Plio-Quaternary morphotectonic evolution recorded in the clastic cave sediments of Sic&#243; massif (central Portugal)
Authors: Dimuccio Luca , Cunha Lúcio , Braucher Régis , Bourlés Didier L. 
Published: June 2022

&lt;p&gt;Carbonate karst covers only approximately 5% of mainland Portugal&amp;#8217;s land surface, with the most expressive landscapes associated to Middle Jurassic units and corresponding to the Sic&amp;#243; and Estremadura massifs in the central region. Multiple and complex phases of karstification were recognized, controlled by tectonics and climate. A discontinuous Meso-Cenozoic siliciclastic cover was responsible for organizing a fluvial network, as demonstrated by a set of suspended dry/blind valleys and canyons that cut the carbonate reliefs. This fluviokarst testifies how the fluvial network tries to follow the progressive and differentiate post-Jurassic tectonic uplifts of the massifs, mainly during Plio-Quaternary.&lt;/p&gt;&lt;p&gt;Despite this scientific knowledge, the timing of karst landscape evolution over Plio-Quaternary, including the quantitative constraints on the tectonic uplifts and long-term fluviokarst incision rates, remains poorly documented. A multi-scalar approach was used to combine geomorphological regional studies (massifs and entrenched valleys level) and local analysis of siliciclastic sediments preserved in selected caves/rock-shelters. New data were produced using a combination of intersecting sedimentological, geomorphological, geochemical, and geochronological analyses of karst record (forms and deposits).&lt;/p&gt;&lt;p&gt;Several types of clastic cave sediments, such as filtrates, fluvial, aeolian and marine deposits, were identified and compared with the local post-Jurassic siliciclastic covers through facies analysis. An extensive dating program of the siliciclastic fraction, relying on the &lt;sup&gt;10&lt;/sup&gt;Be and &lt;sup&gt;26&lt;/sup&gt;Al cosmogenic nuclides, yield burial ages ranging from ~1.2 to 3.0 Ma.&lt;/p&gt;&lt;p&gt;Facies architecture of the siliciclastic sediments preserved in some small caves/rock-shelters (at an altitude of 360 m), opened on the structurally controlled western border of the Sic&amp;#243; massif, as well as on the slopes of the nearby Poio Novo fluviokarst valley, allow a genetic correlation with marine and aeolian deposits that, at an altitude of ca. 120 m, materialize a mainly Pliocene coastal plain. The obtained &lt;sup&gt;26&lt;/sup&gt;Al/&lt;sup&gt; 10&lt;/sup&gt;Be data confirm a late Pliocene/early Pleistocene chronology for these karst infilling (from 2.3 &amp;#177; 0.7 Ma to 1.5 &amp;#177; 0.3 Ma), allowing to estimate local simple linear tectonic uplifts ranging from 0.08 to 0.2 mm/yr for the lasted ~3.0 Ma, being so in agreement with the more empirical values previously admitted by Soares (2006), Cabral (1995), and Ferreira (1991).&lt;/p&gt;&lt;p&gt;Furthermore, these marine and aeolian clastic cave sediments, previously found and describes for the Sic&amp;#243; massif by Cunha (1990), were already recognized in a similar topographic position on the western edge of the Serra de Candeeiros (Daveau, 1973, 1976), permitting to consider a similar uplift history also for the Estremadura massif.&lt;/p&gt;&lt;p&gt;Finally, in addition to strengthening the knowledge on karst landscape evolution, this study highlights the potential of clastic cave sediments as data archives for understanding local/regional morphotectonics.&lt;/p&gt;