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Palynology of the Toarcian–Aalenian Global Boundary Stratotype Section and Point (GSSP) at Fuentelsaz (Lower–Middle Jurassic, Iberian Range, Spain)

Barrón López, Eduardo and Ureta Gil, María Soledad and Goy Goy, Antonio and Lassaleta Coto, Luis (2010) Palynology of the Toarcian–Aalenian Global Boundary Stratotype Section and Point (GSSP) at Fuentelsaz (Lower–Middle Jurassic, Iberian Range, Spain). Review of palaeobotany and palynology, 162 . pp. 11-28. ISSN 0034-6667

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Abstract

The Fuentelsaz Section is located in the Castilian Branch of the Iberian Range (Guadalajara, Spain). Its
exceptional Lower–Middle Jurassic transition outcrops led to its designation as the Global Boundary
Stratotype Section and Point for the base of the Aalenian. The sediments of the Toarcian–Aalenian transition
at Fuentelsaz are composed of marls with interbedded limestones in rhythmic alternation. Marls are
dominant in the Toarcian and the Opalinum Zone up to the middle part of the Comptum Subzone. In the
remaining Comptum Subzone, marly materials are scarce and limestones predominate. Sedimentation at
Fuentelsaz took place over an extensive marine epeiric carbonate platform that was well connected with the
open sea. In the Fuentelsaz Section, a total of 43 palynomorph taxa were recorded: 23 spore taxa, 13 pollen
taxa, 4 acritarchs, 2 prasinophytes and 1 dinoflagellate cyst. The studied sediment samples were always
dominated by terrestrial allochthonous miospores. In general, miospore assemblages are biased due to the
transport of pollen from land or islands to the continental platform. Spheripollenites, Classopollis or indeed
both pollens numerically dominate the assemblages. Other miospores appear in low numbers. Aquatic
palynomorphs are also scarce; Micrhystridium lymensis is the most common. Five palynological assemblages
(PA) were distinguished: PA1, PA2 and PA3 are Toarcian in age, PA4 is located at the boundary between the
Toarcian and the Aalenian and PA5. This latter palynological assemblage which is lower Aalenian in age
shows a strong reduction in palynomorph diversity and preservation in the Comptum Subzone.
Palaeoecological analysis of the palynomorphs indicated the presence of calm, oligotrophic sea water. The
palaeofloral communities of gymnosperms and vascular cryptogams—which grew in subtropical arid
conditions—were poorly diversified.

Item Type:Article
Uncontrolled Keywords:Toarcian–Aalenian stratotype; Palynology; Biostratigraphy; Environmental conditions; Palaeoecology
Subjects:Sciences > Geology > Paleontology
ID Code:16616
Deposited On:03 Oct 2012 12:11
Last Modified:03 Oct 2012 12:11

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