theadjacent
lineandleave
aslittlel
space
as possible
(onefootorless)between
bumpers:
B
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NEW MEXICO GEOLOGICAL SOCIETY * SECOND FIELD CONFERENCE * SAN JUAN BASIN
!
Theeconomy
of theSanJuanBasinis
remarkably
varied.
Thetourist
trade~
particularly
alongthesouthern
boundary
probably
accounts
for
ClayT. Smith
thelargest
dollar
income,
closely
followed
by
NewMexico
Institute
of Miningand Technology
natural
gasandpetroleum
production
mineral
and
coal
mining,
grazing
and
farming.
Coal
mining
TheSanJuanBasin
circular,
t whichis roughly
centered:
mainlyat GallupandDurang
includes
muchof northwestern
New Mexico~
a narrow
0 hasbeendecllning
because
of
loss
of
its
markets
to
petroleum
and
stri
Of
northeastern
Arizona,
and
a
zone
25
miles
p
natural
gasproducts.
Natural
gasisthemostimportwidein:southwestern
Colorado
or a totalareaof
antproduct
of thebasinalthough
a smallbutsteadily
almost¯
20,000
square
miles.
Thegreater
partofthe
increasing
production
of highgravity
crudeoilfrom
basinis:drained
by theSanJuanRiverbutmuchof
several
different
horizons
contributes
aboutone-quarthesouthandwestsidesisdrained
by tributaries
of
terof thecombined
valueof production.
Someof
theLittle
Colorado
River.Theextreme
southwestern
thegasis richinhelium
anda plantatShlprock
opercorneris
withinthewatershed
of theRioGrande.
atedby theU. S. Bureau
of:Mines
in keptin a standExcept
forbadland
surfaces
in areasof
by condition
to expandheliumproduction
whenthe
occasion
warrants.
Newdiscoveries
of uranium
near
Tertiary
sediments,
theinner
portion
ofthebasin
is
Grants
andkagunashowpromise
of increasing
our
characterized
by shallow
Openvalleysseparated
by
ofthisvitalmetal.
Grants
boasts
oneof the
broadmesasor by lowcuestas.
In regions
of Cretaceous supplies
largest
pumice
mining
andmilling
operations
inthe
andolderrocksthesurface
ismorevaried
inappearance.Prominenthogbacks
followthemargins
of the
United
States,
andexploration
of nearby
perlite
deposits
is in progress.
Gold,silvercopper,
leadandzinc
basin
and:aresharp
ridges
wheredipsaresteepas
areproduced
in theSanJuanMountains
alongthe
alongthenorthside.Maximum
altitudes
alongthe
northrimof thebasinandsomefluorite
mining
is
southandwestsidesofthebasinrarely
exceed
9~500
continuing
in theZuniMountains
on theSouthside.
feetanda maximum
relief
of 5000feetis notedat
MountTaylor.
Grazing
andminoramounts
of farming
furnish
theprincipal
occupation
fortheIndians
whomakeup
Theclimate
issemi-arid
to aridalthough
thelargest
partofthepopulati:on
outside
thetowns
someof theuplift
areasreceive
considerable
snowfall,
around
the
margin
of
the
basin.
Elsewhere
in this
Nearly
all
the
precipitation
is
in
the
form
of
scattered
,
guidebook
thegroundwater
conditions
andthepossibilintense
thundershowers
in thesummer
months;
such
itlesforadditional
grazing
andfarming
areestimated.
storms
mayproduce
rainfall
measureable
in inches,
Lack
of
sufficient
precipitation
in
recent
yearshasmade
but0nly:over
an areaof a fewsquare
milesorless.
waterproblems
critical
inthelivelihood
of theseveral
thousand
IndianswhooccupytheNavajo,
Hopi,Zuni,
I~ensity
ofpopulation
ismuchgreater
on
andPuebloReservations
in thebasin.Overone-third
thewell-watered
northsideof thebasin;
Gallup
and
ofthelandinthebasinisinIndian
Reservations
orconGrantsaretheonlytownsof anyconsequence
on the
trolled
by
allotments.
southandwestsides.U. S. Highways
66,84,160,
muchof thebasinrim,butroads
550,and666outline
Sedimentary
rocksin thebasinproper
are
in thecentral
partarepoor.¯NewMexicoHighway
44
crosses
thebasindiagonally
connecting
Albuquerque
almostexclusively
of Mesozoic
ageor younger~
although
olderPaleozoic
andpre-Cambrian
outcrops
occurin the
andDurango,
theprincipal
supplycenters,
through
uplift
areas
or
along
the
steeply
upturned
edges
ofthe
CubaandAztec.Themainllneof theAtchison,
basin.
The
geologic
record
is
more
complete
along
the
T.opekq
andSanta¯
Fe Railroad
crosses
thesouthern
part
northandeastsidesofthebasinthanalongthesouth
of thebasinp
anda narrow-gauge
llneof theDenver
andwestsides.
Thecentral
partofthebasiniscovered
and RioGrandeWesternservesChama,Durango,
Aztec
sedimentary
rocks,
whicharesurroundandFarmington.
Airservice
by Frontier
Airlines
reaches withearlyTertiary
outcrop
of Cretaceous
beds
Gallup,
Farmington,
Durango,
andCortezand.connects ed by a moreor lesscircular
in
a
bewildering
variety
of
facies
changes-and
marine
and
withnorth-south
andecist~west
transcontinental
air!ines
non-marine
intertonguing,general
In
Jurassic
and
at Albuquerque.
Triassic
rocks
marktheouter
limits
ofthedepressed
part
ofthebasinandon thesouthandwestsidestheadjacent
INTRODUCTION
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NEW MEXICO GEOLOGICAL
SOCIETY
* SECOND FIELD CONFERENCE * SAN JUAN BASIN
upliftsare cappedwiththickPermiansediments,
Locally,extensive
areasof pre-Cambrian
rocksare
exposedin the highermoredeeplyerodedpartsof the
upliftareas.Smallintrusive
plugs,dikesand associated
flowsmostlyof basaltic
composition
and Tertiary
and
Quaternary
age are scattered
indiscriminately
along
marginalpartsof the basin.Alongthe southand west
sidesof the basinthe rocksshowonlyslighterosional
disconformltles
throughout
largepartsof the section;
karsttopography
on upperPermianlimestone
I extensive
truncation
at the baseof the upperCretaceous
and on
angularunconformity
at thebase of lowerTertiary
rocks
are the only evidences
Of non-depositlon
and orogeny,
Elsewhere
the rocksare essentially
parallel
throughout
thesection.
The firstfieldconference
of the New Mexico
Geological
Societyvisitedoutcropsalongthe northand
east sidesof the San Juan Basinand examinedrocks
whichhave been exploited
most heavilyduringthe
current
search.forpetroleum.
Sinceit wasimpossible
to coverallof the regionlastyear,the secondfield
conference
is completing
the studyofthenearly
circular
basinby examining
the rockson the southand
westsides.Accessto the westsideof the basinis
limlfed
andtheexposures
aresuchthatit is difficult
¯ to routethetripto seeallof thesection
in as many
¯ As a resultthefirstdayis
placesas is desirable.
spentmostlyin Tertiary
or younger
rockswithonly
limited
viewsof theolderpartsof thesection
until
afternoonwhen Cretaceous
and Permianrocksare along
the route.The laststopof theday allowsstudyof the
pre-Cam.brian
and overlying
Pennsylvania¯
rocksin the
easternend of the Zunl Mountains.
-Mostof the second
day is devotedto Cretaceous
rockswhereexcellent
exposures
of widespreadmarineand non-marine
intertonguing
will be examined
in detail.The lastday
permitsexamination
of Permianrocksas wellas one of
the mostspectacular
Jurassic
sections
exposed
in the
western
UnitedStates.
A greatdealof thetripwillbe on private
land
or on IndianReservation;
pictures
of scenery,
geology,
or of the caravanarepermissable
but pleasedo nat
photograph
the Indiansor theirhomeswithoutpermission.
As you willbe passing
throughsomeof the mostcolorful
and photogenic
countryin the southwest,
you are
welcometo dropout of the caravanfor photography
at
any timeand may regainyourposition
at the nextstop.
Theguidebook
consists
of fiveshortpaperson the
rocksexposedalongthe routeof the fieldconference
and several
papersof a regional
naturewhichdiscuss
the tectonic
history,
mineral
resources,
landstatus,
groundwater
resources,
and the historyof gas and oil
development
and production
in the San Juan Basin.
Someof thesepapersare reprinted
fromthe 1950
guidebook;
someare revisedand completely
rewritten
contributions
fromsimilarpapersin the1950guidebook;
and mostare new discussions
writtenby personsmost
familiar
with thesouthand westsidesof thebasin.The
emphasisin this guidebook
has been placedon the road
log and itsaccompanying
Tllustratlons
andall of the
material
is deliberately
slanted
towardthe southand
westsidesof the basin.For the broaderregional
features
of theSan JuanBasin,the readeris referred
to the 1950guidebook.
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