--> Abstract: Styles Associated to Igneous Intrusions in Sedimentary Rocks, by J. C. D. J. Conceicao and P. V. Zalan; #90987 (1993).

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CONCEICAO, JOAO CLAUDIO DE JESUS, Petrobras/Cenpes, Rio De Janeiro, Brazil; and * PEDRO VICTOR ZALAN, Petrobras/Braspetro, Rio de Janeiro, RJ, Brazil

ABSTRACT: Styles Associated to Igneous Intrusions in Sedimentary Rocks

The geometrical description and the understanding of the origin of the structural styles associated with igneous intrusions in sedimentary rocks is a novel facet of structural geology. Volcanism is a common feature of several types of sedimentary basins (e.g.: rifts, passive margins, intracratonic sags, fore-arc basins) and the emplacement of igneous bodies displaying all kinds of geometries within the sedimentary strata creates a discrete number of characteristic structural assemblages that are repetitive in time and space. These structures are clearly seen in seismic sections and some of them may constitute petroleum traps.

The assemblages here described are related to specific geometries of the intruding igneous body: (a) anticlines contiguous to dykes (seagull structures), (b) synclines contiguous to dykes, (c) folds and reverse/thrust faults adjacent to dykes, (d) anticlines above dyke terminations, (e) normal faults adjacent to dykes, (f) dyke jumps (horizontally and vertically), (g) domes above laccoliths, (h) domes with reverse faults above laccoliths, (i) folds and reverse/thrust faults above sills, (j) sill jumps, (k) horts above bismaliths, (l) flexures adjoining igneous wedges and apophyses, (m) flexures at the base of intrusions, (n) flexures on the top of intrusions.

Some examples of oil/gas occurrences are known to be associated with assemblages (a), (c), (d) and (g).

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.