Multifactorial control of sedimentation patterns in an ocean marginal basin: the Lusitanian Basin (Portugal) during the Kimmeridgian and Tithonian
The Mesozoic Lusitanian Basin developed as a part of the North Atlantic rift system. Tectonic rifting activity was rejuvenated during the Upper Jurassic, leading to intensive differentiation of facies development. Kimmeridgian and Lower Tithonian calcareous and siliciclastic sediments represent basinal and slope, shallow marine, and terrestrial environments. The lithostratigraphic arrangement of facies units is demonstrated. Sediment character, distribution and thicknesses are mainly controlled by synsedimentary faulting, with a partial overprint by uprise of salt diapirs. Eustatic sea level fluctuations, exogenic and biogenic factors resulted in additional control on facies development.
Formation and significance of black pebbles from the ota limestone (Upper Jurassic, Portugal)
Black pebbles are a characteristic facies element of the Upper Jurassic Ota carbonate bank (Portugal). They occur both scattered or concentrated in two horizons, the upper of which is very widespread and may serve as a lithostratigraphic correlation level.
Cyanophyte calcification morphotypes and depositional environments (Alenquer oncolite, upper Kimmeridgian?, Portugal)
Terrigenous red siliciclastics of Upper Kimmeridgian(?) to Portlandian age around Alenguer, Portugal, comprise a narrow level of oncoid-bearing limestones. Oncoid cortices are composed of cyanophytes which appear in different calcification morphotypes according to changing physico-chemical parameters. Recent examples reveal that in most cases each calcification morphotype is related to one single species or one defined association. Hence, the characteristic calcification patterns are mostly biologically rather than abiogenetically controlled. Oncoid shapes, sizes and arrangement, on the other hand, are mainly determined by the hydraulic parameter within the depositional environment.
Seismic and sedimentologic features of Oxfordian-Kimmeridgian syn-rift sediments on the eastern margin of the Lusitanian Basin
Following deposition of widespread middle Oxfordian lacustrine carbonates and evaporites, the Lusitanian Basin was differentiated into a number of sub-basins. The Arruda sub-basin is a half graben basin situated some 30 km north of Lisbon. It accumulated over 2.5 km of Kimmeridgian siliciclastic sediments, and is bounded to the east by the Vila Franca de Xira fault zone. Carbonate deposition persisted over horsts along the fault zone from the Oxfordian to the early Kimmeridgian, and in places to the late Kimmeridgian, and shows a pronounced west-east facies zonation, with higher energy framestones and grainstones accumulating along the exposed western margins. Seismic data indicate a major …