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The Late Cretaceous shallow-water depositional areas of southern Tethys were complexes of unprotected shelves occupied by foramol assemblages that produced loose, diagenetically stable bioclastic debris not involved in significant in situ cementation processes. Both storm- and wind-induced currents and waves exercised a strong control on the distribution of the shifting biogenic sediments which covered the open sea-floor, constituting large coalescing sheets of winnowed fine to coarse skeletal sands. Rudists spread over all shelf sectors, from more open and external areas to more internal ones, occupying different substrata and furnishing the bulk of the skeletal component by means of bioerosion processes. They colonised mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental parameters of the different sectors of the shelf. On the basis of detailed sedimentological, taphonomic and palaeontological data, we recognised two main rudist-rich depositional settings ('end members') in the southern Italy Senonian rudist-bearing successions. In successions pertaining to hypothesised marginal shelf sectors, characterised by high-energy regime deposits, rudist lithosomes are metric in thickness and lateral extent and lens-like in morphology.. rich in bioerosion-derived skeletal sand and silt. Rudists are highly diversified. Large elongated cylindro-conical hippuritids (mostly pertaining to the genera Hippurites and Vaccinites), thick-shelled radiolitids and plagioptychids largely dominate. Rudists clustered in life position are subordinate; they often form small bouquets. More commonly these organisms appear fallen but only barely reworked. The rudist-rich bodies laterally pass into clean bioclastic grainstone in which sedimentary structures, related to current and/or storm erosional action, are common. No evidence of significant original relief of the rudist bodies in respect of the neighbouring sediment can be recognised. The submarine erosion and/or the high-energy processes operating presumably inhibited the aggradation of the tidal sediments above the marginal ones. As a consequence the vertical facies organisation shows widespread subtidal cycles, as commonly recognised in open shelves with ramp-like morphologies. In successions pertaining to more internal and/or low-energy sectors, rudist-rich beds rhythmically alternate with finer-grained foraminiferal limestones. Small elevator radiolitids with oligospecific diversity are dominant, mostly concentrated in clumps. Rudists in growth position are abundant, although a large quantity of shells appear toppled with little reworking. They may form laterally continuous biostromal shell beds. Sedimentary structures such as cross-lamination and gradation are only occasionally present. The resulting facies are commonly arranged in peritidal/shallow subtidal cycles in which evidence of subaerial (up to pedogenic modifications on a large and small scale) and, less frequently, submarine exposure is common. Intermediate successions have been recognised, characterised by deposits of silty-sand plains, which present intercalations of graded, bioclastic, storm-related beds. Sedimentological characteristics seem to document more open conditions in which submarine erosion was intermittently prevalent. In these successions rudist species that are commonly found both in high-energy and low-energy assemblages coexist. (C) 2003 Elsevier B.V. All rights reserved.

The Upper Cretaceous limestones of the Sorrento Peninsula are primarily characterized by wackestone/packstone with benthic foraminifers, thaumatoporellaceans and Aeolisaccus sp. and by rudist floatstones. Rudists in growth position are rare; most of them appear toppled and locally oriented but not reworked. In some cases they form small bouquets no more than 30 cm thick, The successions analyzed in the Sorrento Peninsula encompass a variety of facies representative of inner shelf environments in a ramp-like depositional setting. On the basis of lithologic and sedimentologic characteristics and on a qualitative analysis of the biofacies, three major facies associations have been recognized corresponding to: (a) intertidal silty-sand flats and shallow lagoons; (b) subtidal mobile foraminiferal sand sheets; (c) subtidal rudist dwelt sand plain. In the lower part of the successions periodic (more or less prolonged) emersions (subaqueous with fresh/brackish waters or subaerial exposure) are documented. The upper part of each succession lacks any emersion evidence; submarine exposure surfaces are testified by firmground-related features. The periodic influence of high-energy regimes (some storm-related events) is documented by wave- and cross-laminations, HCS and the lack of fine: sediments. Lithofacies are arranged in depositional cycles that may correspond to individual beds. The boundaries of the depositional cycles show evidence of subaerial or submarine exposures. The nature and position of these discontinuity surfaces in the successions provide an important clue to interpretation in terms of both depositional environment and vertical evolution. The increase in thickness of the depositional cycles and the gradual change from peritidal/shallow-subtidal cycles to dominantly subtidal cycles, document an increase in the amount of accommodation space which resulted from a long-term rise in relative sea-level. A detailed study of benthic associations (micro- and macrofauna) has been carried out in order to identify accurately further signs of periodicity contained within the successions as a whole. These Upper Cretaceous limestones are abundantly fossiliferous with only a moderately diverse fauna. There are no significant differences in terms of species, the assemblages simply reflecting differences in abundance of the same species. Taphonomic studies of rudist-rich beds permit seven major shell-bed types to be distinguished. Six main foraminiferal assemblages have been detected, and the distribution and relative abundance of the species have been examined within the environments inferred through facies analysis. The taphonomic data and the foraminiferal assemblage abundance and diversity, have been compared with lithologic and sedimentologic data in order to elucidate their distribution within depositional cycles and throughout the successions. The successions show little up-section changes in lithology and in taxonomic composition of the foraminiferal assemblages, It is therefore difficult to establish a paleoenvironmental trend independent of the rudist shell concentrations, which do change up-section. We noticed an overall increase in thickness and abundance of the shell beds and a shift in types of shell concentration and in taxonomic composition. These characteristics. associated with the upward disappearance of emersion surfaces, the higher frequency of storm and/or wave intercalations, the increase in thickness of the depositional sequences and the gradual change from peritidal/shallow-subtidal cycles to dominantly subtidal cycles, document a general deepening-upward trend.More open water conditions with a depth between fairweather and storm wave-base became established as a result of relative sea-level rise and to a consequent increase in the available accommodation space. (C) 2000 Elsevier Science B.V. All rights reserved.

Senonian carbonate sediments rich in rudists are widespread throughout central-southern Italy. TheConiacian-Santonian series, analyzed in the Lattari Mountains (Sorrento Peninsula), are almost completely composed of limestones, with very subordinate dolomitic beds. On a field scale we can distinguish rudist-rich beds rhythmically alternating with finer-grained foraminiferal beds. The studied series testify to a deposition in shallow-sea environments. In the lower part of the series periodical, more or less prolonged emersions (subaqueous with fresh/brackish waters or subaerial exposure) are documented. The upper part of the series lacks emersion evidence; submarine exposure surfaces are testified by firmgrounds or hardgrounds. Wave- and cross-laminations, HCS and the lack of fine sediments document an overall deposition under influence of occasional high-energy water regimes with some storm-related events. The sedimentology and taphonomic signature of the rudist shell beds have been described in order to get a better understanding of depositional environment and the physical processes that controlled the Senonian sedimentation. Monospecific tabular beds mainly characterize the lower part of the series; more complex rudist concentrations, characterized by moderate species diversity, increase up-section. The recognized lithofacies are organized in shallowing-upward depositional cycles that show a gradual change from peritidal/shallow-subtidal cycles to dominantly subtidal cycles up-section; this change records a general deepening-upward trend as a possible result of an increase of the accommodation space provided by a relative sea-level rise, according to what is suggested for other coeval Apennine and Sardinia series.

The Cretaceous peri-Tethyan carbonate systems record alternating phases of vigourous development and rapid decay of the shallow-water carbonate factories. After reaching their maximum palaeogeographic extent during the early Bedoulian time, the carbonate factories underwent unhealt episodes in relation to well-known crisis events (OAE1). These events resulted in drowning episodes, as experienced in the northern Tethyan carbonate platforms, or in signals of water stress in the carbonate factories, evidenced by drastic changes in the floro-faunistic assemblages, as experienced in the carbonate platforms of the central-southern Tethyan belt. In interpreting the inception and decay of different carbonate depositional systems, climatic-oceanographic variations together with sea-level oscillations are commonly considered key elements. However, local tectonic controls cannot be ruled out. In attempts to discriminate among the main factors controlling the evolution of the southern Apennine mid-Cretaceous carbonate system, detailed analyses have been performed on Aptian-Albiano carbonate successions in the Matese Group (southern Apennines). Since the middle Aptian, the analysed successions suggest a scenario characterised by a complex, tectonically driven topography, replacing the previous large tropical shallow-water domain. From the Bedulian-Gargasian transition onwards, the analysed area evolved into subdomains characterised by diversified sedimentological trends. A tectonic control influenced the Gargasian evolution of the considered area with local evolution into small intraplatform basins bordered by channelised margins. Nevertheless, since the latest Bedulian onward, the studied successions register palaeoecological signals that cannot be linked exclusively with tectonic disturbance episodes because of the coeval appearance of analogous signals at a global scale, including a significant shift in the biological assemblages and an outbreak of organisms indicative of stress conditions in the water mass. The analysed Gargasian strata show impoverished biota: caprinids totally disappear, both as in situ and storm-related layer components, and hermatypic corals are drastically reduced. Muddy lithofacies prevail in intertidal metric cycles in which cyanobacterial consortia, both in the form of dense laminae and coalescent oncoids, orbitolinids and small gastropods (cerithiids) suggest restricted, nutrient-rich water. Large oncoids of Bacinella irregularis/Lithocodium aggregatus and mollusk (mostly oyster and gastropod) shell fragments significantly contribute to storm-related coarse skeletal intercalations, in which oligotrophic condition-adapted forms are reduced or absent. This pattern suggests generalised conditions of stress in the water mass and in more marginal open areas. Following the mid-Aptian unproductive episode, characterised by the flourishing of assemblages adapted to mesotrophic-eutrophic conditions, the studied southern Apennines shallow-water domain changed again, with a progressive reduction of the previous mainly aragonite-dominated chlorozoan assemblages and an increase of calcite-dominated skeletal components, including rudists with calcitic outer shell layers. Pioneer biota (e.g., cyanobacteria and polychetes) characteristically marked the first phases of recovery in the still-deteriorated shallow-water domains, rapidly evolving into more complex and differentiated assemblages. The outbreak of nerineid and acteonid gastropods seems to be related to a flourishing of cyanobacterial mats and related microphytae and also to the presence of polychetes. Moreover, the grazing activity of the nerineids favoured the flourishing of oysters and oyster-like condrodonta. Among the rudists, the persistence/radiation of rudist species adapted to a wide range of temperatures and that adopted functional strategies that allowed them to thrive in unstable, open, unsuitable sea bottoms such as Requieniidae and Monopleuridae as well as the first elevator Radiolitidae; this suggests some kind of oceanographic change (e.g., seawater chemistry and/or temperature changes). To date, the rudist ecological constraints have yet to be defined. Nevertheless, on the basis of the associated benthic floro-faunistic assemblage, we can infer the complex environmental parameters in which mesotrophic/eutrophic conditions, presumably coupled with cooler and locally oligophotic conditions, cooperatively modified carbonate factory characteristics.

Shallow-water foramol limestones have been studied from a locality in the southern Apennines in which outcrop conditions show an excellent overview of the lateral and vertical evolution of rudist bodies and allow their geometry and the dynamic aspects to be reconstructed. The lithofacies suggest open depositional settings characterized by peloidal siltymuddy sediments. Rudists inhabited well-defined sectors of these shelves, giving rise to wide biostromal bodies, and supplied most of the skeletal debris via bioerosion and minor physical breakdown. In particular, the characteristics of rudist lithosomes document the existence of a complex network of channel-like depressions. In such a depositional context, the evolution of rudist lithosomes was controlled by the environmental hydrodynamic conditions. The resulting composite rudist assemblages are characterized by often-toppled individuals, suggesting continuous sediment removal between the organisms. The good preservation of the shells and the common articulation of the valves, however, point to an absence of sustained transport but rather a slight sediment destabilization. The gross lenticular geometry of the shell beds could be related to the above-mentioned patterns of weak, perhaps channelized, pathways. In such a depositional context, rudist colonization on channel margins assumes particular importance as it documents the rudist ability to exploit a wide array of environments, comparable to that of oysters in Recent seas, and reflecting the probable opportunistic nature of rudists. In the last few decades, several studies carried out on the Upper Cretaceous rudist-bearing carbonate sequences of the central-southern Apennines and northwestern Sardinia, Italy, have shown the inadequacy of the tropical, chlorozoan model applied to the depositional environment of these sequences: a ‘temperate-type’, foramol model was suggested by Carannante & Simone (1987) and Carannante et al. (1995, 1997, 1999) based on the nature of the skeletal grains, biological assemblages, lithofacies organization, sedimentary body geometries and responses to sea-level changes. Similar characteristics have been recognized, on a very large scale, in many other Upper Cretaceous rudist-bearing limestones cropping out in the periMediterranean region (cf. Gili et al. 1995; Moro 1997; Moro et al. 2002; Stossel & Bernoulli 2000; among others). Many complex factors controlled the inception, growth and demise of the carbonate factories and the sedimentary bodies they produced were related to the interplay between eustasy and tectonics in the sedimentation basin, plus ecological factors, which determined the delicate biological balance of the primary sediment producer assemblages (see Carannante et al. 1995, 1997; James & Clarke 1997; Weissert et al. 1998). The temperate-type carbonate depositional model led to critical reinvestigation of many Cretaceous carbonate sequences, characterized by the flourishing of opportunistic rudist-dominated communities. Previous studies allowed a possible sedimentary scenario to be reconstructed for the Upper Cretaceous shallow-water depositional areas, pertaining to the southern Tethys belt. According to recent papers, these depositional areas were complexes of unprotected shelves occupied by foramol assemblages that produced loose, diagenetically stable bioclastic debris not involved in significant in situ cementation processes. Both stormand wind-induced currents and waves exercised strong control on the distribution of the shifting biogenic sediments which covered the open seafloor, constituting large coalescing sheets of winnowed fine to coarse skeletal sands (cf. Simone et al. 2003). Rudists spread over all shelf sectors, from more open and external areas to more internal ones, occupying different substrata and providing the bulk of the skeletal component by means of bioerosion processes. They colonized mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental conditions of the different sectors of the shelf. On the basis of detailed sedimentological, taphonomic and palaeontological data, two main rudist-rich depositional settings (‘end-members’) have been recognized in the central-southern Italy Senonian rudist-bearing successions (Carannante et al. 1993, 2001; Simone et al. 2003). The latter were characterized by contrasting current regimes (high energy vs. low energy; cf. Burchette & Wright 1992) which controlled development and growth of the rudist lithosomes (see also analogous observations in Stossel & Bernoulli 2000). The taphonomic and palaeoecological features of the rudist-dominated benthic communities have been analysed in limestones, showing that they were deposited in very different hydrodynamic conditions. Investigations have pointed out the differences in terms of anatomy of the rudist bodies and their relationship with the availability of accommodation space (cf. Simone et al. 2003, for a review). Several papers deal with the rudist-bearing marginal depositional settings (cf. Simone et al. 2003 and references therein) in which more or less frequent episodes of high energy (storm-related events) resulted in a complete reorganization of the depositional bodies and in which only a few of the organisms were able to keep their original position. Moreover, few papers deal with successions pertaining to more internal and/or lowenergy sectors, in which rudist-rich beds rhythmically alternate with finer-grained foraminiferal limestones (cf. Simone et al. 2003 and references therein). In these sequences, dominated by silt/ mud-rich lithotypes, small elevator radiolitids with oligospecific diversity are dominant. In the related depositional settings, the preservation of the original rudist congregations was associated with the in situ maintenance of the bioerosion-derived finer skeletal debris. Rudists in growth position are abundant, although also a large quantity of shells appears toppled with little reworking. They may form laterally continuous biostromal shell beds. Sedimentary structures such as cross-lamination and grading are present only occasionally. The resulting facies are arranged commonly in peritidal/ shallow subtidal cycles in which evidence of subaerial (up to pedogenic modifications on a large and small scale) and, less frequently, submarine exposure is common. Based on detailed observations, in such sedimentary contexts, peculiar areas have been identified corresponding to current pathways in a persistently subtidal setting (Carannante et al. 2003) which cannot be likened to well-described tide channels in tropical contexts. Several papers deal with temperate, high-energy, recent and ancient depositional systems (cf. James & Clarke 1997 for a review). Low-energy or protected, temperate, shallow-water systems have been described poorly and have come to international attention only recently (cf. Choi & Simo 1998; Gomez-Perez et al. 1998; Lukasik et al. 2000; Carannante et al. 2003; Pufahl et al. 2004). This paper sets out to describe such a peculiar shallow-water environment from late Cretaceous (post-Cenomanian) shallow-water foramol open shelves. A locality was selected in the southern Apennines in which outcrop conditions show an excellent overview of the lateral and vertical evolution of rudist bodies and allow the geometry and the dynamic aspect to be reconstructed.

Rudist bed type and distribution has been investigated in Upper Cretaceous limestones cropping out in the northern Cilento area (southern Italy). These limestones are dominated by fine-grained, peloidal, silty packstone in which rudist-rich beds are intercalated. An inner shelf environment may be inferred on the basis of the recognized sedimentary and taphonomic features. The rudist shell beds are characterized by low species diversity, with slight differences in abundance of a few species belonging to the Durania, Bournonia, Sauvagesia, Gorjanovicia and Biradiolites genera, which usually form oligo- or monospecific congregations. The internal fabric of these levels (i.e. orientation, arrangement, packing and sorting of the skeletal elements; internal microstratigraphy) has permitted us to distinguish two broad shell bed categories: (a) shell beds considered as “Primary Shell Concentration”, in which the shell concentration is essentially created by the behaviour of local shell producers, preserved in situ and in growth position; (b) shell beds considered as “Hydraulic Shell Concentration”, which were deposited under the influence of hydraulic processes and/or input of surrounding bioclastic sediments. The taphonomic analyses allowed us to highlight the role of some of the biotic and abiotic factors that controlled the distribution of the rudists in the various habitats. The increase of physical disturbance (especially hydrodynamism) is the primary difference between these shell bed categories. The establishment and development of the densest rudist congregations appear to be related to the accommodation space made available by means of relative sea level rise. The lowering of the sea level was often accompanied by the increased influence of waves and/or currents on the seabed and the consequent sediment disturbance and demise of the rudist lithosome, although other factors cannot be excluded.

Sedimentological, paleontological and sequence analyses of Cenomanian limestones in Sicily reveal thc facies architecture and dynamics of a Mid Cretaceous rudistdominated platform margin from Western Tethys. The studied deposits outcrop near Palermo, as part of a large structural unit of the Sicilian Maghrebids. They belong to the Panormide carbonate platform, a Mesocenozoic paleogeographic domain of the African margin. The lateral continuity of the beds along three nearly parallel E-W outcrop sections allowed the recording of cm/dm thick lithological and faunal variations. Nine main lithofacies associations have been recognised along about 200 m of subvertical strata. Their vertical and lateral organisation points to a transition from highenergy shelf-margin rudist patches and shoals to more internal lagoonal-tidal environments over a short distance. The lithofacies evolution and stacking pattern along the three sections made it possible to define elementary cycles, composite cycles and larger-scale sequences with a dominant shallowing-upward trend. Their hierarchical organisation implies that sea-level fluctuations were an important factor in their formation. The cycles are characterised by a great variation in facies as a result of transgressive-regressive events in different sectors of the interred Cenomanian shelf. Subtidal cycles typical of the shelf margin (4-10 m-thick) are particularly well identifiable. They are madc of large Caprinidae and Sauvagesiac rudstonc-to-floatstone (about 2/3 of the total thickness), capped by rudist-conglomerates, often organised into 3-5 fining-upward amalgamated beds and showing, in places, effects of surfacerelated diagenesis, in more internal shelf areas the cycles consist of Caprinidae-Radiolitidae floatstonc grading up into amalgamated beds of angular bioclastic rudstone/ grainstone. Alternations of foraminifer/ostracod mudstone/wackestone and bioclastic grainstone/finc-rudstonc, capped by lofcritcs and/or by other emersion-related overprintings, characterise the cycles formed in the peritidal zones. These cycles arc stacked into three incomplete depositional sequences. The sequence boundaries have been identified by the abrupt interposition of peritidal cycles in subtidal rudist-rich cycles, with evidence of brief subaerial exposure.