New Mexico Geol Soc Guidebook 25th Field Conf Ghost Ranch Centra - PDF document

1    New Mexico Geol. Soc. Guidebook,
   New Mexico Geol. Soc. Guidebook, 25th Field Conf., Ghost Ranch (Central-Northern N.M.), 1974 GENERAL GEOHYDROLOGY OF THE PAJARITO PLATEAU by WILLIAM D. PURTYMUN and STEVEN JOHANSEN Environmental Studies Group University of California Los Alamos Scientific Laboratory Los Alamos, New Mexico INTRODUCTION iles northwest of Santa Fe in north-central New Mexico, forms an apron of volcanic and sedimentary rocks around the eastern flanks of the Jemez Mountains (Fig. 1). The plateau slopes gently eastward from The main aquifer lies at depth of 600 to 1200 ft beneath the surface of the plateau in rocks of the Santa Fe Group. This is the only aquifer in the area capable of municipal and indus-trial water supply. GEOLOGY The plateau is formed by rocks of the Santa Fe Group of middle(?) Miocene to Pleistocene(?) age, and volcanic rocks of Pliocene and Pleistocene age (Griggs, 1964). The Santa Fe Group comprises the Tesuque and the Puye Formations and the basaltic rocks of Chino Mesa. These formations crop out along the eastern margin of the Pajarito Plateau. The Puye Formation is a poorly consolidated conglomerate channel-fill deposit overlain by a fanglomerate composed of volcanic debris. The channel-fill deposits are gray and consist of fragments of quartz Basaltic rocks of Chino Mesa consist of basalt and basalt breccia that overlie the Puye Formation along the Rio Grande Major volcanic units in the area are the Tschicoma Forma-tion of Pliocene age and the Bandelier Tuff of Pleistocene age. T h e T s c h i c o m a F o r m a t i o n f o r m s t h e m o u n t a i n s o f t h e S i e r r a de l o s Valles , an d is p r es ent in th e su b s urf a c e ben e at h the weste r n e d ge of the plat eau (Fig. 2) . It w a s extru d e d thr o ugh and ov erlies th e T e su q u e Form ation. T h e Tschicom a volc anics are composed of latite , quartz -l ati t e f l ows , and py ro cl ast i c ro cks . The Tsch ic oma Fo rmati o n is o v erl a in by t h e B a n d el ier Tuff alon g the flanks of t h e mountai ns. Th e Ban d elier Tu ff, a serie s of a s h flow s and ash fall s of rh yo l i t i c t u f f , cap s the P a j a ri to Pl at eau

2 an d unc onfor m a b ly ov erl i es
an d unc onfor m a b ly ov erl i es t h e P u y e Fo rm a - tion an d basaltic rocks of C h i n o M e s a i n t h e c e n t r a l a n d e a s t e r n p a r t s o f t h e p l a t e a u . T h e T s c h i c o m a F o r m a t i o n , t h e B a n d e l i e r T u f f a n d b a s a l t i c rocks of Chin o Mesa contai n only sm all am ounts of water which a r e perc hed above the main aquifer . The mai n a q uife r is in the low e r p a r t o f the Pu y e For m a t io n a n d Te suq u e Fo rma - ti on in th e west ern a n d c e nt ral p a rt of th e pl a t ea u a n d w i th i n t h e T e s u q u e F o r m a t i o n a l o n g t h e e a s t e r n e d g e o f t h e p l a t e a u . HYDROL OG Y T h e u p p e r s u r f a c e o f t h e m a i n a q u i f e r r i s e s w e s t w a r d f r o m the Rio Grande through the Tesuque into th e lower part of th e Puye Formation beneath the central and western parts of the plateau (Fig. 2). The w a ter in the aquifer moves from the m a jor recharg e area in the Valle s Cald era eastward toward the R i o G r a n d e w h ere a pa rt i s d i s c h a r g e d i n t o t h e r i v e r t h r o u g h s e e p s a n d s p r i n g s ( F i g . 3 ) . T h e m a j o r r e c h a r g e a r e a f o r t h e a q u i f e r i s t h e i n t e r m o u n t a i n b a s i ns form e d by the Vall es Cal d er a. The uppe r parts of the s e di ment s in th e basins are l a cu stri ne de pos i ts of c l ay, san d , and gra v els (C onover a n d other s , 1963) , w h ic h are und er l a in b y volcanic d e b r is resulting f r om the collapse of the cal d era. Sed i m e nts and volcanics in th e b a sin are highly p e rm eab l e and are saturated . T h e b a sin fill m a terial recharg e s t h e m a i n a q u i f e r i n s e d i m e n t s o f t h e T e s u q u e F o r m a t i o n . M i n o r a m o u n t s o f r e c h a r g e m a y o c c u r i n t h e d e e p c a n y o n s c o ntaini n g pere nni al st re ams on th e f l anks of the mou n tains. T h e in ter m

3 i t te nt s t rea m s i n ca n y o n s
i t te nt s t rea m s i n ca n y o n s w h i c h a r e cu t i n t o t h e p l a t e a u a d d l i t t l e i f a n y r e c h a r g e t o t h e m a i n a q u i f e r . G r a d i e n t o n t h e s u r f a c e o f t h e a q u i f e r a v e r a g e s a b o u t 6 0 f e e t p e r mil e be ne at h t h e pl at ea u in t h e Puy e Fo rm at i o n w i t h th e dep t h to wate r de crea sing along with th e ge ntle slo p e o f the surface of the plateau from ab out 12 0 0 feet to the w e s t to about 600 feet t o the east . T h e grad i e nt of the aq ui fer steepens to a b out 100 fe et per mile alon g t h e easte r n e dge of th e p l a t eau a s t h e wa ter i n th e aq ui fer m o ves into the l e s s p e rmeab l e sed i ment s o f the T e suq u e F o rmat i o n. T h e aq u i fe r is under wat e r t a ble co ndi t io n s in the we stern margin of th e p l at e a u an d is a r t e si a n a l o n g t h e e a s t e r n e d g e a n d a l o n g t h e R i o G r a n d e ( F i g . 3 ) . T h e R i o G r a n d e i s t h e p r i n c i p a l a r e a f o r g r o u n d w a t e r d i s - c h a r g e f r o m t h e m a i n a q u i f e r . A g a i n i n s t r e a m f l o w o f t h e riv e r a s it passe s thr o ug h W h ite R o ck Can y o n wa s fir s t de- s c ri b e d by S p i e ge l an d B a l d wi n (1 9 6 3 ) . Cus h ma n (1 96 5 ) e s t i m a t e d t h a t t h e 1 1 . 5 m i l e r e a c h o f t h e c a n y o n b e l o w O t o w i Br idg e re ceiv e s a d i scha rge fr om the ma in aqu i fer o f 43 00 to 5 5 0 0 a c r e - f e e t a n n u a l l y . GEOHYDROLOGY — PAJAR I TO PLATE A U 349 T h e f i r s t w a t e r - s u p p l y w e l l s f o r L o s A l a m o s m u n i c i p a l a n d i n d u s t ri al s u p p l y we re de v e l o p e d al o n g t h e eas t e r n e d ge o f P a j a ri t o P l at eau i n 1947. T h es e wel l s are c o mpl e t e d in t h e m a in aq u i fer a n d co ns is t o f six w e ll s in th e Lo s A l am os Can- yon field and seven wells in the

4 Guaje Canyon field. Well depth r a n
Guaje Canyon field. Well depth r a n g e s f r o m 8 7 0 t o 2 0 0 0 f e e t ( P u r t y m u n a n d H e r c e g , 1 9 7 2 ) . A q u i f e r t e s t s o f w e l l s l o c a t e d i n t h e e a s t e r n w e l l f i e l d , w h i c h p e ne tra t e a b o u t 1 6 0 0 fe et o f th e fi ne g r a i ne d sed i m e nt s o f t h e T e suq u e Formation, ind i cate an average coefficient of trans- missi bility of 20, 000 g / d/ft of the aquifer (Cushm an, 1 965). These wells y i eld an av er a g e of 5 0 0 g p m w i t h a s p e c i f i c c a p a c i t y o f 8 g p m / f t o f d r a w d o w n . T h e p a r t i a l s a t u r a t i o n o f t h e c o a r s e v o l c a n i c d e b r i s o f t h e P u ye Fo rma t i o n and co arse volcanic d e bris and ar kosic sands of the T e su q u e Formation h a s also led to the develo pment of hi gh y i el d wel l s f o r muni c i pal and i n dus t r i al s u ppl y i n t h e cen t ral part o f the Pajar i t o Plat eau (P urt y mun and Co o p er, 1969) . T h ree wel l s in the Pajar i t o fiel d w e re developed f r om 1 965 thr o ug h 1 968 . T h ese wells r a ng e in dep t h fr om 2300 to 2550 feet. T h e thr ee wells have pr od uced mor e tha n 40 per - cent o f t h e 4 7 0 0 a c r e - f e e t o f w a t e r u s e d a t L o s A l a m o s s i n c e 1 9 6 8 . A q u i f e r t e s t s o f w e l l s o n t h e p l a t e a u i n d i c a t e a c o e f f i c i e n t of transm issib ility rang e fro m 4 0 , 0 0 0 to 320 ,00 0 g / d / ft of the aqu i fer which i n cludes an ave r a g e of 2 5 0 fe et of Puye Fo r m a- ti on a n d 1550 f eet of the Tesuque Forma t ion. H i g h yi el d wel l s in this area average 10 00 g p m w i t h a s p e c i f i c c a p a c i t y o f a b o u t 3 5 g p m / f t o f d r a w d o w n . T h e c h e m i c a l q u a l i t y o f w a t e r m a y v a r y w i t h i n t h e w e l l f i e l d s d u e to l o cal cond it ion s w i th in th e aq ui fer. I n g e neral th e q u ality o f w a t e r is

5 g ood ; to tal d i sso lved solid s r
g ood ; to tal d i sso lved solid s rang e f r om a b o u t 2 0 0 mg/l to l e ss th a n 500 m g /l. Sil i ca concentra t i o n s r a n g e f r o m 3 5 t o 8 0 m g / l w h i l e t o t a l h a r d n e s s ( a s C a C O 3) r a n g e s f r o m 2 5 t o 1 0 0 m g / l . R E F E R E N C E S C o n o v e r , C . S . , C . V . T h e i s , a n d R . L . G r i e g g s , 1 9 6 3 , G e o l o g y a n d h y d r olog y of th e Valle Gran d e an d Valle Tole d o, San d oval C o u n t y , N e w M e x i c o : U . S . G e o l . S u r v e y W a t e r - S u p p l y P a p e r 1 6 1 9 - Y . Cu s h m a n , R . L . , 1 9 6 5 , A n E v a l u a t i o n o f a q u i f e r a n d w e l l c h a r a c t e r i s t i c s of mu nic i pal we ll f i e l d s i n L o s Al am o s and G u aje Can y o n s, ne ar L o s Al amo s , N e w M e x i c o : U . S . G e o l . S u r v e y W a t e r - S u p p l y P a p e r 1 8 0 9 - D . G r i g g s , R . L . , 1 9 6 4 , G e o l o g y a n d g r o u n d - w a t e r r e s o u r c e s o f t h e L o s A l a m o s A r e a , N e w M e x i c o : U . S . G e o l . S u r v e y W a t e r - S u p p l y P a p e r 1 7 5 3 . P u r t y m u n , W . D . , a n d J . B . C o o p e r , 1 9 6 9 , D e v e l o p m e n t o f g r o u n d - w a te r s u p p lie s on th e P a j a r i to P l a t e a u , L o s A l a m o s C o u n t y , N e w M e x i c o : U . S . G e o l . S u r v e y P r o f . P a p e r 6 5 0 - B . Pu r t y m u n , W . D . , a n d J . E . H e r c e g , 1 9 7 2 , S u m m a r y o f L o s A l a m o s mu n i c i p a l w e ll-fie l d c h ara c te ris t i c s , 1 9 4 7 - 1 9 7 1 : L o s A l a m o s S c i e n - t i f i c L a b o r a t o r y r e p o r t L A - 5 0 4 0 - M S . Sp i e g e l , Z a n e , a n d B r e w s t e r B a l d w i n , 1 9 6 3 , G e o l o g y a n d w a t e r r e - so urces of t h e S a n t a F e A r e a , N e w M e x i c o : U . S . G e o l . S u r v e y W a t e r - S u p p l y P a p e r 1 5 2 5