Geology A VOLCANIC ERUPTION IN THE SALTON TROUGH (SOUTHERN CALIFORNIA) DURING HUMAN PRESENCE --Manuscript Draft-Manuscript Number: Full Title:
A VOLCANIC ERUPTION IN THE SALTON TROUGH (SOUTHERN CALIFORNIA) DURING HUMAN PRESENCE
Short Title:
Salton Trough eruption
Article Type:
Article
Keywords:
zircon; geochronology; obsidian; archaeometry; Lake Cahuilla
Corresponding Author:
Axel K Schmitt, Dr University of California, Los Angeles Los Angeles, CA UNITED STATES
Corresponding Author Secondary Information: Corresponding Author's Institution:
University of California, Los Angeles
Corresponding Author's Secondary Institution: First Author:
Axel K Schmitt, Dr
First Author Secondary Information: Order of Authors:
Axel K Schmitt, Dr Arturo Martin, PhD Daniel F Stockli, PhD Kenneth A Farley, PhD Oscar M Lovera, PhD
Order of Authors Secondary Information: Manuscript Region of Origin:
UNITED STATES
Abstract:
U-Th and (U-Th)/He zircon geochronology redefines the timing of volcanic activity in the Salton Trough (southern California), the subaerial extension of the incipiently oceanic Gulf of California. U-series disequilibrium corrected (U-Th)/He zircon analyses for a granophyre ejecta clast from Red Island indicate an eruption age of 2,480±470 a (between 0 and 940 BCE; error at 95% confidence). This eruption age is supported by U-Th zircon crystallization ages for two rhyolite domes: Red Island (the host for the granophyre) and Obsidian Butte, a prehistoric quarry for obsidian which is widely distributed in southern California and northern Mexico archaeological sites. Lavas and granophyre display overlapping zircon crystallization age distributions, supporting field and compositional evidence that they are cogenetic and contemporaneous. The (UTh)/He eruption age is younger and significantly more precise than previous ages for these volcanoes. These results are the first evidence for an eruption during human presence in the region. They also provide an alternative explanation for the absence of the Obsidian Butte lithic source among early prehistoric cultural artifacts which previously been has been attributed to submergence of the quarry location during hypothesized persistent flooding by ancient Lake Cahuilla.
Suggested Reviewers:
Kathleen Nicoll University of Utah
[email protected] expert on geoarchaeology Peter Reiners University of Arizona
Powered by Editorial Manager® and Preprint Manager® from Aries Systems Corporation
[email protected] U-Th/He geochronology pioneer, especially for xenolith dating young volcanic samples. Joann Stock Caltech
[email protected] Strong background in volcano-tectonic processes during rifting, PI for Salton Sea Seismic Imaging project Opposed Reviewers:
Powered by Editorial Manager® and Preprint Manager® from Aries Systems Corporation
Cover letter Click here to download Cover letter: Letter Wyld revision v2.doc
*Manuscript Click here to download Manuscript: Schmitt_etal_2012_GEOLOGY_revision_v3.doc
1 2
A VOLCANIC ERUPTION IN THE SALTON TROUGH (SOUTHERN CALIFORNIA) DURING HUMAN PRESENCE
3 4
Axel K. Schmitt
5
Department of Earth and Space Sciences, UCLA
6
Los Angeles CA 90095-1567, USA
7
Phone: +310-206-5760; Email:
[email protected]
8 9
Arturo Martín
10
Departamento de Geología, CICESE
11
Km 107 Carr. Tijuana - Ensenada., Ensenada, B.C., México, C.P. 22800
12 13
Daniel F. Stockli
14
Department of Geological Sciences, University of Texas
15
Austin, TX 78712
16 17
Kenneth A. Farley
18
Division of Geological and Planetary Sciences, California Institute of Technology
19
Pasadena, CA 91125
20 21
Oscar M. Lovera
22
Department of Earth and Space Sciences, UCLA
23
Los Angeles CA 90095-1567, USA
24 1
25
Abstract
26
U-Th and (U-Th)/He zircon geochronology redefines the timing of volcanic activity in
27
the Salton Trough (southern California), the subaerial extension of the incipiently oceanic
28
Gulf of California. U-series disequilibrium corrected (U-Th)/He zircon analyses for a
29
granophyre ejecta clast from Red Island indicate an eruption age of 2,480±470 a
30
(between 0 and 940 BCE; error at 95% confidence). This eruption age is supported by U-
31
Th zircon crystallization ages for two rhyolite domes: Red Island (the host for the
32
granophyre) and Obsidian Butte, a prehistoric quarry for obsidian which is widely
33
distributed in southern California and northern Mexico archaeological sites. Lavas and
34
granophyre display overlapping zircon crystallization age distributions, supporting field
35
and compositional evidence that they are cogenetic and contemporaneous. The (U-
36
Th)/He eruption age is younger and significantly more precise than previous ages for
37
these volcanoes. These results are the first evidence for an eruption during human
38
presence in the region. They also provide an alternative explanation for the absence of the
39
Obsidian Butte lithic source among early prehistoric cultural artifacts which previously
40
been has been attributed to submergence of the quarry location during hypothesized
41
persistent flooding by ancient Lake Cahuilla.
42 43
Keywords: zircon; geochronology; obsidian; archaeometry; Lake Cahuilla
44
2
45
INTRODUCTION
46
Volcanic chronostratigraphy is essential in understanding the timing of human origins,
47
migration, and exchange. Radiometric dating of volcanic rocks down to the historical
48
realm is possible in favorable cases by K-Ar (40Ar/39Ar) geochronology (e.g., the 79 CE
49
eruption of Vesuvius; Renne et al., 1997; Lanphere et al., 2007), but often accuracy is
50
compromised by excess 40Ar, parent-daughter mobility, or diffusive fractionation of
51
40
52
Morgan et al., 2009; Flude et al., 2010).
Ar/36Ar (e.g., Cerling et al., 1985; Esser et al., 1997; McDougall and Harrison, 1999;
53
(U-Th)/He geochronology of zircon as one of the first radiometric dating
54
techniques (Strutt, 1908) has experienced a revival as a thermochronometer, but it is
55
equally suitable for rapidly cooled volcanic rocks without subsequent thermal disturbance
56
(e.g., Tagami et al., 2003; Davidson et al., 2004; Schmitt et al., 2006; Blondes et al.,
57
2007). Compared to K-Ar (40Ar/39Ar) geochronology, it offers the advantages of reduced
58
excess 4He due to rapid diffusion (Reiners, 2004), high daughter isotope production rates
59
(4He/40Ar >20 per parent nucleus), and negligible atmospheric contamination (air Ar/He
60
~2000). Its application, however, has been limited by U-series disequilibrium effects,
61
which, in the case of zircon, typically cause severe age underestimation (Farley et al.,
62
2002). To overcome this limitation, a novel combined U-Th ion microprobe crystal rim
63
analysis and (U-Th)/He bulk crystal degassing analysis technique has been developed1.
64
Here, we apply this technique to document an eruption in the Salton Trough (southern
65
California) as recently as 0 - 940 BCE, and age which overlaps with human occupation of
1
to equal extent at UCLA by AKS and OML, and University of Kansas by DFS
3
66
southern California and northern Baja California, and agrees with the onset of obsidian
67
use in these locations (e.g., Schaefer and Laylander, 2007).
68 69
VOLCANISM IN THE SALTON TROUGH
70
The Salton Buttes together with Cerro Prieto and Roca Consag are the
71
morphologically most pristine volcanoes in the northern Gulf of California and Salton
72
Trough rift zone (Fig. 1). They form an ~7 km long, NE-SW trending lineament of five
73
rhyolite domes (1500 1160 BCE 1700 >1450 >750 1400 1400 >1400 640 645 1020
n artifacts source
reference
1 2 1 5 6 1 2 1 1 1 1 1 1 1 7 2 3 3 2 1 2 1 1 1 2 1 3 4 1 1 2 16 2 12 1 5 1 debitage 2
Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Rick et al. (2001) Erlandson et al. (2011) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) McDonald (1992) Kyle (1996) Love and Dahdul (2002) Porcayo-Michelini (2006)
Coso Coso Coso Coso Coso Coso Coso Coso Coso Coso Coso Coso Other Coso Coso Coso Coso Coso Coso Coso Coso Coso Coso Obsidian Butte Obsidian Butte Coso Obsidian Butte Obsidian Butte Obsidian Butte unknown San Felipe San Felipe San Felipe (?) Obsidian Butte Obsidian Butte Obsidian Butte Obsidian Butte Coso Obsidian Butte
all sites with prefix CA except Zaragoza (Baja California, Mexico) all ages CE (unless indicated) with minimum and maximum ages at 2σ absolute ages reported in literature were recalcualted to calendric ages using OxCal v. 3.10 references: Erlandson, J.M., Rick, T.C., Braje, T.J., Casperson, M., Culleton, B., Fulfrost, B., Garcia, T., Guthrie, T.A., Jew, N., Kennett, D.J., M
Kyle, C.E., 1996, A 2,000 year old milling tool kit from CA-SDI-10148, San Diego, California: Pacific Coast Archaeological Society Love, B., and Dahdul, M., 2002, Desert chronologies and the Archaic period in the Coachella Valley. Pacific Coast Archaeologica McDonald, A.M., 1992, Indian Hill rockshelter and aboriginal cultural adaptation in Anza-Borrego State Park, southeastern Cali Porcayo-Michelini, A., 2006, Informe final para el consejo de arqueología de los trabajos arqueologícos realizados en el sitio Ig Rick, T.C., Skinner, C.E., Erlandson, J.M., and Vellanoweth, R.L., 2002, Obsidian Source Characterization and Human Exchange S
T.A., Jew, N., Kennett, D.J., Moss, M.L., Reeder, L., Skinner, C., Watts, J., Willis, L., 2011, Paleoindian Seafaring, Maritime Technologies, and
Coast Archaeological Society Quarterly, v. 32(4), p. 76-87. y. Pacific Coast Archaeological Society Quarterly, v. 38(2-3), p. 66-86. State Park, southeastern California [Ph.D. thesis]: Riverside, University of McDonald, A.M., 1992, Indian Hill rockshelter and aboriginal cult ogícos realizados en el sitio Ignacio Zaragoza. Archivo del Centro INAH, Baja California. ation and Human Exchange Systems on California’s Channel Islands: Pacific Coast Archaeological Society Quarterly, v. 37(3), p. 28-44.
ritime Technologies, and Coastal Foraging on California’s Channel Islands: Science, v. 331, p. 1181-1185.
helter and aboriginal cultural adaptation in Anza-Borrego State Park, southeastern California [Ph.D. thesis]: Riverside, University of Califor
y, v. 37(3), p. 28-44.
side, University of California, 429 p.