Tectono-stratigraphic evidence of salt tectonics during Jurassic extension in the Corbi&#232;res nappe, Eastern Pyrenees, France
Authors: Crémades Antoine , Ford Mary , Charreau Julien 
Published: March 2020

&lt;p&gt;&lt;strong&gt;Tectono-stratigraphic evidence of &lt;/strong&gt;&lt;strong&gt;salt tectonics&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;during&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;Jurassic&lt;/strong&gt;&lt;strong&gt; extension&lt;/strong&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;in &lt;/strong&gt;&lt;strong&gt;the Corbi&amp;#232;res &lt;/strong&gt;&lt;strong&gt;nappe&lt;/strong&gt;&lt;strong&gt;, &lt;/strong&gt;&lt;strong&gt;Eastern Pyrenees, France&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;Antoine Cr&amp;#233;mades&lt;sup&gt;1&lt;/sup&gt;, Mary Ford&lt;sup&gt;1&lt;/sup&gt;&amp;#160;et Julien Charreau&lt;sup&gt;1&lt;/sup&gt;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt;&amp;#160;CRPG, UMR 7358 CNRS, Universit&amp;#233; de Lorraine, Vandoeuvre&amp;#8208;l&amp;#232;s&amp;#8208;Nancy, France&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;In this work, we&amp;#160;investigate the tectono-stratigraphic architecture of a major transfer zone in&amp;#160;the Mesozoic Pyrenean rift system and its subsequent alpine inversion.&amp;#160;The NE-SW to NS-oriented Corbi&amp;#232;res transfert zone&amp;#160;(70km long)&amp;#160;lies between the EW-oriented Pyrenean&amp;#160;(400km long)&amp;#160;and Proven&amp;#231;al&amp;#160;(300km long)&amp;#160;segments&amp;#160;of the Pyrenean orogen. This salt-rich&amp;#160;rift transfert zone was inverted during the Pyrenean orogenesis&amp;#160;(late Santonian - Early Miocene). During the Oligo-Miocene,&amp;#160;most of the&amp;#160;transfert zone was further reactivated&amp;#160;to form the northern&amp;#160;margin&amp;#160;of the Gulf of &amp;#160;Lion rift.&amp;#160;Thus, only the lateral equivalent of the North Pyrenean Zone outcrops&amp;#160;along the western French Mediterranean coast. Unlike the the North Pyrenean Zone,&amp;#160;which is&amp;#160;a narrow fold and thrust belt,&amp;#160;this proximal part of the tranfert zone&amp;#160;was&amp;#160;previously interpreted as a large thrust sheet (the Corbi&amp;#232;res Nappe, 70km long)&amp;#160;corresponding to Mesozoic cover decoupled from Variscan&amp;#160;basement&amp;#160;along a thick level of Upper&amp;#160;Triassic&amp;#160;evaporites&amp;#160;(Keuper,&amp;#160;0m&amp;#160;to 655m) and emplaced&amp;#160;onto the Aquitaine retro-foreland basin during the Priabonian, at the end of Pyrenean orogenesis.&amp;#160;&lt;/p&gt;&lt;p&gt;Our detailed study of the&amp;#160;tectono-stratigraphic architecture&amp;#160;of the Corbi&amp;#232;res&amp;#160;Nappe demonstrates&amp;#160;for the first time the existence of major Jurassic extensional structures&amp;#160;linked to strong halokinetic activity. These structures&amp;#160;were&amp;#160;previously interpreted as compressional&amp;#160;and Pyrenean&amp;#160;in origin: (1) The Treilles Fault&amp;#160;is&amp;#160;a N110 trending,&amp;#160;shallowly&amp;#160;S-SW&amp;#160;dipping fault&amp;#160;at least 12 km long, which&amp;#160;roots&amp;#160;on Triassic evaporites. This normal fault with 2.8&amp;#160;km of displacement&amp;#160;cuts the Corbi&amp;#232;res&amp;#160;Nappe&amp;#160;into two distinct structural units. A&amp;#160;3D hangingwall&amp;#160;dip fan&amp;#160;associated with stratal thickening toward the fault demonstrates&amp;#160;that&amp;#160;this extensional fault was active during the full Jurassic and maybe during the early Cretaceous. (2) In the footwall of the Treilles Fault,&amp;#160;the Valdria NE-SW&amp;#160;trending&amp;#160;fold&amp;#160;pair&amp;#160;was previously&amp;#160;interpreted as a Pyrenean compressional fold.&amp;#160;Detailed mapping of 3D thickness and geometry variations in the Jurassic series&amp;#160;around these folds&amp;#160;reveals&amp;#160;NW verging syn-sedimentary folding during&amp;#160;the Jurassic. We&amp;#160;propose that this folding is linked to the growth of the Feuilla Keuper diapir&amp;#160;that lies&amp;#160;immediately to the south. The highlighting of these complex halokinetic and extensional structures of&amp;#160;Early Jurassic&amp;#160;to Early Cretaceous age have major implications for&amp;#160;(1) the Pyrenean and Tethysian Mesozoic extensional systems in the eastern Pyrenees and (2)&amp;#160;their impact as a major regional inheritance in later orogenic phases,&amp;#160;in particular in the evolution of the Pyrenean Corbi&amp;#232;res&amp;#160;Nappe.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;