Showing papers by "Maurizio Gaetani published in 2005"

Stratigraphic evidence for Cimmerian events in NW Caucasus (Russia)

Abstract: The Upper Permian and Triassic sequences of the NW Caucasus present a good record of the Cimmerian events, rather undisturbed by the subsequent Alpine deformations. Original field work with new fossil identifications, microfacies analysis, and sandstone petrography were carried out. During the late Permian, active strike-slip basins were filled by continental clastics successions. Marine ingressions during the latest Permian, led to the formation of sponge reefs and skeletal carbonate ramps. During the Triassic, several siliciclastic wedges were intercalated within the marine carbonate succession. Most important is a conglomerate body made up of serpentinite pebbles of Spathian age (early Triassic), recording the exhumation and erosion of schistose antigorite serpentinites. By the late Anisian a severe deformation affected the Peredovoy (= Fore) Range of the NW Caucasus. Lower Triassic to Anisian sediments deformed also in chevron folds were overlaid with angular unconformity by a siliciclastic, and also volcaniclastic, conglomeratic and arenitic body, up to several hundred meters thick. By the late Ladinian-earliest Carnian, marine sedimentation resumed locally, forming a carbonate ramp during part of the Norian. Towards the end of the Norian, the entire area emerged and was again mildly tilted. The subsequent post-Cimmerian transgression occurred largely during the Middle Jurassic. Consequently, the most important Cimmerian deformations appear to be of early and middle Triassic age.

Discussion on subsidence history of the north Indian continental margin, Zanskar–Ladakh Himalaya, NW India Journal, Vol. 162, 2005, pp. 135–146

Abstract: E. Garzanti, D. Sciunnach & M. Gaetani write: In their recent paper, Corfield et al . (2005) attempted a subsidence analysis of the northwestern Tethys Himalaya stratigraphic succession, and discussed specifically the implications for the obduction of a section of oceanic lithosphere (Spontang Ophiolite) on top of the Indian passive continental margin (Zanskar Shelf). The emplacement age of the Spontang Ophiolite represents a crucial problem in Himalayan geology, which has been lively debated for two decades (e.g., Searle 1986; Kelemen et al. 1988; Garzanti et al . 1987; Guillot et al . 2003). In a series of papers, Mike Searle and co-workers have long proposed and supported the idea that the Spontang Ophiolite was obducted in the Late Cretaceous, making implicit or explicit correlation with the well-studied Semail Ophiolite of Oman (e.g, Searle 1983; 1986; Pedersen et al . 2001; Corfield et al . 2001, 2005). Semail and Spontang, however, are two very different ophiolite complexes. The Semail crust has a supra-subduction geochemical signature and was generated in the mid-Cretaceous (Searle & Cox 1999). Instead, the Spontang basalts have a MORB-like signature and were generated in the mid-Jurassic (Pedersen et al . 2001), similar rather to the other Oman ophiolite exposed on Masirah Island (Gnos et al . 1997). The analogy with the Semail Ophiolite obduction, associated with Late Cretaceous nappe stacking and high-pressure metamorphism of the underthrusted Arabian margin (Searle & Cox 1999), led Searle (2001) to reject the geochronological evidence for the Eocene age of high-pressure metamorphism of Indian-margin rocks (Kaghan and Tso–Morari eclogites; Tonarini et al . 1993; De Sigoyer et al . 2000). Because of the Eocene age of the eclogites, and of the fact that the Spontang Ophiolite lies tectonically on top of Indian margin sediments as …

Early Permian (Asselian) brachiopods from Karakorum (Pakistan) and their palaeobiogeographical significance

Abstract: Early Permian (Asselian) brachiopods collected from the Gircha Formation of western Karakorum (Pakistan) are described. They include Bandoproductus girchensis sp. nov., Kiangsiella sp. indet., Trigonotreta lyonsensis Archbold and Thomas, Trigonotreta larghii sp. nov., Spirelytha petaliformis (Pavlova), Punctospirifer afghanus Termier, Termier, de Lapparent and Marin, and ?Dielasma sp. indet. and belong to the Trigonotreta lyonsensis–Punctospirifer afghanus Assemblage Biozone, the oldest so far recovered from the Permian succession of Karakorum. The faunal succession of Karakorum records a significant biotic change from the Asselian to the Sakmarian, a shift in diversity and composition that is also recorded along most of the Gondwanan margin and Peri-Gondwanan regions and that should be related to a major climatic change: the end of the Gondwanan glaciation. A palaeobiogeographical analysis has been performed by means of multivariate methods applying cluster and ordination analyses based on the Jaccard Coefficient and Simpson Index to a matrix consisting of the presence/absence of 23 brachiopod genera from seven geographical operational units from central Afghanistan to eastern Australia. The results suggest the occurrence of a single biotic province during the Asselian, the Indoralian Province, embracing all the faunal stations examined, as a consequence of the global cold phase related to the last pulse of the Gondwanan glaciation.

Middle Permian Brachiopods from Greece and their palaeobiogeographical significance: New evidence for a Gondwanan affinity of the Chios Island upper unit

Abstract: Synopsis Wordian (Middle Permian) brachiopods from the allochthonous Upper Unit of Chios (Greece) are described and used to perform a palaeobiogeographical analysis to establish the pa‐laeogeographicalaffinities of the unit. Species of the genera Stenoscisma Conrad, 1839, Cleiothyridina Buckman, 1906, Martinia McCoy, 1844 and Dielasma King, 1859 are reported for the first time from Chios and their systematic descriptions are given. In addition, the revision and discussion of the genus Kotlaia Grant, 1993 and its comparison with Orthotichia Hall & Clarke, 1892 are provided in the systematic section. A matrix of presence/absence data of Wordian (Middle Permian) brachiopod genera from Crimea, Sosio, Oman, Chios, the Salt Range and Timor was analysed using multivariate methods. Cluster analysis, principal coordinate analysis, non‐metric multidimensional scaling, minimum spanning trees and bond analyses indicate a similarity between Chios and the Gondwanan data sets of Oman and the Salt Range. However, maximum...

Magnetostratigraphy and biostratigraphy of the Late Triassic Guri Zi section, Albania: Constraint on the age of the Carnian-Norian boundary

Abstract: We present the magnetostratigraphy and conodont biostratigraphy across the Carnian-Norian boundary from a 70 m-thick limestone section located at Guri Zi in northern Albania. A total of 14 magnetozones were observed. The Carnian-Norian boundary is placed in a thin stratigraphic interval between the last occurrence of Paragondolella nodosa and the first occurrence of Epigondolella abneptis. Data from Guri Zi are in substantial agreement with already published data from Silicka Brezova in Slovakia and Pizzo Mondello in Sicily, which complessively indicate that the conodont Carnian-Norian boundary, when magnetostratigraphically traced onto the Newark astrochronological polarity time scale (APTS), has an age of ~228-227 Ma.

Palaeozoic (Silurian and Devonian) radiolarians and conodonts from chert olistoliths of the Volissos Turbidites, Chios island, Greece

Abstract: The Volissos Turbidites (also known as Chios Melange) are a thick Palaeozoic wildflysch sequence that crops out on the Greek island of Chios. It consists of chert, limestone and volcanic olistholits floating in a siliciclastic turbiditic matrix. During the Early Carboniferous (Mississippian), these turbidites were severely deformed and structurally thickened probably at the toe of an accretionary wedge. Whereas there are many studies on the fossiliferous content of the limestone olistoliths, scant attention was given to the cherts. We report here for the first time some radiolarian and conodont assemblages from the chert olistholiths (ribbon radiolarites) embedded in the siliciclastic sequence of the Volissos Turbidites. The radiolarites sampled near Kardamila and Marmaro (northeastern Chios), where the Volissos Turbidites are not affected by metamorphism, have given identifiable radiolarians and conodonts. The different samples document different ages. Some radiolarians document Silurian, possible Pridolian age, whereas the conodonts indicate a distinct Famennian (late Late Devonian). The radiolarians of other samples delineate a more general range (Devonian- ?Early Carboniferous).