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Title: Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy

Abstract

The Umbria-Marche Apennines provide a new region in which the nature passive-margin extensional faulting can be studied in outcrop. In these dominantly pelagic carbonate rocks of Jurassic and Cretaceous age, horsts acted as shallow, nonvolcani seamounts, while tilted half grabens formed deeper basins. One well-exposed seamount-basin transition agrees in general with the model of listric normal faulting and tilted half grabens, but shows interesting and significant divergences when studied in detail. A small sedimentary wedge at the faulted margin of a horst-block seamount thickens unexpectedly toward the adjacent basin. This wedge developed because of local convex-upward curvature of the shallowest part of a fault which at depth must have concave-up, listric geometry. The local sedimentary wedge resulted from deposition on the hanging wall as it tilted, followed by differential compaction of younger limestones that lapped onto the gentle slope leading from the horst-block seamount toward the basin. The map pattern of listric normal faulting in the Umbria-Marche Apennines suggests that both principal strain axes were extensional, in contrast to the usual pattern of listric faults crossed by transfer faults.

Authors:
 [1]
  1. Univ. of California, Berkeley (USA)
Publication Date:
OSTI Identifier:
6213078
Resource Type:
Journal Article
Journal Name:
Geology; (USA)
Additional Journal Information:
Journal Volume: 18:5; Journal ID: ISSN 0091-7613
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ITALY; MOUNTAINS; GEOLOGIC FAULTS; CARBONATE ROCKS; CRETACEOUS PERIOD; DEFORMATION; GEOLOGIC DEPOSITS; GEOLOGIC HISTORY; GEOLOGIC STRUCTURES; JURASSIC PERIOD; LIMESTONE; SEDIMENTARY BASINS; STRAINS; TECTONICS; EUROPE; GEOLOGIC AGES; GEOLOGIC FRACTURES; MESOZOIC ERA; ROCKS; SEDIMENTARY ROCKS; WESTERN EUROPE; 580000* - Geosciences

Citation Formats

Alvarez, W. Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy. United States: N. p., 1990. Web. doi:10.1130/0091-7613(1990)018<0407:POEFIP>2.3.CO;2.
Alvarez, W. Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy. United States. https://doi.org/10.1130/0091-7613(1990)018<0407:POEFIP>2.3.CO;2
Alvarez, W. 1990. "Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy". United States. https://doi.org/10.1130/0091-7613(1990)018<0407:POEFIP>2.3.CO;2.
@article{osti_6213078,
title = {Pattern of extensional faulting in pelagic carbonates of the Unbria-Marche Apennines of central Italy},
author = {Alvarez, W},
abstractNote = {The Umbria-Marche Apennines provide a new region in which the nature passive-margin extensional faulting can be studied in outcrop. In these dominantly pelagic carbonate rocks of Jurassic and Cretaceous age, horsts acted as shallow, nonvolcani seamounts, while tilted half grabens formed deeper basins. One well-exposed seamount-basin transition agrees in general with the model of listric normal faulting and tilted half grabens, but shows interesting and significant divergences when studied in detail. A small sedimentary wedge at the faulted margin of a horst-block seamount thickens unexpectedly toward the adjacent basin. This wedge developed because of local convex-upward curvature of the shallowest part of a fault which at depth must have concave-up, listric geometry. The local sedimentary wedge resulted from deposition on the hanging wall as it tilted, followed by differential compaction of younger limestones that lapped onto the gentle slope leading from the horst-block seamount toward the basin. The map pattern of listric normal faulting in the Umbria-Marche Apennines suggests that both principal strain axes were extensional, in contrast to the usual pattern of listric faults crossed by transfer faults.},
doi = {10.1130/0091-7613(1990)018<0407:POEFIP>2.3.CO;2},
url = {https://www.osti.gov/biblio/6213078}, journal = {Geology; (USA)},
issn = {0091-7613},
number = ,
volume = 18:5,
place = {United States},
year = {Tue May 01 00:00:00 EDT 1990},
month = {Tue May 01 00:00:00 EDT 1990}
}