Devonian graptolites from southwestern Europe: a review with new data

Abstract

Lower Devonian graptolite faunas have been recognized in the Normandy and southeastern regions of the Armorican Massif, France; the Pyrenees and Catalonian Coastal Ranges regions and northern Minorca, Balearic Islands, Spain; the southern Hesperian Massif (Ossa Morena Zone) of the Iberian Peninsula; and from southeastern Sardinia, Italy. All but one the of the graptolite faunas collected throughout this large region are from Lochkovian age strata, representing the Monograptus uniformis, Monograptus praehercynicus, and Monograptus hercynicus biozones corresponding to the lower, middle and upper Lochkovian, respectively, and mostly represented by monospecific or low diversity assemblages. Although many individual sections contain representatives of two of the biozones, relatively few reveal all three. A single, poorly preserved faunule, collected in the Ossa Morena region of Spain from strata dated by brachiopods as Pragian–early Emsian may represent the only known graptoloid fauna of post-Lochkovian age. Almost all graptolites have been recovered from condensed successions of black shales and limestone nodules, similar to those of other proto-Tethyan (i.e. outer shelf, with dominantly pelagic faunas) regions such as Thuringia, Bohemia, the Carnic Alps and northwestern Africa. The two exceptions are an occurrence in a shallow-water, coarser clastic sequences at the Carteret locality in Normandy and in deep water turbidites on the island of Minorca. Graptolites are not known from any other thick, shallow water clastic sequences, although whether this is because of paleo environmental exclusion or simply lack of recovery to date is unknown. Other fossil evidence (e.g. chitinozoans), however, indicates continuous marine sedimentation from the Silurian to Devonian. © 1996 John Wiley & Sons, Ltd.