10 Myr evolution of sedimentation rates in a deep marine to non‐marine foreland basin system: Tectonic and sedimentary controls (Eocene,Tremp–Jaca Basin,Southern Pyrenees,NE Spain)

The propagation of the deformation front in foreland systems is typically accompanied by the incorporation of parts of the basin into wedge‐top piggy‐back basins, this process is likely producing considerable changes to sedimentation rates (SR). Here we investigate the spatial‐temporal evolution of SR for the Tremp–Jaca Basin in the Southern Pyrenees during its evolution from a wedge‐top, foreredeep, forebulge configuration to a wedge‐top stage. SR were controlled by a series of tectonic structures that influenced subsidence distribution and modified the sediment dispersal patterns. We compare the decompacted SR calculated from 12 magnetostratigraphic sections located throughout the Tremp–Jaca Basin represent the full range of depositional environment and times. While the derived long‐term SR range between 9.0 and 84.5 cm/kyr, compiled data at the scale of magnetozones (0.1–2.5 Myr) yield SR that range from 3.0 to 170 cm/kyr. From this analysis, three main types of depocenter are recognized: a regional depocenter in the foredeep depozone; depocenters related to both regional subsidence and salt tectonics in the wedge‐top depozone; and a depocenter related to clastic shelf building showing transgressive and regressive trends with graded and non‐graded episodes. From the evolution of SR we distinguish two stages. The Lutetian Stage (from 49.1–41.2 Ma) portrays a compartmentalized basin characterized by variable SR in dominantly underfilled accommodation areas. The markedly different advance of the deformation front between the Central and Western Pyrenees resulted in a complex distribution of the foreland depozones during this stage. The Bartonian–Priabonian Stage (41.2–36.9 Ma) represents the integration of the whole basin into the wedge‐top, showing a generalized reduction of SR in a mostly overfilled relatively uniform basin. The stacking of basement units in the hinterland during the whole period produced unusually high SR in the wedge‐top depozone.     

Relationships between tectonic activity and sedimentary source-to-sink system parameters in a lacustrine rift basin: A quantitative case study of the Huanghekou Depression (Bohai Bay Basin,E China)

Lacustrine rift basins commonly preserve a fairly complete record of the sediment source-to-sink (S2S) system, and consequently may form an ideal natural laboratory for establishing quantitative relationships between the various elements within the S2S system. The tectonic-activity rate in the source (e.g., fault-growth rate and fault-activity rate), accommodation space and depositional system in the sink (e.g., areal extent and volume, as well as the depositional dip of the fan- and braid-deltas) are genetically related and their quantitative correlations are explored. The Palaeogene succession on the southwestern margin of the Huanghekou Depressionin the Bohai Bay Basin, one of the largest lacustrine rift basins in eastern China, was chosen to study these relationships, using 3-D seismic, core and well-log data. The tectonic activity was strongly related to the sediment supply, accommodation space and morphology of the sink area. Three different rates of tectonic activity are identified; these led to changes in the basic features of the S2S system that influenced each other. In Members 4 and 3 (lower unit) of the Shahejie Fm. (40.44–44.7 Ma), strong tectonic activity led to significant uplift, resulting in the widest exposure of the provenance area to erosion, to a high sediment-supply rate, to a steep slope and to a large accommodation space which controlled the development of several fan-deltas with steep progradational angles. In Member 3 (upper unit) of Shahejie Fm. (37.89–40.44 Ma) and Member 3 of Dongying Fm. (30.2–33.28 Ma), decreased tectonic activity led to slower uplifting, resulting in a wider alluvial plain, longer transport distances, a lower sediment-supply rate and less accommodation space, so that braid-deltas with larger volumes and a gentler slope developed; In Members 1 and 2 of Shahejie Fm. (33.28–37.89 Ma) and Member 2 of Dongying Fm. (26.71–30.2 Ma), still further decreasing tectonic activity led to a still lower sediment-supply rate, a more gentle depositional slope, less accommodation space, and the development of several braid-deltas with a gentle angle. The quantitative relationships established here advance our understanding of the relationships within lacustrine source-to-sink systems, especially for tectonically controlled rift basins.     

The synrift phase of the early Domeyko Basin (Triassic,northern Chile): Sedimentary,volcanic, and tectonic interplay in the evolution of an ancient subduction‐related rift basin

The geodynamic setting along the SW Gondwana margin during its early breakup (Triassic) remains poorly understood. Recent models calling for an uninterrupted subduction since Late Palaeozoic only slightly consider the geotectonic significance of coeval basins. The Domeyko Basin initiated as a rift basin during the Triassic being filled by sedimentary and volcanic deposits. Stratigraphic, sedimentological, and geochronological analyses are presented in order to determine the tectonostratigraphic evolution of this basin and to propose a tectonic model suitable for other SW Gondwana‐margin rift basins. The Domeyko Basin recorded two synrift stages. The Synrift I (~240–225 Ma) initiated the Sierra Exploradora sub‐basin, whereas the Synrift II (~217–200 Ma) reactivated this sub‐basin and originated small depocentres grouped in the Sierra de Varas sub‐basin. During the rift evolution, the sedimentary systems developed were largely controlled by the interplay between tectonics and volcanism through the accommodation/sediment supply ratio (A/S). High‐volcaniclastic depocentres record a net dominance of the syn‐eruptive period lacking rift‐climax sequences, whereas low‐volcaniclastic depocentres of the Sierra de Varas sub‐basin developed a complete rift cycle during the Synrift II stage. The architecture of the Domeyko Basin suggests a transtensional kinematic where N‐S master faults interacted with ~NW‐SE basement structures producing highly asymmetric releasing bends. We suggest that the early Domeyko Basin was a continental subduction‐related rift basin likely developed under an oblique convergence in a back‐arc setting. Subduction would have acted as a primary driving mechanism for the extension along the Gondwanan margin, unlike inland rift basins. Slab‐induced dynamic can strongly influence the tectonostratigraphic evolution of subduction‐related rift basins through controls in the localization and style of magmatism and faulting, settling the interplay between tectonics, volcanism, and sedimentation during the rifting.