Quaternary intraplate surface uplift and opening of the Cenozoic Madrid Basin (Central Iberia)

Abstract

The Central Range, the Iberian Chain and the Toledo Mountains in central Iberia were built during the Paleogene and Neogene alpine deformation, in response to shortening and thickening of the crust. The Cenozoic Madrid Basin in central Iberia was filled under endorheic conditions, fed by clastic sediments supplied from these mountains. This sediment influx led to the accumulation of over 3km of clastic sediments, primarily occurring during the Oligocene and early Miocene epochs. Presently, the river network, connected to the Atlantic Ocean, has carved into the sedimentary basin, resulting in an incision exceeding 200 meters. The most recent endorheic lacustrine sediments in the center of the Basin are commonly believed to have been deposited during the late Miocene (~6 Ma). Recently published dating of alluvial pediments in the northwestern part of the Basin using the cosmogenic nuclide method suggests that the basin experienced a semi-endorheic period lasting around 3 Ma (~6.4 Ma to >2.4 Ma). It is proposed that the onset of glacial/interglacial oscillations at ~3.35 Ma (M2 event) would have driven the overspilling of the closed sedimentary Basin, establishing its connection to the Atlantic River network (Karampaglidis et al., 2020). We present a new stratigraphic framework based on a new magnetostratigraphic analysis of the Plio-Quaternary deposits located in the center of the Madrid sedimentary Basin, incorporating new paleontological data and absolute U-Pb carbonate dating. Our findings indicate lacustrine endorheic conditions prevailed at least until 2.6 Ma. Moreover, on top of the lacustrine deposits, an accumulation of clastic deposits and carbonated paleosoils persisted until 1.7+-0.3 Ma. Modeling the transient incision within the Basin revealed a subsequent wave of incision propagating from the South to the North along the Central System mountains. Consequently, the onset of river incision appears to be more recent than previously acknowledged and unrelated to the onset of Quaternary climate oscillations. The long-wavelength deformation and the southward tilting of the youngest lacustrine deposits, combined with the age of the overlying paleosoils, suggest a mantle-driven surface uplift of Central Iberia during the last 1.7+-0.3 Ma. Previous studies suggested that regional surface uplift and the building of the Iberian Meseta began either at 20 Ma or after 3 Ma, depending on the methodology employed. The observed incision history in the Madrid Basin aligns with the latter estimation and even suggests a more recent age for a mantle-related surface uplift and the opening of the Cenozoic Madrid Basin.   Reference: Karampaglidis, T., Benito-Calvo, A., Rodés, A., Braucher, R., Pérez-González, A., Pares, J., Stuart, F., Di Nicola, L., and Bourles, D., 2020, Pliocene endorheic-exhoreic drainage transition of the Cenozoic Madrid Basin (Central Spain): Global and Planetary Change, v. 194, p. 103295.