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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 deep marine 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 hemicycles. 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 possibly related to the northeastward motion of Africa, and/or onset of shortening at the Iberia-Europe boundary in the central and eastern Pyrenees 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 evidence for the first time a pre-orogenic flexure at the Iberia-Europe plate boundary induced by regional plate reorganisation between Africa and Europe during the Coniacian and the early Santonian.

The Mauléon Basin, in the northwestern Pyrenean Belt, is related to Early Cretaceous rifting and mantle denudation. Here we review the evolution of depositional systems in the Mauléon Rift Basin during Albian and Cenomanian time. This review includes the lithostratigraphy, regional distribution, boundaries, age and facies sedimentology of the basin’s syn-rift formations and their members. We construct paleogeographic maps to elucidate (1) the 3D distribution of sedimentary facies and depositional systems during the Albian and Cenomanian from the Iberian proximal margin to the hyperextended domain and (2) the link between major extensional structures and sedimentation during rifting and mantle denudation. The Mauléon Rift was supplied during most of the Albian by sediments from the Iberian proximal margin. The southern margin had a steep and abrupt topographic boundary related to a northward crustal rollover along the south-dipping Saint-Palais detachment. This feature controlled the deposition of coarse-grained turbidites at the base of the margin that abruptly gave way to low-density turbidites, then deep-basin deposits in the hyperextended domain. During uppermost Albian to Early Cenomanian time, mantle denudation occurred in the eastern Mauléon Basin and the vergence of the detachment systems reversed. Minor debris-flow deposits formed at the foot of fault scarps associated with the newly formed north-dipping detachments. Elsewhere, sediment from deltaic systems to the west in the Saint-Jean-de-Luz area deposited low-density turbidites in the hyperextended domain. During the post-rift stage, the flux of coarse sediment from the detachment footwall gradually declined as deformation waned, and low-density turbidites expanded onto the hyperextended domain from the European Upper Cretaceous carbonate platform. These paleogeographic reconstructions, in addition to offering a synthetic view of the evolution of sedimentary environments during rifting, offer new insight into the post-rifting exhumation of the lower crust and mantle.