Keszthelyi, Laszlo and Thordarson, Thorvaldur (2000): Rubbly pahoehoe; a previously undescribed but widespread lava type transitional between aa and pahoehoe

Leg/Site/Hole:
ODP 183
Identifier:
2003-071227
georefid

Creator:
Keszthelyi, Laszlo
University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ, United States
author

Thordarson, Thorvaldur
CSIRO Exploration and Mining, Australia
author

Identification:
Rubbly pahoehoe; a previously undescribed but widespread lava type transitional between aa and pahoehoe
2000
In: Anonymous, Geological Society of America, 2000 annual meeting
Geological Society of America (GSA), Boulder, CO, United States
32
7
394
In Hawaii, basaltic lavas can be readily divided into 2 major types: aa and pahoehoe [Macdonald, 1953]. Aa flows are defined by having angular, spinose, breccia at both the top and base of the flow and a massive interior. This massive interior typically contains angular vesicles and partially melted breccia clasts. Pahoehoe flows are characterized by piece-wise continuous surfaces that often include folds (ropes). Larger pahoehoe flows are inflated [Hon et al., 1994], producing a diagnostic three-part cross section with a vesicular flow top and dense core of roughly equal thickness and a thin vesicular base [Self et al., 1998]. The transition between the two flow types is controlled by a combination of lava viscosity and strain rate [Peterson and Tilling, 1980]. In Hawaii, transitional lava types are relatively uncommon and have been described as slab pahoehoe and spiny/sharkskin/toothpaste pahoehoe [e. g., Rowland and Walker, 1987]. However, none of these terms adequately describe a lava type found on the surfaces of many basaltic lava flows found in Iceland, the Kerguelen Plateau, the Columbia River Basalts, and elsewhere. These flows have been previously described as "brecciated", "scoriacious", and "aa". Unlike true aa flows, these flows are characterized by a flow top breccia dominated by fluidal fragments of pahoehoe lava. The base of the breccia typically grades into a coherent vesicular top. Many of these flows have dense interiors that contain partially re-melted vesicular breccia clasts. Flow base breccias are often absent. The vesicle shapes are generally distorted but sub-rounded. Details of this type of lava flow is reported from the Kerguelen Plateau as seen during ODP Leg 183 and from field work in this summer on the 1783 Laki flowfield in Iceland. We propose the name "rubbly pahoehoe" for this lava type.
English
Coverage:Geographic coordinates:
North:66.3000
West:-179.0000East: 98.0000
South:-62.0000

Igneous and metamorphic petrology; aa lava; breccia; Cenozoic; clasts; Columbia River Basalt Group; East Pacific Ocean Islands; Europe; Hawaii; Iceland; Kerguelen Plateau; lava; Leg 183; Miocene; Neogene; Ocean Drilling Program; Oceania; pahoehoe; Polynesia; strain; Tertiary; textures; United States; vesicular texture; viscosity; Western Europe;

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