The depositional sequences in the Lusitanian Basin during the Early Cretaceous

1994 ◽  
Vol 21 (3) ◽  
pp. 155-157
Author(s):  
Jacques Rey
2018 ◽  
Vol 74 (3-4) ◽  
pp. 317-326 ◽  
Author(s):  
Mário Miguel Mendes ◽  
Mário Pedro Dinis ◽  
Jiří Kvaček

Several mesofossil floras discovered in the Early Cretaceous rocks from the Lusitanian Basin of western Portugal comprise numerous well-preserved conifer remains. Here we report the occurrence of four conifer types in the mesofossil flora from the Catefi ca locality, about 4 km south of Torres Vedras in the Estremadura region on the western Portuguese Basin. The specimens were recovered from rocks belonging to the Almargem Formation, interpreted to be of late Aptian - early Albian age. It includes three Cheirolepidiaceae genera Frenelopsis SCHENK, Pseudofrenelopsis NATH. and Watsoniocladus V.SRINIV., and one conifer twig of Pagiophyllum-type. These conifers, which co-occurred in the same depositional bed with a well-diversified early angiosperm assemblage including flowers, seeds, fruits and dispersed stamens with pollen in situ, provide new insights into Early Cretaceous palaeoecology.


Author(s):  
Alireza Asadi ◽  
Hossain Rahimpour-Bonab ◽  
Mohsen Aleali ◽  
Mehran Arian

AbstractIn this study, our attempt is to integrate sedimentological and petrophysical data for reservoir evaluation in the sequence stratigraphic framework. Petrographic analysis of the Late Jurassic–Early Cretaceous Fahliyan Formation reservoirs of two oilfields in the northwest of the Persian Gulf led to recognition of twelve microfacies. They can be classified into four facies associations, including open marine, shoal, lagoon and tidal flat, which are deposited in a homoclinal ramp carbonate. Sequence stratigraphy of the studied successions led to the recognition of three third-order depositional sequences based on vertical changes in microfacies and gamma ray analysis. Except for the upper boundary of the third sequence, the other sequence boundaries are type I (SBT.1). Dissolution is the most important diagenetic feature that affected the lower depositional sequence which is caused by the development of subaerial exposure after the deposition of the Fahliyan Formation, whereas cementation is the main diagenetic feature affecting the second- and third depositional sequences, causing their lower reservoir quality. In order to identify the flow units, the flow zone index methods, porosity throat radius (R35) and modified Lorenz based on stratigraphy were applied. The key wells studied in this area have shown good correlation throughout the studied oilfields which may potentially be used for hydrocarbon exploration and field development in the Late Jurassic–Early Cretaceous deposits of the Persian Gulf. This study integrates geological and petrophysical data (rock typing) toward sequence stratigraphic framework.


Clay Minerals ◽  
1995 ◽  
Vol 30 (2) ◽  
pp. 119-133 ◽  
Author(s):  
J. F. Barrenechea ◽  
M. Rodas ◽  
J. R. Mas

AbstractThe clay mineral distribution in the Early Cretaceous depositional sequences along the Cameros Basin has been established on the basis of XRD traces and TEM/EDAX analyses. Samples from the Latest Berriasian-Barremian depositional sequences are characteristic of epimetamorphic conditions. Illite ‘crystallinities’ are broader than expected (0.35–0.490°Δ2θ), due to the consistent presence of K-mica-paragonite mixed-layer and discrete paragonite associated with the illite 10 Å peak. The Late Barremian-Early Aptian depositional sequence, around the depocentral sector of the basin, represents a sudden change to anchimetamorphic conditions, marked by the presence of pyrophyllite and rectorite and by a significant decrease in the A1IV content of the chlorites. Towards the northwestern border of the basin, this sequence was affected by deep diagenetic conditions, as deduced from the clay mineral association and the ‘crystallinity’ values (0.57°Δ2θ). The changes in the clay mineral assemblages and ‘crystallinity’ data can hardly be explained in terms of the varying burial depth and are related to changes in the circulation of fluids associated with varying facies (modal composition, grain size). Permeability is regarded as the main factor controlling the circulation of these migratory fluids.


2011 ◽  
Vol 166 (3-4) ◽  
pp. 152-162 ◽  
Author(s):  
Mário Miguel Mendes ◽  
Jorge Dinis ◽  
João Pais ◽  
Else Marie Friis

2004 ◽  
Vol 41 (10) ◽  
pp. 1259-1271 ◽  
Author(s):  
Daniela Schwarz ◽  
Regina Fechner

Lusitanisuchus mitracostatus is a small mesoeucrocodilian crocodylomorph from the Upper Jurassic (Kimmeridgian) of Guimarota–Leiria in Portugal, which was originally described as an anguimorph lizard (Lisboasaurus mitracostatus Seiffert, 1970) based on jaw fragments and isolated teeth. A recent reexamination of the crocodylomorph material of Guimarota yielded new skull and dentary remains assignable to Lusitanisuchus mitracostatus. The new skull material not only enables for the first time a skull reconstruction of this taxon, but also leads to renaming and reclassifying Lisboasaurus mitracostatus. Teeth of Lusitanisuchus are also reported from the locality Porto Dinheiro–Lourinhã, Early Cretaceous (Berriasian) of Portugal. The presence of this crocodylomorph taxon in two Portuguese localities suggests its occurence in the Lusitanian Basin during the Kimmeridgian to the Berriasian.


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