THE JEMEZ MOUNTAINS OBSIDIAN SOURCES

Distributed in archaeological contexts over as great a distance as Government Mountain in the San Francisco Volcanic Field in northern Arizona, the Neogene and Quaternary sources in the Jemez Mountains, most associated with the collapse of the Valles Caldera, are distributed at least as far south as Chihuahua through secondary deposition in the Rio Grande, and east to the Oklahoma and Texas Panhandles through exchange. And like the sources in northern Arizona, the nodule sizes are up to 10-20 cm in diameter; El Rechuelos, Cerro Toledo Rhyolite, and Valles Rhyolite (Cerro del Medio) glass sources are as good a media for tool production as anywhere. While there has been an effort to collect and record primary source obsidian, most effort has been expended to understand the secondary distribution of the Jemez Mountains sources. Until the recent land exchange of the Baca Ranch properties, the Valles Rhyolite primary dome (Cerro del Medio) was off-limits to most research. The discussion of this source group here is based on collections by Dan Wolfman and others, facilitated by Los Alamos National Laboratory, and the Museum of New Mexico, and collections courtesy of the Valles Caldera National Preserve and Anna Steffen (see Broxton et al. 1995; Shackley 2005; Wolfman 1994).

Due to its proximity and relationship to the Rio Grande Rift System, potential uranium ore, geothermal possibilities, an active magma chamber, and a number of other geological issues, the Jemez Mountains and the Toledo and Valles Calderas particularly have been the subject of intensive structural and petrological study particularly since the 1970s (Bailey et al. 1969; Gardner et al. 1986, 2007; Heiken et al. 1986; Self et al. 1986; Shackley et al. 2016; Smith et al. 1970; Figure below). Half of the 1986 Journal of Geophysical Research, volume 91, was devoted to the then current research on the Jemez Mountains. More accessible for archaeologists, the geology of which is mainly derived from the above, is Baugh and Nelson’s (1987) article on the relationship between northern New Mexico archaeological obsidian sources and procurement on the southern Plains, and Glascock et al’s (1999) more intensive analysis of these sources including the No Agua Peak source in the Mount San Antonio field on the Taos Plateau at the Colorado/New Mexico border (see also Shackley 2005).

Topographical rendering of a portion of the Jemez Mountains, Valles Caldera, and relevant features (from Smith et al. 1970; formation explanations in Smith et al. 1970).

Analysis of major and minor compounds for Jemez Mountains and Taos Plateau obsidian sources1

Sample

SiO2

Al2O3

CaO

Fe2O3

K2O

MgO

MnO

Na2O

TiO2

Cerro Toledo Rhy.

081199-1-7

78.31

11.3

0.19

1.13

4.13

0

0.06

4.27

0.09

Valles Rhyolite

CDM3-B

77.39

11.58

0.43

1.21

4.63

0.2

0.05

4.1

0.12

El Rechuelos

080999-2-1

78.43

11.77

0.36

0.57

4.28

0

0.06

3.98

0.1

No Agua West

081000-1-3

77.8

12.33

0.4

0.57

4.24

0

0.15

4.37

0.07

1 Samples analyzed by WXRF as polished nodules. All measurements in weight percent. 

Collection Localities

The collection localities discussed here are the result of a systematic survey to collect and record all the potential sources in the Jemez Mountains, as well as an attempt to understand the secondary depositional regime of the sources flowing out from the Jemez Mountains into the surrounding stream systems, as noted above.

El Rechuelos

El Rechuelos is mistakenly called "Polvadera Peak" obsidian in the archaeological vernacular (see also Glascock et al. 1999). Polvadera Peak, a dacite dome, did not produce artifact quality obsidian. The obsidian artifacts that appear in the regional archaeological record are from El Rechuelos Rhyolite as properly noted by Baugh and Nelson (1987). Indeed, El Rechuelos obsidian is derived from a number of small domes north of Polvadera Peak as noted by Baugh and Nelson (1987) and Wolfman (1994; see image here). Collections here were made at two to three small coalesced domes near the head of Cañada de los Ojitos and as secondary deposits in Cañada de los Ojitos (collection locality 080999-1&2). The center of the domes is located at UTM 13S 0371131/3993999 north of Polavadera Peak on the Polvadera Peak quadrangle. The three domes are approximately 50 meters in diameter each and exhibit an ashy lava with rhyolite and aphyric obsidian nodules up to 15 cm in diameter, but dominated by nodules between 1 cm and 5 cm. Core fragments and primary and secondary flakes are common in the area.

Polvadera Peak in background with glass producing rhyolite domes on the left and small domes in foreground.

Small nodules under 10-15 mm are common in the alluvium throughout the area near Polvadera Peak. It is impossible to determine the precise origin of these nodules. Presumably they are remnants of various eruptive events associated with El Rechuelos Rhyolite. The samples analyzed, the results of which are presented in the table below are compositionally similar to the data presented in Baugh and Nelson (1987) and Glascock et al. (1999).

El Rechuelos obsidian is generally very prominent in northern New Mexico archaeological collections. Although it is not distributed geologically over a large area, it is one of the finest raw materials for tool production in the Jemez Mountains. Its high quality as a toolstone probably explains its desirability in prehistory. Cerro Toledo Rhyolite and Valles Rhyolite (Cerro del Medio), while present in large nodule sizes, often have devitrified spherulites in the glass, so more careful selection had to be made in prehistory. In nearly 500 nodules collected from the El Rechuelos area, few of the nodules exhibited spherulites or phenocrysts in the fabric. Additionally, El Rechuelos glass is megascopically distinctive from the other two major sources in the Jemez Mountains. It is uniformly granular in character, apparently from ash in the matrix. Cerro Toledo and Valles Rhyolite glass is generally not granular and more vitreous.

POLVADERA GROUP

El Rechuelos Rhyolite

Elemental concentrations for El Rechuelos Rhyolite obsidian source samples (all measurements in parts per million.  Those samples with a "PP" prefix are from the Wolfman collection, those with the "08099" prefix are Shackley collection.

SAMPLE Ti Mn Fe Zn Rb Sr Y Zr Nb Ba Pb Th
PP-1           451 6538   160 9 21 76 48 51    
PP-2           434 7055   165 10 22 79 52 51    
PP-3           430 6362   157 9 23 76 48 50    
PP-1B             436 6504   149 4 25 68 49      
PP-2B             420 6922   156 2 23 75 45      
080999-1-1         147 10 23 78 45 16    
080999-1-2         150 10 23 79 46 20    
080999-1-3         146 10 23 77 45 15    
080999-1-4         147 10 23 78 45 11    
080999-1-5         146 10 22 77 45 17    
080999-1-6         148 10 23 78 46 10    
080999-2-1         151 11 23 79 46 16    
080999-2-2         157 11 24 80 48 20    
080999-2-3         154 11 24 81 47 21    
080999-2-4         148 11 24 78 46 17    
080999-2-5 890 419 7658 36 155 10 21 76 48 0 22 35
-6 851 452 7943 41 157 13 26 80 43 0 25 23
-7 870 412 7624 40 149 16 25 78 53 0 20 19
-8 848 412 7646 45 153 11 24 74 49 0 31 30
-9 831 402 7672 37 151 16 22 77 42 1 29 27
-10 876 416 7744 36 152 13 25 79 44 0 23 24
-11 849 370 7456 43 144 13 20 69 48 0 23 28
-12 903 427 7798 43 153 14 25 72 48 0 22 14
-13 885 376 7607 41 147 12 21 72 45 0 26 21
-14 1102 421 8445 37 149 12 27 72 49 0 26 15
-15 829 409 7880 42 163 14 25 77 48 0 27 21
-17 1057 396 8525 42 157 14 25 78 50 0 33 28
-18 900 397 7841 43 152 12 28 76 47 0 26 26
-19 1040 349 8094 38 137 9 24 74 49 0 21 19
-21 988 412 8530 47 152 13 25 73 47 0 23 21
-22 891 413 7969 40 157 13 20 77 46 0 25 22
-23 871 381 7621 49 182 13 22 70 37 3 23 12
-24 896 404 7680 42 153 14 21 74 47 0 23 20

 

Mean and central tendency for El Rechuelos Rhyolite obsidian from data in table above

 

 

Rabbit Mountain Ash Flow Tuffs and Cerro Toledo Rhyolite

Known in the archaeological vernacular as "Obsidian Ridge" obsidian, is derived from the Cerro Toledo Rhyolite eruptions, and following Baugh and Nelson (1987) and the geological literature are all classified as Cerro Toledo Rhyolite (Bailey et al. 1969; Gardner et al. 1986; Heiken et al. 1986; Self et al. 1986; Smith et al. 1970).

There were six pyroclastic eruptive events associated with the Cerro Toledo Rhyolite:

All tuff sequences from Toledo intracaldera activity are separated by epiclastic sedimentary rocks that represent periods of erosion and deposition in channels. All consist of rhyolitic tephra and most contain Plinian pumice falls and thin beds of very fine grained ash of phreatomagmatic origin. Most Toledo deposits are thickest in paleocanyons cut into lower Bandelier Tuff and older rocks [as with the Rabbit Mountain ash flow]. Some of the phreatomagmatic tephra flowed down canyons from the caldera as base surges (Heiken et al. 1986:1802).

Two major ash flows are relevant here. One derived from the Toledo embayment on the northeast side of the caldera is a 20 km wide band that trends to the northeast and is now highly eroded and interbedded in places with the earlier Puye Formation from around Guaje Mountain north to Santa Fe Forest Road 144. This area has eroded rapidly and obsidian from this tuff is now an integral part of the Rio Grande alluvium north of Santa Fe. The other major ash flow is derived from the Rabbit Mountain eruption and is comprised of a southeast trending 4 km wide and 7 km long "tuff blanket" interbedded with a rhyolite breccia three to six meters thick that contains abundant obsidian erupted as lapilli during the Rabbit Mountain ash flow (Heiken et al. 1986). All of this is still eroding into the southeast trending canyons toward the Rio Grande. The surge deposits immediately south of Rabbit Mountain contain abundant obsidian chemically identical to the samples from the ridges farther south and in the Rio Grande alluvium, as well as in sediments above the Puye Formation between Española and the Toledo Embayment (Shackley 2005, 2012). Heiken et al. NAA analysis of Rabbit Mountain lavas is very similar to those from this study (1986:1810; see data here).

Lower Cochiti Canyon from Forest Road 289 looking south.  Bandelier Tuff exposed on east canyon walls with Rabbit Mountain tuffs above eroding into Rio Grande.  Sandia Mountains in background.

While Obsidian Ridge has received all the "press" as the source of obsidian from Cerro Toledo Rhyolite on the southern edge of the caldera, the density of nodules and nodule sizes on ridges to the west is greater by a factor of two or more. All these ridges, of course, are remnants of the Rabbit Mountain ash flow and base surge, and the depth of canyons like Cochiti Canyon is a result of the loosely compacted tephra that comprises this plateau. At Locality 081199-1 (UTM 13S 0371337/3962354), nodules on the ridge top are up to 200 per m2 with over half that number of cores and flakes. This density of nodules and artifacts forms a discontinuous distribution all the way to Rabbit Mountain. The discontinuity is probably due to cooling dynamics and/or subsequent colluviation. Where high density obsidian is exposed, prehistoric production and procurement is evident. At the base of Rabbit Mountain the density is about 1/8 that of Locality 081199-1, and south of this locality the density falls off rapidly. At Locality 081199-1 nodules range from pea gravel to 16 cm in diameter (Figures 3.14 and 3.15). Flake sizes suggest that 10 cm size nodules were typical in prehistory.  Nodule sizes at Rabbit Mountain are up to 30 cm or more (Gauthier, personal communication, 2006).

Locality 081199-1 south of Rabbit Mountain in the ash flow tuff. This locality has the highest density of artifact quality glass of the Rabbit Mountain ash flow area. The apparent black soil is actually all geological and archaeological glass; one of the highest densities of geological and archaeological obsidian in the Southwest.

Mix of high density geological obsidian and artifact cores and debitage (test knapping) at Locality 081199-1 south of Rabbit Mountain. Nodules » 200/m2, cores and debitage » 100/m2, some of the latter could be modern. 

Cerro Toledo Rhyolite obsidian both from the northern domes and Rabbit Mountain varies from an excellent aphyric translucent brown glass to glass with large devitrified spherulites that make knapping impossible. This character of the fabric is probably why there is so much test knapping at the sources – a need to determine the quality of the nodules before transport. While spherulitic fabric occurs in all the Jemez Mountain obsidian, it seems to be most common in the Cerro Toledo glass and may explain why Valle Grande obsidian occurs in sites a considerable distance from the caldera even though it is not secondarily distributed outside the caldera while Cerro Toledo obsidian is common throughout the Rio Grande alluvium. Indeed, in Folsom period contexts in the Albuquerque basin, only Valle Grande obsidian was selected for tool production even though Cerro Toledo obsidian is available almost on-site in areas such as West Mesa (LeTourneau et al. 1996). So, while Cerro Toledo Rhyolite obsidian is and was numerically superior in the Rio Grande Basin, it wasn’t necessarily the preferred raw material.

Cerro Toledo Rhyolite (Cerro Toledo and Rabbit Mountain combined)

Elemental concentrations for Cerro Toledo Rhyolite obsidian source samples (all measurements in parts per million)

SAMPLE Ti Mn Fe Zn Rb Sr Y Zr Nb Ba Pb Th
BCC-1          600 10616   217 5 66 192 97 44    
BCC-3          552 9986   215 5 66 187 97 49    
BCC-4          547 10102   214 5 62 183 99 42    
OR-1           550 10278   222 0 66 192 103 43    
OR-2           425 8727   190 4 59 175 94 42    
OR-3           534 9921   216 6 65 188 97 42    
OR-4           577 10218   218 5 69 188 99 42    
OR1B             536 9810   214 0 63 182 103      
OR2B             408 8242   179 1 58 162 92      
CCA-1          499 9446   197 4 60 174 90 39    
CCA-2          516 9714   211 6 66 189 98 0    
CCA-3          529 9759   208 0 60 184 97 41    
081199-1-1         199 7 62 178 96 0    
081199-1-2         198 7 61 177 94 1    
081199-1-3         200 7 62 179 96 1    
081199-1-4         207 6 63 187 99 1    
081199-1-5         204 6 63 181 98 4    
081199-1-6         204 7 63 184 99 9    
081199-1-7         205 6 63 182 99 0    
081199-1-8         217 7 67 193 105 15    
080900-1         205 8 63 177 100 19    
080900-2         204 7 62 175 99 3    
080900-3         201 7 62 172 97 3    
080900-A1         203 8 62 177 99 73    
080900-A2         204 7 63 175 99 14    
080900-A4         203 6 63 176 98 0    
080900-A5         209 6 65 184 103 5    
080900-A6         210 7 62 171 97 1    
080899-3-1 897 584 11589 112 222 9 65 179 100 0 41 21
-2 1138 545 12001 119 285 9 64 196 105 4 43 30
-3 862 441 9859 84 187 9 60 167 100 0 28 23
-4 932 553 11002 104 215 14 68 186 102 0 40 35
-5 819 452 9918 95 194 11 59 171 98 0 35 31
-6 980 527 11250 103 215 9 65 184 101 0 38 29
-7 867 510 10595 97 210 10 66 175 97 0 36 25
-8 881 463 10365 100 204 9 63 178 100 0 37 21
-9 1094 504 10959 96 204 11 59 185 94 0 33 27
-10 864 425 9686 82 187 9 62 167 100 0 31 29
-11 837 460 9683 83 193 9 57 169 91 0 32 30
-12 1011 427 10079 87 194 12 57 174 89 0 28 21
-13 785 440 9849 96 195 11 60 181 94 0 27 19
-14 1094 505 11851 103 221 11 65 183 105 0 43 27
-15 887 419 9789 78 178 10 56 169 89 1 29 16
-16 971 471 10634 99 205 9 62 172 96 0 31 22
-17 1007 418 10058 88 183 9 63 170 93 0 32 26
-18 913 448 10221 97 199 10 63 171 94 0 32 19

 

Mean and central tendency for data in table above

 

Valles Rhyolite (Cerro del Medio)

Originally the primary domes like Cerro del Medio of Valles Rhyolite were not visited due to restrictions on entry to the caldera floor, surveys of the major stream systems radiating out from the caldera were examined for secondary deposits; San Antonio Creek and the East Jemez River, as well as the canyons eroding the outer edge of the caldera rim.  After the land transfer to the Department of Agriculture and then Department of the Interior, samples were collected directly from Cerro del Medio proper.

In 1956 two geology graduate students from the University of New Mexico published the first paper on archaeological obsidian in the American Southwest, a refractive index analysis (Boyer and Robinson 1956). In this examination of the Jemez Mountain sources, they noted that obsidian did not occur in the alluvium of San Antonio Creek where it crosses New Mexico State Highway 126, but did occur "in pieces as large as hen’s eggs, but the material is not plentiful and must be searched for with care" in the East Jemez River alluvium where it crosses State Highway 4 (Boyer and Robinson 1956:336). A return to the latter locality (Locality 102799-2) exhibited about the same scenario as that recorded 43 years earlier. The alluvium exhibits nodules up to 40 mm in diameter at a density up to 5/m2, but generally much lower. Boyer and Robinson did find nodules up to 15.5 cm in diameter along the upper reaches of San Antonio Creek as shown in their plate reproduced here (Boyer and Robinson 1956:337; Figure below).

Valles Rhyolite obsidian nodules photographed by Boyer and Robinson collected along San Antonio Creek in the caldera (1956:337).

My survey along San Antonio Creek from its junction with State Highway 126 for two miles upstream did not reveal any obsidian, as in the Boyer and Robinson study. It appears then that Valles Rhyolite obsidian does not enter secondary contexts outside the caldera, at least in nodules of any size compared to Cerro Toledo Rhyolite (see Church 2000; Shackley 2012).

Valles Rhyolite obsidian exhibits a fabric that seems to be a combination of El Rechuelos and Cerro Toledo. Some of the glass has that granular texture of El Rechuelos and some has devitrified spherulites similar to Cerro Toledo, and much of it is aphric black glass. Flakes of Valle Grande obsidian can be indistinguishable from El Rechuelos or Cerro Toledo in hand sample. An elemental analysis of samples collected by Dan Wolfman from Cerro del Medio and the nodules in San Antonio Creek in this study are identical indicating that Cerro Toledo glass does not enter the East Jemez River system (see Appendix).

Elemental concentrations for Valles Rhyolite (Cerro del Medio) obsidian source samples (all measurements in parts per million).

Sample Source Name Location Zone Easting Northing Ti Mn Fe Rb Sr Y Zr Nb Ba
102799-2-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       155 10 43 168 54 30
102799-2-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       157 10 44 172 55 25
102799-2-3 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       159 10 44 169 55 35
102799-2-4 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       158 10 43 171 55 27
102799-2-5 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       160 9 43 170 54 41
102799-2-6 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       154 10 42 167 54 39
102799-2-7 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       159 9 43 174 54 47
102799-2-8 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       162 10 44 168 55 41
102799-2-9 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       158 10 43 170 55 45
102799-2-10 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       166 10 43 168 54 23
102799-2-11 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       176 10 43 168 55 29
102799-2-12 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       140 11 40 178 53 26
102799-2-13 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       154 11 42 164 54 42
102799-2-14 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       144 10 41 179 55 25
102799-2-15 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314       172 10 44 177 55 23
060304-1-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 884 430 8374 153 9 46 164 58  
060304-2-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 907 410 8449 150 12 32 162 49  
0304-2-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 979 444 9165 159 7 41 164 64 16
0304-2-3 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 934 406 8438 154 13 39 170 51 20
060304-2-4 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 961 456 9494 164 10 47 172 50 21
060304-3-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 1040 503 10031 171 10 46 177 57 17
060404-2-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 913 445 8551 147 5 37 177 53 16
-2-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 954 462 8690 155 6 45 167 55 20
-2-3 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 884 472 9096 163 8 40 170 48 15
-2-4 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 1066 439 8604 151 13 49 171 63 11
-2-5 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 892 403 8424 143 6 37 159 54 17
060404-4-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 838 447 8638 156 10 39 168 44 10
-4-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 883 447 8575 150 13 43 168 56 44
-4-3 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 938 439 8522 164 15 43 166 56 49
-4-4 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 942 398 8505 148 8 43 153 48 42
-4-5 Valles Rhy-Cerro del Medio Jemez Mtns, N NM 13 369144 3975314 916 393 8358 143 14 37 151 54 43
CDMA-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         593 13500 160 10 44 173 56 31
CDM3B Valles Rhy-Cerro del Medio Jemez Mtns, N NM         595 13549 159 10 44 174 56 39
CDMV-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         580 13319 158 10 44 173 55 32
CDMA-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         596 13536 158 10 43 174 55 34
CDMA-3-B Valles Rhy-Cerro del Medio Jemez Mtns, N NM         576 13220 156 10 43 172 54 35
CDM 3-1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         561 13465 178 10 42 170 54 62
CDM 3-2 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         579 13443 158 10 44 174 55 38
CDM 3-3 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         575 13243 156 10 43 171 54 27
CDM 1A Valles Rhy-Cerro del Medio Jemez Mtns, N NM         581 13325 156 10 43 172 54 31
CDM CM1 Valles Rhy-Cerro del Medio Jemez Mtns, N NM         585 13384 159 10 44 174 56 28
CDM CM-3-E Valles Rhy-Cerro del Medio Jemez Mtns, N NM         606 14160 161 11 43 172 54 55

"CDM" samples were collected by Dan Wolfman, but the exact locality on Cerro del Medio is unknown.

Valles Rhyolite (Cerro del Medio) from table above

 

Canovas Canyon Rhyolite and Bear Springs Peak

Perlitic lava with remnant marekanites in the Canovas Canyon Rhyolite formation.  Large marekanite in the center of image is 47 mm in diameter.

The oldest (Tertiary, ca. 8.8-9.8 mya) artifact quality obsidian source in the Jemez Mountains is the Bear Springs Peak dome complex, part of the Canovas Canyon Rhyolite domes and shallow intrusions (Tcc) as reported by Smith et al. (1970), and more recently by (Kempter et. al. 2004; see also Gardner 1985; Figure 3 here).  These pre-caldera domes appear to be overlain by a rhyolite tuff, but field inspection suggests to Kempter et al. (2004) that they are contemporaneous.  Our work at Bear Springs Peak and domes structures to the north suggest that the obsidian was produced from obsidian zones on the margins of the domes as part of a lava eruptive event.  The lava has mostly devitrified into perlite, leaving the most vitreous portions of the flow as remnant marekanites (see image above). 

            Located at the far southern end of the Jemez Mountains, just south and adjacent to Jemez Pueblo (Walatowa) Nation land, this Tertiary Period source exhibits only relatively small marekanites now, most smaller than 2 cm in diameter (image above).  Although the nodule size was apparently small, Bear Springs Peak obsidian was used in prehistory as a toolstone, and was recovered in samples analyzed from early historic period contexts at Zuni Pueblo, probably a result of relationships between the Zuni and Jemez in the 17th Century (see Howell and Shackley 2003; Shackley 2005:102-105).   The source data suggest that this may be the “Bland Canyon & Apache Tears” source as reported by Glascock et al. (1999:863), collected by Wolfman and reported by him in 1994, and reported as “Canovas Canyon” by Church in his 2000 study of secondary deposits in the lower Rio Grande (Tables here).

            As with many of the Tertiary Period sources in the Southwest, Bear Springs Peak obsidian is present as marekanites in perlitic lava at the Bear Springs Peak dome proper and domes trending along north-south faults active during the Mid-Miocene toward and into Jemez Pueblo land.  Biotite in the crystalline rhyolite that underlies the obsidian zone yielded 40Ar/39Ar dates of 8.81±0.16 and 9.75±0.08 mya (Kempter et al. 2004).

            Nodules up to 5 cm occur as remnants in the perlite not unlike the environment at Sand Tanks, Superior (Picketpost Mountain), Devil Peak, and many other Tertiary period sources in western North America (Shackley 2005; Shackley and Tucker 2001).  The density of the nodules from pea gravel to 5 cm in the perlite lava is as high as 100/m2, although most of the marekanites are under 2 cm (see image above).  The glass itself is nearly transparent in thin flakes similar to Cow Canyon and Superior obsidian, and some have noticeable dark black and nearly clear banding.  It is an excellent media for tool production so that bipolar flakes are easily produced and pressure flaking is effective, typical of these high silica rhyolite glasses.

            The marekanites have eroded into the stream systems to the south as far as the lower Rio Grande (Church 2000).  Church recovered two specimens called “Canovas Canyon” in the Vado (Camp Rice) collection area in the Rio Grande gravels, south of Las Cruces; these two samples match the Bear Springs Peak data as presented here (Church 2000:660, Table IV).  This suggests that the Canovas Canyon Rhyolite obsidian has eroded into the ancestral Rio Grande between about 9 million years ago and the present, although based on Church’s (2004) study are available today in very low proportions compared to Cerro Toledo Rhyolite, El Rechuelos, and Mount Taylor obsidian.   Probably the reason this source is not found in archaeological contexts more frequently is that it simply cannot “compete” with the more recent large nodule, high quality sources just to the north including Cerro Toldedo Rhyolite, Valles Rhyolite (Cerro del Medio) and El Rechuelos obsidian (Shackley 2005).  However, the high quality, and perhaps its location on Jemez Pueblo territory, may have caused it to be viable as a toolstone, at least in the historic period, perhaps at a time when the Jemez and Zuni enjoyed an exchange relationship.  The Zuni could have made trips into the Jemez Mountains for any number of reasons as a result of this relationship.

Elemental concentrations for Canovas Canyon Rhyolite obsidian source samples (all measurements in parts per million)

Sample Ti Mn Fe Zn Rb Sr Y Zr Nb Ba Pb Th
060604-1-1 849 431 5464 22 106 35 18 88 64     31
-3 974 511 6447 23 117 41 16 104 60     38
-4 1012 485 6443 31 113 41 20 100 58     29
-5 976 497 6457 27 117 40 22 104 57     22
-6 1087 609 7685 33 128 47 23 112 61     39
-3 1029 530 6608 29 114 47 20 106 59     35
-4 976 498 6245 32 113 48 19 107 48     31
-5 1065 559 6710 29 118 50 22 108 53     30
-6 990 516 6361 31 114 48 22 100 49     20
-7 1067 510 6386 33 110 44 22 108 50     12
-8 1259 451 9346 46 118 51 24 109 49 426 22 21
-9 1172 393 8799 39 116 48 26 106 50 476 23 23
-10 1157 422 8897 37 115 46 17 111 52 471 21 29
-11 999 392 8313 38 110 49 23 114 53 462 23 33
-12 1048 380 8162 76 106 36 20 96 51 414 24 34
-13 1182 416 8782 43 122 51 25 111 47 454 27 29
-14 1110 420 8773 39 123 49 26 115 55 481 25 33
-15 1023 373 8204 37 111 47 21 105 55 448 33 30
-16 1076 414 8569 41 119 48 23 115 55 464 25 18
-17 1121 409 8456 56 117 50 23 108 48 447 28 27
-18 987 371 7883 29 104 42 22 110 54 499 23 37
-19 1248 402 8891 213 112 48 22 111 54 509 25 25
-20 1059 451 8880 53 122 42 20 103 56 402 25 25
-21 1020 455 8689 33 126 52 24 112 53 487 27 33
-22 1207 447 9660 52 120 47 23 107 48 430 25 21
-23 1109 425 8470 43 110 38 24 103 55 437 27 22
-24 1257 398 9401 39 114 46 18 110 55 449 26 22
-25 1053 423 8651 49 121 45 23 106 46 429 20 28
-26 1028 400 8290 43 115 45 22 113 52 460 24 28
-27 1114 426 8529 43 118 49 27 113 52 473 30 28
-28 1032 426 8352 38 108 45 23 105 49 426 20 26
-29 1133 411 9101 41 117 50 24 110 52 455 26 23
-30 1381 371 9140 40 103 38 19 93 43 390 19 29
-31 1054 374 8360 39 110 44 22 109 50 471 21 29
-32 1131 450 9100 51 116 50 28 113 50 466 35 23
-33 1143 402 9011 50 113 53 24 108 57 449 21 28
-34 1111 385 8549 41 114 49 21 114 51 487 21 16
-35 1188 374 8566 44 113 50 20 104 45 451 23 23

 

 

Mean and central tendency table for Canovas Canyon Rhyolite data from table above

 

 

 

Bearhead Rhyolite (Paliza Canyon)            

Recent geological and archaeological investigations published in New Mexico Geology of what has been called "Paliza Canyon" obsidian in the literature has been determined to be Bearhead Rhyolite, part of the Keres Group in the southern Jemez Mountains (Baugh and Nelson 1987; Shackley et al. 2016).  The New Mexico Geology paper can be found here.  The text, tables and figures are from that publication. The geological origin of all other archaeological obsidian sources in the Jemez Mountains have been reported and are well documented in the literature. But the so-called "Paliza Canyon" source, important as a toolstone to Pueblo Revolt Colonial period occupants of the Jemez Mountains area and present in regional archaeological contexts throughout prehistory, had remained unlocated and undocumented.  The Bearhead Rhyolite origin for the "Paliza Canyon" obsidian (which we suggest should now be named “Bearhead Rhyolite”) solves this ambiguity and provides more precise geological and geographical data for archaeological obsidian source provenance in the region.

FIGURE 1---Orthophoto over digital elevation model of approximate location of collection localities (i.e. 090413-2 etc.), topographic points, USGS quadrangle borders in red, and Pueblo Revolt sites (LA numbers) from the 2009 and 2012 research that are present in our study area (Liebmann 2012; Shackley 2009a, 2012b).  Our precise collection localities are shown in Figure 2.  Abbreviations: CR = creek; Rhy = rhyolite; SR = state highway; FR = Santa Fe National Forest route.

FIGURE 2---Simplified geologic map of the upper Paliza Canyon area, southern Jemez Mountains, New Mexico (modified from Kempter et al., 2004 and Goff et al., 2006 with labels and terminology from Goff et al., 2011). Qal (dark yellow) = stream alluvium; Qvec (pale yellow) = El Cajete Pyroclastic Beds; moderately sorted beds of rhyolitic pyroclastic fall and thin pyroclastic flow deposits (74.7±1.3 ka, Zimmerer et al., 2016); locally the beds are extremely thin; Qbt (orange) = Tshirege Member, Bandelier Tuff; rhyolitic ignimbrite (1.25±0.01 Ma, Phillips et al., 2007); Tpv (olive green) = volcaniclastic deposits, debris flows, hyper-concentrated flows, and stream deposits of the Paliza Canyon Formation; Tbh (brown) = Bearhead Rhyolite; domes and flows of aphyric to slightly porphyritic lava (dome in northern Bear Springs Peak Quadrangle is 6.66±0.06 Ma, Kempter et al., 2004; faulted dome in Redondo Peak Quadrangle is 7.62±0.44 to 7.83±0.26 Ma, Goff et al., 2006); Tpa (green) = Paliza Canyon Fm. andesite, undivided, lava flows containing plagioclase and pyroxene (8.78±0.14 to 9.44±0.21 Ma, Justet, 2003); Tpd (rose) = Paliza Canyon Fm. dacite, domes and flows of very porphyritic lava, near Ruiz Peak; Tpbhd (red) = Paliza Canyon Fm. porphyritic biotite-hornblende dacite, dome and flows (9.24±0.22 Ma, Justet, 2003); Tpb (blue) = Paliza Canyon Fm. basalt, lava flows most containing visible olivine (9.45±0.07 to 9.54±0.08 Ma, Goff et al., 2006 and Kempter et al., 2004).

TABLE 1---Mean and central tendency for Bearhead Rhyolite obsidian from data in Table 2 and mean data from the four "Paliza Canyon" samples originally reported by Baugh and Nelson (1987). 


Element

N

Minimum

Maximum

Mean1

σ

Zn

61

41

145

60 (n.r.)2

22.5

Rb

61

87

111

100 (100.8)

5.3

Sr

61

76

99

87 (86.2)

5.1

Y

61

20

29

25 (8.5)

2.2

Zr

61

112

142

128 (124)

7.1

Nb

61

27

41

33 (18.1)

2.8

Ba

61

1445

1883

1660 (1352)

75.1

Pb

61

15

25

20 (n.r.)

2.1

Th

61

7

21

14 (n.r.)

3.1

1 Baugh and Nelson (1987) mean values reported in parentheses.

2 n.r. = not reported by Baugh and Nelson (1987) 

 Table 2. Oxide values (%) for one sample of Paliza Canyon obsidian and USGS RGM-1 rhyolite standard, and El Cajete pumice and Banco Bonito obsidian from the Self et al. (1988) study.

Sample

SiO2

Al2O3

CaO

Fe2O3

K2O

MgO

MnO

Na2O

TiO2

Σ

 

 

 

 

 

 

 

 

 

 

 

091115-2-7 (Tpv)4

67.96

17.06

1.29

5.74

3.81

1.07

0.13

1.91

0.78

99.74

091115-2-8 (Tpv) 4

64.06

19.70

1.49

7.002

3.82

1.16

0.08

1.66

0.71

99.69

091115-2-9 (Tpv) 4

68.61

15.73

1.65

5.93

3.72

1.35

0.08

1.83

0.72

99.62

090413-3-2 (Qvec)5

74.67

13.10

0.89

1.48

5.42

0.21

0.13

3.37

0.28

99.55

Banco Bonito F82-71

73.9

13.6

1.59

1.86      

4.15    

0.64    

0.05    

3.87     

0.29    

99.95

El Cajete F82-62       

72.8    

14.0     

1.87     

2.11     

4.16    

0.78    

0.05    

3.84     

0.33     

99.94

Paliza Cyn dacite3

68.99

13.35

2.62

3.84

2.96

0.77

0.09

3.97

0.74

99.75

RGM-1 (this study)

75.68

12.48

1.30

1.81

4.55

<0.1

0.04

3.77

0.20

99.82

RGM-1 USGS recommended

73.4

13.7

1.15

1.86

4.30

0.28

0.036

4.07

0.27

99.06

1from Gardner et al., (1986)

2from F. Goff, (unpub. data)

3 from Ellisor et al. (1996)

4 Pumice samples associated with obsidian localities formerly mapped as El Cajete pumice above and east of Paliza Canyon (Kempter et al., 2004).

5 Obsidian sample from an area formerly mapped as El Cajete pumice above and east of Paliza Canyon (Kempter et al., 2004)

Data not normalized to USGS recommended values.

 Table 3. "Raw" data of selected elements for Paliza Canyon obsidian, USGS RGM-1 rhyolite standard, and mean data from Jemez Mountains obsidian sources. (all measurements in parts per million)

 Sample*

Zn

Rb

Sr

Y

Zr

Nb

Ba

Pb

Th

090413-2-1

81

101

91

23

132

34

1667

19

13

090413-2-2

117

103

89

26

121

33

1611

20

12

090413-2-3

145

87

76

21

112

30

1592

16

14

090413-2-4

124

107

90

23

120

32

1608

20

18

090413-2-5

111

95

79

22

117

32

1664

18

21

090413-2-6

92

99

87

22

126

38

1605

18

14

090413-2-7

92

101

79

24

119

34

1711

19

13

090413-3-1

56

109

94

24

128

34

1741

24

12

090413-3-11

61

100

87

25

121

36

1612

17

17

090413-3-12

58

101

86

22

120

34

1665

19

12

090413-3-14

52

103

86

28

123

35

1685

19

16

090413-3-18

78

105

87

24

122

32

1672

21

12

090413-3-19

101

97

85

23

113

30

1689

18

13

090413-3-2

57

95

85

25

124

38

1607

15

15

090413-3-20

81

102

82

24

120

31

1577

22

10

090413-3-21

87

95

81

23

115

27

1707

17

17

090413-3-23

89

100

85

25

119

27

1656

22

16

090413-3-24

71

93

79

22

128

33

1606

18

10

090413-3-3

47

99

86

26

120

32

1640

23

11

090413-3-4

46

99

86

22

136

33

1445

18

12

090413-3-5

56

105

89

20

138

37

1706

22

19

090413-3-6

47

101

86

20

125

34

1680

19

19

090413-3-7

53

105

93

24

128

29

1560

22

7

090413-3-8

55

102

89

24

134

29

1609

20

13

090413-3-9

47

96

85

24

130

31

1661

22

17

091115-1-1

45

93

85

26

140

41

1651

18

17

091115-1-3

43

100

86

26

130

31

1597

19

8

091115-1-5

56

111

91

26

135

34

1630

23

18

091115-1-6

49

102

86

27

129

35

1699

19

20

091115-1-7

59

98

86

27

132

33

1673

19

14

091115-1-8

54

101

88

25

129

34

1668

20

13

091115-1-9

54

105

89

28

137

36

1601

20

15

091115-2-1

51

101

89

24

129

33

1679

19

11

091115-2-2

49

99

88

25

125

31

1707

18

17

091115-2-3

52

99

85

21

135

30

1602

22

20

091115-2-4

41

104

85

26

130

29

1542

17

12

091115-2-5

57

108

95

28

136

37

1613

25

12

091115-2-6

55

105

90

26

128

32

1594

21

14

100915-2-1 ("Paliza Canyon" source area)

49

104

90

27

135

36

1661

21

14

100915-2-10 ("Paliza Canyon" source area)

50

95

84

25

127

35

1879

18

10

100915-2-2 ("Paliza Canyon" source area)

54

108

94

27

133

36

1693

19

11

100915-2-3 ("Paliza Canyon" source area)

42

94

80

28

121

31

1642

16

11

100915-2-4 ("Paliza Canyon" source area)

51

105

92

27

140

37

1778

20

14

100915-2-5 ("Paliza Canyon" source area)

45

98

88

24

122

32

1639

20

19

100915-2-6 ("Paliza Canyon" source area)

44

108

93

29

133

32

1593

21

13

100915-2-7 ("Paliza Canyon" source area)

44

99

99

23

128

34

1643

22

14

100915-2-8 ("Paliza Canyon" source area)

41

90

79

23

122

30

1646

16

11

100915-2-9 ("Paliza Canyon" source area)

50

102

94

27

132

31

1686

21

15

F04-31-1 (Bearhead Rhyolite Dome)

45

91

79

25

123

32

1883

15

18

F04-31-2 (Bearhead Rhyolite Dome)

46

104

90

25

142

32

1766

22

16

F04-31-3 (Bearhead Rhyolite Dome)

44

100

85

27

132

29

1655

21

17

Valles Rhyolite (Cerro del Medio)1

26 6

160

10

43

172

54

35

27.7 6

17.5 6

Cerro Toledo Rhyolite1

n.r.

207

5

63

183

98

23

n.r.

23 4

El Rechuelos Rhyolite1

n.r.

152

9

23

77

47

24

n.r.

16.7 5

Canovas Canyon Rhyolite1

21 3

116

43

21

108

53

352

n.r.

12.9 7

El Cajete Rhyolite pumice

322

136

185

27

125

36

616

19

18

Banco Bonito Rhyolite obsidian

303

143

192

28

136

39

596

20

18.6

RGM-1 (this study)

39

151

104

27

218

8

806

24

18

RGM-1 USGS recommended

32

150

110

25

220

8.9

810

24

15

 

Bearhead Rhyolite obsidian samples were collected from areas previously mapped as El Cajete pumice (red, blue, green, and purple text), 10 samples of alluvial obsidian from the "Paliza Canyon" source area (orange text), and 3 samples of obsidian from the F04-31 Bearhead Rhyolite dome (light blue text; Goff et al. 2006). Comparative samples include: El Cajete pumice, one sample each from known artifact quality obsidian sources from the Jemez Mountains, and the USGS RGM-1 rhyolite standard (see Shackley 2005). Note that color-coded localities  correspond with colors plotted in elemental plots (Figures 5 and 6).

1 Mean concentrations mainly from Gardner et al's. 2007 unit Qvdmw (see Shackley 2005, Appendix)

2Zn concentration from F. Goff, unpub. data

 3Zn concentration from Gardner et al., 1986

4Th concentration from Stix et al., 1988

5Th concentration from Loeffler et al., 1988

6Zn, Pb and Th concentrations from Gardner et al., 2007 (obsidian unit Qvdmw)

7Th concentration from Gardner et a., 1986

8Except for Zn, the El Cajete pumice and Banco Bonito obsidian values are from Self et al. (1988).

n.r. = no report 


Discriminating Jemez Mountains sources with XRF data

The Jemez Lineament obsidian sources can be discriminated mainly with Y and Nb and one other incompatible element (i.e. Sr or Zr) as shown below.  Niobium in the two Mount Taylor (Grants Ridge and Horace/La Jara Mesa) sources are quite distinctive with concentrations over 186 ppm, much higher than the Jemez Mountains sources (see Mt Taylor page here). 

 

Sr versus Y and Zr versus Y bivariate plots of the Jemez Mountains obsidian sources discriminating all sources.  Confidence ellipses at 95%.


 

References cited for Bearhead Rhyolite

Baugh, T.G., and Nelson, F.W. Jr. 1987, New Mexico obsidian sources and exchange on the Southern Plains: Journal of Field Archaeology, v.14, p. 313-329.

Church, T., 2000, Distribution and sources of obsidian in the Rio Grande gravels of New Mexico: Geoarchaeology, v. 15, p. 649-678.

Ellisor, R., Wolff, J. & Gardner, J.N., 1996, Outline of the petrology and geochemistry of the Keres Group lavas and tuffs, in Goff, F, Kues, B.S., Rogers, M.A., McFadden, L.D., and Gardner, J.N. eds., The Jemez Mountains Region: New Mexico Geological Society, 47th Annual Field Conference, Guidebook, p. 237-242.

Gardner, J.N., Goff, F., Garcia, S., and Hagan, R.C., 1986, Stratigraphic relations and lithologic variations in the Jemez Volcanic Field, New Mexico: Journal of Geophysical Research, v. 91, B2, p. 1763-1778.

Gardner, J.N., Sandoval, M.M., Goff, F., Phillips, E., and Dickens, A., 2007, Geology of the Cerro Del Medio moat rhyolite center, Valles caldera, New Mexico, in Kues, B.S., Kelley, S.A., and Lueth, V.W., eds., Geology of the Jemez Region II: New Mexico Geological Society, 58th Annual Field Conference, Guidebook, p. 367-372.

Gardner, J.N., Goff, F., Kelley, S., and Jacobs, E., 2010, Rhyolites and associated deposits of the Valles-Toledo caldera complex: New Mexico Geology, v 32, p. 3-18.

Glascock, M.D., Kunselman, R. and Wolfman, D., 1999, Intrasource chemical differentiation of obsidian in the Jemez Mountains and Taos Plateau, New Mexico: Journal of Archaeological Science, v. 26, p. 861-868.

Goff, F., and Gardner, J.N., 2004, Late Cenozoic geochronology of volcanism and mineralization in the Jemez Mountains and Valles caldera, north central New Mexico, in Mack G. and Giles, K. eds., The Geology of New Mexico —A Geologic History: New Mexico Geological Society, Special Publication 11, p. 295-312.

Goff, F., Kues, B.S., Rogers, M.A., McFadden, L.D., and Gardner J.N. eds., 1996, The Jemez Mountains region: New Mexico Geological Society, 47th Annual Field Conference, Guidebook, 484 p.

Goff, F., Gardner, J.N., Reneau, S.L., and Goff, C.J., 2006, Geology of the Redondo Peak 7.5 minute quadrangle, Sandoval County, New Mexico: New Mexico Bureau of Geology and Mineral Resources Open-File Geologic Map OF-GM 111, scale 1:24,000.

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Kelley, S.A., McIntosh, W.C., Goff, F., Kempter, K.A., Wolff, J.A., Esser, R., Braschayko, S., Love, D., and Gardner, J.N., 2013, Spatial and temporal trends in pre-caldera Jemez Mountains volcanic and fault activity: Geosphere, v. 9, p. 614-646.

Kempter, K., Osburn, G.R., Kelley, S.A., Rampey, M., Ferguson, and J.N. Gardner, J.N., 2004, Preliminary geologic map of the Bear Springs Peak quadrangle, Sandoval County, New Mexico: New Mexico Bureau of Geology and Mineral Resources Open-File Geologic Map OF-GM 74, scale 1:24,000. 

Kues, B.S., Kelley, S.A., and Lueth, V.W., 2007, Geology of the Jemez Region II: New Mexico Geological Society, 58th Annual Field Conference, Guidebook, 499 p.

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Liebmann, M., 2012, Revolt: An archaeological history of pueblo resistance and revitalization in the 17th century New Mexico: Tucson, University of Arizona Press, 328 p.

Loeffler, B.M., Vaniman, D.T., Baldridge, W.S., and Shafiqullah, M., 1988, Neogene rhyolites of the northern Jemez volcanic field, New Mexico: Journal of Geophysical Research, v. 93, p. 6157-6167.

Nelson, F.W., Jr., 1984, X-ray fluorescence of some western North American obsidians, in Hughes, R.E., ed., Obsidian Studies in the Great Basin: Berkely, University of California, Contributions of the University of California Archaeological Research Facility 45, p. 27-62. 

Phillips, E.H., Goff, F., Kyle, P.R., McIntosh, W.C., Dunbar, N.W., and Gardner, J.N., 2007, The 40Ar/39Ar age constraints on the duration of resurgence at the Valles caldera, New Mexico: Journal of Geophysical Research, v.112, B08201, 15 p.

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Self, S., Kirchner, D.E., and Wolff, J.A., 1988, The El Cajete Series, Valles Caldera, New Mexico: Journal of Geophysical Research, v. 93, B6, p. 6113-6127.

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Shackley, M.S., 2009b, Two newly discovered sources of archaeological obsidian in the Southwest: archaeological and social implications: Kiva v. 74, p. 269-280.

Shackley, M.S., 2009c, The Topaz Basin archaeological obsidian source in the Transition Zone of central Arizona: Geoarchaeology, v. 24, p. 336-347.

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Revised: 27 July 2018