Time filter

Source Type

United States

The section of Gorgo a Cerbara in Italy has been proposed as the Global Stratotype Section and Point (GSSP) for the Barremian/Aptian boundary (Lower Cretaceous). This section displays the transition between the white pelagic limestones of the Maiolica Formation (Tithonian–lowermost Aptian) and the polychrome marls of the Marne a Fucoidi Formation (Aptian–Albian). The Oceanic Anoxic Event 1a (OAE 1a) anoxic horizon (Selli Level) is located in the latter formation. Here, we report for the first time a palynostratigraphical assessment of this key section, with a very high resolution in the Selli Level. Palynomorph groups recorded include acritarchs, microforaminiferal test linings, 58 dinoflagellate cysts, 44 sporomorph taxa, and freshwater fungal and algal bodies. These include such biostratigraphical markers as Rhynchodiniopsis aptiana and Odontochitina operculata among the dinoflagellate cysts and Afropollis cf. jardinus among sporomorphs. Biostratigraphical events recognised allow comparisons with previously studied successions in other similar areas (e.g. Cismon apticore in the Southern Alps, Italy). The distribution of taxa recorded in the Gorgo a Cerbara section is generally consistent with published data, but several differences between the assemblages recorded in the Cismon apticore and in this study were noted. The best global markers for the Barremian/Aptian boundary are represented by the disappearance of R. aptiana and by the appearance of O. operculata, but in this section these occurred 0.65–1.35 Myr after the magnetostratigraphically defined boundary, within the Selli Level. The angiosperm pollen A. cf. jardinus is recorded only within the Selli Level (from 1.4 to 1.6 Myr after the Barremian/Aptian boundary), consistent with an Early Aptian age. A cluster of 10 extremely short-ranging dinoflagellate cyst excursion taxa appear in this section coincident with the Nannoconid Crisis event and its associated thermal peak, ca. 10–20 kyr before the onset of the OAE 1a. Several short-ranging Pteridophyta spore species are found only within the Selli Level itself. © 2015 AASP – The Palynological Society Source

Mortimore R.,ChalkRock Ltd | James L.,RPS Energy
Proceedings of the Geologists' Association | Year: 2015

Suitable onshore analogues for offshore wind-farm turbine foundations in the Chalk of the North Sea would be invaluable. Such foundations require examples of near surface weathering illustrating both glacial and periglacial Quaternary processes as well as lithology and tectonic structure of the Chalk. From the Cenomanian to Early Campanian, the coast of East Yorkshire illustrates hard, high density, glacially eroded chalks similar to those found immediately offshore. Higher in the Campanian offshore East Yorkshire, younger, low density chalks, not present onshore, have been found (the Westermost Rough Member). In contrast, north Norfolk and its coastal cliffs provide examples of soft, high porosity, part glacially and part periglacially weathered chalks. Complex sedimentary structures seen in offshore seismic sections are similar to those on the French coast of the Pays de Caux. These coastal sections are compared with results from offshore wind farm ground investigations. Seismic sections illustrate Quaternary channels cutting into the Chalk and a landscape of hills and valleys similar to the onshore Wolds. High resolution 2D digital seismic sections, combined with cored boreholes, provide the evidence for applying the detailed Chalk lithostratigraphy to the offshore southern North Sea and illustrate the relationship between tectonic structure and sedimentation in the Chalk. The map for the offshore extension of Chalk provinces is revised, with Transitional Province lithologies typical of the Chiltern Hills and East Anglia, extending north-eastwards from Norfolk into the Dowsing Fault zone. Geotechnical properties are related to the buried offshore Chalk landscape as well as to Chalk lithostratigraphy. © 2015 The Geologists' Association. Source

The trace fossil Desmograpton Fuchs, 1895, as many other graphoglyptids, has been considered to be a typical pre-turbidite, three-dimensional burrow system formed in mud and preserved as a casting at the sole of turbidites. This classic interpretation was mostly based on hypichnial preservation, due to the lack of direct evidence (e.g. modern seafloor pictures) for pre-depositional or post-depositional origin. Due to the accidental series of processes invoked to explain the perfect hypichnial preservation of this delicate trace fossil, several doubts and questions have been raised. To try to clarify the sedimentary processed that lead this trace fossil to be preserved, 26 thin sections of Desmograpton dertonensis Sacco, 1888 and Desmograpton ichthyforme Macsotay, 1967 have been performed at sand/clay interface of thinbedded sandstone turbidites in the Miocene marl deposits of Verghereto, Northern Apennines (Italy). Petrographic analysis of textures and grains of the burrow-filling sediments points out that most of the grains of burrows differ from those of overlying sand, being either more or less sorted and differ in composition and locally also in grain size. Burrows are occasionally characterised by an upper rim, more or less thick, enriched in glauconite, phosphates, pyrite or quartz. Axial cuts of the strings show that rim was involved in diagenetic compaction, squeezing and fluid migration modifying the original shape of the trace fossil. In pre-depositional conditions the oblique-oriented filling is the only explication to preserve the upper rim of original mud, while compaction produced asymmetry in hypichnial tunnels. This petrographic approach, performed for the first time on this graphoglyptid genus, also elucidates the complex interaction of several taphonomic processes that led to the preservation of Desmograpton. The application of a similar petrographic approach to other graphoglyptids could help to better understand their origin, ethology and their preservation processes. Source

Compton R.,RPS Energy
75th EAGE Conference and Exhibition Incorporating SPE EUROPEC 2013 | Year: 2013

Concerns regarding the potential impacts of underwater sound upon marine species such as whales, dolphins and porpoises has led to the implementation of mitigation measures during marine seismic operations. These measures include the use of personnel and passive acoustic equipment to monitor for species within a given safety zone around the source, delay and shutdown to the source during operations. These procedures have become a common part of marine seismic surveys and represent best practice with regard to environmental responsibility. Source

Frijia G.,University of Potsdam | Parente M.,University of Naples Federico II | Di Lucia M.,RPS Energy | Mutti M.,University of Potsdam
Cretaceous Research | Year: 2015

Shallow-water carbonates are invaluable archives of past global change. They hold the record of how neritic biologic communities reacted to palaeoenvironmental changes. However, attempts to decipher these geological archives are often severely hampered by the low stratigraphic resolution attained by biostratigraphy. This is particularly the case for the Upper Cretaceous carbonate platforms of the central Tethyan realm: their biostratigraphy suffers from very low resolution and poor correlation with the standard biochronologic scales based on ammonites, planktic foraminifers and calcareous nannoplankton.In this paper we show how this problem can be tackled by integrating biostratigraphy with isotope stratigraphy. We present a detailed record of the benthic foraminiferal biostratigraphy and carbon and strontium isotope stratigraphy of three upper Cenomanian-middle Campanian sections belonging to the Apennine Carbonate Platform of southern Italy. For the upper Cenomanian-Turonian interval, the carbon isotope curves of the studied sections are easily correlated to the reference curve of the English Chalk. The correlation is facilitated by the matching of the prominent positive excursion corresponding to the Oceanic Anoxic Event 2. For the Coniacian-middle Campanian interval, the correlation is mainly based on strontium isotope stratigraphy. We use the 87Sr/86Sr ratios of the low-Mg calcite of well preserved rudist shells to obtain accurate chronostratigraphic ages for many levels of the three studied sections. The ages obtained by Sr isotope stratigraphy are then used to better constrain the matching of the carbon isotope curves.From the high-resolution chronostratigraphic age-model stablished by isotope stratigraphy, we derive the chronostratigraphic calibration of benthic foraminiferal biostratigraphic events. For the first time the benthic foraminiferal biozones of the Apennine Carbonate Platform can be accurately correlated to the standard ammonite biozonation. This result is of great relevance because the biostratigraphic schemes of other carbonate platforms in the central and southern Tethyan realm are largely based on the same biostratigraphic events. © 2014 Elsevier Ltd. Source

Discover hidden collaborations