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Chemical changes in hot springs, as recorded by thermal waters and their deposits, provide a window into the evolution of the postglacial hydrothermal system of the Yellowstone Plateau Volcanic Field. Today, most hydrothermal travertine forms to the north and south of the ca. 631 ka Yellowstone caldera where groundwater flow through subsurface sedimentary rocks leads to calcite saturation at hot springs. In contrast, low-Ca rhyolites dominate the subsurface within the Yellowstone caldera, resulting in thermal waters that rarely deposit travertine. We investigated the timing and origin of five small travertine deposits in the Upper and Lower Geyser Basins to understand the conditions that allowed for travertine deposition. New 230Th-U dating, oxygen (δ18O), carbon (δ13C), and strontium (87Sr/86Sr) isotopic ratios, and elemental concentrations indicate that travertine deposits within the Yellowstone caldera formed during three main episodes that correspond broadly with known periods of wet climate: 13.9−13.6 ka, 12.2−9.5 ka, and 5.2−2.9 ka. Travertine deposition occurred in response to the influx of large volumes of cold meteoric water, which increased the rate of chemical weathering of surficial sediments and recharge into the hydrothermal system. The small volume of intracaldera travertine does not support a massive postglacial surge of CO2 within the Yellowstone caldera, nor was magmatic CO2 the catalyst for postglacial travertine deposition.
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Paleothermometry of an enigmatic travertine deposit: Cottonwood Travertine, Stillwater Range, NV
ABSTRACT Hot and cold spring travertine deposits record integrated histories reflecting changing hydrologic conditions, informing our understanding of the driving forces behind factors impacting local hydrology. We present results from a geologic and geochemical investigation of Cottonwood Travertine, located in Dixie Valley, NV, where it is unclear if the paleospring system that deposited the travertine was driven by deeply sourced hydrothermal fluids, or high fluid flow driven by wetter paleoclimate conditions. The temperature of the spring water that precipitated the Cottonwood Travertine has implications for the relative importance of hydrothermal versus climatic processes influencing the formation and cessation of this enigmatic deposit. We identified four groups of samples based on geologic setting, sample textures, and stable and clumped isotopic analysis: 1) calcite cemented upper gravels, 2) a mound area at the upper bench of the deposit, 3) samples from the flanks and from vuggy veins and fault zone cements from the base of the deposit, and 4) fibrous sub-travertine veins. The calcite-cemented gravels yielded δ18OC values as low as -18.4‰ (VPDB) and apparent TΔ47 of 52°C. The top mound of the deposit returned calcite δ18OC values between -12.8‰ and -11.7‰ (VPDB) and clumped isotope temperatures (TD47) of 24 – 32°C. Higher d13C and d18Oc values at the mound site are interpreted to reflect off gassing of CO2 and disequilibrium conditions. δ18OC and TD47 values from the slopes and base of the deposit are between -15.9‰ and -14.5‰ (VPDB) and around 20°C, respectively. Structurally, texturally, and isotopically (δ18OC = -29.4‰ (VPDB); TΔ47 = 93°C), the fibrous sub-travertine veins are more consistent with the local Jurassic host rock and probably do not reflect recent hot spring conditions. Our analysis suggests that, despite the impressive volume, Cottonwood Travertine formed from springs that were not particularly hot, and the deposit instead reflects vigorous warm spring activity in a wetter climactic regime rather than fluid flow from an extinct higher temperature hydrothermal system.
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- Award ID(s):
- 2040716
- PAR ID:
- 10400574
- Date Published:
- Journal Name:
- Proceedings 48th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California.
- Page Range / eLocation ID:
- SGP-TR-224
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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