Eruptive conditions and depositional processes of Narbona Pass Maar volcano, Navajo volcanic field, Navajo Nation, New Mexico (USA)

Abstract

Phreatomagmatic deposits at Narbona Pass, a mid-Tertiary maar in the Navajo volcanic field (NVF), New Mexico (USA), were characterized in order to reconstruct the evolution and dynamic conditions of the eruption. Our findings shed light on the temporal evolution of the eruption, dominant depositional mechanisms, influence of liquid water on deposit characteristics, geometry and evolution of the vent, efficiency of fragmentation, and the relative importance of magmatic and external volatiles. The basal deposits form a thick (5-20 m), massive lapilli tuff to tuff-breccia deposit. This is overlain by alternating bedded sequences of symmetrical to antidune cross-stratified tuff and lapilli tuff; and diffusely-stratified, clast-supported, reversely-graded lapilli tuffs that pinch and swell laterally. This sequence is interpreted to reflect an initial vent-clearing phase that produced concentrated pyroclastic density currents, followed by a pulsating eruption that produced multiple density currents with varying particle concentrations and flow conditions to yield the well-stratified deposits. Only minor localized soft-sediment deformation was observed, no accretionary lapilli were found, and grain accretion occurs on the lee side of dunes. This suggests that little to no liquid water existed in the density currents during deposition. Juvenile material is dominantly present as blocky fine ash and finely vesiculated fine to coarse lapilli pumice. This indicates that phreatomagmatic fragmentation was predominant, but also that the magma was volatile-rich and vesiculating at the time of eruption. This is the first study to document a significant magmatic volatile component in an NVF maar-diatreme eruption. The top of the phreatomagmatic sequence abruptly contacts the overlying minette lava flows, indicating no gradual drying-out period between the explosive and effusive phases. The lithology of the accidental clasts is consistent throughout the vertical pyroclastic stratigraphy, suggesting that the diatreme eruption did not penetrate below the base of the uppermost country rock unit, a sandstone aquifer ∼360 m thick. By comparison, other NVF diatremes several tens of kilometers away were excavated to depths of ∼1,000 m beneath the paleosurface (e.g.

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

“…The deposit wall is exceptionally steep. It does not show any obvious zonation, either in colour or structure, when observed from a certain distance, as do some maar tuff rings (e.g., the Narbona Pass Maar, Mexico in USA [19]. This absence of zonation might be due to the impact of excessive moisture on the deposits generated by the evergreen forest.…”

“…It was, therefore, not able to be accessed in its entirely, reducing the main descriptions to proximal sections, where some deposits features are displayed. Beds and layers were described, and lithofacies recorded, using a combination of grain size, bed thickness, fabric, structures, relative sorting, grading pattern, lithification, unconformities, and sedimentary features and the relative juvenile to lithic pyroclasts ratio according to [8][9][10][11][12][13][14][15][16][17][18][19], [29,38]. Determination of clasts sizes, shapes, types, and abundances were limited to qualitative appreciations.…”

“…They are, therefore, considered nowadays as one of the main volcanic landforms of monogenetic volcanic fields, especially among those areas where groundwater is abundant. However, some recent studies [19,29,30] demonstrated that maar deposits can perform complex, contrasting stratigraphy, and multiple eruptive styles, with evidence of short or prolonged inactivity periods between depositional units [6]. This implies that they exhibit longer eruption durations than expected [6], [31] and might be suggestive of polygenetic activity.…”

“…Maardiatreme volcanoes are surrounded by a low rim of bedded pyroclastic ejecta, of several metres to over 100 m high, with a radial width of 2-5 km (when measured from the centre of the maar) [4,6,7]. Recent studies following a tephrostratigraphic approach have significantly enhanced our knowledge on the evolution of the tephra ring around maar craters, with an emphasis on pyroclastic facies and depositional processes [8][9][10][11][12][13][14][15] [ [16][17][18][19][20][21][22]. Research by Houghton and Hackett [23] and Martin and Németh [24] offer insights on the identification of strombolian and phreatomagmatic eruption styles, whereas [25][26][27] discussed the explosion mechanism, and [1], [25], [28] the quantification and control of water during fragmentation.…”

A combined field and numerical approach to understanding dilute pyroclastic density current dynamics and hazard potential: Auckland Volcanic Field, New Zealand

“…The massive, poorly sorted nature of the LT1-TB1 tuff breccia suggests local (near source) transport in a highly concentrated flow, such as a remobilized debris flow (e.g., lahar). This type of deposit is common in proximal regions of maar volcanoes and often occurs as syn-eruptive debris flow filled gullies (e.g., Nemeth and Cronin, 2007;Brand et al, 2008). This lithofacies is important to note here as its proximal nature suggests that the Maungataketake eruption may have been initiated on the northwest side NOTICE: this is the author's version of a work that was accepted for publication in Journal of Volcanology and Geothermal Research.…”