Scale-dependent influence of pre-existing basement shear zones on rift faulting: a case study from NE Brazil

James Kirkpatrick, Hilario Bezerra, Zoe Shipton, Aderson do Nascimento, Stella Pytharouli, Rebecca Lunn, Aisling Soden

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Rifting of continental crust initiates faults that are commonly influenced by pre-existing structures. We document newly identified faults cutting Precambrian units in the interior of the NE Brazilian margin to assess the effects of structural inheritance on both rift geometry and fault architecture. Stratigraphic and structural data indicate that the faults were active in the main phase of rifting of Gondwana. The influence of pre-existing structures on the Mesozoic rift faulting is scale dependent. Regionally, the faults trend parallel to subvertical, crustal-scale Brasiliano (c. 750–540 Ma) shear zones. Mylonitic foliations and broadly distributed low strain in the lower crust indicated by shear-wave splitting controlled the overall orientation and kinematics of the rift faults. However, outcrop observations of the faults show that at scales up to hundreds of metres, mylonitic foliations have little influence on fault architectures. Faults cross-cut shear zones and do not commonly utilize foliation planes as shear fractures. Instead, slip zones and fractures have a range of orientations that form acute angles to the local foliation orientation. This observation explains the range of focal mechanisms associated with seismicity that coincides with ancient shear zones in intra-continental areas.
LanguageEnglish
Pages237 –247
Number of pages11
JournalJournal of the Geological Society
Volume170
Issue number2
DOIs
Publication statusPublished - Mar 2013

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shear zone
faulting
foliation
rifting
wave splitting
focal mechanism
active fault
Gondwana
lower crust
continental crust
seismicity
S-wave
Precambrian
outcrop
kinematics
geometry

Cite this

Kirkpatrick, James ; Bezerra, Hilario ; Shipton, Zoe ; do Nascimento, Aderson ; Pytharouli, Stella ; Lunn, Rebecca ; Soden, Aisling. / Scale-dependent influence of pre-existing basement shear zones on rift faulting : a case study from NE Brazil. In: Journal of the Geological Society. 2013 ; Vol. 170, No. 2. pp. 237 –247.
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Scale-dependent influence of pre-existing basement shear zones on rift faulting : a case study from NE Brazil. / Kirkpatrick, James; Bezerra, Hilario; Shipton, Zoe; do Nascimento, Aderson; Pytharouli, Stella; Lunn, Rebecca; Soden, Aisling.

In: Journal of the Geological Society, Vol. 170, No. 2, 03.2013, p. 237 –247.

Research output: Contribution to journalArticle

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