Fracture morphology and tectonics of Mikhajlovgrad Anticline, Northwest Bulgaria

Pages: 
pp. 31-42
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Department of Geology, Wichita State Unluersity, Wichita, Kansas 67208, U.S.A.
Abstract: 

Field data are used to describe fracture morphology and to determine fracture patterns in Mesozoic sediments of the Mikhajlovgrad Anticline within an Alpine-age folded belt. Tectonic stress fields are based on fracture patterns, which give orientations of the principal stress axes. The maximum principal axis was used in a vector trend analysis, showing the regional tendency of the orientation of this axis to follow dip directions. A descriptive model of fracture generation requires the existence of two stress fields, a tensile (creating joint set bc) and compressive (creating set ac and system hko), which should be repeated at least several times during tectonic evolution of the area. Fracturing is deformation in a brittle or quasibrittle medium with longitudinal cracks corresponding to the ac set. This study consisted of four phases: (1) field descriptions and measurements; (2) separation of fracture sets using stereographic projections; (3) construction of tectonic stress fields; and a (4) vector-trend analysis of principal stress axes.

VOLUME 18 (3)/June 1988

Paul-Hindemilh-Ring 4 b, D-6054 Rodgau 1 (Jügesheim), F. R. Germany
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Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Department of Geology, Wichita State Unluersity, Wichita, Kansas 67208, U.S.A.

Геологический институт Болгарской академий наук, 1113 София
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Оксфордский университет, Отдел геологии и минералогии, Oxford OX1 3PR

Выший горно-геологический институт, 1156 София
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НИИ по черной металургии, 1900 Ботунец
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Институт математики и механики, Болгарская академия наук 1113 София
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Институт математики и механики, Болгарская академия наук 1113 София
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Институт математики и механики, Болгарская академия наук 1113 София

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria