The vale das fontes formation in the alcobaça area (Lusitanian basin, portugal): Organic petrology characterization and thermal maturation [A Formação de Vale das Fontes na área de Alcobaça (Bacia Lusitânica, Portugal): Caracterização petrológica e maturação térmica]

• Type: Article in International Scientific Journal
• Date: 2014

Authors

Pereira, JL (Author) Other; Goncalves, PA (Author) Other; Mendonca Filho, JG (Author) Other; Flores, D (Author) FCUP

Journal

Title: Comunicações Geológicas

Vol. 101

Pages: 533-536

ISSN: 0873-948X

Publisher: LNEG - Laboratório Nacional de Energia e Geologia

Indexing

ISI Web of Knowledge

Scopus - 2 Citations

Other information

Authenticus ID: P-00G-53P

Abstract (EN): The Lower Jurassic of the Lusitanian Basin (Portugal) is characterized by marly-limestone sedimentary deposits, rich in organic matter (OM). This paper focuses on the study of the Vale das Fontes Formation (Pliensbachian) in the Alcobaça area. Its objectives are the petrographic characterization of the OM and evaluation of the thermal maturation based in organic petrographic analysis, such as vitrinite (%Rr) and solid bitumen reflectances and the identification of maceral groups, and organic geochemistry analyses, such as total organic carbon (TOC) and insoluble residue (IR). The petrographic analysis shows that OM belongs mostly to a type II kerogen. The mean random vitrinite reflectance ranges between 0.56-0.70 %Rr. The interpretation of solid bitumens reflectance and their optical characteristics allowed to distinguish three different families. The solid bitumen family with the lowest reflectance, which values range between 0.39-0.65 %Rr, was classified as grahamite. The solid bitumen families with reflectance values between 0.72-0.85 %Rr and 1.04-1.61%Rr were classified as impsonites. The vitrinite reflectance indicates that the OM is thermally mature. TOC values range between 0.55-2.91 wt.%, pointing out a fair to very good content of organic carbon. IR values lower than 50% confirms the presence of carbonate sediments. © 2014 LNEG ¿ Laboratório Nacional de Geologia e Energia IP.

Language: Portuguese

Type (Professor's evaluation): Scientific