Abstract An integrated high-resolution biostratigraphic study was conducted using calcareous nannofossils, planktonic and benthic foraminifers, and palynomorphs from two wells in the western Gulf of Mexico. Sediments range in age from early Pleistocene to middle Miocene. The early Pleistocene is represented by nannoflora of biozone NN19 and microfauna from the Globorotalia truncatulinoides truncatulinoides biozones and by the dinocyst species Spiniferites delicatus , Spiniferites membranaceous , Multispinula quanta , and Hystrichokolpoma rigaudiae . These sediments were deposited under inner to middle neritic bathy-metric conditions. The Pliocene was characterized by nannofossil biozones NN18, NN17, NN16, and NN15, and the NN14–NN12 interval; foraminifera biozones of Globorotalia miocenica , Globorotalia tosaensis tosaensis , Globorotalia margaritae , and the dinoflagellate cyst species; and Polysphaeridium zoharyi , Lingulodinium machaerophorum , Melitasphaeridium choanophorum , and Operculodinium crassum . Paleobathymetry was inner neritic-upper bathyal. Late Miocene sediments produced microfossils indicating nannofossil biozones NN11, NN10, NN9, and the Globorotalia humerosa and Globorotalia acostaensis planktonic fora-miniferal biozones. Dinoflagellate cysts found in these sediments were Spiniferites mirabilis , Dapsilidinium pastielsii , Sumatradinium hispidum , and Achomosphaera and alusiensis . These sediments were deposited under outer neritic-upper bathyal conditions. Middle Miocene strata are represented by calcareous nannofossil biozones NN9, NN8, NN6, and NN5, and by the planktonic foraminiferal biozones Globorotalia mayeri , Globigerinoides rubber , Globorotalia fohsi lobata-Globorotalia fohsi robusta , Globorotalia fohsi fohsi , and probably by the upper part of the Globorotalia fohsiperipheroronda bio-zone. These strata were deposited mainly in outer neritic-upper bathyal environments. Nannofossil diversity and abundance show notable variations throughout the two wells. A strong predominance of calcareous nannofossils and marine palynomorphs is present in outer neritic settings, and a planktonic foraminifer increase is observed mainly in the upper bathyal of well A. Continental palynomorphs are abundant in inner neritic-middle neritic settings, and a reduction is observed in the outer neritic-upper bathyal in well B.

A quantitative model is proposed for the long-term evolution of lakes and internally drained basins resulting from tectonic vertical motions, sediment infill, outlet erosion, and climatic regime. The model accounts for the formation of a water body in the topographic basin created by tectonic uplift across a river, where incision capability is calculated using a stream power-law. The model also addresses the notion that, after cessation of tectonic forcing, lakes are transitory phenomena over geological time scales. High uplift rates across an antecedent river, in combination with low upstream precipitation, result in river defeat and lake formation. In addition to geometrical, lithological, and tectonic parameters, the evaporation rate at the lake surface is revealed as a key factor triggering drainage closure (endorheism) and significant lake life extension by preventing outlet erosion. Post-tectonic lake extinction is ensured by sediment overfill and/or outlet erosion. Once uplift comes to an end and drainage reopens (lake capture), shallow lakes at high altitudes undergo a faster reintegration into the drainage network and extinction. Vertical isostatic movements of the lithosphere significantly delay this process in lakes larger than 50–200 km. The development of an internally drained basin out of an open lacustrine basin requires that uplift across the outlet persists until the lake is large enough to evaporate all collected water. The evolution of tectonic lakes has, therefore, similar dependency on geometrical constraints (initial relief, length of the river, hypsometry of the catchment), lithological parameters (rock erodibility), tectonics (uplift rate, duration, and its spatial distribution), and climate (precipitation and evaporation rates).

Abstract The deep marine Grès d'Annot Formation is one of the best exposed analogues to sand-rich turbidite sub-surface systems. Provenance and reservoir heterogeneities have been investigated through a geochemical study of different areas and facies in this formation. Most compositions may be described as mixtures between carbonate and three clastic end-members, i.e. clay, framework grains and a subset of the heavy minerals (zircon, Tioxide, apatite, monazite). These end-members have a nearly uniform chemistry over the studied area and a granite-dominated provenance consistent with a Corsica-Sardinia source hypothesis. This rather uniform provenance makes the Annot Formation a favourable case for exploring the relationships between facies and geochemistry. Not only do different facies differ in average composition, but chemical variations at the bed scale fingerprint the depositional mechanism: archetypal (graded) turbidites and traction-dominated (over-bank) deposits display contrasting variation trends in geochemical plots. The local-scale variation patterns and the general relationship between grain size and chemistry are tentatively integrated in a single differentiation model, providing a rationale for the use of geochemistry in provenance studies, and a possible way to characterize sedimentary facies.