geology of northern new mexico - princeton · pdf file! 4 princeton and new mexico geology...

Princeton University Department of Geosciences

GeoGrad Reunion Trip

September 4-10, 2014

Geology of Northern New Mexico

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© 2014, Trustees of Princeton University. All rights reserved.

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View toward the north over the Rio Grande Gorge bridge (our STOP 4.2). The Rio Grande cuts 800 feet deep to expose the three 4.8-2.6 Ma Servilleta basalt flow packages, separated from each other by layers of basin fill sediment. In 2013, this area was designated The Río Grande del Norte National Monument and includes approximately 242,500 acres of public land managed by the Bureau of Land Management. See The Rio Grande by Paul Bauer, 2011, published by the New Mexico Bureau of Geology and Mineral Resources. Photo credit: http://www.abqjournal.com/181216/news/new-national-monument.html

Cover image: Ansel Adams' famous 1941 photograph Moonrise, Hernandez, New Mexico. Licensed under fair use of copyrighted material via Wikipedia.

View westward from Ancestral Tsankawi Pueblo toward the Valles Caldera; the skyline is the topographic rim of the caldera. The cliffs expose products of the two major eruptions of the Bandelier tuff (1.23 and 1.61 Ma). Photo by Jesse Chadwick ’08.

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Princeton and New Mexico Geology Welcome to New Mexico!

Over my four decades at Princeton, we have capitalized on our Princeton connections in New Mexico to lead field trips and to feed us as we passed through. These trips have been going almost annually for the past 35 years. They have involved undergraduate and graduate student groups, and trips specific to courses.

A profound early influence for the study of New Mexico geology was the gift by Art Montgomery ’36 of the Harding mine to the University of New Mexico. We will enjoy the benefit of this legacy on our last field trip day.

The most influential geologist for inspiring continuing Princeton involvement in New Mexico geology was Jeff Grambling *79. Jeff began his thesis in the Truchas Mountains, which we will see on the horizon on the last day of our trip. Jeff had heard that the three Al2SiO5 polymorphs occurred there, and he set out to do his thesis on these occurrences. The result was a classic paper that mapped out the phase diagram for Al2SiO5 across the front of Mt. Truchas, including the location of the triple point. Before his early death from a brain tumor, Jeff had led several memorable field trips for Princeton students.

Jeff attracted many outstanding students to study with him at the University of New Mexico. These are my professional grandchildren. One of his undergraduates came to do his Ph.D. with me at Princeton. He grew up on the Pojoaque Pueblo and we will pass by his elementary school, which is now a casino. One of Jeff's graduate students came to Princeton for a postdoc. He did the definitive study showing that previous interpretations of the timing of metamorphisms of the New Mexico Proterozoic were incorrect. Inspired in part by this work and in part by Jeff's earlier work, my undergraduate classes collected and analyzed a suite of rocks from the Tusas Mountains (in view from several of our stops); Jeff would have approved of our data and conclusions. This led to my most recent (2012) hard-core metamorphic petrology paper, which is co-authored by two former undergrads, one former grad, and one former postdoc. A Princeton production!

In my many interactions with New Mexico, I found a home away from home with a former undergraduate (class of 1975) and her family, who have provided a base from which I, and my family, have explored many aspects of New Mexico, from geology to culture to political.

Another Princeton connection was made when my class enjoyed an All Saints Day feast at the home of the governor of Cochiti Pueblo, a former undergrad, who was serving as the first Native American on Princeton's Board of Trustees.

Not to be forgotten is that Princeton-based scientists developed the atomic bomb, and the resulting Los Alamos National Lab has provided careers for many Princeton geo-grads. Our graduates can also be found at other institutions in the Rio Grande valley, notably the New Mexico Institute of Mining and Technology, the University of New Mexico, Sandia Labs, and the United States Geologic Survey.

Thanks for coming; we are looking forward to a wonderful week!

Lincoln S. Hollister

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Geology of Northern New Mexico

Princeton Geosciences

GeoGrad2014

4 Welcome! Princeton and New Mexico Geology

6 Trip Personnel

6 Participant List

8 Overview road map

9 Overview satellite and geologic maps

11 Detailed itinerary and List of Stops

Day #1: Thursday, September 4 Santa Fe Arrival

14 Day #2 Stops: Friday September 5 The Chama River Valley: Ghost Ranch and Posh-ouinge

25 Day #3 Stops: Saturday, September 6 Tsankawi and Valles Caldera

44 Day #4 Stops: Sunday, September 7 Taos Plateau and Chimayo

Day #5: Monday September 8 A free day in Santa Fe.

54 Day #6 Stops: Tuesday, September 9 Harding Pegmatite, Picuris Pueblo, Las Trampas, Truchas

Day #7: Wednesday, September 10 Departure

60 “Arnold Guyot and the Pestalozzian approach to geology education”

61 Background References

62 Selected Papers

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Trip Personnel

Lincoln Hollister retired from Princeton after 43 years on the faculty. A metamorphic petrologist, he has published on metamorphic rocks from the Himalayas, British Columbia, Alaska, and New Mexico; and he was a principal investigator for study of the Apollo returned lunar samples. Several of his former students live and work in New Mexico. Currently, he is on a team involved in the quest for understanding the origin and meaning of the only known natural quasicrystal.

Laurel Goodell (B.S. Bucknell, M.A. Princeton) started out as a structural geologist; now as Instructional Laboratory Manager for the Department of Geosciences, she writes curricula, teaches labs, runs field trips, works with graduate student AI’s, runs PD workshops for schoolteachers, edits The Smilodon, helped compiled this guidebook and is a general resource for geo-education around the Department. She is also active in the national geo-education community, and is currently part of the NSF-funded InTeGrate project, which aims to improve earth-science literacy of undergraduate students, in part through development of peer-reviewed, flexible and field-tested classroom materials.

Blake Dyer began his geologic education close to home, at Rice University where he focused on high temperature geochemistry with Cin-ty Lee and worked on crustal xenoliths. He left the xenolith world to study Earth History and carbonate sedimentology with Adam Maloof at Princeton. Ten months of fieldwork in the western U.S. forms the basis of his Ph.D. dissertation, which combines physical and chemostratigraphic data to understand carbonate cycles during the Late Paleozoic Ice Age. He is particularly interested in early diagenesis in ancient and modern carbonates. Blake is also an avid bird watcher, fly fisherman and backpacker.

C. Brenhin Keller grew up in southern California and in Ithaca, NY. As an undergrad at Cornell, he split time between the Chemistry and Earth Sciences departments. He started his Ph.D. at Princeton with Blair Schoene in 2010. His research is centered in the fields of geochronology and high-temperature geochemistry, with particular emphasis on integrated accessory phase geochronology and trace element geochemistry. As part of the new U-Pb TIMS lab, he integrates with geochemical techniques to observe how geological processes unfold over time.

Alan Osborne is a native Oklahoman and descendent of pioneer Benjamin Franklin Clampitt, who settled Indian Territory in the legendary Cherokee Strip. A graduate of Oklahoma State University, he has studied the history of the American Indians, Spanish Colonial Borderlands, Mexican-American Territories and the American West at the University of New Mexico. He is a co-founder of New Mexico Elderhostel and Southwest Seminars, an award-winning cultural educational non-profit institution based in Santa Fe. He has lectured for and toured with numerous educational and museum groups.

Connie Eichstaedt, a native New Mexican, is the executive director of Southwest Seminars, a nonprofit institution that specializes in developing educational programs in Southwest Studies through seminars and tours. Southwest Seminars was a recipient of a 2008 City of Santa Fe Heritage Preservation Award.

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Participant List Allen*62, John (Jack) & Joan Lewisburg, PA Bamber*61, Wayne & Violet Calgary, Alberta Canada Chase*63, Richard Vancouver, BC Canada Cotter*63, Edward & Jacqueline Lewisburg, PA Dyer GS, Blake Princeton, NJ Evans*88, John Santa Cruz, CA Garrison*65, Robert & Jan Santa Cruz, CA Goodell*83, Laurel Lawrenceville, NJ Helsley*60, Charles (Chuck) & Barbara Honolulu, HI Hollister*66, Lincoln & Sarah Princeton, NJ Keller GS, Brenhin Princeton, NJ MacDonald*65, William (Bill) & Nuna Vestal, NY MacGregor*64, Ian, & Susan Garbini Napa, CA Macqueen*65, Roger & Marjorie Calgary, Alberta Canada Moberly*56, Ralph & Pat Honolulu, Hawaii Moore*71, J. Casey, & Hilde Schwartz Santa Cruz, CA Moores*63, Eldridge & Judy Davis, CA Morgan*64, W. Jason Wayland, MA Murray*64, James (Jim) & Evelyn Vancouver, BC Oxburgh*60, Ron & Ursula Cambridge, UK Palmer*63, H. Currie London, ON Phinney*61, Robert (Bob) Princeton, NJ Sigloch*08, Karin, & Patrick Regan Oxford, UK Simkin*66, Sharon Arlington, VA Smith *63, Alan Cambridge, UK Stott*57, Donald Sidney, BC Canada Sutherland-Brown*54, Atholl Victoria, BC Canada Temple*65, Peter & Carol Albuquerque, NM Travers*72, William & Joanne Ketchum, ID Vierbuchen*79, Rick, & Joanna Ajdukiewicz*77 Afton, VA Vine *65, Frederick & Sue Norwich, UK Wood*85, Scott & Dolores (Lori) Fargo, ND Yang*87, Mary & Bill Kuni Solana Beach, CA Zimmerman*68, Jay Jr., & Isabel Carbondale, IL

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Zimmerman*68, Jay Jr. & Isabel Carbondale, IL

Overview map of northern New Mexico. “Day Trips” are those suggested by http://santafe.org/Visiting_Santa_Fe/Things_to_Do/Day_Trips/ We’ll be following our own path…

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20 mi

20 mi

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Geology of Northern New Mexico – GeoGrad2014 Detailed Itinerary and List of Stops

Day #1: Thursday, September 4: Santa Fe Arrival

Arrival and check into Hotel Santa Fe on your own.

6:00pm Reception, cash bar

7:00pm Dinner - Amaya Restaurant, Hotel Santa Fe

Day #2: Friday September 5: The Chama River Valley: Ghost Ranch and Posh-ouinge

7-8:00am Continental breakfast - Amaya Restaurant, Hotel Santa Fe

8:30am Bus departs Hotel Santa Fe.

Drive by Pojoaque Pueblo, through Espanola through Hernandez, pause at "Moonrise over Hernandez” site. STOP 2.1 Abiquiu formation (page 15) behind Abiquiu elementary school NMGS #47, Stop 4, pp. 22-23. STOP 2.2 Cañones fault, angular unconformity (page 16) NMGS #46, Stop 2, pp. 24-25; NMGS#56, Optional Stop 2, p. 14

Noon-ish STOP 2.3 Ghost Ranch (page 18)

Picnic lunch. Ghost Ranch Paleontology museum and unique vertebrate fossils quarried from the area (Paleontologist, Alex Downs). NMGS #46, Stop 6, pp. 26-28. STOP 2.4 Cerro Pedernal (page 21, see also Stop 2.3 Fig 1.37) View Cerro Pedernal and Colorado Plateau from City Slicker Cabin.

Ref: Smith, Gary A.; Huckell, Bruce B., 2005, The geological and geoarchaeological significance of Cerro Pedernal, Rio Arriba County, New Mexico, in: NMGS #56, pp. 425-‐431. https://nmgs.nmt.edu/publications/guidebooks/56/home.cfm - p425 STOP 2.5 Chama River viewpoint (page 22) Discussion of the Colorado Plateau and Rio Grande Rift NMGS #58, pp. 17-19 and map p. 132.

Ref: Koning, Daniel J.; Kelley, Shari A.; Kempter, Kirt A., 2007, Geologic structures near the boundary of the Abiquiu embayment and Colorado Plateau-‐A long history of faulting, in: NMGS #58, pp. 43-‐46.

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STOP 2.6 Poshu-ouinge Pueblo (page 24) Hike to Poshu-ouinge Pueblo, Ancestral Tewa Pueblo site NMGS #46, Stop 3, pp. 21-22.

5:30pm Dinner at the Abiquiu Inn, Abiquiu on the Chama River.

7:30pm Depart

8:30pm Bus arrives Hotel Santa Fe.

Day #3: Saturday, September 6: Tsankawi and Valles Caldera


8:30 am Bus departs Hotel Santa Fe.

STOP 3.1 Tsankawi (page 25) Explore ruins and Bandalier tuffs.

11:30 Depart

STOP 3.2 White Rock Canyon overlook (page 30) Picnic lunch White Rock overlook, view of Rio Grande Gorge NMGS #47 Stop 4, pp. 66-69. Depart. Continue to Valles Caldera National Preserve. “STOP” 3.3 Ancho Canyon drive-by (page 32) NMGS #47 Stop 5, pp. 71-74. “STOP” 3.4 drive over Pajarito fault (page 35) NMGS #47 Stop 6, pp. 37-38.

STOP 3.5 Valles Grande Overview (page 37) NMGS #58, Stop 1, pp. 55-58, and map p. 134. Ref: Self, S., and Sykes, M.L., 1996, Field guide to the Bandelier Tuff and Valles caldera, in: New Mexico Bureau of Mines and Mineral Resources Bulletin 134, esp. pp. 7-17. Ref: Phillips, Benjamin R. (*05) et al., 2007, Duration of the Banco Bonito rhyolite eruption, Valles Caldera, New Mexico, based on magma transport modeling, in: NMGS #58, pp. 382-387. https://nmgs.nmt.edu/publications/guidebooks/58/home.cfm - p382

3:00pm Depart

4:00pm Return to Hotel Santa Fe.

6:00pm Dinner at La Choza Restaurant, Santa Fe.

8:30pm Bus returns to Hotel Santa Fe (or 0.5 mi walk).

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Day #4: Sunday, September 7: Taos Plateau and Chimayo


8:30am Bus departs Hotel Santa Fe.

STOP 4.1 Taos Overlook, Embudo fault (page 44) North of Pilar, east of gorge, 0.25mi from rest stop. NMGS #55 optional Stop 7, p. 64; NMGS #55 Stop 57-58.

STOP 4.2 Rio Grande Gorge Bridge (page 47) Overlook & walk, basalt stratigraphy. NMGS #55 Stop 8, pp. 30-33.

Noon-ish Picnic lunch at bridge. Depart

STOP 4.3 Staurolite/garnet locality (page 51) South of Pilar. Discuss Proterozoic geology of the Picaris, mineralogy of Pilar cliffs. NMGS #55, Stop 6, pp. 66-68. Ref: Bauer, P. W., 2004, Proterozoic rocks of the Pilar Cliffs, Picuris Mountains, New Mexico, in NMGS #55, pp. 193-205. https://nmgs.nmt.edu/publications/guidebooks/55/home.cfm#p193 Ref: Barnhart, K. B., Walsh, P. J., Hollister, L. S., Daniel, C.G., and Andronicos, C. L., 2012, Decompression during Late Proterozoic Al2SiO5 Triple-Point Metamorphism at Cerro Colorado, New Mexico, Journal of Geology, 120, 385-404.

STOP 4.4 Santuario de Chimayo

5:30pm Dinner (incl. Margarita!) at Rancho de Chimayo, Chimayo, NM

6:30pm Depart

7:30pm Bus arrives at Hotel Santa Fe.

Day #5: Monday September 8 A free day in Santa Fe.

7-9:00am Hot breakfast at Amaya Restaurant, Hotel Santa Fe (note longer time) Activities, lunch, and dinner on your own.

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Day #6: Tuesday, September 9 Harding Pegmatite and Picuris Pueblo


8:30am Bus departs Hotel Santa Fe

STOP 6.1 Harding Pegmatite (page 54) Ref: Jahns, Richard H.; Ewing, R. C., 1976, The Harding mine, Taos County, New Mexico, in: NMGS #27, pp. 263-‐276. https://nmgs.nmt.edu/publications/guidebooks/27/home.cfm - p263 Daniel, Christopher G. (former Princeton Hess Fellow) and Pyle, Joseph M., 2006, Monazite–Xenotime Thermochronometry and Al2SiO5 Reaction Textures in the Picuris Range, Northern New Mexico, USA: New Evidence for a 1450–1400  Ma Orogenic Event, J. Petrology, pp. 97-118.

Picnic lunch at Harding pegmatite.

1:00pm Depart

STOP 6.2 Picuris Pueblo (page 57) http://www.indianpueblo.org/19pueblos/picuris.html STOP 6.3 Church of San Jose de Gracia de Las Trampas

STOP 6.4 Truchas overlook (page 58) NMGS #55 Stop 1, p 101. Grambling, Jeffrey A., 1981, Kyanite, andalusite, sillimanite and related mineral assemblages in the Truchas Peaks Region, New Mexico, American Mineralogist, v. 66, pp. 702-722.

4:30pm Arrive Santa Fe

6:45pm Bus leaves Hotel Santa Fe for Farewell Dinner at La Casa Sena (including glass of wine.) Or ~1 mile walk from Hotel Santa Fe.

Day #7: Wednesday, September 10 Departure

7-9:00am Continental breakfast at Hotel Santa Fe (Note longer time) On your own departure

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STOP 2.1 Abiquiu formation

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STOP 2.2 Cañones fault, angular unconformity

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STOP 2.3 Ghost Ranch

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See also Stop 2.4.

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STOP 2.4 Cerro Pedernal

425GEOLOGICAL AND GEOARCHAEOLOGICAL SIGNIFICANCE OF CERRO PEDERNALNew Mexico Geological Society, 56th Field Conference Guidebook, Geology of the Chama Basin, 2005, p. 425-431.

INTRODUCTION

Rising to an elevation of 2986 m, the pinnacle of Cerro Peder-nal is a widely recognized and visible landmark in northern New Mexico (Fig. 1). Referred to in the accounts of Spanish explorers and American surveyors, and made famous as a common land-scape element in Georgia O’Keefe’s paintings, the narrow, flat-topped peak is also significant to diverse geological and archaeo-logical studies.

This paper summarizes current knowledge of two aspects of northern New Mexico geology that center on Cerro Pedernal and localities close to the peak. First, Cerro Pedernal preserves an erosional remnant of Rio Grande rift-basin stratigraphy that overlaps onto the Colorado Plateau. Stratigraphic correlation of the Cerro Pedernal strata to sections in the Cañones-Abiquiu area provides insights into the history of rift-basin subsidence and sed-iment accumulation. Second, the peak is the type locality of the Pedernal member of the Abiquiu Formation, an enigmatic succes-sion of siliceous layers that have served as a significant regional source for lithic tool manufacture since the appearance of the first humans in New Mexico. The Spanish name for the peak (“ped-ernal” translates as flint, in English) calls attention to this curious rock occurrence. The durability of the chert during weathering and transport causes it to be widespread as cobbles in alluvial deposits of northern New Mexico, which aids provenance study of the sediment and provides innumerable secondary contexts for human use.

GEOLOGIC SIGNIFICANCE OF CERRO PEDERNAL

Cerro Pedernal is located within a band of en-echelon normal faults that form the western margin of the Abiquiu embayment within the Española basin of the Rio Grande rift (Fig. 2). A Ter-tiary section that includes Eocene El Rito Formation, Oligocene-lower Miocene Abiquiu Formation, middle Miocene Tesuque Formation, and upper Miocene Lobato Basalt is flat lying and

rests disconformably on Mesozoic strata at the base of the butte. The lack of stratal tilting and the absence of large-displacement faults to the west of Cerro Pedernal support placement of the peak at the eastern margin of the Colorado Plateau. The capping 7.8 Ma Lobato Basalt lava flow (Manley and Mehnert, 1981), erupted nearby in the Jemez Mountains to the southeast (Fig. 2), preserves more than 400 m of Oligocene and Miocene rocks that are better known from thicker sections within the Rio Grande rift in the Abiquiu area.

Rift-Basin Subsidence History

Manley and Mehnert (1981) and Baldridge et al. (1994) called attention to the fault displacement of roughly 7.5-10 Ma Lobato

THE GEOLOGICAL AND GEOARCHAEOLOGICAL SIGNIFICANCE OF CERRO PEDERNAL, RIO ARRIBA COUNTY, NEW MEXICO

GARY A. SMITH1 AND BRUCE B. HUCKELL2 1Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131

2Maxwell Museum of Anthropology, University of New Mexico, Albuquerque, NM 87131

ABSTRACT.—Cerro Pedernal is an isolated basalt-capped peak of substantial geologic and geoarchaeological significance. The peak is located on the Colorado Plateau near the boundary of the Rio Grande rift. Oligocene-Miocene stratigraphic units on Cerro Pedernal correlate to thicker sections within the rift and document initiation of rift-basin subsidence before 25 Ma. Ces-sation or near cessation of sedimentation on the nascent rift margin led to hypothesized extensive weathering and formation of pedogenic calcrete horizons that were later buried by volcaniclastic deposits that overlapped the rift margin. Diagenesis of vitric volcaniclastic detritus likely led to silica replacement of the calcareous soils to form the Pedernal chert, which was commonly used for lithic-tool manufacture for more than 13 millennia of human occupation in northern New Mexico. Heav-ily utilized chert quarries in the Cerro Pedernal-San Pedro Parks region were important lithic-material sources, but so were redeposited cobbles of chert that are ubiquitous in alluvial deposits on the Colorado Plateau and in the Rio Grande rift. The combination of primary and secondary chert sources has confounded efforts to determine the exact source locations of artifact raw materials. Fire, along with simple prying tools and hammerstones were likely used to dislodge large chert pieces for tool manufacture. Preliminary working of cores and bifaces produced large volumes of irregular flakes and rejected pieces that were mistaken by some early workers as finished products of more ancient tool-making cultures.

FIGURE 1. View of Cerro Pedernal from the north. Miocene basalt caps a pinnacle of poorly exposed lower and middle Tertiary strata that rise above a base of Mesozoic rocks. Photo courtesy of Lisa W.Huckell.

See also Stop 2.3, Fig. 1.37.

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STOP 2.5 Chama River viewpoint

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Figure 1.32. Major structures in the northern Jemez Mountains and southern Chama Basin. White lines are Laramide structures. Black lines are younger normal faults. Red box outlines area of geologic map below. Red dot in both figures is Stop 2.5.

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STOP 2.6 Poshu-ouinge Pueblo

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STOP 3.1 Tsankawi

The Tsankawi ruins: a geologic and archeological treasure By Lincoln S. Hollister

Within the Tsankawi ruins area are displayed many features of the two Bandelier tuffs. The ancestral Pueblo people had two means of shelter. One was in caves; the other was in the Pueblo on top of the mesa. The caves are carved in un-welded ash flow tuff. This relatively soft material is under a lid of hard, jointed welded tuff. The ancestral Pueblo people carved petroglyphs into the vertical joints of this welded tuff. The floor of the unit (with the caves) is the welded tuff of the first Bandelier Tuff. This forms a prominent, jointed shelf below the ruins.

Our trail takes us up across the units of the upper Bandelier Tuff (Tshirege member). When we reach the plateau we will have a panoramic view of the Pajarito plateau, the rim of the Valles Caldera, the Sangre de Cristo Mts, and the Sandias. And we will have a clear view of the two Bandelier tuffs across the canyon.

The lower Bandelier Tuff, the Otowi Member, is 1.61 Ma. Looking at the cliffs across the canyon to the north, we can see the Guaje Plinian pumice deposits at the base, the un-welded ignimbrite flow units and the ledge forming, jointed welded ignimbrite. Erosion removed the un-welded units from above the welded tuff, prior to deposition of the upper Bandelier Tuff.

The surface of the Pajarito Plateau is the top of the welded tuff unit of the upper Bandelier Tuff (1.23 Ma). Erosion has striped the un-welded ash-flow material down to the welded portion.

After crossing through the ruins of the pueblo, we climb down a ladder across the welded tuff to a cluster of caves. The return trail takes us past many caves, past petroglyphs, and past a nicely preserved surge deposit.

1.61Ma

1.23Ma

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STOP 3.2 White Rock Canyon overlook

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“STOP” 3.3 Ancho Canyon

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“STOP” 3.4 drive over Pajarito fault

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STOP 3.5 Valles Grande Overview

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1.61Ma

1.23Ma

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STOP 4.1 Taos Overlook, Embudo fault

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STOP 4.2 Rio Grande Gorge Bridge

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STOP 4.3 Staurolite/garnet locality

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Petrogenetic grid for Fe-Mg units of Cerro Colorado based on a grid developed by Davidson*91 et al. (1997). The grid is calculated for a fixed garnet composition, Alm 74, and is for a pseudo three-component, five phase system, where Fe/Fe + Mg of one of the phases, garnet, is fixed, and quartz and water are in excess. Arrows show the PT paths taken by sample(s)…on the basis of observed reaction textures. A path for TCC-3 is not shown because the pressure of the invariant point is higher. All three reactions imply decompression at temperatures close to 600°C, with the staurolite bearing samples below 600°C and the staurolite absent rocks above 600°C. Figure 18. from Barnhart ’08 et al., 2012.

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STOP 6.1 Harding Pegmatite

Overview map – box outlines area of Figure 4 on next page.

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Lincoln Hollister, mine manager Gilbert Griego, and Jason Morgan at the Harding Pegmatite.

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STOP 6.2 Picuris Pueblo

From http://www.indianpueblo.org/19pueblos/picuris.html

Once one of the largest northern Pueblos early in the fifteenth century, today the Picuris population has shrunk to less than three hundred.

Largely responsible for this decline is the period of the revolt, from 1680 to 1696 when all the Pueblos fought the Spanish conquerors for their land and their autonomy.

Finding it impossible to continue to resist the invaders, the Picuris, dispersed by the wars, returned to their once-abandoned Pueblo in 1706 and joined with their former oppressors in campaigns against hostile Apaches and Comanches who were attacking both Spanish and Pueblo settlements.

After the cessation of these hostilities the Picuris settled down again. Peace brought many changes to the lifestyle of the Pueblo. The old ceremonies and rituals had been replaced by Christian religious practices and the tribal government had yielded to the Spanish authorities and later the Americans.

By the mid-nineteen-twenties, the Picuris began their traditional customs and again became self-governing.

The amenities of Anglo civilization which the Picuris had become accustomed to in the years of co-existence still found their way into the Pueblo: electricity, telephone, television and paved roads changed the aspect of the Pueblo.

Most of the adult population work off the reservation and the children go to school in a nearby town. Still Picuris life today is marked with many of the traditional ceremonies which have been revived and can be seen throughout the year.

The Feast of St. Lawrence brings Sunset Dances and races in which all ages participate and in June and August there are Corn Dances and Buffalo Dances.

The Picuris craftsmen produce an unusual pottery, different from most Pueblo art, in that it is strictly utilitarian and without ornament. It is made of micaceous clay and has an interesting texture with a subtle glitter caused by the small chips of mica in the mixture.

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STOP 6.4 Truchas overlook .

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720

Temperolure, oC

Fig. 15. P-? conditions of metamorphism deduced fromchloritoid quartzite (calculated equilibrium curve is plotted) andcordierite schist (heavy dot) in kyanite-andalusite-sillimanitezone. Uncertainty in P-Tconditions is indicated by stippled box.Shown for comparison are experimental kyanite-andalusite-sillimanite curves of Althaus (1967) labeled l; of Richardson et a/.(1969) labeled 2; and ofHoldaway (1971) labeled 3. Dashed linesgive experimentally determined positions of reaction 7-10 for X1a": I and x (H2O) : I from Seifert (1970), Seifert and Schreyer(1970) and Bird and Fawcett (1973).

sures between 3 and 5 kbar. Effects of reducedP(HrO) are not extreme: reduction of P(HrO) to 0.6P(total) shifts the equitbrium curve to lower temper-atures by only 25'C.

Error analysis indicates an uncertainty of +30oC(l esQ in calculated equilibrium temperatures, in-cluding uncertainty in the experimental data.

Geothermometry and geobarometry based oncordierite schist

Mineral assemblages in cordierite schist can beused to define pressure and temperature of crystalli-zutiot of the kyanite-andalusils-5illimanite rocks,since X(HrO) in cordierite schist has been establishedabove. Pertinent experimental data are shown in Fig-ure 15, based on results of Seifert (1970), Seifert andSchreyer (1970), and Bird and Fawcett (1973). Bal-anced for an assumed cordierite water content of 0.5moles, reactions are:2 M g C h l + 8 A 1 s i l + l l Q :

5 Mg Cord + 3.5 H,O (7)

I Mg Chl + I Musc + 2Q:

I Phlog + I MgCord + 3.5 H,O (8)

3 Mg Cord + 2 Musc:

GRAMBLING: KYANITE. ANDALUSITE, SILLIMANITE' NEW MEXICO

Y

I

3 M g C h l * 5 M u s c :5Ph log+ 8A ls i l+ I Q+ 12H,O (10)

Reactions 7-10 intersect in an invariant point which,for the pure Mg system, lies close to 640oC and 6.5kbar P(H,O). Variance of the assemblage increasesas Fe, Mn, Ti, and Na are added.

Cordierite schist contains all phases present at theMg invariant point (Table l0), if textural evidencefor prograde chlorite and biotite is accepted. The P-? conditions of the Mg invariant point can be cor-rected for solid solution effects and for reducedX(H"O) by calculating the offset of any two of reac-tions 7-10, using equation 6, and determining theirintersection graphically. Reactions 7 and 8 are bestconstrained by experimental results, so they wereused in calculations. Estimates of AS' and ASe, ob-tained from experimental data and the Clausius-Clapeyron equation, are 6300 and 2500 cm3-bars/Kmol respectively, based upon experimental results ofSeifert and Schreyer (1970) and Seifert (1970). Thesehave been assigned an uncertainty of +5Mo.

All minerpls are treated as ideal ionic solutions,with biotite mixing on 3 sites, chlorite on 5, cordieriteon 2 and muscovite on l. Resulting equilibrium con-stants are:

a' - (Xt".o.o,"o.o)to(&.o)t t^,:_____EJFI Y ,"oJ'(Xrr"r,".,)'(X".o)''tKr: \a!4eess1

(X,Jt(X*.-"*)

Because the cordierite schist has undergone minorretrogradation, it is necessary to determine prograde,equilibrium mineral compositions to calculate K'and Kr. For the calculation it was assumed that cor-dierite and muscovite have the correct compositions(Tables 3, 6) and that prograde chlorite and biotitehad compositions equal to those in specimen 76'566,the most Mg-rich chlorite-biotite pair analyzed. Re-sulting equilibrium constants are K7 : '77 (esd .46),K, : .19 (esd .09), for X(HrO) : 0.56 (esd.05).

Inserting these values for Kr, K8, AS, and AS. intoequation 6 and solving graphically yields a calculatedpressure and temperature of 4 kbar and 540oC. Un-certainty in the calculation is +600 bars, +25'C' Ad-ditional uncertainty arises because (1) equilibriumcompositions of chlorite and biotite are not wellknown; andQ) the value of X(H,O) : 0.56 is a maxi-mum, as discussed above. Uncertainty associatedwith the first possibility is +5oC and tl00 bars; thatassociated with the second would shift P and T to2 P h l o g + S A l s i l + 7 Q + 1 . 5 H , O ( 9 )

7M

that intersected the stability fields of kyanite and an-dalusite before peaking at a temperature slightlyabove the andalusite-sillimanite univariant bound-ary.

Andalusite clearly crystallized later than kyanite inthe southwestern corner of the triple-point zone, butelsewhere the aluminum silicates tend to show no ap-parent order of crystallization (Fig. 5). In most rockssome kyanite grains have been deformed but others,together with andalusite and sillimanite, are un-strained. Most of the kyanite-andalusite-sillimanitezone apparently was metamorphosed to P-T condi-tions very near the equilibrium value for the AlrSiO,triple point.

Numerous quafiz veins intrude quartzite andschist along the base of a 400 m deep cirque carvedinto the north face of Pecos Baldy, at the south-eastern corner of the triple-point zone. These veinsconsist predominantly of milky white quartz. Theyare 5 to 30 cm across, up to l0 m long, and typicallyare lenticular. Sillimanite occurs as matted fibroliticselvages, up to 5 cm thick, lining the quartz veins.Such sillimanite generally is associated with minoramounts of tourmaline and, in places, with kyaniteand andalusite. Rocks more than I m away fromsuch quartz veins contain kyanite and andalusitewith only traces of sillimanite, suggesting that sel-vages are places where reactions that formed silli-manite proceeded to a greater extent than elsewherein the rocks. Selvages may have formed from a typeof contact metamorphism, induced by hot fluids mi-grating along channels now represented by quartzveins (Ferry, 1980, p. 380-381). These fluids mayhave been of metamorphic origin, migrating upwardfrom deeper, hotter rocks. Alternatively, local con-

GRAMBLING: KYANITE, ANDALUSITE, SILLIMANITE, NEW MEXICO

Table l. Microprobe analyses of kyanite, andalusite, andsillimanite

47

|(y .48 .89Fe^o.* Anda'lz 5 s i l I .56 .88

Ky 53 .l '1 62 '09Al ro i Anda l

s i l l 62 .a6 62 .55

Ky 37 .10 37 .o9Si0^ Anda lt s i l t 36 .92 37 .36

Range Ky .43- .69-in .53 ' l .09

Fero, Andal

-oJ .+o1 . 2 8 1 . 1 6

. 5 9

b J . z c o J . f l62 .58 62 .65

6 2 . 5 I

36 .81 36 .9535.86 36 .79

37 .08

. 4 7 - . 4 1 -

. 7 9 . s l1 . 2 3 - L l 4 -I . 3 3 1 . 2 1

t o - t o - t 6 -472 529a 547

77- 77- 77-49 324 34la

s i l l . 53 - . 80 -. c d . v o

.90 .591 . 7 0

.80 .71

6 1 . 6 0 6 2 . 6 66 t . 3 26 1 . 7 9 5 2 . 1 1

36.59 37 . l 53 6 . 4 13 6 . 3 9 3 7 . l l

.83-

.94I . 4 1 -'I .96

. 7 1 -

.99

.56-

.63

.63-

. 79

K * *e0x ides

cations based on 5 oxygens

^ . Kv .01 .02Fefi e"naat

s i l l . 0 1 . 0 2

l (y 2 .00 I .98Al Andal

s i l l 2 . o 0 ' l . 9 8

l ( y 1 . 0 0 1 . 0 0si Andal

s i l l 1 . 0 0 ' l . 0 0

. 9 9 9 1 . 0 0 1

HM HM

*Al' l Fe as Fe3+(Atoms A l , s i l l ) /2 : a - x mode ls f rom Grew (1977)**K" ' 1Ator . A l , kv ) /2

' ind Ha len ius (1978)

H = h e m t r l = m a g I = i ' l m R = r u t i l e

centrations of fluids may have acted as a simple cata-lyst in the polymorphic reactions.

A luminum silic at e c hemi stryMost rocks that contain aluminum silicate miner-

als also contain primary hematite. The Fe'* contentof these aluminum silicates could be high (Strens,1968; Albee and Chodos,1969; Chinner et al.,1969)and variable partitioning of Fe3* might result inbivariant equilibrium between two polymorphs.Aluminum silicates were analyzed to test this pbssi-bility (Table l).

Andalusite consistently has more Fe than kyaniteand sillimanite which have similar FerO, contents.Single grains of all polymorphs show ranges in FerO.that are larger than would be expected from analyi-cal error. Variations may reflect slight compositionalinhomogeneities but probably result from varyingdegrees of contamination by microscopic hematiteinclusions. Variations are all less than 0.3 weight per-cent FerOr, generally less than 0.1 weight percent,and do not afect the following discussion.

.01 .01.03 .03

.012 .OO 2 .01

1 . 9 9 1 . 9 9t o o

.99 .99.99 .99

1 .00

I .001H R H I R

.02 .01

.04

.02 .021 . 9 9 1 . 9 91 . 9 8' t . 99 1 .98' | .00 1.001 . 0 0I . 00 1 .00

L002 .997

HM HR

Fig. 5. Photomicrograph of specimen with kyanite (K),

Ameican Mineralogist, Volume 66, pages 702-722, 1981

Kyanite, andalusite, sillimanite, and related mineral assemblagesin the Truchas Peaks region, New Mexico

Jnrrnnv A. GnennuNco"o*'*";i:if :,"]:::;o'"1';;:::!"1{i;wMexico

Abstract

The Truchas Peaks region of northern New Mexico includes an apparent equilibrium oc-currence of the AlrSiO, triple point. Andalusite occurs in rocks at the southern end of theTruchas Peaks uplift. Kyanite is present along the eastern edge and sillimanite in the north-ern part. Kyanite, andalusite, and sillimanite coexist in the center of the area. Near the triplepoint zone, isograds are controlled by topography: kyanite occurs along ridges, kyanite-an-dalusite on hillsides and kyanite-aadalu5ils-sillimanite in valleys. The distribution of miner-als fits a model of near-horizontal isotherms and isobars, with pressures and temperatures in-creasing with depth and geothermal gradients increasing from north to south.

Where three aluminum silicates coexist, quartzite contains the assemblage chloritoid-staurolite-kyanite-andalusite-sillimanite-magnetite-hematite-quartz. Experimental data onthe phase boundary Fe chloritoid + Al silicate : Fe staurotte + quartz at the hematite-mag-netite/(Or) buffer, corrected for minor elements, indicates temperature near 535oC. Garnet-biotite geothermometry gives a similar t€mperature. Pelitic schist contains cordierite-biotite-chlorite-kyanite-muscovite-quartz in the same area, and graphic and algebraic analysis sug-gests that this schist crystallized with X(H,O) less than l. Comparison with experimentaldata, taking into account mineral compositions and estimated X(H2O), yields Z : 540oC,P(total) : 4 kbar. Calculated P-T conditions are consistent with the position of the triplepoint according to Holdaway (1971).

IntroductionThe P-Tconditions of invariant equilibrium in the

AlrSiOs system are not well defined. Experimentaldeterminations of the invariant point range from 2 to8 kbar and 450 to 850'C (Zen, 1969; Richardson elal., 1969; Brown and Fyfe, l97l; Holdaway, l97l).Several factors may be responsible for this experi-mental scatter, but all relate to the small free-energydifferences among kyanite, andalusite and sillimaniteclose to equilibrium (Holdaway, l97l; Greenwood,1976, p.217-220).

Kyanite, andalusite and sillimanite coexist in theTruchas Peaks region of northern New Mexico. Geo-logic evidence indicates that they crystallized nearequilibrium. The first part of this study documentsthis conclusion and interprets AlrSiO, isograd geom-etry in tenns of regional variations in metamorphicpressures and temperatures.

The second part ofthis study addresses the P andZ of the aluminum silicate invariant point. Chlori-toid and staurolite coexist with kyanite, andalusitew3 -0/y.X / 8 | / 070E-0702$02.00

and sillimanite in several rocks from the TruchasRange. Other rocks contain cordierite with chlorite,biotite, muscovite and Al-silicates. Because condi-tions for equilibrium among these minerals areknown, they can be used to define the physical condi-tions at which the kvanite-andalusite-sillimanite as-semblages formed.

Geologic settingThe Truchas Peaks are located in the southern

Sangre de Cristo Mountains, 35 km northeast ofSanta Fe, New Mexico (see inset, Fig. l). Metamor-phic rocks are exposed in a 5 x l0 km block-faulteduplift. Exposures are excellent, with topographic re-lief exceeding 1000 m and post-metamorphic faultsproviding structural relief in excess of several kilo-meters. Local relief is sufficient to allow three-dimen-sional mapping of isograds.

The Precambrian geology of the Truchas Peaksuplift is described by Grambling (1979b). Metamor-phic rocks include massive crossbedded quartzite, pe-

702




Abstract











702




Abstract











702

60

Excerpts from: Arnold Guyot (1807-1884)

and the Pestalozzian approach to geology education Philip K. Wilson, 1999, Eclogae Geologicae Helvetiae, pp. 321-325.

…When the 1848 Swiss revolution against Prussian rule closed the Academy. Guyot, following his colleague and sometimes roommate, Louis Agassiz, fled to the United States. Guyot was initially employed by the Massachusetts State Board of Education to conduct teacher's institutes" (i.e., workshops) devoted to improving the methods of geography teaching. His local and national popularity in the states escalated as he spoke to over 1500 teachers a year between 1849 and 1855 at various normal schools and at teacher's institutes held at the Anderson School of Natural History on Penikese Island., Nantucket. Massachusetts (Libbey 1884:25). In 1855, he began what resulted in a thirty-year professorship in Physical Geography and Geology at the College of New Jersey (now Princeton University)…

…According to Guyot's student. T. Pickney Huger's 1859 geology class notes, his instructor defined geology as "the preface of the first part of the history of the world…”

…For Guyot. "three great facts" existed: 1) The stratification of the Earth: 2) The dynamic forces which gave the globe its shape: and 3) The fossil evidence of a history of life forms (Huger 1859:20). As a history student of Jules Michelet, and a former professor of Universal History and Geography himself, Guyot envisioned that history implied succession and processes which naturally take time. The historical changes of our globe, for example, had he argued, occurred over millennia…

…Guyot in his lectures, argued that it was only through direct observation of the solid earth, the water surrounding it. and the plants and animals in and on the earth that they would learn the facts of geology. From these facts, he argued, you can then inductively determine truths - truths such as the answer to whether the earth was "always as it now is.” To begin answering such critical questions. Guyot first turned students' attention to their own Princeton campus and then to the Allegheny Mountains in nearby Pennsylvania…Only after understanding the solid granite composition of the local Pennsylvania mountains should students compare and contrast it with that found further from home, such as in the Swiss Alps…

Like Pestalozzi, Guyot began his course with a direct study of nature - not books. According to his student William B. Scott, the professor "threw aside the old routine methods and brought the student face to face with nature, showing the bearing of the earth's physical features upon every department of human interest.” …Like Pestalozzi, Guyot adopted the medium of multi-colored pictorial maps as part of his pedagogy. With the assistance of his nephew, Ernest Sandoz, Guyot designed at least 46 large wall hangings to illustrate central points of his lectures…

…Moving from the simple to the complex, from gathering facts to formulating conclusions, from observing the particular towards building the view of a harmonious, complete, interconnected universe – these Pestalozzian principles represent Guyot’s new epistemology of geological pedagogy…Not only would these processes build a complete intellectual foundation, Guyot argued that a student’s thorough understanding of his direct connectedness with the cosmos would help shape his moral values as well…

61

Background References Highly recommended: a superb geology road map, New Mexico Geologic Highway Map, is published by NM Bureau of Geology and Mineral Resources.

Roadside Geology of New Mexico by Halka Chronic lays out basic background for beginners.

Basin and Range by John McPhee gives a great overview on the geology of the west; it is written for non-professionals.

An excellent book for beginners is Valles Caldera, a Geologic History by Fraser Goff. Published by University of New Mexico Press. (2009)

The Rio Grande by Paul Bauer contains geology background mainly for river rafters on the Rio Grande. There are excellent graphics and photos, and a summary of the origin of the Rio Grande gorge. Published by New Mexico Bureau of Geology and Mineral Resources. (2011).

Geologic Map of the Jemez Mountains, New Mexico, by R.L. Smith, R.A. Bailey, and C.S. Ross, US Geological Survey Map I-571.

IPhone application called Geology New Mexico with many useful geology and geography layers.

The Milagro Beanfield War, a 1974 novel by John Nichols, set in fictitious Chamisaville County, NM. It is also the title of a 1988 film adaptation directed by Robert Redford and filmed mostly in Truchas (our Stop 6.4).

Most of our stops are described in the road logs of these publications (specific pages given in the detailed itinerary):

NM Geological Society Guidebook, 46th Field Conference, 1995, Geology of the Santa Fe Region, Bauer, P. W.; Kues, B. S.; Dunbar, N. W.; Karlstrom, K. E.; Harrison, B.; [eds.], 338p.

NM Geological Society Guidebook, 47th Field Conference, Jemez Mountains Region, 1996,Goff, F.; Kues, B. S.; Rogers, M. A.; McFadden, L. S.; Gardner, J. N.; [eds.], 484p.

NM Geological Society Guidebook, 55th Field Conference, Geology of the Taos Region, 2004, Brister, Brian; Bauer, Paul W.; Read, Adam S.; Lueth, Virgil W.; [eds.], 440.

NM Geological Society Guidebook, 56th Field Conference, Geology of the Chama Basin, 2005, Lucas, Spencer G.; Zeigler, Kate E.; Lueth, Virgil W.; Owen, Donald E.; [eds.], 456p.

NM Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Region II, 2007, Kues, Barry S., Kelley, Shari A., Lueth, Virgil W.; [eds.], 499p.

NM Geological Society Guidebook, 62nd Field Conference, Geology of the Tusas Mountains and Ojo Caliente, 2011, Koning, Daniel J.; Karlstrom, Karl E.; Kelley, Shari A.; Lueth, Virgil W.; Aby, Scott B., 2011, 418p.

S. Self, G. Heiken, M. L. Sykes, K. Wohletz, R. V. Fisher, and D. P. Dethier, 1996, Field excursions to the Jemez Mountains, New Mexico, New Mexico Bureau of Geology and Mineral Resources, Bulletin #134, 72 pp.

62

Selected papers Bauer. P. W., 2004, Proterozoic rocks of the Pilar Cliffs, Picuris Mountains, New Mexico, in: Geology of the Taos Region, Brister, Brian S.; Bauer, Paul W.; Read, Adam S.; Lueth, Virgil W., ed(s), New Mexico Geological Society, Guidebook, 55th Field Conference, pp. 193-205. https://nmgs.nmt.edu/publications/guidebooks/55/home.cfm#p193

Barnhart, K. B., Walsh, P. J., Hollister, L. S., Daniel, C.G., and Andronicos, C. L., 2012, Decompression during Late Proterozoic Al2SiO5 Triple-Point Metamorphism at Cerro Colorado, New Mexico, Journal of Geology, 120, 385-404.

Daniel, Christopher G. and Pyle, Joseph M., 2006, Monazite–Xenotime Thermochronometry and Al2SiO5 Reaction Textures in the Picuris Range, Northern New Mexico, USA: New Evidence for a 1450–1400  Ma Orogenic Event, J. Petrology, pp. 97-118.

Grambling, Jeffrey A., 1981, Kyanite Andalusite, Sillimanite and Related mineral assemblages in the Truchas Peaks Region, New Mexico, American Mineralogist, v. 66, pp. 702-722.

Jahns, Richard H.; Ewing, R. C., 1976, The Harding mine, Taos County, New Mexico, in: Vermejo Park, Ewing, Rodney C.; Kues, Barry S., New Mexico Geological Society, Guidebook, 27th Field Conference, pp. 263-276. https://nmgs.nmt.edu/publications/guidebooks/27/home.cfm - p263

Koning, Daniel J.; Kelley, Shari A.; Kempter, Kirt A., 2007, Geologic structures near the boundary of the Abiquiu embayment and Colorado Plateau-A long history of faulting, in: Geology of the Jemez Region II, Kues, Barry S.; Kelley, Shari A.; Lueth, Virgil W., ed(s), New Mexico Geological Society, Guidebook, 58th Field Conference, pp. 43-46.

Phillips, Benjamin R.; Baldridge, W. Scott; Gable, Carl W.; Sicilian, James M., 2007, Duration of the Banco Bonito rhyolite eruption, Valles Caldera, New Mexico, based on magma transport modeling, in: Geology of the Jemez Region II, Kues, Barry S.; Kelley, Shari A.; Lueth, Virgil W., ed(s), New Mexico Geological Society, Guidebook, 58th Field Conference, pp. 382-387. https://nmgs.nmt.edu/publications/guidebooks/58/home.cfm - p382

Smith, Gary A.; Huckell, Bruce B., 2005, The geological and geoarchaeological significance of Cerro Pedernal, Rio Arriba County, New Mexico, in: Geology of the Chama Basin, Lucas, Spencer G.; Zeigler, Kate E.; Lueth, Virgil W.; Owen, Donald E., ed(s), New Mexico Geological Society, Guidebook, 56th Field Conference, pp. 425-431. https://nmgs.nmt.edu/publications/guidebooks/56/home.cfm - p425

Wilson, Philip K., 1999, Arnold Guyot (1807-1884) and the Pestalozzian approach to geology education, Eclogae Geologicae Helvetiae, pp. 321-325.

geology of northern new mexico - princeton · pdf file! 4 princeton and new mexico geology...

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