Jurassic biostratigraphy and paleoenvironmental evolution of the ...

26 J.E. Caracuel et al. / Geobios 39 (2006) 25–42
Cornacaldense), Algovianum (sous-zones à Ragazzoni, Bertrandi, Accuratum et Levidorsatum) et Emaciatum (sous-zones à Solare et Elisa)
dans le Domérien; les zones à Polymorphum et Serpentinum dans le Toarcien inférieur ; les Zones à Bifrons et Gradata dans le Toarcien moyen
et la Zone à Reynesi dans le Toarcien supérieur ; la partie supérieur du Bajocien inférieur et le Bajocien supérieur ; le Callovien inférieur,
Zones à Bullatus et Gracilis ; les Zones à Transversarium, Bifurcatus, Bimammatum et Planula dans l’Oxfordien moyen/supérieur et les Zones
à Platynota, Strombecki, Divisum et Beckeri dans le Kimméridgien.
L’évolution de l’environnement du Jurassique Malaguide dans la Sierra Espuña montre beaucoup d’affinités avec les autres paléomarges
de la Téthys méditerranéenne. La précision biostratigraphique et l’analyse des lithofaciès et des biofaciès nous ont permis d’interpréter la
paléomarge Malaguide comme une paléomarge passive, avec le développement d’une plate-forme carbonatée sommaire jusqu’au Domérien
(Zone à Lavinianum). Ensuite eut lieu la fracturation de cette plate-forme (Domérien inférieur, Zone à Levinianum-Toarcien supérieur, Zone
à Reynesi) liée au commencement de la phase de « rifting », caractérisée par le développement d’un système de horsts et grabens et l’enfoncement
de cette région. L’extension se poursuit entre le Callovien inférieur (Zone à Gracilis) et l’Oxfordien Moyen (Zone à Transversarium), en
indiquant le début d’une phase de « drifting » qui aurait déclenché la réactivation du système de horsts et grabens, conduisant au dépôt de
calcaires nodulaires condensés dans les parties les plus élevées du fond marin.
© 2005 Elsevier SAS. All rights reserved.
Keywords: Jurassic; Ammonite biostratigraphy; Paleoenvironmental evolution; Internal Betic Zone; Malaguide Complex; Southeastern Spain
Mots clés : Jurassique ; Biostratigraphie des ammonites ; Évolution de l’environnement ; Zone Interne Bétique ; Complexe Malaguide ; Sud-Est de l’Espagne
1. Introduction
The Jurassic evolution of the Betic Cordillera took place
under distensive tectonic conditions related to Tethyan rifting.
Although, the rifting age has been considered quite similar
throughout the cordillera, controversy continues concerning
the synchronism versus diachronism for the pre-, synand
postrifting periods in the different domains into which
the Betic Cordillera has traditionally been divided: the Internal
and the External Zones.
The External Zones belong to the South Iberian Paleomargin
and consist of post-Triassic unmetamorphosed rocks.
Thus, the Jurassic paleogeographic evolution and the age of
the onset of the rifting (Carixian = Lower Pliensbachian), and
the post-rifting phase (boundary Middle/Upper Jurassic) has
been well-characterized (Vera, 1988). On the contrary, the
Internal Betic Zones belong to a microplate (Mesomediterranean
Terrain, Guerrera et al., 1993) derived from the North
African continental margin, which collided against the External
Zones during the Early Miocene. These zones are built up
by the stacking of four complexes (in order upwards): Nevadofilabride,
Alpujarride, Malaguide and “Dorsal”. The Nevadofilabride
and Alpujarride are composed mainly of Paleozoic
and Triassic (and older), metamorphic rocks, while the
Malaguide and “Dorsal” Complexes include unmetamorphosed
Paleozoic (Malaguide) and Meso-Cenozoic (Malaguide
and “Dorsal”) sedimentary rocks. In general, the scarcity
of Jurassic unmetamorphosed successions, together with the
intense tectonic activity, have hampered the dating of the main
Jurassic events in the Internal Zones.
The Malaguide is the uppermost Complex (and, consequently,
the most internal) of the Internal Zones, which outcrops
mainly from Malaga Province (westward) to Murcia
Province (eastward). In contrast to the other complexes, the
Malaguide Complex includes Jurassic sedimentary covers,
favoring the analysis of the Jurassic evolution of the Internal
Betic Zones. The Sierra Espuña area, in Murcia Province, is
probably the most extensive, and the best exposed Jurassic
outcrop belonging to the Malaguide in the Betic Cordillera.
Except for the pioneer work by Fallot (1945), the main
papers on the Jurassic of Sierra Espuña are from the 1960s
and 1970s (Peyre and Peyre, 1960; Mac Gillavry et al., 1963;
Navarro and Trigueros, 1963; Paquet, 1962, 1969; Geyer and
Hinkelbein, 1971, 1974; Kampchuur et al., 1974; Seyfried,
1978, among others). Almost no recent studies have been
made on the biostratigraphy and the paleogeographic evolution
of the Jurassic of Sierra Espuña. In the present work, we
analyze some classical Jurassic sections, together with new
sections, in order to update the biostratigraphic framework
and to approach the paleoenvironmental evolution of the
Jurassic Malaguide from Sierra Espuña. Moreover, this will
improve the knowledge of the Jurassic of the Internal Betic
Zones, in addition to providing a fuller understanding of the
External Betic Zones, and their relationships.
2. Geographical and geological setting
The Sierra Espuña area is located in Murcia Province,
accessible by road from the villages of Alhama and Totana,
from the south, and Mula from the north (Fig. 1). The Malaguide
outcropping area of Sierra Espuña bounds tectonically
with the Alpujarride Complex to the SE, and with the External
Betic Zones (Subbetic) to the NW. Laterally, the nearest
outcrop of Jurassic Malaguide in the region is located 40 km
westward, near Vélez Rubio in the Province of Almeria
(Castillón Fm., Geel, 1973).
The outcropping Malaguide Complex in Sierra Espuña is
composed of two tectonic units (Martín-Martín, 1996); Morrón
de Totana and Perona (Fig. 1). The Morrón de Totana
Unit is the footwall while the Perona Unit is the hanging wall,
which, paleogeographically came from a more proximal position
(Martín-Martín and Martín-Algarra, 1997). Both units
include a marine Jurassic sedimentary cover, although in the