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<br />9-1
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<br />TilE \\'..\S:\I:\:'\:'\ ]Ol"R:'\.\I. OF BIOI.()(;\", \'01.. ,q, :'\0. I. \tl;'1
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<br />uncleI' structural control (:\Ielton. 1960, 19(IS; Cooley ancl D;l\'i,i.
<br />son. 196,)). B\' thi~ time. much of the soulhl'rn '('(I~e of 11ll' I'll
<br />tl'au had Iil'l'n ~:aptul"ed by ~ollth.flowing strl';II11~, and the \llIgII]!
<br />Rim (fig. 9) wa~ well estahlishl'cI as the cli\'idt' between the t,
<br />and Ihe Little Coloraclo rin'rs (\lcKl'(' allcl :\lcK('l', 1(72). .,.
<br />Bill "'illiams Riwr area ha~ been little sludil'd, hut il lie~ "ou:
<br />west of the \Iogol1on Highlancl~ in :1Il area oi relatiw stabilil\,
<br />anclmay long ha\'e occupied its pre~l'nt position,
<br />Gila rO/I/I.\/a, or its progenitor. must ha\'l' liwcl in the IO\\,'!"
<br />ha~in at ka~t by thl' J'lioC('Il(, and perhaps prior \0 the cuttill~ ..:
<br />the (;rancl Call\'on. Earl\' acc('~~ was po~~iblt, through Illa""i\t'
<br />\1l'adwan\ \"r"sj,:n and C;I\:I\II"(" "j lilt' 9ll1lhl'rn part of the ("Ill...
<br />rado I'lall'aU b,. the anc('stra1 Salt and C;ila ri\'('r~ in !all' \liot',;"
<br />or Illort. likeh' i'n t 111' I'lincl'n(' (Cooley and ))a,'id~on, Il)(J.l: \ Ie I, '.'
<br />ancl \IcK('I,.'1972). E~tabli~hnlt'llt of a sharp drainage cli\'idl' "i,i,
<br />uplift on the \Jogollon Rilll in mid.I'lioCl'nl' Illay han:' pro\'id,d
<br />eifeCli\'l' isolation. :mcl till' lippeI' Yl'rdl' ba~in was cliwrtl'd south
<br />b\' upliit of the Black Hills (t"i.~. 9) at about Ihi~ time (LehlH"r,
<br />1;'SS: Coole,' ancl I>a,'ic!":on, 10(1.)), ,\ccl'~s imm the we~t ob,'j.
<br />ou~h' could ,;ot ha\'(' occurred prior to cutting oi the lower Colorad"
<br />Ri,';'r ancl may h:I"(' been hlockl'd for a time by the I'lioCl'lll'
<br />Bou"(' Ellllla\'lllellt (11:lIllihon, !l)(JO: \Il'tzger. 1l)(IS; Lucchil1:\,
<br />Jlli]). \Jill:'r (l'lIda) sug~l'~tl'd that the cli~tinctin' iauna "i
<br />Ihl' (;ila Ri\"l'r indic:ltl'd a rather lTCl'nt connectillll with the (',,10'
<br />radoRi\"l'r. 1111\\"(','er. for pari oi Ihl' 1'lioCt'lll', the lower ha-ill
<br />mlbt ha\'e I)("en ac("('~sible to chuh~ irolll that din'clioll.
<br />En'nh in Ialer I'liocene a.~ain cut off Illuch of tIll' upper par:
<br />oi 11ll' ance;;tral (;ila Rin'r Ila;;in irom 1111' ('olor:lllo Illain~trl'alll.
<br />and provided bolation illl" diiien'ntiation of I hI' chubs, Lacu~tril1l'
<br />and ilu,'ial Illalerial IH'n' depo;;ilL'd to dl'llth,,; 1'\l'L'edill,~ (100 111 ill
<br />the extensi\'e ;;tructmal trough, partially a grallen, that IllHIIHI~ till'
<br />Colorado I'lateau frolll Ihe Illouth oi the (;rand Canyon 10 norllwrr
<br />Chihuahua, ~fexi("O (Brand, 11)37: Feth and He 111 , IlJ(J3: Felh
<br />1')(..1). ~uriaCl' dl','ation;; oi these d('po~ih :Irl' rt'lllarkallly ~illlilar
<br />throudlllUt the area, and fo~~il~ included in a nlll11hl'r of then'
<br />corn'btl' \\'l'1I (Taylor, It)6.,; Feth and llel11, !1)(J3\ ;;ugge~till'
<br />tlll'ir ~ynchrony. I'onding oi the ri\"l'rs \\"a;; l'fieCll'd hy l'xtru~iol1
<br />of \'olcanic l11all'rial~ and upliit in Ihe lo\\"er ~alt River area (iig
<br />0) east of till' prl'~enl city of I'htll'nix (\It-lton, It){IO. (lJ(I.'i). :\1
<br />
<br />CYPRI:'\lf) FISII":S-RI:'\:'\E
<br />
<br />95
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<br />this time till' upper (;ila Rin'r (not including thL' rl'ach ('ast of
<br />Safford) may haw joined till' Salt Riwr north of thL' pre~ent
<br />10 I\" 11 oi (;)olw. :\11 extension oi the extru~il'l'~ to the north along
<br />the "l'n!l' impOUIHll'd Ihal streal11 (Jenkins, IlJ23) and 10 the east
<br />of Florence, the ~an I'l'dro segment of the basin was silllilarh'
<br />j;;olated, Thl' Santa ('ruz and olher h's~l'r ril'l'r~ ('lllerin~ Ihl' 101H:r
<br />(;ila valley \\'l're searn,ly aiiected and flo\\"ed far \\'e~t to enter
<br />lhl' drainage, The upper (;ila River, ahove Saiford, wa~ nol ap-
<br />parently intl'.grated to the \\'est until lllid-I'll'i~tocelll', after the
<br />on;;l't of il1ci~ion of Ihl' volcanic dalll~, and prior 10 that lime
<br />pn'~ulllallly flowed ~out h into.a closl'd !J:l~ill: or perhaps into \ll'x-
<br />ico (\lorri,on, 11l(1.1: ("ooley :md 1);I\'id~ol1. {l)(J.): ~leltol1. \l)().'i:
<br />Kollltm~ki (/ (/1.. !WI.') ).,
<br />The ance~lor of (,oi/(/ ill/,.,-/I//'I/ill could ha\'e displ'r~ed into north.
<br />flo\\"ing tribul:lries oi the ancestral (;ila basin at allllo,t am' time
<br />in Ihe I'liocl'nl' or l'h'i~loCl'ne and rl'lllain('d in relatively' small
<br />head\\'ater situation~ to the south and we;;t of the \Io"ollon Hi"h.
<br />land~ Illo,'ing into that region as di~section (down-c'~ltin.~) I;~o-
<br />gre~~ed. (;enl'ral di~tribution of this fbh in recelll tillles ill the
<br />southern tributarit's oi Ihl' (;ila (fi,~, I), perhaps refh-ct~ mo"elllent
<br />owr lowered di,'ides re~ultin,g from alluviation of valle,'s bet\\"el'n
<br />tIll' ~;\Ilta ('rIIZ alld San Pedro rin'r~ in lhe I'kistocen~' (:\Ielton,
<br />IWJ.:; I or conceivably, actu:i\ ridin~ of I:tnd Illa~se~ tlll'l11~elvl'~ (~\n.
<br />dl'r~on. l!JiO: Elder~ dill., IlJi2). The occurrence of G. ill/I'I"/I/I'r/i/1
<br />in Ihl' t'xtn'Ill(' uppl'r \'erde Illay n'~u)t frolll a di"l'r~ion of part of
<br />the ..\gua Fria Rin'r to tll(' "l'rde in the area ea~l-nortlll'ast oi
<br />I'r('."colI (('hillO \"alll'y). Little prl'serwd malerial oj (,'i/(/ (two
<br />uncatalo,~ed specilllens availabll' to 1111') i~ known frolll Ihe :\gua
<br />Fria. TIll';;I' two ii~Ill'~ an' unmi~takabh' G. ill/,.,/I//'{/ill. Thl'" al'l'
<br />idl'lllical with spl'cil11ell,- "l'l'll alld idl',;tified IJY "', L. ~Iill'ckh-y
<br />(personal comlllllllicalion) in !l)(dJ. Recently Ihey haw' bet'll re.
<br />ported by Forest Ser\.ice Jll'rsonnel (personal COllllllllllication to
<br />:\linckll'Y) in that same ~treal1l.
<br />('lIl1in~ oi d:llllS Ih:ll 1,locket! lhe ril'ers was initiated in early
<br />mid-I'lei~tocl'ne with ces~ation of \"ulcanism and upliit at points
<br />of dal1lllling. Breaching oj dam~ reintt'gratl'd milch oi tht, systelll:
<br />ba"l' le\'l'b in 111l' allu\"ialed ,'alleys lI'l'rl' high aho\'e that of tlw
<br />lower part oi the sy~lem and further down-cut tin,g progressed
<br />fai r1y rapidly. Thi~ dl'grada t ion leit rl'mnan t popu!a t ions 0 f fishes,
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