Palaeohydrogeological control of palaeokarst macro-porosity genesis during a major sea-level lowstand: Danian of the Urbasa–Andia plateau, Navarra, North Spain

Citation

Material Information

Title:
Palaeohydrogeological control of palaeokarst macro-porosity genesis during a major sea-level lowstand: Danian of the Urbasa–Andia plateau, Navarra, North Spain
Series Title:
Sedimentary Geology
Creator:
Baceta, Juan Ignacio
Wright, V. Paul
Beavington-Penney, Simon J.
Pujalte, Victoriano
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Palaeokarst ( local )
Mixing Zone ( local )
Paleocene ( local )
Palaeocaves ( local )
Dissolution ( local )
Carbonates ( local )
Genre:
serial ( sobekcm )

Notes

Abstract:
An extensive palaeokarst porosity system, developed during a pronounced mid-Paleocene third-order lowstand of sea level, is hosted in Danian limestones of the Urbasa–Andia plateau in north Spain. These limestones were deposited on a 40–50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse-grained bioclastic accumulations. The sea-level fall that caused karstification was of approximately 80–90 m magnitude and 2.5 Ma in duration. During the exposure, a 450 m wide belt of sub-vertical margin-parallel fractures developed a few hundred metres inboard of the shelf edge. Most fractures are 90–100 m deep, average 1 m in width, and are associated with large erosional features created by collapse of the reefal margin. Inland from the fracture belt, three superimposed laterally extensive cave systems were formed over a distance of 3.5 km perpendicular to shelf edge, at depths ranging from 8–31 m below the exposure surface. The palaeocaves range from 0.3 to 2 m in height, average 1.5 m high. They show no evidence of meteoric processes and are filled with Thanetian grainstones rich in reworked Microcodium, a lithology that also occurs infilling the fractures. The caves are interpreted as due to active corrosion at the saline water–fresh-water mixing zone. Caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing-zone cave development beyond the fracture zone. Towards the platform interior, each cave system passes into a prominent horizon, averaging 1 m in thickness, of spongy porosity with crystal silt infills and red Fe-oxide coatings. The spongy horizons can be traced for 5.5 km inboard from the cave zone and occur at 10.5 m, 25 m and 32 m below the exposure surface. In the inland zone, two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m. All are analogous to Swiss-cheese mixing-zone corrosion in modern carbonate aquifers and probably owe their origins to microbially-mediated diss
Original Version:
Sedimentary Geology, Vol. 199, no. 4-Mar (2007-02-02).

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University of South Florida Library
Holding Location:
University of South Florida
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This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.

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Karst Information Portal

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