Page 98 - Land Snails of New Mexico

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Table4.AbundanceoffossillandsnailsfromQuaternarydepositsinDryCave,EddyCo.,NewMexico. Originallocalitynumbers andradiocarbondeterminationsfortheassemblages(fromA.H.Harris)areasfollows: AnimalFair(Loc.22,15,030+ 210BP),Bison C h a m b e r ( L o c A ; p r o b a b l y b e t w e e n 1 0 , 7 3 0 a n d 1 4 , 4 7 0 B P ) , S t a l a g 1 7 ( L o c . 2 3 , 1 1 , 8 8 0 + 2 5 0 B P ) , a n d T e s t T r e n c h II ( L o c . 5 4 , 1 0 , 7 3 0 = 150BP). Speciesthatpresentlyarelivingatelevationsof6,600-7,500ftalongPeñascoCanyon,SacramentoMountains,OteroCo., areindicatedatfarright. Ofthese,onlyHawaiiaminusculaandasuccineidpresentlyliveintheareanearDryCave.
Animal Species Fair
Cionella lubrica 3 Pupilla blandi 3
Pupoides albilabris
Pupoides hordaceus
Gastrocopta armifera }
Gastrocopta contracta Gastrocoptaprocera 5
Gastrocopta pellucida
Vallonia perspectiva 6 5
Vallonia cyclophorella Valloniagracilicosta 8
Rabdotus dealbatus 5
Helicodiscus singleyanus Succineidae 8 2
Glyphyalinia indentata 5 3 Hawaiiaminuscula 24
Thysanophora hornii
BisonSinkislocated61m (200ft)south-southeastofthe p r e s e n t m o u t h o f t h e c a v e . F r o m it h a v e b e e n d e r i v e d s e d i m e n t s depositedinBison Chamber (Loc. 4). Higher on a debris slope, and younger than Bison Chamber, is a locality designated Test T r e n c h II ( L o c . 5 4 ) , w i t h a n a s s o c i a t e d d a t e o f 1 0 , 7 3 0 + 1 5 0 B . P . , hence, of latest Wisconsin age. The Bison Chamber (Loc. 4) sediments are probably older than Test Trench II and younger than sediments at another site (Loc. 6) with an associated date of
14,470+250 B.P.
Localities mentioned above and species and quantities of
fossil snails recovered are indicated in Table 4, derived from Metcalf (1977:Table 2). All Pleistocene assemblages differ greatlyfrom the present fauna of the area, which comprises few species: Gastrocopta pellucida, Pupoides albilabris, Hawaiia minuscula, a succineid, and Thysanophora hornii.
Table 4 indicates species taken in Dry Cave, which also are found living at 2,013-2,287-m (6,600-7,500-ft) elevations along Peñasco Canyon in the Sacramento Mountains, Otero Co., 120 k m (75 mi) northwest of Dry Cave. Samples were collected at
91-m (300-ft) intervals along Peñasco Canyon. The greatest
numberofsharedspecieswasatanelevationof2,195m (7,200
ft). Metcalf (1977:63) suggested that conditions of effective moisture similar to those at the elevations noted in Peñasco
X 6 2 X
7
3 8
2 12 X
X 153 54 X
3 2 1 5
10 4 X
13 9 X 94 91 X 12 X
1 3
68 1054 X
Entrance Fissure SOUlrCe area
Bison Sink SOUlrCe area
Bison Test Chamber Trench II
Stalag 17
1 2
4 1
1
1 3
Canyon mightbe hypothesized as occurring atDry Cave during lateWisconsintimes,duringwhichtheassemblages atLocalities 4, 22, and 23 existed. In regard to annual precipitation, this wouldsuggestanincreaseofsome25.4cm(10in.)overthe 30.5cm (12in)receivedintheDryCaveareatoday.Interms oflife-zonedepression,afigureof915m (3,000ft)isindicated ifthe 1,280-m (4,200-ft) elevation of Dry Cave is compared with the 2,195-m (7,200-ft) elevation in Peñasco Canyon, noted above. However, itis clear that, topographically, the foothills area around Dry Cave is quite differentfrom mountain-flanked Peñasco Canyon, and Metcalf (1970:45) suggested that the Dry CaveareainlateWisconsintimemighthaveresembledthe present foothill grasslands (vegas) in the vicinity of Las Vegas,
SanMiguelCo.,NewMexico. TheassemblagefromTestTrenchIIseemstobenearthe
Pleistocene/Holocene boundary, judging by the associated radiocarbon date. B y Test Trench II time, Pupilla blandi no longer occurred in the assemblage, and proportions of Gastrocopta procera and Vallonia gracilicosta had been reduced from those of the Bison Chamber assemblage. This suggests onset of a climatic trend toward less effective precipitation.
Inregardtovertebratespeciesfound inmid-Wisconsin strata
1
5
4 30 150 X
921 X
Peñasco Canyon (living)