Upper Jurassic (Upper Oxfordian-Tithonian) palynostratigraphy from the Lusitanian Basin (Portugal)

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Abstract

Sixty-six samples for palynologic study were collected in Upper Oxfordian -Tithonian beds from the Lusitanian Basin. The scarce and the poorly preserved palynomorphs (spores, pollen and dinoflagellates, and/or acritarchs) were ascribed to morphological groups. For each sample, the relative abundance of the morphological groups was calculated. Their variation for the concerned time interval was also anlysed. A chart shows the changes in a bundance of morphological groups: a) For the Upper Oxfordian , dinoflagellates and/or acritarchs are the most representative group (about 33%). They occur at Casal da Ramada section and may be related to marine influences. Verrucati , monosulcate, bisaccate and undetermined spores and pollen show values between 10 and 16%. The groups with the lowest values (2-6%) are laevigati, cavati/zonati , reticulati and muronati; there is no occurence of foveolati, apiculati, cingulati , spores with complex ornamentation, inaperturate and circumsulcate; b) For the Kimmeridgian, the cavati/zonati group was not detected . With values between 14 and 22% there are foveolati, cingulati and inaperturate; muronati, verrucati, reticulati , spores with complex ornamentation, undetermined spores and pollen , and dinoflagellates and/or acritarchs between 4 and 9%; the remaining groups show 1 to 3% values. c) For the Tithonian, foveolati and dinoflagellates and/or acritarchs were not found; inaperturate show values close to 2%; the other morphological groups have between 4 and 11 percentages. The distribution some morphological groups suggest that the deposits may be Tithonian in age. It is shown that Lusitanispora trevisaniae (Baleal and Montejunto-Portela do Sol sections), corresponds indeed to a spore. This is the only known spore with complex ornamentation, formed by polyhedric elements. Although rare, it seems to have biostratigraphic value for the Upper Jurassic-Lower Cretaceous. It is also presented an analys is on the spores and pollen which are both bio and cronostratigraphically more interesting for the studied age span. The association Leptolepidites sp. 1, Trilobosporites spp. and bisaccate pollen may characterize the "Lourinhã Formation" (Tithonian).
Original languageEnglish
Pages (from-to)49-77
JournalMemórias da Academia das Ciências de Lisboa (Classe de Ciências)
VolumeXXXVII
Publication statusPublished - 1998
EventColóquio: Paleoambientes do Jurássico superior em Portugal. Geologia, Vegetação, Ovos & Dinossauros, Mamíferos - Lisboa, Lisboa, Portugal
Duration: 4 Jul 19974 Jul 1997

Keywords

  • esporo s
  • pólenes
  • Oxfordiano superior a Titoniano
  • Bacia Lusitânica

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