Search

Modern and Cenozoic deep-sea hydrothermal-vent and methane-seep communities are dominated by large tubeworms, bivalves and gastropods. In contrast, many Early Cretaceous seep communities were dominated by the largest Mesozoic rhynchonellid brachiopod, the dimerelloid Peregrinella, the paleoecologic and evolutionary traits of which are still poorly understood. We investigated the nature of Peregrinella based on 11 occurrences world wide and a literature survey. All in situ occurrences of Peregrinella were confirmed as methane-seep deposits, supporting the view that Peregrinella lived exclusively at methane seeps. Strontium isotope stratigraphy indicates that Peregrinella originated in the late Berriasian and disappeared after the early Hauterivian, giving it a geologic range of ca. 9.0 (+1.45/-0.85) million years. This range is similar to that of rhynchonellid brachiopod genera in general, and in this respect Peregrinella differs from seep-inhabiting mollusks, which have, on average, longer geologic ranges than marine mollusks in general. Furthermore, we found that (1) Peregrinella grew to larger sizes at passive continental margins than at active margins; (2) it grew to larger sizes at sites with diffusive seepage than at sites with advective fluid flow; (3) despite its commonly huge numerical abundance, its presence had no discernible impact on the diversity of other taxa at seep sites, including infaunal chemosymbiotic bivalves; and (4) neither its appearance nor its extinction coincides with those of other seep-restricted taxa or with global extinction events during the late Mesozoic. A preference of Peregrinella for diffusive seepage is inferred from the larger average sizes of Peregrinella at sites with more microcrystalline carbonate (micrite) and less seep cements. Because other seep-inhabiting brachiopods occur at sites where such cements are very abundant, we speculate that the various vent- and seep-inhabiting dimerelloid brachiopods since Devonian time may have adapted to these environments in more than one way., Open-Access-Publikationsfonds 2014

La pubblicazione costituisce parte del Volume descrittivo della escursione scientifica tenuta sulla geologia e paleontologia delle successioni stratigrafiche affioranti sul Promontorio del Gargano (FG) in occasione della IX edizione delle Giornate di Paleontologia (2009) organizzata dalla Società Paleontologica Italiana

Post-Turonian (Late Cretaceous) rudist-bearing limestones of the Nurra region in northwestern Sardinia (northern Tethyan margin) and in the central-southern Apennines and Apulia (central Tethyan domain) have recorded relevant changes in the characteristics of the carbonate platforms following the “middle” Cretaceous crisis events which affected the peri-Tethyan region as well as other regions worldwide. Rudist bivalves became the dominant lithogenetic taxon owing to their proliferation in shallow-water environments and strong dominance of Late Cretaceous carbonate factories. Their inception, evolution, and demise were seemingly controlled by a complex interplay of environmental processes that, acting on a global scale, profoundly modified the Early Cretaceous hydrosphere–atmosphere system and forced Tethyan depositional systems to change their organization, internal architecture, and facies patterns. As a result, wide, open shelves developed where the almost ubiquitous mode of carbonate fixation was that of foramol factories. In this paper, evidence of the remarkable regional variability in the rudist-bearing carbonate platforms of the Mediterranean Tethys is presented. The analysis of the resulting shallow-water facies has demonstrated that, in spite of several stratigraphic similarities and common sedimentological features, some remarkable differences occurred between the northern Tethyan margin and the central Tethyan banks as regards the areal partitioning of the main paleoecologic controlling factors. This resulted in the deposition of rhodalgal successions in Sardinia (northern Tethyan margin) and rudist-rich foramol facies in the Apennine–Apulia (central Tethys) regions, respectively. Such Late Cretaceous carbonate systems can be viewed as geological products which have closely and coherently recorded the globally changing environmental conditions of the oceanic realm. In spite of this, the difference of the facies partitioning in different Tethyan regions according to a latitudinal gradient is interpreted as derived mainly from local variable paleoceanographic and paleoclimatic conditions.

The most different faunal and floral assemblages have experienced several events of extinction, diversity reduction and diversification during Cretaceous. Such events are basically coeval to rapid reorganizations of the regional-to-global hydrosphere/atmosphere systems following relevant geotectonic pulses. Biotic assemblages shifted repeatedly among phases of carbonate production modes dominated by oligotrophic specialized and meso-eutrophic opportunistic taxa, namely k- and r-mode forms, as a consequence of major turning points in the evolving paleoceanographic conditions. Stratigraphic data on several Cretaceous successions of southern Apennines and Apulia (southern Italy) have demonstrated that brachiopods were a main component of r-mode assemblages which developed in Latemost Valanginian, late Early Aptian, earlymost Cenomanian, and latemost Campanian. With the exception of the latemost Campanian event, all of these time intervals correspond to severe global environmental disruptions of the oceans and climate coupled to biocalcification crises. However, all of them correlate to Tethyan oceanic anoxic events (Weissert and Selli OAEs) and/or platform drownings (Late Valanginian, late Early Aptian, Early Cenomanian and latemost Campanian). Noteworthy, all of the investigated events reflect regional shifts among chlorozoan, foramol and microbial production modes of the mediterranean shallow-water carbonate factories. The remarkable association of brachiopoda with cyanobacteria, though in complex stratigraphic relationships, especially in Late Valanginian, late Early Aptian, and Early Cenomanian times accounts for drastic environmental deterioration of the surface oceanic waters which were highly unfavourable for oligotrophic, k-mode organisms. We assume that such a relevant correlation between Cretaceous brachiopod beds and disruptions of the paleoceanographic conditions may provide an additional tool to improve the comprehension of the internal structure of major paleoecologic changes due to the environmental collapse of oceanic waters during drowning events of carbonate platforms and/or OAEs.

The most different faunal and floral assemblages have experienced several events of extinction, diversity reduction and diversification during Cretaceous. Such events are basically coeval to rapid reorganizations of the regional-to-global hydrosphere/atmosphere systems following relevant geodynamic pulses. Biotic assemblages shifted repeatedly among phases of carbonate production modes dominated by oligotrophic specialized and meso-eutrophic opportunistic taxa, namely k- and r-mode forms, as well as microbes, as a consequence of major turning points in the evolving paleoceanographic conditions. Stratigraphic data on several Cretaceous successions of southern Apennines and Apulia (southern Italy) have demonstrated that brachiopods were a main component of r-mode assemblages which developed in latest Valanginian, late Early Aptian, earliest Cenomanian, and latest Campanian. With the exception of the latest Campanian event, all of these time intervals correspond to severe global environmental disruptions of the oceans and climate coupled to biocalcification crises. However, all of them correlate to the Cretaceous Tethyan oceanic anoxic events (WEISSERT and SELLI OAEs) and/or platform drownings (Late Valanginian, late Early Aptian, Early Cenomanian and latest Campanian). Noteworthy, all of the investigated events reflect regional shifts among chlorozoan, foramol and microbial production modes of the Mediterranean shallow- water carbonate factories. The remarkable association of brachiopoda with cyanobacteria, though in complex stratigraphic relationships, especially in Late Valanginian, late Early Aptian, and Early Cenomanian times accounts for drastic environmental deterioration of the surface oceanic waters which were highly unfavourable for oligotrophic, k-mode organisms. We assume that such a relevant correlation between Cretaceous brachiopod beds and disruptions of the paleoceanographic conditions may provide an additional tool to improve the comprehension of the internal structure of major paleoecologic changes due to the environmental collapse of oceanic ecosystems during drowning events of carbonate platforms and/or OAEs.

Middle Cretaceous (Aptian-Turonian) time was a period of unusually intense geodynamic activity that lead to major paleogeographic/paleoceanographic changes. These are coincident with relevant geological events as turnovers of biotic communities, oceanic anoxic events (OAEs), thermal maximum and disruptions of geochemical cycles in seawater. The Late Cretaceous evolution of rudist-rich carbonate platforms of central Mediterranean Tethys is investigated here to derive possible genetic links between geodynamically induced environmental changes and the observed stratigraphic record. Stratigraphic and palaeoecologic data are coupled to available geochemical proxies to fulfil a detailed integrated approach to event and genetic stratigraphy. Several major paleoceanographic events falling in the latest Albian, C-T boundary, middle-late Turonian boundary, Coniacian-Santonian boundary and middle Campanian have been individuated. Our results suggest that rudist-rich carbonate platforms have coherently reflected the fluctuating environmental conditions of the oceanic realm mostly induced by changing temperature, Mg/Ca ratio and pCO2. These platforms are the result of biosphere-geosphere interactions which were induced by large-scale, long-term geodynamic forcings.

Coniacian-Santonian limestones from north-western Sardinia and southern Apennines (Italy), evidenced the dominance of foramol lithofacies over chlorozoan-chloralgal ones. The large spreading of the foramol assemblages in tropical/subtropical sedimentary settings would be consistent with changing in the environmental conditions which developed due to different types of stress in the water mass. The resulting depositional contexts were open-shelves prone to the more opportunistic forms of the foramol assemblages. They were characterized by the diffusion of the rudists that covered, with their detritus, increasingly larger sectors of the shelf without building real reefs. The different nature and organization of the sediment-producer assemblages as well as the abundance of the bioerosion-derived skeletal detritus resulted in sheets of loose bioclastic sediments that covered bottoms lacking protective rims. The large spreading of molluscs (rudists), which became dominant in the whole shelf, coincided with a reduction of the corals. These latter persisted in the marginal and deep sectors of the shelf as subordinated forms. Both the studied examples refer to post-emersive sedimentary contexts. A tectonically-related topography controlled the inception of the carbonate factories which suffered the effects of local induced upwellings and/or hyperproductivity by terrestrial runoff on post-emersive and/or tectonized transgressed substrata. These local controls superimposed on global fluctuating environmental conditions.The resulting major turning points in the stratigraphic record strictly are coincident with major variation in the global scale chemical/phisical parameters of the Hydrosphere/Atmosphere System.

A major shift from largely prevailing chlorozoan/chloralgal reef-producers and/or aragonite-dominated lithofacies to rhodalgal/molechfor (foramol sensu lato), calcite-dominated lithofacies, rich in opportunistic forms may proposed in the Cenomanian-Santonian. The large spreading of the foramol assemblages in the tropical/subtropical Late Cretaceous seas would be consistent with a change from oligotrophic to meso-eutrophic environmental conditions. Looking at the major global scale variations in the chemical/physical parameters of the Cretaceous Hydrosphere/Atmosphere system, the inception of the early Senonian Tethyan carbonate factories seems to be related with dramatic, geodinamically-induced global environmental changes in the ocean waters following the onset of the eo-alpine (mid-Cretaceous) orogeny.

Volume dei Proceedings del COFIN 2000 (vedi titolo del libro) presentati in occasione del Workshop tenuto a Pozzuoli (NA) il 25-27 Febbraio 2003.

Erlanger geol. Abh., Sonderband

Erlanger geol. Abh., Sonderband

James N.P. & Clarke J.D. (Eds.) "Cool-water carbonates", SEPM. Spec. Publ.

Atti del 76° Congresso della Soc. Geol. It.

SEPM-IAS Research Conference

Modern and Cenozoic deep-sea hydrothermal-vent and methane-seep communities are dominated by large tubeworms, bivalves and gastropods. In contrast, many Early Cretaceous seep communities were dominated by the largest Mesozoic rhynchonellid brachiopod, the dimerelloid Peregrinella, the paleoecologic and evolutionary traits of which are still poorly understood. We investigated the nature of Peregrinella based on 11 occurrences world wide and a literature survey. All in situ occurrences of Peregrinella were confirmed as methane-seep deposits, supporting the view that Peregrinella lived exclusively at methane seeps. Strontium isotope stratigraphy indicates that Peregrinella originated in the late Berriasian and disappeared after the early Hauterivian, giving it a geologic range of ca. 9.0 (+1.45/-0.85) million years. This range is similar to that of rhynchonellid brachiopod genera in general, and in this respect Peregrinella differs from seep-inhabiting mollusks, which have, on average, longer geologic ranges than marine mollusks in general. Furthermore, we found that (1) Peregrinella grew to larger sizes at passive continental margins than at active margins; (2) it grew to larger sizes at sites with diffusive seepage than at sites with advective fluid flow; (3) despite its commonly huge numerical abundance, its presence had no discernible impact on the diversity of other taxa at seep sites, including infaunal chemosymbiotic bivalves; and (4) neither its appearance nor its extinction coincides with those of other seep-restricted taxa or with global extinction events during the late Mesozoic. A preference of Peregrinella for diffusive seepage is inferred from the larger average sizes of Peregrinella at sites with more microcrystalline carbonate (micrite) and less seep cements. Because other seep-inhabiting brachiopods occur at sites where such cements are very abundant, we speculate that the various vent- and seep-inhabiting dimerelloid brachiopods since Devonian time may have adapted to these environments in more than one way., Open-Access-Publikationsfonds 2014

We describe a new terrestrial, plant-rich Fossil-Lagerstatte discovered at Magliano Vetere (Campania region, S Italy) in the middle Cenomanian of the Apennine Carbonate Platform. The deposit, 1.42 m thick, is made up of a thin-bedded interlayering of evenly laminated dolomicrites, lenticular dolorudites and carbonaceous seams, which contain well-preserved remains of terrestrial plants yielding cuticles and minor fishes. This study focuses on plant remains, to provide systematical, taphonomical and palaeoenvironmental considerations; nevertheless, a preliminary analysis carried out on fossil fishes has led to the identification of pycnodontids and teleosts. The Fossil-Lagerstatte retains sterile foliage-bearing shoots with epidermal features belonging to the genus Frenelopsis of the extinct conifer family of the Cheirolepidiaceae. Plant remains possibly represent a stable biotope, as floral composition displays no variation along the deposit. Nevertheless, episodes of harsh environmental conditions occurred as demonstrated by a fish mortality event and Ca-sulphate evaporite precipitation. Taphonomical considerations and sedimentological evidence from the encasing sediments suggest a parautochthonous deposition of fossil plants in a supratidal/intertidal mudflat, including a salt-marsh that was characterised by a restricted sea-water circulation, deposition of primary dolomite and episodical wildfires. The presence of xeromorphic features in Frenelopsis from Magliano Vetere could represent an adaptation to haline environment which was subjected to microtephra supply from a distant, orogenic volcanism. The facies evolution of the studied Fossil-Lagerstatte records a rapid regressive and a following slower transgressive trend, and constitutes the lowermost portion of a ~20 m thick interval characterised by several dolomitic plattenkalk, up to 1.50 m thick, which are separated by cyclically stacked peritidal limestones. We infer that: 1) the ~20 m thick, Plattenkalk-bearing interval represents a Sequence Boundary Zone in the stratigraphical record of the middle Cenomanian ApCP; 2) Frenelopsis thrived at the verge of an arid–semiarid climatical phase during a major pulse of relative sea-level fall.

This study reports an integrated facies analysis carried out on a new section from the Upper Aptian of the SE Matese Mts. (Civitella Licinio, northern Campania, S. Italy), which includes several decimeter-to-meter scale lacustrine intervals straddling a meter-scale plant-rich Plattenkalk. These intervals are assigned to the late Gargasian–early Clansayesian by their stratigraphic relationship with the upper Salpingoporella dinarica acme as well as lithologic and biostratigraphic supra-regional key-markers found in the Apennine Carbonate Platform (ApCP), including the Orbitolina Level. We infer that the monogeneric parautochthonous plant remains (Frenelopsis sp.) were deposited in a supratidal-to-paralic coastal mudflat close to a restricted, shallow-marine lagoon, at the verge of an arid–semiarid climatic phase. The Plattenkalk was rapidly replaced by persistent lacustrine lithofacies at the onset of a major climatic turnover (Glacial Trigger). The overlying shallow-marine deposits are capped by a deeply incised palaeokarstic surface and, in turn, by unconformable middle Clansayesian transgressive shallow-marine deposits. Interlayering of reliable lithologic indicators of palaeoclimate and High-Resolution Event Stratigraphic (HIRES) correlation of the Civitella Licinio succession with the astrochronologically tuned Mt. Faito reference section of the ApCP bring evidence of rapidly fluctuating hydroclimatic conditions (wet and arid phases) in the short (100 ky) and long (400 ky) eccentricity time band. HIRES and astrochronological age assignment to crucial key markers and humid/arid phases at Civitella Licinio permit to further refine the detailed stratigraphy of the Mt. Faito reference section and to assign the upper S. dinarica acme of the ApCP to a numerical age of 118.55–118.50 My. SEM and EDS analyses document common to abundant windblown volcanic particles (glass shards and sanidine crystals) throughout the Frenelopsis-rich Plattenkalk (~ 118.3 to ~ 118.2 My) and the encasing units, especially in the overlying brackish–lacustrine deposits. Palaeogeographic and palaeoclimatic reconstructions suggest that the pyroclastic material was probably transported by northeasterly trade winds from orogenic volcanic centers located within the Dinaridic–Carpatho-Balkan arc–trench system and have been supplied to the ApCP for a time span of ~ 3 My during the Late Aptian. A preliminary tephrostratigraphic correlation of the Upper Aptian volcaniclastic levels of the ApCP with the bentonite levels of the Vocontian Basin is proposed.