Middle Pleistocene seismically induced clay diapirism in an intraplate zone, western Brittany, France. Issue 1 (31st August 2018)

• Record Type: Journal Article
• Authors: van Vliet-Lanoë, Brigitte; Authemayou, Christine; Molliex, Stéphane; Field, Michael Hugh; Frechen, Manfred; Le Roy, Pascal; Perrot, Julie; Andrieu-Ponel, Valérie; Grégoire, Gwendoline; Hallégouët, Bernard
• Is Part Of: Quaternary research. Volume 91:Issue 1(2019)
• Page Start: 301
• Page End: 324
• Publication Date: 2018-08-31
• Subjects: Clay diapirism, -- Liquefaction, -- Earthquake, -- Saprolite, -- Brittany, -- Variscan structures, -- Paleoseismology, -- Intraplate, -- Middle Pleistocene; Geology, Stratigraphic -- Quaternary -- Periodicals; Glacial epoch -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; Époque glaciaire -- Périodiques; Geology, Stratigraphic; Glacial epoch; Quaternary Geologic Period; Electronic journals; Periodicals; 551.79
• DOI: 10.1017/qua.2018.63
• Languages: English
• ISSNs: 0033-5894

Abstract

Abstract: The Brittany region of France is located in a low seismicity intraplate zone. Most of the instrumented earthquakes are limited to a shallow crustal depth without surface rupture. A paleoseismological analysis was performed on deposits on the Crozon Peninsula and in the Elorn estuary. We highlight hydroplastic deformations induced by liquefaction leading to clay diapirism, which were likely triggered by past earthquakes. This diapirism seems to be frequent in continental nonconsolidated sediments and to develop on the inherited tectonic structures, when a shallow water table and confining layers exist. Timing of deformation is dated using paleoenvironmental data, and electron spin resonance and infrared-stimulated luminescence dating methods. Two seismic periods were identified in western Europe during early Marine Oxygen Isotope Stage (MIS) 10 (~380 ka) and early MIS 8 (~280–265 ka). The lack of similar deformations affecting the Holocene tidal deposits in the Bay of Brest suggests that the magnitude of the triggering paleoearthquakes is probably higher ( M w ~6) than the recent events ( M w 5.4). These unusual intraplate major paleoearthquakes need specific factors affecting the far-field crustal stress loading to be triggered, such as a brief acceleration of the Africa-Eurasia lithospheric plate convergence, glacio-isostatic stress perturbations associated with the onset of major glaciations in northern Europe, or other processes induced by orbital forcing.