Jurassic biostratigraphy and paleoenvironmental evolution of the ...

40 J.E. Caracuel et al. / Geobios 39 (2006) 25–42
Fig. 7. Synthetic Jurassic successions at Sierra Espuña, with indication of biofacies, microfacies and paleoenvironmental interpretation for the main lithofacies.
M (mudstones), W (wackestones), P (packstones), G (grainstones). Legend for bioclasts in Fig. 2.
Fig. 7. Succession synthétique du Jurassique de la Sierra Espuña, avec indication des biofaciès, microfaciès et interprétation paléoenvironnementale du lithofaciès
principal. M (mudstones), W (wackestones), P (packstones), G (grainstones). Légende des bioclastes Fig. 2.
inner moulds, mostly reworked; frequent loss of bodychambers
and truncations incompatible with the stratification.
In the nodular-brecciate facies, inner moulds of ammonites
are often fragmented and imbricate.
Finally, at the end of the Jurassic the generalized thermal
subsidence tends to deepen the paleomargin, while the huge
relief caused by the horst and graben system is smoothed.
Consequently, the area evolved to a basin in Lower Berriasian
(probably already from the uppermost Tithonian) with
deposition of periplatform limestones together with the local
sedimentation by planktonic microfossils (calpionellids, foraminifers,
radiolarians, as well as algae).
7. Conclusions
A multidisciplinary study has enabled greater precision in
updating the biostratigraphic framework and the paleoenvironmental
interpretation of the Jurassic succession at Sierra
Espuña. This area, which is one of the bigger, better exposed
and more fossiliferous Jurassic outcrops of the Malaguide
domain, can be considered a clue area to analyze the evolution
of the Internal Zones of the Betic Cordillera.
As a whole, ammonite biostratigraphic data from the Internal
Zones are scanty, and related only to the “Dorsal” and
Malaguide domain such as the Sierra Espuña area. Particularly
for this area, the previous biostratigraphic data, which
comes from the 1960s and 1970s, need to be updated and
revised. Thus, three previously studied and two new Jurassic
sections at Sierra Espuña were sampled, leading to a more
precise biostratigraphic ammonite framework. Ammonite
assemblages have enabled the recognition of the Domerian,
Lavinianum (Cornacaldense Subzone), Algovianum (Ragazzoni,
Bertrandi, Accuratum and Levidorsatum Subzones) and
Emaciatum (Solare and Elisa Subzones) Zones, the Lower
Toarcian, Polymorphum and Serpentinum Zones, the Middle
Toarcian, Bifrons and Gradata Zones, the Upper Toarcian,
Reynesi Zone, the uppermost Lower/Upper Bajocian, the
Lower Callovian (Bullatus and Gracilis Zones), the Middle
and Upper Oxfordian (Transversarium, Bifurcatus, Bimammatum
and Planula Zones) and the Lower and Upper Kimmeridgian
(Platynota, Strombecki, Divisum and Beckeri
Zones). Some of these zones and subzones are recognized, or
documented with reported faunas, for the first time.
As a whole, benthic assemblages dominated during the
Lower Jurassic, while benthonic/planktonic assemblages