Structural Architecture and Styles of the Zagros Fold-Thrust Belt, Kurdistan Region of Iraq

Abstract

Located along the northeastern margin of the Arabian tectonic block, the Zagros fold-thrust belt in the Kurdistan Region of Iraq includes numerous recent hydrocarbon discoveries. Geological field work, seismic interpretation, and balanced cross section construction undertaken along the length of the fold-thrust belt indicates that the region has evolved through the development of distinct, though laterally changing structural systems during south- to southwest-vergent Tertiary compressional deformation. Structural systems identified along the Zagros fold-thrust belt include: (a) large-scale, open, upright, and variably faulted anticlines that overlie detachment surfaces located within a lower Paleozoic and/or Precambrian stratigraphic section; (b) very tight, symmetric to asymmetric anticline-syncline pairs underlain by detachment surfaces located within the upper Paleozoic and/or Mesozoic stratigraphic section and that have developed as either fault propagation or faulted detachment folds; (c) faulted fold-trains that have developed as either emergent structural systems or as structural duplexes that involve the Mesozoic and Tertiary stratigraphic sections; (d) paired fore-thrust and back-thrust systems that have developed at multiple scales and at multiple stratigraphic levels within the fold-belt; (e) passive-roof duplexes generally located along or near the Zagros “mountain front”; and (f) stacked fold-fault systems that have developed through and/or resulted in structural interference and overlap. Along individual fold-fault systems internal deformation within a given stratigraphic unit may be intense, and may include the development of intra-formational duplexes. The construction of balanced structural cross sections across the Zagros fold-thrust belt is critical to understanding: (a) the overall structural architecture of the region, (b) local and regional structural styles within the fold-thrust belt; (c) variations in structural styles along and across the fold-thrust belt; and (c) the structural evolution of both the fold-thrust belt and individual structural systems within the region. In addition, understanding variations in structural styles along and across the fold-thrust belt, and within different stratigraphic packages of the Zagros, is critical to understanding the development of structural hydrocarbon traps.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016