Jurassic biostratigraphy and paleoenvironmental evolution of the ...

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36 J.E. Caracuel et al. / Geobios 39 (2006) 25–42 Fig. 5. Lower and Middle Jurassic ammonites from Sierra Espuña. All the specimens are figured at natural size except for A (× 0.7). A. Phymatoceras (Furloceras) chelussi (Parisch and Viale), MC.180.8, Middle Toarcian, Gradata Zone, Morrón Chico section 1.8 m. B. G. speciosum (Janensch), MC.1000.1, Upper Toarcian, Reynesi Zone, Morrón Chico section 10 m. C. Hecticoceras (Chanasia) bannense Elmi, MI.251.1, Lower Callovian, Gracilis Zone, Malvariche
Taramelliceras (Ta.) cf. trachinotum (Oppel) (Fig. 6E), Ta. (Ta.) sp., Glochiceras (Lingulaticeras) gr.crenosum (Quenstedt), Pseudowaagenia aff. micropla (Oppel), Ataxioceras (Schneidia?) sp., and Ataxioceras sp., along with abundant Sowerbyceras silenum (Fontannes), which dated the uppermost Platynota or the Strombecki Zone. The remainder Lower Kimmeridgian (Strombecki or Divisum Zone) was recorded 2.6 m above, with the record of Nebrodites (Nebrodites)gr.hospes (Neumayr), Ne.(Ne.) sp., Ta. (Ta.) subcallicerum (Gemmellaro) (Fig. 6D), Ta.(Ta.) cf. pseudoflexuosum (Favre), Ta.(Ta.) sp., and Streblites sp. (Fig. 6). In the last 6 m appeared scarce and badly preserved Ta. (Ta.)gr.pugile (Neumayr), Discosphinctoides (Di.) aff. capillaceous (Dumortier) with Ho. mediterraneum (Neumayr) and So. silenum (Fontannes), which belong to the Divisum Zone. The Upper Kimmeridgian was recognized in the top of four nodular-breccioids levels at 260 m in the Malvariche section (Figs. 2 and 6). Ammonites were badly preserved as reworked inner moulds with common fragmentation, imbrication and generalized disarticulation of body chambers and phragmocones along the septa. The recorded assemblage is dominated (more than 80%) by Phylloceratina [mainly So. loryi (Munier-Chalmas) morphs loryi and pseudosilenum, and few Ho. polyholcum (Benecke)]. The four horizons studied were attributed to the Beckeri Zone, with a similar ammonite assemblage composed, as more relevant, of Hybonoticeras (Hy.) beckeri beckeri (Neumayr) (Fig. 6H), Hy. (Hy.) beckeri harpephorum (Neumayr) (Fig. 6G), Hy. (Hy.) gr. beckeri (Neumayr), Ta. (Ta.) pugile pugile (Neumayr), Ta.(Ta.) gr. pugile (Neumayr), Glochiceras (Lingulaticeras) sp., Shaireria cf. episa (Oppel), Aspidoceras cf. sesquinodosum (Fontannes), Torquatisphinctes cf. laxus Olóriz, Biplisphinctes cf. uracensis Berckhemer and Discosphinctoides (Discosphinctoides) sp. (Fig. 6) No Tithonian ammonites were recorded in the Malvariche or in the Prat Mayor section. Thus, the Upper Tithonian was evidenced by the FAD of hyaline calpionellids, and the record of the Crassicollaria Zone, at 295 m in the Malvariche and 285 m in the Prat Mayor sections (Fig. 2). Finally, the Tithonian/Berriasian boundary was approached by the bloom of large and isometric C. alpina (Calpionella Zone) at 330 m in the Malvariche and 305 m in Prat Mayor sections. 6. Paleoenvironmental interpretation The evolution of the Jurassic from the Malaguide at Sierra Espuña is comparable to other sectors of the Tethyan paleo- J.E. Caracuel et al. / Geobios 39 (2006) 25–42 margins belonging to Internal and External Zones: the Subbetic (S Spain, Vera, 1988), the Venetian Alps (N Italy, Zempolich, 1993), the Apennines (Central Italy, Colacicchi et al., 1999), the Trapanese, (W Sicily, Catalano et al., 2002)orthe Ghomarids (N Africa, Maate, 1996). During the Jurassic it evolves as a passive margin, beginning with the pre-rifting stage, followed by the platform break-up of the rifting stage (starting from the Domerian, Lavinianum Zone), and finally the drifting stage (from the Lower Callovian, Gracilis Zone). As shown in Fig. 7, over the earliest Liassic dolostones, the outcropping pre-Domerian deposits are built up by oo-oncolitic limestones, sometimes breccioids, evolving upwards to crinoidal limestones. These are interpreted as restricted inner-shelf deposits of oolitic shoals, nearby algal and/or crinoidal meadows. Accordingly, the recorded faunas are solely abundant and well-diversified shallow-water benthos such as algae, crinoids, sponges, gastropods, bivalves (pectinids, ostreids and Lithiotis), brachiopods, solitary corals, echinoderms, and benthic foraminifers, among others. These benthic faunal assemblages are dominated by suspension feeders, with little resedimentation processes, even lying in living position (Lithiotis, corals). In such a context, the recorded upwardly thickening and coarsening parasequences (more developed in the Malvariche section; Fig. 3) may be interpreted as upwardly shallowing cycles. Above, the Domerian-Toarcian guide interval of alternating yellowish marly/silty limestones (slightly nodular) with ferruginous oolites and oncoids, records the beginning of the rifting stage with the break-up of the platform (drowning unconformity). This event is linked to a tectonic pulse (active listric faulting and tilting blocks), evidenced by the variable thicknesses and lithofacies among sections (Fig. 3) and the presence of neptunian dykes (e.g. Morrón Chico section, Fig. 3). The restricted inner platform, where the underlying oolitic limestones developed, may drown at relatively shallow depth, leading to drastic reduction of carbonate productivity with changes in current circulations and water chemistry, probably with contribution of upwelling of eutrophic water, rich in Fe–Mn oxi-hydroxides (influx of trophic resources and plankton coming from the open sea into the platform). Thus, the faunal assemblages are alternatively dominated by benthos of low diversity (mainly brachiopods, echinoderms, bivalves), and, for the first time, pelagic assemblages; stunted ammonites and belemnites of low diversity, with intense reworking, sometimes wrapped by ferruginous centimetric-decimetric oncoids. The interpreted depositional environment may be an open shelf, with variable depth, water chemistry and hydrodynamics, due to the intricate bottom topography (block faulting section 251 m. D. Rehmannia (Rehmannia) freii (Jeannet) sensu Cariou (1980), MI.251.3, Lower Callovian, Gracilis Zone, Malvariche section 251 m. E. M. gracilis (Spath), MI.251.2, Lower Callovian, Gracilis Zone, Malvariche section 251 m. Fig. 5. Ammonites du Jurassique inférieur et moyen de la Sierra Espuña. Tous les spécimens sont représentés à grandeur naturelle sauf A (× 0.7). A. Phymatoceras (Furloceras) chelussi (Parisch et Viale), MC.180.8, Toarcien moyen, Zone à Gradata, section de Morrón Chico 1,8 m. B. G. speciosum (Janensch), MC.1000.1, Toarcien supérieur, Zone à Reynesi, section de Morrón Chico 10 m. C. Hecticoceras (Chanasia) bannense Elmi, MI.251.1, Callovien inférieur, Zone à Gracilis, section de Malvariche 251 m. D. Rehmannia (Rehmannia) freii (Jeannet) sensu Cariou (1980), MI.251.3, Callovien inférieur, Zone à Gracilis, section de Malvariche 251 m. E. M. gracilis (Spath), MI.251.2, Callovien inférieur, Zone à Gracilis, section de Malvariche 251 m. 37
Page 1 and 2: Abstract Jurassic biostratigraphy a
Page 3 and 4: Perona Unit only outcrops Liassic s
Page 5 and 6: to Seyfried (1978); Prat Mayor, Mor
Page 7 and 8: parasequences (2-5 m thick), with s
Page 9 and 10: In the lower level of yellowish sil
Page 11: together with inner molds, sometime
Page 15 and 16: and tilting). Fig. 3 shows three te
Page 17 and 18: developed within the Middle-Upper J

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