Volcaniclastic rocks of the Keres Group: Insights into mid-Miocene volcanism and sedimentation in the southeastern Jemez Mountains
Alexis Lavine, Gary Smith, Fraser Goff, and W. C. McIntosh

Abstract:

Volcaniclastic rocks of the Keres Group (13-6 Ma; Gardner et al., 1986) in the southeastern Jemez Mountains consist of autoclastic flow breccias, pyroclastic-flow deposits, and debris-flow, hyperconcentratedflow, and streamflow deposits that were deposited primarily between 11 and 9 Ma. Volcaniclastic sediments are interbedded with pyroclastic-flow and fall deposits and lava flows of the Paliza Canyon Formation, and are derived primarily from basalts, andesites and dacites of the Paliza Canyon Formation. Channel orientations and thickness of volcaniclastic sediments suggest that most of the sediments were derived from the northeast. Volcaniclastic sediments near Boundary Peak are interbedded with several pyroclastic-flow deposits and andesitic lava flows indicating proximity to eruptive centers. The much thicker volcaniclastic sediments in Sanchez Canyon, to the southwest, are dominated by shallow braided stream deposits, typical of volcaniclastic aprons, and are in part the distal equivalent of deposits near Boundary Peak. The greater accumulation of volcaniclastic sediments in Sanchez Canyon also may have been accommodated by faulting. Volcaniclastic sediments in Cochiti Canyon are channeled into cone-forming andesitic flow breccias, but were largely derived from andesitic and dacitic sources to the northeast. The lack of interbedded rhyolitic pyroclastic deposits, and sparsity of rhyolite clasts in sediments suggests that there was little or no explosive rhyolitic volcanism during this time or that rhyolites were deposited elsewhere.


Citation:

  1. Lavine, Alexis; Smith, Gary; Goff, Fraser; McIntosh, W. C., 1996, Volcaniclastic rocks of the Keres Group: Insights into mid-Miocene volcanism and sedimentation in the southeastern Jemez Mountains, in: The Jemez Mountains Region, Goff, Fraser; Kues, Barry S.; Rogers, Margaret Ann; McFadden, Les D.; Gardner, Jamie N., New Mexico Geological Society, Guidebook, 47th Field Conference, pp. 211-218.

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