•

•

Report tOI National Park Servioe Date I Ootober. 1966 •

From. J. Sohoenwetter , Title. Pollen Statistios frclll Pratt Caw t Prel1miDllry Report

I N'l'RODU CTI 011

'!.Ir. A. S ohroeder of the National Park Servioe submitted ten sedimellt sEllIIples to the Palynological !J1bora tory of the Uusel.ll1l of New Moxioo in July of 1965. Nine of these proved extremely rich in preserved pollen. Be also submitted oopies of hiD maps of the plan views and stratigraphy of this caw in the Guadalupe Mountains. No desoriptions of the modern vegetation patterns of the area aooompanied the samples. however, and at the time of writing no aDlllysis of the archaeological and formal material8 of the site are available. The oonclu8iona and interpretations of this report suffer from a laok of oanparative and oontrol data, then. and it 18 to be expected that turther oonsideration will be g�.veD to tooSIt matters as and When suoh data beOOlll0S available. At present. all judge:ments must bs made upon the pollen reoord alone.

The objootives of this atalyllill were mads explicit by lIr. Sohroeder when the 8amples arrived. 14any aadiment samples for pollen sDIllysia were oolleoted during the excavations at Pratt Caw. but only a f_ wore '

submitted. These were to stand as a test series to determine if suffioient pollen could be reoovered for analysi8� if hori�on marker pollen speotra could bs recogni�ed which would assist in the definition ot II&tural stl'lltigraphio units within the cave fill, am if elIVirozmantal or olimatio ohange did evidently ocour through tho period of sedimeut deposition.

AVAILABILITY OF FOLLEN

The ssdimeuts aro very rioh in pollen. Using the extraotion prooedures normally appl!� 4;0 Soutmn,stsrn sediments by this laboratory. Dins of the samples produoed �housands of pollen grains per mioro-alide. The tenth, whioh was of a calichlfied sod1ma1lt with muoh oharooal. probably contains sufficient pollen for analysis but must be proceBsed differently to relllOV9 the vast quaut1ties of �rganio dotr1;u8 it oontains before analysis will be profitablo. Pollen is avaUa'lle in suoh quantities that a number of pollen statistioal operations oa� be oarried out llimultansously with ease. In the present oount AJnbrosieae, Chenopodiaoeae. and speoifically riparian pollen taxa ware exoluded from the pollon SUg of 200 grains. Beoause of the vast quantities of pollen available on eaoh slids. even ths dominant pollen type (Querous) could be exoluded

without making the am-lysis ted1ouo •

0

+ +

• > D .. • ..

". 'i 0 .. .! > ..

• .. � � � � ;; 0 .. • .. • > a ...

+ +

-

-

+

+ +

-- -

----

• •

+ +

+ +

+

- --- -

-

----

� N .... • '" .. .. ;;

• ;; 'i ! ;; i , > > •

s • � � • � oJ

TY : iii '"

; .. .. • .. ii OJ .. .. ii

•

•

•

•

2

ENVIRONMENTAL VARIATIONS THROUGH TIllE

ThiIJ analysis was primarily designed to indioate the ooourronoe of el19'irODnental variations thro ugh t1m3 if suoh cid take place. The frequenoies of Ambrcsioe.e an!. Chenopodiaceae pollen were dropped from the pollen Bum to iDnrease the statistically relevaul: frequenoies of auoh pollen taxa as Graminaae. Ar temisia and Lllliaoeae; the frequenc ies of riparian pollen taxa (Betula:. AlDUS. Juglans and Celtia) were excluded beoause they represent vegetation or a specialized eoology.

There were two surfaoe samples to aot 90S oontrols. indioators of the pollen rain-vegetation response to modern envirolllllsntal oonditions at the sito. That 110 data _a aval1.able to indioate what, exaotly. these oontrol samples represent in ten18 of modern vegetation is relatively unilnportant. Change through MIliS could be recogDized even if om might be unsure of tho signifioaDOe and preo ise IlBture of such ohange.

The pollen statistios of the tvo surfaoe samples are 81gnificangly different in a ll11!Ilber of instanoes. Since one sample oomes from o\ltside the cave and om camas frcm inaide. this oould be simply interpreted as a function of the greater potential for the exterior sample to trap pollen of Pims. JUDiSrus. Graminea(l and LUl10eae beoause it is ol08er to the souroes � suoh pollen. If suoh an int.erpretatiDll is acoeptod. one must grant that +-he statistioal dU'rertlnaee beocwaen these two pollen speotra. T1hlle real. are _ningless in terms of expressin g rele-vant onvl!'fr.ll!l8ntal differeDOeso Then one .... ould compensate for them stat1stloally in aalyt:ing the subsurfaoe pollen spectra.

But there are in dio.tiona that th.1s interpretation is n ot wholly aocsptable I tho oaTe iul:orior aodilDaul:s are of quite a softsr and more dusty ohal'aoter than those outBide; artifaots of some antiquity. as well as oharooal and other anoient human dsbria. are soattered on the surfaoe of the oaw intoriorJ and pot bunters' holes and other previou8 excavations in the cave attoDt to tho disturbar.oe of those sediments in rolatively reoeul: yeareo Th888 faotors allow ths possibility that the surfaoe sediment oollected for pollen analysis oould be more ancient than that oolleoted outside tho oave. or it could be from a disturbe" horizon in ,.hioh pollen of ono or more amient periode was 1lendsd. or it oould be from some m�:tt7Jr8 of both :medGrn and allOient hQl"izoDs. These theoretioal possibilities are attested to in polleD studies from othsr dry caves. In the Navajo Reservoir Zeta )ollen °7i13s reoowred from ths su.rfaoo scd1lr.ent of a cave oonta1'iirng ii" .. "ajo remains (Sohoemvetter aDd Eddy .. 1964, p. 90). Fllins were taken in tblt case to o btain a ,,,,rl'aoe sampls whioh wae in a proteoted poaition and probably undilitur1Md. yet some of the pollen it contained must have been depoa1ted OWl' 2'JO years ago •

•

•

3

I believe that the most adequate interpretation of the differences between the two surfaoe samples is that the differences are mostly functions of differenoes in their age. As I see it. the two itldioate B ohange in environmental c cnditiona since the end of sedimentation in the oave whioh increased the quantity of pim. juniper. grass. L111i&00ae and Ambroeieae pollon. This would seem to indioate a somawhat �oister or oooler oondition occurring now than previously. I sus,eot that the inorea89 in Chenopodiaosae pollen is a function of tho localizod taluB slops habitat.

The samples from 18velo 1. 3 and 4 haw essentially the same palynologioal charaoteristios as that from the surfaoe of the oave adjaoent and seam to be represents t i,", of the same envirollment. The samples fran levels 5 and 6 at be. lkll 25-27. and frcm leve 1 2 and the silty layel' at balks 13-15. are oharaoterbed by the occurrence of biroh pollen. These latter samplea wt"8 oollected relatIvely mBrer the oave bedrock than the eo.mphs from levels 1. 3 and 4 and Beem to represent an earUer onndition. 1 t appeal'S to have been a ti_ when birch trees gronr sublltantially oloser tc the oave than they lIC111' do. This oClUld be due ' .• 0 af1:' of eo number of disparate faotors. A generally very moist cl1unte might have nearly saturated th8 sedimellts juet outside the cave so that birch o«lld grew there. but thh 8eSlllt' highly ir!p!'o!lable in view of tho simultaIl80us ocourroncEl of Acaci .. (catclaw) and Cactacsao. whioh are indicative ot desert or desert grassland o onditioIlllo Perhaps a Dearby eprill); W3S aot1'18 at th8 tima •

or the main challllltl of the MoKittrick Canyon had not yet elltrenched and the cave was on the margin of all indis88cted floodplain.

I n any case this ancient period of dif.'ferent 8nvironment 1I8.S differellt maiDly ill tho seuso that 1t supported a speoialized vsgetation pattern whioh even nCll' exists within the range of vegetation patteI'M of the district" While there seems same justification for ooneideriq& that the site area 1e now ac:mnbat cooler or moister than it was during the cooupation of the cave, even this distiootion does not appear to be II. very major om. It is quite dClubtful from the present data that any major environmental variatioll occurred in this regioll during th\9 period of deposition of sediments in Pratt Cave. All suoh changes as did coour probably fall within the range of varIation ill conditions nO'lr existing within a 5-mile radius fram the cave. CertaiDly the paople who once inhabited the cave did DOt experience a much difforent onvironment than nOlI' oocura. nor were there different mt1lral resouroes available to them than now exist there. The quantities and dlstributioWl of suoh rescurcea may have been e!llD8What different than _ now ebeerve. but it is unl1kely that they were 00 different as to have baen of economio importanoe.

STRATIGRAPHIC HORIZONS

ThG dUforellOes in enviroIllllaDl;al oo!ld1t10ns in the pollen seque_ oroate a series of horizon marker pollen speotra. In thie co.se an early horizon marked by tho presence of birch pollen. a late horbon marked by quantities of pim, jU1l1per and Ambr oeieae pollan, and a middla horizon without birch am with low frequencies of the other taxa.

•

•

'rbo present amlyB1s dces not yield quite enough information to unaqu1vocelly justify the case, but it seems likely to me that tho middle pltriod oould be spU'" im:o at least two hor1zo!13 with further work. This amlysis was prj.marily designed to yield ini'm"l!lat1on about enviroI!lllllntal variation. Another o.mlyt10 dosign oould bG oetabl1shed which w ould yield infornntion of more preoise stratigraphic value. By el1mimting eak from the pollen sum� signifioant varia tions in the statist'.C8 of Aoacia, Prosopis. Gramlnee.e. Art emisia. Lilliacee.e. Ephedra anl others !Iligfi€ bGo ClOO relevant all hcrhon markBrs. The occaalcnal OCCUI'rences of Geraniaoea e (6). rragraoeae (0). Nyotaginaceae (N) and a distinotive unknown pollen type which I haft oalled Type A also wculd beoame lIIore oosningful in enviro1llD9ntal lnterpl""taticn.

If the modern condition 1s oalled Z one I. and th" earliellt condition called Zom IV. I think that the praSGllOe of Proao�1s p .. llen might differentlato s Zons II tran a Zona In in the iiiid 19 t1:ne horizon. On thi8 baSiS, two sample 8 8hm pollen oharacteristics 01" '�"Wo r.OD!lIl. This Beema due to their plaoement at balka lS-15 where dep08ition owr a long time was o&mpressed into level 2.

SUGGESTIONS

(1) The deoision to oontinuo pollon rolearoh on 8amples tram this cave must we1gh a number or faotors, co st am the nlue of refiDSd interpretation being foremqt amollg them. The cutl1ms of suoh environnental changes as ocourred 8ee m now reoognizable. Further amlyds thrcu@;h polllln would substantiate them. but other types of amlya"e may already have dona so. Re1'i_nta in the reoovery of strat igraphic horizons may be of litt16 value beoause of the oontrols over the excavation. Pollan analysis, for example., might a11� reoognition of thre" or tour separate horizons w itl('l .... 1 3. but if tlT.8 exoavated materials were only oolleoted by whole lew1 1Ul1ts this information will not 1l110¥1 their s egregation in relative t1ll8.

(2) It would S88m judicious to delay further pollen alll1lysia until s uoh tims as the presom: ly 11'98. 1 lab l.e . data can be lnteJ!:rat"d with the o ultural ... nil palecntologioal -reCCIl'dIt. Then" eerie. of que,t10M oa'.l be posed e10h the palynologiJt osn des!{;n hi. study to re.o1 ....

REFERENCE

SohoellSi8tter, Jemo II and F.W. Eddy 1964 AlluTial and Pa1lbjl;10al Roconstruotions of Envir01llDL!lnt • Wivai{J0a,,",oir .. lot. Iluseum of New 1reiioo Filpers

n X apology 1S. Santa Fo.