20.4 Junctionwith asphaltroad; turn right,
go northward. Note sinkholesin vary,.
ing stagesof developmentalong bluff
to east.
21.0 Lazy Lagoonon left.
22.6 Junctionwith upperroad; end of loop.
Turn left to Roswell,13.4mi.
Geology
The PecosValley near BottomlessLakesis
cut in sedimentaryrocks laid down about 230
m.y. (million years)ago in an arm of the vast
Permiansea.Periodically,when this areawas
a huge, shallowbaylike feature,the gypsum
and reddishsiltstonesof the ArtesiaGroup of
rocks were deposited.The entire area was
tilted very gently (2" to 3o) to the east.The
PecosValley was cut during relativelyrecent
geologic time in these Permian sediments.
Originally, the Pecos River flowed several
miles westof Roswell.but the tilt of the beds
causedthe river to shift eastwardas downcutting continued.
Sedimentsdepositedin the valley by the
river are sand,somegravel,and quantitiesof
clay and silt. The presentriver channeloccupies the lowest area and is bordered by
floodplains with oxbow lakes and swamps
marking abandonedchannels(such as Lazy
Lagoonin the northwestpart of the park).
Abovethe floodplain,especiallyon the west
sideof the river, are higherterracescomprised
of older sandsand silts.The upperterrace,the
Orchard Park, is about 40 ft above the floodplain. The lower terrace, the Lakewood, is
about 20 ft abovethe floodplain. Theseterrace sedimentswere depositedand truncated
during varying periodsof the Pleistocene
Ice
Age, 10,000 to 20,000 years ago, as huge
volumes of glacier melt-watercame roaring
down from the Sangrede CristoMountains.
Someof theseArtesia Group rocks are exposedin road cutsalongUS-380at Comanche
Hill on the eastsideof the valleybetweenBottomlessLakes StatePark and Roswell.Here
the rocks are pink, green,and red siltstones
interbeddedwith grayishto white bedsof gypsum. Similar rock beds occur in the park,
alongthe roadsand surroundinglakes.
A notable feature of these beds are the
"PecosDiamonds," small,doubly-terminated
quartz crystalsfound for nearly 100mi along
the eastsideof the PecosValley, from Dunlap
in De BacaCountyto the north, acrossChaves
County, to just south of Artesia in Eddy
County. In areaswherethe gypsumbedscome
to the surface,as at severaloverviewsin the
park, the sparkleof sunlightfrom the quartz
crystalsis quite noticeable.Gypsum crystals
also reflect the sunlight. Perfect quartz
crystals are difficu.lt to find, but beautiful
PecosDiamondsare prominentin the collectionsof many mineralogists.
How did the lakes form? One of the best
Gravitational
oreseparalion
November 1979
New Mexico Geology
Flora and fauna
Among the vegetationin the valley are mesquite, creosotebush, salt brush, salt grass,
snakeweed,salt cedar(tamarisk),yucca,and
cactus.Sparsegrassand scatteredshrubsconservethe sandysoil of the uplands.
Roadrunners and jackrabbits rule the
brush. Rare fish, such as the zebra killifish
and Texascyprinodon,inhabit the salty lake
waters.
D
-F. E. Kottlowski
NMBM&MR
This systemhas the following advantages.l) Powerconsumptionfor processing copperore was 35 percentlessthan a
secondarycrusherand a ball mill would
haverequired. 2) Capital cost savingsas a
result of the elimination of secondary
crushing and milling when these operations are combinedinto a singleprocess.
3) Reducedmaintenancecostsdue to reduced wear and lessdown time. 4) Machineoperateson a limited water supply,
and at low pollution levels. 5) Minimal
skillsarerequiredfor operation.
Because these advantages may encourage successfulmining ventures in
more remote areas,the developmentof
this type of machinery is both economically soundand essential.
lcontinuedfrom page55)
various water inlets and the overflow,
which evacuates
air from the pulsewater,
allow a very subtle bed movement.The
patentedvalve systemregulatesthe suction of the movement.Thesethree variables allow concentration of material
down to 325 mesh. In the Hansonburg
district, our materialwill be concentrated
in threecarefullyscreened
groups:50-150
mesh,150-200
mesh,and materialpassing
200mesh.
Resultswith the jig have been highly
satisfactoryon our ore, with galenaand
barite recoverieswell above 90 percent.
Fluorspar recovery is somewhat lower
(70-80 percent). The remaining tailings
will be treated by gravity separation,
using magnetic material as previously
mentioned.The price of fluorspar at the
moment doesnot warrant recoveryfrom
the tailings.It will be stockpileduntil better pricesjustify further processing.
The pulverizer(fig. 2) is basicallysimilar to any other pulverizer. The most
significantdifferenceslie in the designof
the breakingplates,the rotor outlet, and
the rotor itself. The useof specialwedgeshapedsteelplatesand the curvatureof
placesto comprehendtheir origin is at the
overlook above Lea Lake where the bluffs
coincidewith a sharp flexure in the Artesia
Group beds.The regionaldip is gentleand to
the east, yet along this river-valleyescarpment, the dip is rather steepto the southwest.
The pronouncedreversalof dip is probably
due to the solutionof gypsumand consequent
slumping of overlying beds. Underground
channelsand cavernswere dissolvedout by
circulating ground water, resulting in deep,
steep-walleddepressionsnow filled by the
lakes.'These collapse structurescausedby
ground-water solution of rocks are called
sinkholes.
The lake water, fed from salty underground
flow, is high in sulfates(4,000to 14,000ppm)
from the gypsumbeds.Thus the necessityof
piping in water from Roswell-to make the
swimmingmoreenjoyable.
Rotor
Acknowledgrnents
My thanks to Dr. Frank Kottlowski,
Director; Robert W. Eveleth, Mining
the ore-breakingplates maintain the im- Engineer;and Neila MacDonald, Assopact force perpendicularto the plates,
ciateEditor, NM Bureauof Mines& Minthus holding plateswear to a minimum. eral Resources,without whose help this
The lid can be lifted hydraulically and paperwould not havebeenpossible.
easily swung aside. The ring containing
Reference cited
the breakingplatescan be removedin 5
minutes;the rotor is similar in design- Kottlowski, F. 8., 19'19,Barite-fluorite-lead mines
of the Hansonburg mining district in central New
the tungsten-carbideplates are attached
Mexico, in New Mexico Geology: NM Bureau of
with a few bolts, enablingtheir replace- Mines & Mineral
Resources,v. l, no. 2,p.l7-20
_
mentin a matterof minutes.
FIGURE 2-Tne pulvsR.rzEn.