Growth faults and the record of tectonic and sedimentary signals in growth strata
Final Report Abstract
Large-scale growth faults typically occur in deltas and along sediment-rich continental margins above thick shale sequences forming half-graben shaped depocentres of 10-50 km width, and the fill of the hanging-wall growth succession may be up to 10 km thick. Deposition is rapid in individual growth-fault depocentres, and may represent only a few million years of sedimentation. Today, kilometre-scale growth faults and growth-faulted sedimentary successions have been identified in many parts of the world from 2D and 3D seismic-reflection data. Yet the sheer scale of these structures makes them difficult to identify from typically discontinuous, spatially restricted outcrops. While growth faults on the scale of several tens to a few hundreds of metres have been described, for example, from Svalbard, Utah, Ireland, Italy, France, Spain, Chile and onshore Borneo, outcrop examples that match seismic scales are rare. To obtain good exposures of such features requires that outcrops represent kilometrescale cross-sections through faulted, sediment-rich continental margin successions. Hence the margins of geologically young mountain belts where late orogenic strata have been rotated, exhumed and exposed along large, relatively simple folds, offer the best opportunity for investigating the structure and stratigraphic pattern associated with major growth faults. The project focused on a comparative surface and subsurface analysis and discussion of (1) the relative importance of the main controlling factors for syn-sedimentary faulting and syn-tectonic deposition; (2) the mechanisms that control the initiation, activity and abandonment of kilometre-scale growth-fault-bound depocentres; and (3) the predictability of lithological properties of growth successions from geophysical subsurface data lacking well or outcrop control. Research on kilometrescale growth faults exposed in the southern foreland of the Makran fold-thrust belt, SW Pakistan, for example, revealed major syn-sedimentary faults and associated growth stratigraphy on high-resolution Landsat ETM+ and SPOT satellite data, displacing kilometre-thick Miocene-Pliocene sandstone-shale units by several hundreds to a few thousands of metres. The observed counter-regional structures are of scales comparable to those of major subsurface growth faults previously only known from seismicreflection data. The satellite data show in unprecedented detail the structural and stratigraphic architecture of the growth faults and growth sequences, which can be discussed as field analogues for buried systems recorded on lower-resolution geophysical data. Remote-sensing interpretations include detailed fault-damage zone analyses, interpretations of the interaction between sedimentation and faulting with particular respect to the initiation of growth faults, and comparative analyses of the Makran outcrops with seismic subsurface examples from Nigeria and NW Borneo, which were documented and interpreted in a subsurface research-component of the project.
Publications
- (2011). Niger Delta Growth Faults and Growth Stratigraphy - The Interaction between Delta Tectonics and Sedimentation. AAPG International Conference and Exhibition, Milano, Abstracts volume, 1071935
Fazli Khani, H. & Back, S.
- (2012). Temporal and lateral variation in the development of growth faults and growth strata in the western Niger Delta, Nigeria. AAPG Bulletin, v. 96, p. 595-614
Fazli Khani, H. & Back, S.
(See online at https://doi.org/10.1306/08291111023) - (2012). The control of sedimentary loading on rollover development and accommodation creation in deltas: an example from the western Niger Delta. GSA Annual Meeting, Charlotte, North Carolina, USA
Fazli Khani, H. & Back, S.
- (2014). The influence of compaction on the development of growth faults. SDGG, v. 85, p. 302
Haake, B. & Back, S.
- (2015). The influence of differential sedimentary loading on rollover and accommodation creation in deltas. Marine and Petroleum Geology, v. 59, 136-149
Fazli Khani, H. & Back, S.
(See online at https://doi.org/10.1016/j.marpetgeo.2014.08.005) - (2015). The influence of pre-existing structure on the growth of synsedimentary normal faults in a deltaic setting, Niger Delta. Journal of Structural Geology, v. 73, 18-32
Fazli Khani, H. & Back, S.
(See online at https://doi.org/10.1016/j.jsg.2015.01.011)
