Kinematic evolution of a regional-scale gravity-driven deepwater fold-and-thrust belt: The Lamu Basin case-history (East Africa)

Abstract. Foreland fold-and-thrust belts (FTBs) record long-lived tectono-sedimentary activity, from passive margin sedimentation, flexuring, and further evolution into wedge accretion ahead of an advancing orogen. Therefore, dating fault activity is fundamental for plate movement reconstruction, resource exploration, and earthquake hazard assessment. Here, we report U–Pb ages of syn-tectonic calcite mineralizations from four thrusts and three tear faults sampled at the regional scale across the Jura fold-and-thrust belt in the northwestern Alpine foreland (eastern France). Three regional tectonic phases are recognized in the middle Eocene–Pliocene interval: (1) pre-orogenic faulting at 48.4±1.5 and 44.7±2.6 Ma associated with the far-field effect of the Alpine or Pyrenean compression, (2) syn-orogenic thrusting at 11.4±1.1, 10.6±0.5, 9.7±1.4, 9.6±0.3, and 7.5±1.1 Ma associated with the formation of the Jura fold-and-thrust belt with possible in-sequence thrust propagation, and (3) syn-orogenic tear faulting at 10.5±0.4, 9.1±6.5, 5.7±4.7, and at 4.8±1.7 Ma including the reactivation of a pre-orogenic fault at 3.9±2.9 Ma. Previously unknown faulting events at 48.4±1.5 and 44.7±2.6 Ma predate the reported late Eocene age for tectonic activity onset in the Alpine foreland by ∼10 Myr. In addition, we date the previously inferred reactivation of pre-orogenic strike-slip faults as tear faults during Jura imbrication. The U–Pb ages document a minimal time frame for the evolution of the Jura FTB wedge by possible in-sequence thrust imbrication above the low-friction basal decollement consisting of evaporites.

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Controls on the evolution of passive-margin salt basins: Structure and evolution of the Salina del Bravo region, northeastern Mexico

Geological Society of America Bulletin ◽

10.1130/b35283.1 ◽

2019 ◽

Vol 132 (5-6) ◽

pp. 997-1012 ◽

Cited By ~ 3

Author(s):

Michael R. Hudec ◽

Tim P. Dooley ◽

Frank J. Peel ◽

Juan I. Soto

Keyword(s):

Seismic Data ◽

Passive Margin ◽

Salt Tectonics ◽

Structural Systems ◽

Thrust Belt ◽

Entire Region ◽

Fold And Thrust Belt ◽

Gravity Driven ◽

Northeastern Mexico ◽

Uplift History

Abstract Passive-margin salt basins tend to be much more deformed than their nonsalt equivalents, but they are by no means all the same. We used seismic data to study the Salina del Bravo region, northeast Mexico, to investigate the ways in which margin configuration and postsalt uplift history can influence passive-margin salt tectonics. The Salina del Bravo area contains four main structural systems, all of which trend NNE across the entire region. These structures are the Bravo trough, Sigsbee salt canopy, Perdido fold-and-thrust belt, and BAHA high. Gravity-driven deformation did not begin until more than 130 m.y. after salt deposition, because of buttressing against the BAHA high. We suggest that deformation was ultimately triggered in the Cenozoic by Cordilleran uplift that tilted the margin seaward and created a major sediment source terrane. Sediments shed from the uplift expelled salt seaward to form the Sigsbee canopy. At the same time, tilted and loaded sediments were translated seaward on the Louann salt until they were buttressed against the BAHA high, forming the Perdido fold-and-thrust belt. A physical model was built to test this hypothesis. The model was able to reproduce most of the major structures in the region, suggesting that the hypothesis is reasonable. The Salina del Bravo region shows how a downdip buttress can inhibit gravity-driven salt deformation in passive-margin salt basins. Furthermore, the area also shows the importance of postsalt uplift, which can destabilize a margin through a combination of tilting and sedimentation.

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Structure of the Gare Kakheti foothills using seismic reflection profiles: implications for kinematic evolution of the Georgian part of Kura foreland fold-and-thrust belt

10.5194/egusphere-egu2020-2564 ◽

2020 ◽

Author(s):

Alexander Razmadze

Keyword(s):

Cross Sections ◽

Seismic Reflection ◽

Structural Evolution ◽

Foreland Basin ◽

Thrust Belt ◽

Fault Propagation ◽

Seismic Reflection Data ◽

Growth Strata ◽

Kinematic Evolution ◽

Fold And Thrust Belt

Gare Kakheti foothills are located between Lesser Caucasus and Kakheti Ridge and are mainly represented by the series of NEN dipping thrust faults, most of which are associated with fault&#8208;related folds. Gare Kakheti foothills as a part of the Kura foreland fold-and-thrust belt developed formerly as a foreland basin (Oligocene-Lower Miocene) (e.g. Alania et al., 2017). Neogene shallow marine and continental sediments in the Gare Kakheti foothills keep the record on the stratigraphy and structural evolution of the study area during the compressive deformation. Interpreted seismic profiles and structural cross-sections across the Udabno, Tsitsmatiani, and Berebisseri synclines show that they are thrust-top basins. Seismic reflection data reveal the presence of growth fault-propagation folds and some structural wedges (or duplex). The evolution of the Udabno, Tsitsmatiani, and Berebisseri basins is compared with simple models of thrust-top basins whose development is controlled by the kinematics of competing for growth anticlines. Growth anticlines are mainly represented by fault-propagation folds. The geometry of growth strata in associated footwall synclines and the sedimentary infill of thrust-top basins provide information on the thrusting activity in terms of location, geometry, and age. This work was supported by Shota Rustaveli National Science Foundation (SRNSF - #PHDF-19-268).&#160;

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