A geophysical and geological study of Laguna de Ayarza, a Guatemalan caldera lake
Journal of Volcanology and Geothermal Research
By: L.J. Poppe, C. K. Paull, C. G. Newhall, J.P. Bradbury, and J. Ziagos
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Abstract
Geologic and geophysical data from Laguna de Ayarza, a figure-8-shaped doublecaldera lake in the Guatemalan highlands, show no evidence of postcaldera eruptive tectonic activity. The bathymetry of the lake has evolved as a result of sedimentary infilling. The western caldera is steep-sided and contains a large flat-floored central basin 240 m deep. The smaller, older, eastern caldera is mostly filled by coalescing delta fans and is connected with the larger caldera by means of a deep channel. Seismicreflection data indicate that at least 170 m of flat-lying unfaulted sediments partly fill the central basin and that the strata of the pre-eruption edifice have collapsed partly along inward-dipping ring faults and partly by more chaotic collapses. These sediments have accumulated in the last 23,000 years at a minimum average sedimentation rate of 7 m/103 yr. The upper 9 m of these sediments is composed of > 50% turbidites, interbedded with laminated clayey silts containing separate diatom and ash layers. The bottom sediments have >1% organic material, an average of 4% pyrite, and abundant biogenic gas, all of which demonstrate that the bottom sediments are anoxic. Although thin (<0.5 cm) ash horizons are common, only one thick (7-16 cm) primary ash horizon could be identified in piston cores. Alterations in the mineralogy and variations in the diatom assemblage suggest magnesium-rich hydrothermal activity. ?? 1985.
Suggested Citation
Poppe, L., Paull, C.K., Newhall, C.G., Bradbury, J., Ziagos, J., 1985, A geophysical and geological study of Laguna de Ayarza, a Guatemalan caldera lake: Journal of Volcanology and Geothermal Research, v. 25, no. 1-2, p. 125-144.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | A geophysical and geological study of Laguna de Ayarza, a Guatemalan caldera lake |
| Series title | Journal of Volcanology and Geothermal Research |
| Volume | 25 |
| Issue | 1-2 |
| Year Published | 1985 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Volcanology and Geothermal Research |
| First page | 125 |
| Last page | 144 |