Paleoenvironments
ol theSouth
Hospah
coal
deposits,
McKinley
Gounty,
NewMexico
as the baselinefor future biostratigraphic investigationsthat are vital to a better understanding of the geology of this region.
byAbollulJaneossanaie,
Department
of Geological
Sciences,
Michigan
StateUniversity,
EastLansing,
Ml 4882+1
115
Geographic and stratigraphic
position of the study area
The study area is located on the South
This is a preliminary report on an exten- Hospah lease,about 19 road mi northeastof
s.ivepalynologicalstudy of the coal-bearing C r o w n p o i n t , i n t h e e a s t - c e n t r a lp a r t o f
depositsin the South Hospaharea.The paly- McKinley County (Fig. 1). It includes sec. L
noflora documentedin this study will be used of T16N, R10Wand secs.25-27and 34-36 of
Abstract
Coal-bearing deposits in the South Hospah area were sampled from four core sec-
'':A#
/ rc,i
r\
ss\ \
3-l
I
36
studied.
Introduction
Microscopic,
--'l
organic-walled,
acid-resis-
F - 1
t-t
Sondovol
,
- II
\
y oreo
Mc Kni l e y
Legend:
@ Corehote
I
A-B
outcropsection
'lll '
- < L e o fc o l l e c l i osni t e
P l o n t - b e o r i ncgo n c r e t i o n
O
f,
ros
e Siricified
il
New Mexico
S c o l e I i n c h : 2 , O 0 Of t ( l : 2 4 O O O )
denced by the extensive application of this
discipline in oil and coal exploration.
FIGURE 1-Iaoc9!io1 map of the study area in the South Hospah area, McKinley County. The four core
sectionsare highlighted in blue and the elevations given were determined at the surfaie; see Fig. 3 for
profilesand exactlocationsof the cores.
MojorCyclesof TronsWestern Interior gressionond Regression
ReferenceSection (ofter Weimer.1960)
Soulh
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I
Nno Mexico Ceology
t
doo-z'so'
)fr
4l
GreenhornLimes'loneMember
FIGURE2-Stratigraphic setting of the Upper Cretaceousdeposits in the San
Juan Basin (from Jameossanaie,1983)
May 1986
ben
1OUSe.5S.O-8OOfr
-@
Lower Moncos Shole SOOfl
TI
o - 4 0 0t r
-4
Juono Lopez(Sonostee)
Member
Pfeifer Sh.
JefmoreChk.
B e l l eF o u r c h e
Shole
roo
\r----->sj
--Huerfonito
Upper Mbr.-t--
no.loH
Eogle Ss.
f
,o
Pic
Il_____5
Cloggetl
cycre
o-500fr
rt-
FruitlondFm....-
T17N, R10W in Orphan Annie Rock quadrangle and Laguna Castillo quadrangle. The
area is bounded between 107"50' to107" 54'
west long. and 35'52' to 35'40' north lat.
The rocks exposed in the area are mainly
shalebeds and crossbeddedsandstonesassociatedwith coal depositsthat are assigned
to the Cleary Coal Member of the Menefee
Formation (King and Wengerd, 1957).The
stratadip about 2-3" to the northeast towards
the cent-erof the San Juan Basin. Coal seams
are exposed locally at the surface.
Major coal-bearing formations in
New Mexico
The Mesaverde Group is the oldest coalbearingterrestrialrock unit in New Mexico.
It consistsof the CrevasseCanyonFormation
with two coal-bearing members, the Dilco
and the Gibson,and the MenefeeFormation
with a lower coal-bearingmember,the Cleary
Coal Member, and an upper unnamed coalbearingmember (Fig. 2). The most economically significant coal in the basin is in the
stratigraphicallyhigher Fruitland Formation
(Beaumont,1968).
Methods of Study
The locations of the four cored sections
that were sampled for this study are shown
in Fig. 1. The cored sections include a total
oI 233ft of subsurfacerocks (Fig. 3).
One hundred seventy-six samples of coal
and associatedrockswere preparedfor palynologicalanalysis.Sampleswere treatedwith
hydrofluoric acid to remove the silica and
partially dissolve the clay material. The residues were then bleached by cold sodium
hypochlorite (trade name Clorox) and stained
red with O.l%oSafuanin-O for microscopic
study. Some coal samples that did not respond to the Clorox treatment were treated
with a standard Schulzesolution (one part
saturated potassium chlorate solution and
nine parts commercial strength nitric acid)
on a steam table for 15 minutes followed by
a quick wash with 5% potassiumhydroxide.
are younger than the Santonian assemblage
describedby Tschudy (1975)from the Gibson
Coal Member of the CrevasseCanyon Formation in McKinley County and the basal
MenefeeFormation in Sanjuan County. They
are older than the assemblagedescribed by
Delfel (1979)from the La Ventana Sandstone
in Sandoval County. Delfel reported the
ocurrence ol Aquilapollenitesin the La VentanaSandstonesamples,which is absentfrom
the South Hospah assemblagesand indicates
a younger age. Palynologicaldata presented
by Delfel (L979)suggest that the La Ventana
Sandstoneis not younger than Campanian
(fameossanaie,
1983).Thus, the name MenefeeFormation assignedto the terrestrial coalbearingrock unit exposedin the South Hospah areais appropriate(seeFig. 2).
Gymnospermous bisaccate pollen grains
were rarely encountered in the South Hospah assemblage.The relative percentageof
these palynomorphs, where present, nrely
exceeded0.3Voof the total. Bisaccatepollen
grains occur more regularly in other terreshial Late Cretaceoussectionsin New Mexico
such as the Crevasse Canyon Formation
(Tschudy, 1975).The scarcity or absence of
the bisaccatepollen from the South Hospah
assemblagesindicates that the number of
coastal-plain,delta-plain, or swampland
conifersproducing this pollen type must have
been extremely low in or near the depositional site. It also suggeststhat any upland
conifers of this type must have been located
at a considerabledistance from the site.
Members of taxodiaceousplants are rePresented in the South Hospah assemblages
and
Taxodiaceaepollenites,
by Sequoiapollenites,
(Fig. 4, nos. 9-1 1), which
Inaperturopollenites
support the lowland habitat of the plants
contributing to the palynoflora of this site.
Of four living speciesin this family that are
native to North America three are adapted
to moist or wet lowland habitats.
Members of the palm family are also represented in the South Hospah assemblages
EC-r50
6'e92ft
[nTn ctoyevcool
coot
!
fFlSondstone
E-E siltstone
Flsnore
F.-l Brecciored
6,880 ft
3mllOft
Beige
6,869tl
oto
T o t o lc o r e : 2 3 0 f i
Ton
6.985 fr
Bronze
Discussion
Acid-resistant marine phytoplankton such
as dinoflagellates and acritarchs were not
found in the South Hospah palynologicalassemblages.The absenceof other marine microfossils and marine invertebrate remains
in the rock samples,and the presenceof freshwater algal bodies (Palambages
and Schizosporrs)
in the macerationresidues(Fig.4, nos.
19-21)indicate that the sedimentswere deposited in terrestrial fresh-water environments.
The presenceof Pseudoplicapollis
neramanii
(Fig. 4, nos. 3 and 4), Schizosporis
scabratus
Fig. a, no. 20), Cingulatisporitesdakotaensis
(Fig. a, no. 18), kiporoletesnooomexicanus
(Fig.
4, no. 13), Schizaea
reticulata(Fig. , no. 14),
and Kuylisporitesscutatus(Fig. a, no. 17) in
the South Hospah palynoflora indicates that
the depositsare early Campanianin age.They
.'..:.,.
Blue
Blue
Blue
6778 fl
Green
C o r e :l O 2 f t
6,832fr
Green
EJ-g,gll
Core:54 ft
f1
Core:160ft
profiles of the four South Hospah core sections. The exact locations
FIGURE 3-Stratigraphic
are as follows: EC-75, SE1/+NE1/q,sec. 35, T17N, R10W EC-100, NW1/+NE1/+,sec. 36, T17N,
R10W; EC-L50, SEllcSEll+,sec. 36, T17N, R10W EC-50, SW1/+NE1/+,sec. 1, T16N, R10W. The
elevations given were determined from the top of the cores. Surface elevations and approximate locations are given in Fig. 1.
I
I
New Melico Ceology May 1986
by both pollen and leaf impressions. All nine
extant genera of palms native to North
America occur in lowland and coastal areas
of Florida and the southern coastal plains
except for the California Washingtonia
(Washingtonin
filifera), which is native to the
southem United Statesat 150-1,000m elevations (Elias,1980).
The association of taxodiaceous and araucarianpollen with pollen assignableto the
gum tree family (Nyssaceae;Fig. 4, nos. 5
and 6) and palm family (Fig. 4, nos. 7 and
8), along with a high relative frequenry of
gleicheniaceousfern spores (Fig. a, nos. 1.5
and 16) is an indication of lowland depositional environments and
a wet, warm-temperate climatic regime. An abundance of araucarian twigs,
needles, and
Sequoia-type
palm leaves in outcrops of
the study area (Fig. 1) supports the palynological
interpretation(Cross,et al.,
1 9 8 3 ) .I t s e e m s t h a t t h e
maritime climate moderated
the interior seaway,which
6 by
2
4
3
prevailedin the areafor most
of the Late Cretaceous,provided a high level of equability in which a wide range
of plant populations could
flourish sirnultaneously.The
moderating effect of the
Cretaceousseawayis apparent by the occurrenceof pollen grains representing
familieswith the present-day
tropical or subtropical distribution in the Late Cretaceousdepositsof areasasfar
north as Alberta, Canada
(Srivastava,1970;Norris et
al., 1.975).Paleontological
studies on the Cretaceous
foraminifers(Bergquist,1971)
and gastropods(Sohl, 1971)
of the western hemisphere
also indicate a warm-temperate condition for the
southern part of the Western Interior region.
Pollenspectraof the main
coal seams, "blue" and
"green" coals (Fig. 5), are
distinguishedby exceptionally high relative frequencies of gleicheniaceirusfern
spores (Fig. 4, nos. 15 and
16)and triporate angiospermous pollen of the type
comparable to those produced by the families Myricaceaeand Corylaceae(Fig.
4, nos. 1 and 2). The type of
vegetation representedby
the pollen flora in the "blue"
and- "green" coals may be
characterizedby shrubby
and arborescentangiospermsand gleicheniaceous
ferns. This type of plant
communitv mav indicate a
marsh environment. The
15
term marsh is used here to
refer to the unforested wetFIGURE 4-Some significant palynomorphs from the South Hospah area (all illustrations X 1,000). l, 2, Triporpollenites
land habitatsas opposed to
spp.;3,4, Pseudoplicapollis
newmaniiNichols
and Jacobson,7982;5,6,
Margocolporites
spp.;7,8, Monocolpopollenites
reticulatus
forested swamp environNichols, Ames, and Traverse, 1973;9, Taxodiaceaepollenites
hiatus Potoni6, 7958;10, Sequoiapollenites
sp ; 11, lnaperturopollenitesdubius (Potoni6 and Venitz) Thomson and Pflug, 1953; 12, Balmeiopsislimbatus(Balme) Archangelsky, 7977; 13, ments supporting mainly
vegetation.Fem(Anderson) Srivastava, 7975;14, Schizaea
Triporoletes
noaomexicanus
reticulataCookson, 1957; 15, Gleichenii.dites
senonicus arborescent
Ross,1949;15, Gleicheniidites
sp.;17, Kuylisporites
scutfltusNewman, 1965;18,Cingulatisporites
dakotaensis
Stanley,1965; dominated marshesare one
19, Schizosporis
cooksoniPocock, 1962;20, Schizosporis
scabratusStanley, 7965;21,,Palambages
sp
of the major peat-forming
ry#"--*
May 1986
Nau Mexico Geologtl
environments in the Okefenokee marshswamp complex of southern Georgia and
northern Florida. Dense stands of Virginia
nd
chain fern ( Woodwardia airg inica) grow aro--u
the edgesof the swampsin the Okefenokee.
The pollen signature of the Woodwardiapeat
is distinguished from other marsh types by
its higher averagepercentage of Woodwardia
spores (Spackmanet aI., t974). In the absenceof grasses,sedges,and severalother
herbaceousdicotyledonousangiospermsthat
had not yet evolvedby early Campaniantime,
the gleicheniaceousferns and shrubby angiospermscould have occupiedthe available
ecologicalniches of these modern taxa in
marsh environments. This is evidencedby
the pollen signature in a considerableportion of main coal seams(Fig. 5). The minor
coal beds above the main seamshave a different pollen signature. They contain an
abundanceof Nyssa-typetricolporatepollen
(Fig. a, nos. 5 and 6) and tricolpate pollen
grains. The frequenciesof gleicheniaceous
sporesand taxodiaceouspollen are not significant in these coals (Fig. 5). The peat for
theseminor coalsseemsto haveaccumulated
in forestedswamps composedof Nyssa-type
vegetationas a major component.
The relative percentageof taxodiaceous
pollen is 4% or less in the "pure" coal beds.
This pollen is abundant in some noncoalproducing organicshalesat a few points along
the section, indicating that taxodiaceous
gymnosperms,although abundant at some
levels in the South Hospah section, did not
contribute significantlyto the peat. The clayey
coals and clay shalesthat contain high relative frequenciesof taxodiaceouspollen in
this areaare also dominatedby cuticular tissues, but they are very low in fusinite and
vitrinite particles.This seemsto be in conhast with modem taxodiaceouspeat in which
the wood and the pollen are both abundant
(Spackmanet al., 1974).
The "blue/green" coal complex is overlain
by a generallycoarsening-upwardsequence
characterizedby relatively thick depositsof
fine- to medium-grained, grayish to white,
arkosicsandstoneand light-gray silty shale.
This sequenceis interrupted by a few thin
coal beds and associatedblack shales.The
crossbeddingin these sandstonesindicates
an increasein the energyof the depositional
environment.A sharp contactwas noted between the "blue" coal and the overlying white
sandstonein EC-50, which indicatespartial
erosion of the coal and subsequentdeposition of sandstoneat this level (Fig. 3).
This hend correspondsto the progradation of the South Hospah delta, which resultedin migration of the peat swampsfrom
the study area along with the regression of
the sea (Fig. 2). Subsequently,the area was
occupiedby the fl uvial-dominatedupper-delta
environmentson which sandstoneswere deposited over the previously accumulatedpeat.
Conclusions
The South Hospah depositsare estimated
to be early Campanian. They correlate with
the Menefee Formation according to paly-
nological data. The environment of deposition was a lowland, freshwater swamP
ing-upward sequenceand migration of the
coal swamps out of this area.
AcKNowlEDcttcrvrs-Funding for this study
was provided in part by the New Mexico
Bureauof Mines and Mineral Resourcesand
ChacoEnergy Co. The author wishes to express his gratitude to Dr. Frank Kottlowski
for his continuous support and encouragement throughout this investigation.Thanks
are due to ProfessorAureal Cross of Michigan State University, Dr. Raymond Christopher of ARCO Exploration and Technology
Co., and Dr. Satish Srivastavaof Chevron
Oil ResearchCo. for carefully reviewing the
manuscriptand making useful suggestions.
References
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9a
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33
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43eI
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4421
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t9_
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oor.{
6l
Thomson and
Arecipites
W odehotse, Monocolpopollezifes
el
tranquillus":
Pflug, and the species "Monocolpopolenites
I
"
l
Taxon, v. 22, nos 213,pp.241,-256
16 39
++s
I
l
N o r r i s ,G , l a r z e n , D M , a n d A w a i - T h o r n e , BY . , 7 9 7 5 ,
coor
EI
!
Evolution of the Cretaceoustefiestrial palynoflora in
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FIGURE S-Relative frequencies of major palyPocock, S. A J , 1962,Microfloral analysis and age denomorph groups in core section EC-150. The freboundtermination of strata at the Jurassic-Cretaceous
ary in the western Canada plains; Palaeontographica, quenciesfor key palynomorphs at eachlevel of the
section have been highlighted in gray.
Abt. B, v 111,nos. 1J, pp 1-95.
-
37
ffi."
I
o,u.l
I
I
I
ffi
_t
ffi ffi
lii,.,,
m:g'1"
Nao MexicoGeology May 1.986
n
i:h