FACIES ARCHITECTURE OF SUBAQUEOUS VOLCANISM IN THE CABO DE GATA VOLCANIC FIELD, SPAIN

Thursday, 2 February 2017: 09:15
Sovereign Room (Hobart Function and Conference Centre)
Nancy Riggs, Northern Arizona University, Flagstaff, AZ, United States, Carles Soriano Clemente, Instituto de Ciencias de la Tierra Jaume Almera, Barcelona, Spain and Guido Giordano, Università degli Studi Roma Tre, Dipartimento di Scienze, Roma, Italy
Abstract:
The Miocene Cabo de Gata (CdG) volcanic field in southeastern Spain comprises a succession of dominantly subaqueous to partially emergent andesitic and dacitic dome complexes, together with minor rhyolitic-dome rocks and possible caldera-related facies, all of which are locally interbedded with carbonate and siliciclastic sedimentary rocks. Four areas within CdG are representative of the range of subaqueous facies and processes.

The andesitic El Barronal succession illustrates dome facies. In general, domes spilled passively onto the seafloor. Feeder dikes and sills commonly have hyaloclastic margins, and in effusive facies, in-situ and clast-rotated hyaloclastite make up the transitional boundary between flow-banded lava and glass-rich volcaniclastic breccia and sandstone. Massive flow facies are commonly columnar jointed and rosette structures in some cases indicate extrusion of flow lobes. Resedimented breccia and sandstone contain dense and vesicular lava clasts as well as tube-pumice- and shard-bearing clasts and abundant fine-grained comminuted glassy lava.

Rhyolitic dome facies are well exposed at Cala Genoveses. A small dome developed a pumiceous carapace breccia that interacted with water and with finely reworked hyaloclastite to form an intricate mixture of dome, carapace, and hyaloclastic facies, in some cases with semi-peperitic margins.

Deposits at Las Negras and Cala Higuera illustrate aspects of subaqueous debris-avalanche deposits. At Las Negras, block-facies deposits include radially jointed blocks up to 6 m in diameter; clasts in mixed facies deposits are commonly jigsaw fractured. A bed of well-rounded cobbles in the lower deposit likely reflects rounding along a shoreline. The avalanche deposit at Cala Higuera is laterally associated with a dome of the same composition. Block facies include clasts commonly as large 103 m3, and most are flow banded with contraction-jointed margins, and the pattern of mega-blocks suggests hummocky topography.

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