GWYNN AND EWE CANYONS (NEGRITO MOUNTAIN)

WESTERN NEW MEXICO

Updated 10/3/2013

Sections 19,30,31,32 R16W, T9S USGS Telephone Canyon 7.5' Quad; Sections 30,31,32 R16W T9S; Secs. 4.5.9 R16W, T10S USGS Negrito Mtn 7.5' Quad (and see below), Gila National Forest, south central Catron County, New Mexico.

The Gwynn Canyon source was not personally surveyed during the original study. The information and samples used here was provided by Chris Stevenson (then) of New Mexico State University's Obsidian Hydration Laboratory (see also Hughes 1988). The specimens for the original field collection were all procured in Ewe Canyon south of another source area  in the Gwynn Canyon area (discovered first; see 2013 collection below). The nodules (at least 5 cm in diameter) are found mainly in a volcanic alluvium and within the washes. The glass is a high quality material, but only 15 nodules were available for study. No specific reduction areas were noted by Stevenson, but most nodules were picked up in the Gwynn Canyon bottom. The 15 nodules studied all have waterworn black cortex and the aphyric glass ranges from an opaque black to a nearly transparent brown. Banding did not occur in this small sample.

There are no known published references on this new source other than the regional geologic map (Weber and Willard 1959).

[updated 1995] In the earlier study (Shackley 1988), this source was not personally mapped or surveyed. My survey in 1993 indicated that marekanites were directly associated with glassy, perlitic rhyolite in Ewe Canyon to the south derived from a dome complex called Feathery Hill on the Telephone Canyon USGS 7.5' Quad. This stream system erodes west toward the San Francisco River. These coalesced domes shown as Feathery Hill on the quadrangle map, exhibit nodule densities in the regolith up to 200 per m2. This locality is located in Sections 19 and 20 T9S R16W Telephone Canyon 7.5' Quad 1963, Catron County, New Mexico. Unmodified marekanites on the domes have maximum diameters near 50 mm, although the vast majority (95%) are 30 mm and smaller. Bipolar cores and flakes were found on and near Feathery Hill, but in low densities (<1 per 100 m2).

As noted above, marekanites are eroding into the Ewe Canyon system and possibly the upper San Francisco River, although no nodules were noted in the San Francisco River alluvium as far north as Alma, New Mexico. Published references for the geology of this source include Findlow and Bolognese (1982:56), the regional geology map by Weber and Willard (1959), and Ratté et al. (1984).

The Gwynn Canyon and two of the Mule Creek groups (Antelope Creek and Mule Mountains) are very similar in trace element composition. Zirconium plotted against Nb, Y, and/or Ba is the best method to discriminate these sources using EDXRF. This can be an important issue in western New Mexico late prehistory because these sources are located in very different environments that may have had cultural significance in prehistory. It is possible that in the late period Gwynn Canyon obsidian could have been controlled by the Cibola branch of the Mogollon while the Mule Creek sources could have been controlled by the Mimbres branch. This may or may not influence the spatial distribution of these obsidian sources in the region and confident source assignment can become crucial. Again, the secondary distribution of Mule Creek is quite extensive to the west through the San Francisco and Gila River systems, and the presence of Mule Creek glass in archaeological contexts to the west may not necessarily indicate that it was procured in the highlands, but could have been procured from the Gila River alluvium (see Shackley 2005).

Table 1. Elemental concentrations for the "original" Gwynn Canyon source standards, and the 2013 sample. Samples GC 11-20 from Feathery Hill at the head of Ewe Canyon, the rest (GC 1-10) are from secondary samples from Gwynn Canyon submitted by Chris Stevenson. All measurements in parts per million (ppm)

SAMPLE

Mn

Zn

Rb

Sr

Y

Zr

Nb

Ba

Pb

Th

2013 samples

 

 

 

 

 

 

 

 

 

 

Feathery Hill

 

 

 

 

 

 

 

 

 

 

092813-1-1

376

47

208

24

30

145

24

54

27

28

092813-1-2

379

41

215

23

27

139

21

54

26

36

092813-1-3

445

54

235

22

29

151

23

99

31

37

092813-1-4

388

42

211

19

30

150

19

46

27

26

092813-1-5

396

51

222

21

35

149

23

24

28

28

Gwynn Canyon dome

 

 

 

 

 

 

 

 

 

 

092813-2-1-1

545

38

206

22

31

145

22

63

28

34

092813-2-1-2

370

53

218

21

33

140

25

35

27

36

092813-2-1-3

466

61

239

24

29

151

21

<1

36

31

092813-2-1-4

406

57

219

20

33

142

19

65

29

32

092813-2-1-5

337

53

211

21

28

143

22

39

27

32

092813-2-1-6

370

63

209

22

28

150

20

50

30

32

2ndary deposit Gwynn Canyon

 

 

 

 

 

 

 

 

 

 

092813-2-2-1 (perlite sample)

449

54

227

23

33

154

26

60

28

35

092813-2-2-2

453

51

243

25

32

153

23

43

32

33

092813-2-2-3

390

53

216

22

30

145

21

60

28

29

092813-2-2-4

426

58

221

25

35

145

29

88

31

35

092813-2-2-5

348

43

205

21

32

139

25

25

28

25

0-2813-2-2-6

432

53

227

21

31

144

22

26

23

43

original samples - 1993

 

 

 

 

 

 

 

 

 

 

GC-1

418

 

237

20

31

161

23

86

 

 

GC-2

459

 

243

21

30

159

27

85

 

 

GC-3

438

 

228

19

30

154

22

85

 

 

GC-4

414

 

216

18

33

153

20

90

 

 

GC-5

414

 

221

23

32

166

18

94

 

 

GC-6

453

 

229

19

31

152

26

87

 

 

GC-7

454

 

237

22

31

155

21

87

 

 

GC-8

427

 

226

18

31

150

23

86

 

 

GC-9

446

 

221

17

33

167

21

87

 

 

GC-10

417

 

220

16

29

151

23

82

 

 

GC11

420

 

231

21

30

158

22

78

 

 

GC12

508

 

244

21

32

164

24

78

 

 

GC13

460

 

237

19

33

156

21

81

 

 

GC14

363

 

196

18

28

137

20

88

 

 

GC15

376

 

223

17

28

151

21

77

 

 

GC16

415

 

230

18

31

158

21

81

 

 

GC17

501

 

243

20

32

162

22

80

 

 

GC18

328

 

198

18

27

144

17

91

 

 

GC19

456

 

227

21

36

163

24

108

 

 

GC20

414

 

222

19

34

150

15

80

 

 

RGM1-S4 (USGS)

273

37

147

106

24

216

8

865

19

17

Table 2.  Mean and central tendency for the Gwynn and Ewe Canyon samples 

 

N

Minimum

Maximum

Mean

Std. Deviation

Mn

37

328

545

420

47

Fe

37

7368

10860

8980

782

Zn

17

38

63

51

7

Rb

37

196

244

223

13

Sr

37

16

25

21

2

Y

37

27

36

31

2

Zr

37

137

167

151

8

Nb

37

15

29

22

3

Pb

17

23

36

29

3

Th

17

25

43

32

5

 

Table 3.  Oxide values for one sample from dome complex in Gwynn Canyon (see map below)

Sample

SiO2

Al2O3

CaO

Fe2O3

K2O

MgO

MnO

Na2O

TiO2

 092813-2-2-2

75.709

11.375

0.608

1.265

6.037

0

0.094

4.456

0.206

RGM1-S4

74.501

12.051

1.505

2.294

5.182

0

0.053

3.874

0.293

 

Sr, Rb, and Zr concentration plot of the Gwynn Canyon and Mule Creek sources. Note the genetic similarity.

 

Survey and collection, 28 September 2013 with Jeff Ferguson. 

On this date Jeff Ferguson and I re-surveyed the Gwynn/Ewe Canyon area and Feathery Hill and collected more samples.  The location and general character of the Feathery Hill locality eroding into Ewe Canyon was confirmed, but another locality to the northwest above Negrito Creek in Gwynn Canyon was located that produced artifact quality marekanites.  Initial survey of Gwynn Canyon above this locality at UTM 12S 0728596/3713894 ± 3m, indicated that no obsidian was present in Gwynn Canyon.  Below the above noted locality however, abundant marekanites are entering Negrito Creek in Gwynn Canyon and possibly eroding into upper San Francisco River.  This locality is a dome complex consisting of perlitic lava near the military crest of the domes with a thin lahar below.  While no marekanites were found in-situ in the perlite, there were marekanites in the perlitic sand eroding directly from the perlitic lava.  The marekanites up to about 30 mm down to pea size were found in a small wash eroding into Negrito Creek.  The Feathery Hill obsidian erodes south through Ewe Canyon, while the obsidian in Gwynn Canyon is eroding west through Negrito Creek potentially into the San Francisco River system (see map below).

The elemental composition between these localities is similar (see Tables 1 and 2).  A perlite sample analyzed from the dome complex on the north side of Gwynn Canyon is well within the range of variability indicating that the marekanites recovered are from the same magma source, although none were located in-situ.

The 2013 collection also expanded the character (opacity, sphericity) of these marekanites at the source.  All of the marekanites from both localities are sub-rounded.  A few of the samples from Feathery Hill are entirely mahogany to black/mahogany, not seen in the earlier collections or noticed in the archaeological record.  The character varies from nearly opaque black to nearly transparent with black banding.  There is no detectable elemental differences between colors.

 

References

Findlow, F.J., and M. Bolognese, 1982, A preliminary analysis of prehistoric obsidian use within the Mogollon area.  In P.H. Beckett (Ed.) Mogollon Archaeology: Proceedings of the 1980 Mogollon Conference, pp. 297-316.  Ramona, California: Acoma Press.

Hughes, R.E., 1988, Archaeological significance of geochemical contrasts among southwestern New Mexico obsidians. Texas Journal of Science 40:297-307.

Ratté, J.C., R.F. Marvin, and C.W. Naeser, 1984, Calderas and ash flow tuffs of the Mogollon Mountains, southwestern New Mexico.  Journal of Geophysical Research 89:87113-8732.

Shackley, M.S., 1988, Sources of archaeological obsidian in the Southwest: an archaeological, petrological, and geochemical study.  American Antiquity 53:752-772.

Shackley, M.S., 2005, Obsidian: Geology and Archaeology in the North American Southwest.  Tucson: University of Arizona Press.

Weber, R.H., and M.E. Willard, 1959, Reconnaissance geologic map of Mogollon 30 minute quadrangle.  New Mexico Institute of Mining and Technology, Socorro.

 

This page maintained by Steve Shackley (shackley@berkeley.edu).
Copyright © 2013 M. Steven Shackley. All rights reserved.
Revised: 19 August 2015

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