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Detachment-controlled triangle zones in extension and inversion tectonics

Simon A. Stewart
Detachment-controlled triangle zones in extension and inversion tectonics (in Salt tectonics and interpretation, Mark G. Rowan (prefacer), Thomas E. Hearon (prefacer), Francis J. Peel (prefacer), Simon A. Stewart (prefacer), Oriol Ferrer (prefacer), J. Carl Fiduk (prefacer), Steve Holdaway (prefacer), Webster U. Mohriak (prefacer), Van Mount (prefacer), David G. Quirk (prefacer) and Tim Seeley (prefacer))
Interpretation (Tulsa) (November 2014) 2 (4): SM29-SM38


"Triangle zone" geometry is well established in thrust tectonics, where the leading edge of a frontal thrust branches backward onto a hinterland-directed roof thrust, and the triangle zone thus formed defines the thrust system's leading edge. Similar geometries occur in extension and inversion settings, where a triangle zone can form between a deep-seated master fault and a roof fault or backthrust located in a hanging-wall detachment. In basement-controlled extension, triangle zone development can occur when the shear strength of the master fault plane in the zone above a hanging-wall detachment cutoff exceeds that of a new or reactivated antithetic fault detaching on the hanging-wall dip slope. This structural style is characterized by pronounced hanging-wall synclines linked to detached extensional faults higher up the hanging-wall dip slopes. The same principles apply during early phases of inversion tectonics. The part of the master fault that is above the hanging-wall detachment cutoff may constitute a buttress that causes displacement to backthrust along any available detachment into accommodation structures such as emergent ramps. This structural style is characterized by compressional structures within the graben while there is minor or even no sign of inversion on the graben margin faults. These geometries could be accounted for by other processes, for example, localized deep-seated fault-controlled structures within graben, or salt redistribution. However, fieldwork and analog models demonstrate the admissibility of triangle zone kinematics across a range of tectonic settings in the presence of detachment layers that are thin relative to the overall stratigraphy -- typically tens to hundreds of meters in thickness. These models can guide seismic interpretation of unusual fold structures in extensional and inverted graben. Seismic interpretation examples were evaluated from the North Sea and Saudi Arabia.

ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 2
Serial Issue: 4
Title: Detachment-controlled triangle zones in extension and inversion tectonics
Title: Salt tectonics and interpretation
Author(s): Stewart, Simon A.
Author(s): Rowan, Mark G.prefacer
Author(s): Hearon, Thomas E., IVprefacer
Author(s): Peel, Francis J.prefacer
Author(s): Stewart, Simon A.prefacer
Author(s): Ferrer, Oriolprefacer
Author(s): Fiduk, J. Carlprefacer
Author(s): Holdaway, Steveprefacer
Author(s): Mohriak, Webster U.prefacer
Author(s): Mount, Vanprefacer
Author(s): Quirk, David G.prefacer
Author(s): Seeley, Timprefacer
Affiliation: Saudi Aramco, Area Exploration Department, Dhahran, Saudi Arabia
Affiliation: Rowan Consulting, Boulder, CO, United States
Pages: SM29-SM38
Published: 20141101
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 54
Accession Number: 2015-007654
Categories: Structural geologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: sects.
N17°00'00" - N32°30'00", E34°45'00" - E57°00'00"
Secondary Affiliation: ConocoPhillips, USA, United StatesNational Oceanography Centre, GBR, United KingdomSaudi Aramco, SAU, Saudi ArabiaRoyal Holloway University of London, GBR, United KingdomSchlumberger, USA, United StatesChevron, USA, United StatesUniversidade do Estado do Rio de Janeiro, BRA, BrazilAnadarko, USA, United StatesMaersk, DNK, DenmarkHess, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201504
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