Large-scale vertical movements in Cenomanian to Santonian carbonate platform in Iberia: indicators of a Coniacian pre-orogenic compressive stress

Abstract

The Cenomanian to early Santonian interval is usually considered a time of postrifting tectonic quiescence around the northern margins of Iberia that preceded the onset of the Pyrenean convergence by crustal thrusting in the latest Santonian. However, plate kinematic models of the Mesozoic evolution of Iberia poorly constrain the Turonian-Santonian position of Iberia relative to Eurasia. This study reconstructs changes in the sedimentary facies and architecture of the Iberian carbonate platform throughout the Late Cretaceous and sheds new light on the geodynamic evolution of the Iberia-Eurasia relationship at that time. Sixteen outcrop sections were described and 24 sedimentary facies identified that define 5 depositional environments ranging from the basin to the continental setting. From these and previously published field data we reconstruct the evolution of the Pyrenean carbonate platform, on an east-west transect nearly 400 km long, on the basis of 11 short-term depositional sequences and 5 long-term systems tracts. In our interpretation, the Cenomanian and Turonian correspond to a postrift stage during which the European and Iberian margins, together with the deep basin between them, subside gently, as shown by accommodation rates varying from ~15 to 30 m/My in the margins and ~100 to 150 m/My in the basin. The Coniacian and early Santonian are characterized by a large-scale flexural response consisting of (1) uplift of the southern Iberian margin, with negative accommodation rates, karstified surfaces and paleosols, and (2) increasing subsidence rates in the basin and its edges (the northern Iberian margin and eastern Aquitaine platform), with accommodation rates several times greater than during the Turonian. We propose that far-field stress associated with slight northward motion of the Iberia plate led to the incipient large-scale flexural deformation in the Pyrenean domain. The late Santonian and Campanian are an early orogenic stage marked by rapid subsidence throughout the Pyrenean domain, except at its western end. We argue that the initiation of the Pyrenean convergence, usually considered to occur during the latest Santonian, occurred in the Coniacian.

The role of inheritance in forming rifts and rifted margins and building collisional orogens: a Biscay-Pyrenean perspective

“…The age and the location of convergence onset in the Biscay-Pyrenean system are poorly constrained (Mattauer and Proust, 1967;Thinon et al, 2001) but are commonly assumed to be Latest Santonian to Campanian time (anomaly 34; 84 Ma) (Andrieu et al, 2021). However, most evidence for onset of convergence is indirect.…”

Review of the syn-rift to early post-rift depositional systems of the Cretaceous Mauléon rift: sedimentary record of continental crust hyperextension and mantle denudation (Western Pyrenees)

“…The Axial Zone, representing the inverted Iberian proximal margin, is composed of Neoproterozoic to Paleozoic rocks that were highly deformed and metamorphosed late during the Variscan orogeny (Denèle et al, 2014;Cochelin et al, 2017). This basement is unconformably overlain by Upper Cretaceous shallow marine carbonates of the Calcaires des Cañons Formation (Souquet, 1967;Andrieu et al, 2021).…”

“…The Calcaires des Cañons Formation is composed of carbonate and subordinate siliciclastic rocks that are most common in its lower part (Souquet, 1967;Alhamawi, 1992;Ternet et al, 2004). The sedimentary section measured in the Aldudes unit includes the base of the formation (Saspiturry, 2019;Andrieu et al, 2021), although the lowest part of the Cenomanian deposits, consisting of limonitic limestone microbreccia, is not present there but is described nearby (Le Pochat et al, 1978). In the Aldudes section, a 15 m thick of siliciclastic siltstone to conglomerate rests unconformably on Devonian basement (Fig.…”

“…However, the toe-of-slope Saint-Etienne-de-Baïgorry breccias and the lowermost part of the Errozaté breccias, which are both supplied from the Calcaires des Cañons platform, are characterized by the presence of uppermost Albian to lower Cenomanian limestones clasts. Thus, the Calcaires des Cañons carbonate platform started to developed since the uppermost Albian as along the whole Pyrenean Axial Zone (Andrieu et al, 2021). Two hypotheses can be put forward to explain the fact that the uppermost Albian Calcaires des Cañons transgressive prism does not crop in the Western Pyrenees: (1) this sedimentary succession has been completely eroded and reworked in the toe-of-slope breccias, localized in the Lakhoura detachment hanging-wall, leaving a hiatus of latest Albian to early Cenomanian age or (2) the uppermost Albian transgressive prism is buried in the footwall of the Lakhoura thrust.…”

“…The basal siliciclastic unit is a transgressive sequence marked in its lowermost part by an erosive conglomerate that reworks the underlying substratum. Based on the limestone texture and faunal assemblages, the carbonate platform facies is interpreted as deposited in inner ramp-lagoon to shoreface depositional system (Souquet, 1967;Merle, 1974;Alhamawi, 1992;Andrieu et al, 2021).…”