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The early geological exploration of the Nice region (French Maritime Alps) in the late 18th–19th centuries
Abstract and Figures
At the southeastern termination of France, the Nice region during the late 18th–19th centuries represented one of the liveliest hearts of the geological ferment in Europe. The ‘capital’ of the French Riviera, this city attracted scores of renowned European naturalists including famous British geologists such as Thomas Allan, William Buckland, Henry Thomas De la Beche and Charles Lyell. Together with their local colleagues, these scientists contributed to shape the geological knowledge about this part of the Maritime Alps, and laid the foundations to the systematic and modern geological studies which have been carried out in this region starting from the second half of the 19th Century.
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... De la Beche's contribution was also accompanied by a geological map of the coastal region between Nice and Ventimiglia. The British geologist was the first to clearly distinguish and draw separately the rocks of the Alpine Foreland Basin succession ("Brown micaceous Sandstone, with Marl", corresponding to the Annot Sandstone, and the "Grey-Blue Limestone with Nummulites", corresponding to the Nummulitic Limestone), even if he considered these rocks as part of the "Green-Sand Formation", and thus Cretaceous in age (De la Beche, 1829; see also Barale, 2016). ...
The aim of this contribution is to outline a few differences, interactions and complementarities of geological investigations in the Italian-French cross-border areas in the Western Alps during the 19 th and early 20th centuries. With this objective, this contribution selects a few studies that have been references for further investigations, resulted fundamental for the present knowledge of the Western Alps.
... In the nineteenth century, the French Riviera and its 'capital' Nice, lying on the Mediterranean coast of the Maritime Alps, were popular destinations for wealthy European travellers, and were visited by the preeminent European naturalists of the time, including the British geologists William Buckland, Henry Thomas De La Beche, Roderick Impey Murchison and Charles Lyell (Barale 2016), attracted by the richness of the natural and geological features of the region, as well as by the renowned mildness of its climate. Indeed, 'While it afforded the most ample opportunities for investigating its geological structure, the pleasing and diversified aspects, which this broken ground, clothed with the orange and the olive, every where presented, stimulated as well as recompensed the labours of research' (Allan 1818: 429). ...
In the early nineteenth century, the Scottish geologist Thomas Allan (1777-1833) stayed for a period of vacation in Nice (Maritime Alps, SE France), the 'capital' of French Riviera. Allan had the occasion to run several excursion in the surroundings of the city, thus making numerous original observations about the geological setting of the region, which he reported in a paper published in 1818 in the Transactions of the Royal Society of Edinburgh. Making constant reference to the familiar rocks of Great Britain and Ireland, Allan described the stratigraphic succession of the Nice area in one of the earliest geological works on that region-and the first written in the English language. A colour geological sketch map, attached to the paper, represents the first published geological map of the region.
In the Maritime Alps (north-west Italy – south-east France), the Middle Triassic–lowermost Cretaceous platform carbonates of the Provençal Domain locally show an intense dolomitization. Dolomitized bodies, irregularly shaped and variable in size from some metres to hundreds of metres, are associated with tabular bodies of dolomite-cemented breccias, cutting the bedding at a high angle, and networks of dolomite veins. Field and petrographic observations indicate that dolomitization was a polyphase process, in which episodes of hydrofracturing and host-rock dissolution, related to episodic expulsion of overpressured fluids through faults and fracture systems, were associated with phases of host-rock dolomitization and void cementation. Fluid inclusion analysis indicates that dolomitizing fluids were relatively hot (170 to 260°C). The case study represents an outstanding example of a fossil hydrothermal system, which significantly contributes to the knowledge of such dolomitization systems in continental margin settings. The unusually favourable stratigraphic framework allows precise constraint of the timing of dolomitization (earliest Cretaceous) and, consequently, direct evaluation of the burial setting of dolomitization which, for the upper part of the dolomitized succession, was very shallow or even close to the surface. The described large-scale hydrothermal system was probably related to deep-rooted faults, and provides indirect evidence of a significant earliest Cretaceous fault activity in this part of the Alpine Tethys European palaeomargin.
The Col de Braus section (Maritime Alps, SE France) offers a continuous and beautiful exposure of the Jurassic–Cretaceous Provençal succession and the lower part of the Alpine Foreland Basin succession, over a total thickness of about 1200 m. This stratigraphic succession is the result of a long geological history, corresponding to a time span of about 130 Myr, and records different stages of the evolution of the palaeo-European passive margin of the Alpine Tethys and the subsequent development of the Alpine Foreland Basin. The Col de Braus section represents a classic locality for the geology of the Maritime Alps and of SE France in general. It has been known since the late eighteenth century and is here identified as a highly significant geological heritage, due to its multiple interests which go far beyond scientific value. A geological itinerary along the Col de Braus section is also proposed, which is developed along a main road and can be enjoyed by both specialists and a general public thanks to the multiple levels of information offered by the selected outcrops.
The 1:10,000 geological map here presented extends over about 32 km2 around the Col de Braus pass in the Maritime Alps (SE France). This area has attracted the attention of geologists since the late eighteenth century due to superb exposures of the Jurassic–Cretaceous Provençal succession, and has become a classic geological locality continuously studied until the present day. In this area, Early Cretaceous synsedimentary tectonics is evidenced by important lateral thickness and facies variations. This sector is presently placed at the western termination of a large structural domain extending from the westernmost Ligurian Alps into the French–Italian Maritime Alps, thus representing a key-area for understanding the structural setting of this part of the Western Alps.
Free download of the geological map:
http://www.tandfonline.com/doi/suppl/10.1080/17445647.2015.1077167?scroll=top
Surface-dwelling colonies of Velella velella occur throughout tropical to cold-temperate oceans of the world and sometimes are stranded in masses along hundreds of kilometers
of beaches. Large-scale blooms in the Western Mediterranean Sea in 2013 and 2014 allowed the study of diet, prey digestion
times and predation rates. Gastrozooid content analyses showed that 59% of the 769 identified prey were euphausiid larvae
(calytopsis and furcilia) captured at night. Copepods (41%), fish eggs (2.2%) and larvae (0.5%) were captured both at day
and night. Digestion times at ambient temperature (∼17°C) of calytopsis, furcilia and copepods were estimated to be >6.5,
4.4 and 3.9 h, respectively. Estimated prey consumption was substantially lower in 2014 than in 2013 (41 vs. 75 prey day−1 colony−1). Velella velella and other gelatinous species bloomed in the Mediterranean Sea and the northeastern Atlantic and Pacific oceans in 2013 and
2014. Because of the wide distribution of V. velella colonies, their mass occurrences, potential importance as predators and competitors of fish, additional production from symbiotic
zooxanthellae and stranding on beaches, they could be important in open-ocean carbon cycling and in transport of pelagic production
to landmasses.
L'exploration géologique de la Provence deux siècles et demi de débats et de controverses Des premières observations naturalistes de la seconde moitié du XVIII e siècle émerge une première vision d'ensemble de la Provence, divisée en trois régions : marneuse, calcaire et schisteuse. L'étape suivante, qui débute dans les années 1820, est dominée par la nécessité de définir le cadre stratigraphique et marquée par la publication des premières descriptions géologiques régionales. À partir de 1884, sous l'impulsion de Marcel Bertrand et de ses disciples, la Provence se trouve placée au centre des préoccupations de nombreux géologues, suite à la découverte des grands chevauchements de la couverture sédimentaire et du socle cristallin. Ainsi s'ouvre une période faste qui se poursuivra pendant le premier quart du XX e siècle. Toutefois, à partir des années 1930, les conceptions de Marcel Bertrand sont remises en question par les géologues autochtonistes. Puis, au cours des années 1960, celles-ci sont à leur tour réfutées par de nouveaux travaux qui conduisent à une réhabilitation éclatante de l'oeuvre du célèbre tectonicien. Au cours des décennies suivantes, l'exploration géologique et géophysique se développe et s'étend au précontinent. Stimulées par l'établissement de la carte géologique à 1/50 000, les recherches vont accorder une place importante à l'étude des grands problèmes stratigraphiques, paléogéographiques et structuraux, conduisant ainsi, au tout début du XXIe siècle, à l'établissement de synthèses géodynamiques de la Provence dans le cadre de la tectonique globale. L'ouvrage relate les différents épisodes de cette exploration ainsi que les débats et les controverses qui l'ont accompagnée. Illustré de nombreuses coupes et cartes originales il renferme plus de 500 références bibliographiques, ainsi que les biographies des principaux acteurs de cette longue et passionnante aventure scientifique. BON DE COMMANDE 46 euros frais d'expédition compris) Veuillez remplir le bon de commande; puis envoyez votre commande accompagnée de votre paiement (chèques à l'ordre de Transvalor) Transvalor – Presses des MINES 60, Bd Saint Michel, 75272 Paris cedex 06 -France ou http://www.pressesdesmines.com Cette offre est strictement limitée aux ventes directes (site presses des mines ou vente par correspondance).
Situé à l’extrémité sud orientale del’Arc de Castellane (Alpes-Maritimes, sud-est de laFrance), l’affleurement crétacé inférieur de laMontagne de Ruth est décrit. La biostratigraphiedes dépôts est basée sur la biozonation par ammonites, récemment revue pour le Barrémiensupérieur. Cet affleurement présente un faciès de plate-forme ennoyée avec un assemblage fauniquediversifié caractérisé par des faunes benthiques etnectoniques (céphalopodes). Les sédiments duBarrémien supérieur à l’Albien inférieur ontenregistré les évènements tectonosédimentairesconnus à cette période sous la forme de niveaux decondensation, de remaniements, de lacunesstratigraphiques, et de surfaces durcies, scellés par un encroûtement ferrugineux microbien. Lesobservations effectuées sur cet affleurementconfortent les reconstitutions paléogéographiquesantérieures.
Advances in the development of quantitative models of foreland basin stratigraphy have outpaced the observational data used to con- strain the input parameters in such models. Underfilled peripheral foreland basins comprise a broad threefold subdivision of depositional realms that translates into three stratigraphic units which are com- monly superimposed during basin migration; these units are here termed the "underfilled trinity." The three units of the trinity reflect (1) carbonate deposition on the cratonic margin of the basin (the lower unit), (2) hemipelagic mud sedimentation offshore from the cratonic margin of the basin (the middle unit), and (3) deep water turbiditic siliciclastic sedimentation toward the orogenic margin of the basin (the upper unit). Theoretical predictions of how such a complex basin fill initiates and evolves through time are not currently available; hence this study reviews the stratigraphy of underfilled peripheral foreland basins and provides a unique data set comprising rates of thrust advance and basin fill migration for the Tertiary foreland basin of the European Alps. The Paleocene to Oligocene Alpine foreland basin of France and Switzerland comprises a well-developed underfilled trinity that is pre- served within the outer deformed margins of the Alpine orogen. Struc- tural restorations of the basin indicate a decrease in the amount of basin shortening from eastern Switzerland (68%) to eastern France (48%), to southeastern France (35%). Structurally restored chrono- stratigraphic diagrams allow rates of basin migration to be calculated from around the Alpine arc. Paleogeographic restorations of the Num- mulitic Limestone (lower unit) illustrate a radial pattern of coastal on- lap on to the European craton. Time-averaged rates for northwest- ward coastal onlap of the underfilled Alpine basin across Switzerland were between 8.5 and 12.9 mm/yr. Time-equivalent westward to south- westward coastal onlap rates in France were between 4.9 and 8.0 mm/yr. The direction of migration of the cratonic coastline of the basin was parallel to the time-equivalent thrust motions, and oblique to the Africa-Europe plate motion vector. By comparing rates of thrust propagation into the orogenic margin of the basin to rates of coastal onlap of the cratonic margin of the basin, it is possible to suggest that the Alpine foreland basin of central Switzerland migrated with an ap- proximately steady state geometry for at least 210 km northwestward over the European craton. The westward and southward decrease in the basin migration rate around the Alpine arc was associated with an increase in the degree of syndepositional normal faulting on the Euro- pean plate; this is thought to relate to the opening of the Rhine-Bresse- Rhône graben system.
À l'issue de la découverte et de la publication, à la fin du XVIIIe siècle, de dépôts bréchiques ossifères et continentaux dans les falaises du rocher de Gibraltar, la communauté scientifique va se pencher sur des dépôts similaires qui jalonnent les côtes méridionales de l'Europe. La découverte des brèches du château de Nice, dès le début du XIXe siècle, s'inscrit dans le cadre de ces études, à une période marquée par une opposition nette, au sein de la communauté scientifique, entre la doctrine transformiste et le paradigme catastrophiste,
jusqu'à l'émergence de la théorie de l'évolution, à l'issue de la publication, en 1859, par Charles Darwin de son ouvrage "L'origine des espèces". Les brèches du château de Nice, qui firent l'objet de nombreuses publications durant la première moitié du XIXe siècle, avant de sombrer dans l'oubli, s'inscrivent par conséquent dans l'histoire des sciences.
Following the discovery and publication, in the late XVIIIth century, of ossiferous and continental breccia deposits in the cliffs of the Rock of Gibraltar, the scientific community examined similar deposits that line the coast of southem Europe. The discovery of such deposits at the castle of Nice, from the early XIXth century, is a part ofthese studies, during a period marked by a clear contrast between the transformist doctrine and the catastrophist paradigm until the publication in 1859 by Charles Darwin of his book "On the Origin of Species".
The breccia of the castle of Nice, which was the subject of numerous publications in the first half of the XIXth century, before sinking into oblivion, belongs to the history of science.
Eocene nummulite accumulations, also referred to as nummullte “banks”, form Important hydrocarbon reservoirs in Tunisia and Libya and may constitute exploration targets in other parts of North Africa, the Mediterranean and the Middle East. Porosities commonly average 10–20% and permeabilities 10–50md. Foraminifera of the genus Nummulites may comprise up to 98% of the bioclasts in these carbonate reservoirs, although only one or two species may be present. The absence of associated fauna is generally taken to indicate an oligotrophic depositional environment.
In this paper, the palaeoecology of the genus Nummulites is discussed together with depositional models for two nummulitic carbonate reservoirs — the Middle Eocene Seeb Limestone of Oman and the Early Eocene El Garia/Jdeir Formation of Tunisia and Libya. The El Garia and Seeb Limestone Formations were deposited in ramp settings, and comprise a series of amalgamated sheets or low-relief banks. In the Hasdrubal field offshore Tunisia, where the El Garia Formation constitutes the reservoir rock, most of the nummulites have been redeposited from shallow into deeper waters whilst in the Bourri field (offshore Libya) they occur as an in situ “bank”.
Nummulite accumulations often show evidence that both physical reworking (scouring, winnowing and imbrication) and biological processes (reproduction strategies and bioturbation) have influenced their formation. A general model is outlined for discriminating between physically and ecologically produced biofabrics, and the implications for reservoir quality are discussed.
Tertiary foreland sedimentation in SE France occurred along the western sidewall of the Alpine orogen during collision of the Apulian indentor with the European passive margin. A detailed reappraisal of the stratigraphy and structure of the Southern Subalpine Chains (SSC) in SE France shows that Tertiary depocentres of differing character developed progressively toward the foreland during ongoing SW-directed shortening. The geodynamic controls on each of four stages of basin development are evaluated using a flexural isostatic modelling package of thrust sheet emplacement and foreland basin formation. (1) The initial stage (mid to late Eocene) can be explained as a flexural basin that migrated toward the NW, closing off to the SW against the uplifting Maures–Esterel block. This broad, shallow basin can be reproduced in forward modelling by loading a lower lithospheric plate with an effective elastic thickness of 20 km. (2) The end of detectable flexural subsidence in the early Oligocene coincides with the emplacement of the internally derived Embrunais–Ubaye (E-U) nappes, which caused 11 km of SW-directed shortening in the underlying SSC. The lack of Oligocene flexural subsidence dictates that the E-U units were emplaced as gravitational nappes. Within the SSC, Oligocene sedimentation was restricted to small thrust-sheet-top basins recording mainly continental conditions and ongoing folding. Further west, Oligocene to Aquitanian NNW–SSE extension generated the Manosque half-graben as part of the European graben system that affected an area from the Gulf of Lion to the Rhine graben. (3) Following the Burdigalian breakup of the Gulf of Lion rift, a marine transgression migrated northward along the European graben system. Subsequent thermal subsidence allowed 1 km of marine sediments to be deposited across the Valensole and Manosque blocks, west of the active SSC thrust belt. (4) Mio-Pliocene conglomeratic deposits (2 km thick) were trapped within the Valensole basin by the uplifting Vaucluse block to the west and the advancing Alpine thrust sheets to the east. Late Pliocene thrusting of the SSC across the Valensole basin (approx. 10.5 km) can be linked along a Triassic detachment to the hinterland uplift of the Argentera basement massif.
Nice is situated on the shore of the Mediterranean, in lat. 43° 41′ 16″ N. and long, east of Greenwich 7° 16′ 37″. The county of which Nice is the capital, was comprehended in the Roman province of the Maritime Alps: it was included, while under the influence of France, in a department to which the same name was given; and now, it is restored to the sovereignty of Piémont, it may be considered as bounded on the west by the Var, which separates it from France, on the north and east by the mountains of Dauphiné and Piémont, and on the south, it is washed by the Mediterranean.
Ancient Revolutions of the Mineral Kingdom.—Vain attempts to explain them.—Dependence of Geology on Chemistry.—Importance of the Carbonate of Lime.—Dr Black's discovery of Carbonic Acid, subverted the former theories depending on Fire, but gave birth to that of Dr Hutton.—Progress of the Author's Ideas with regard to that Theory.—Experiments with Heat and Compression, suggested to Dr Hutton in 1790.—Undertaken by the Author in 1798.—Speculations on which his hopes of success were founded.
The importance of the Grimaldi complex of caves and rock shelters is twofold: scientific and historical. Scientifically, it is one of the major Upper Paleolithic sites, considering the variety of mobiliary and parietal art, the number of single and multiple burials and associated grave goods, and the abundant lithic and fauna remains. Historically, the documentation of activity that took place in this site starting from the second half of the 19 th century and the studies carried out on the materials that have been recovered in the decades between 1870s-1910s, provide instructive examples of methods and goals of Paleolithic archeology and anthropology of the epoch. This paper combines the scientific and the historic interest of the site through a chronicle of the events that took place during the period of the most sensational discoveries, i.e. beginning with the identification in 1872 of the first Upper Paleolithic burial and ending with the results of the excavations carried out in 1901 at Grotte des Enfants published in four volumes a few years later. The paper discusses early interpretations and modern views on the different findings and documents changes in perspectives and goals of paleoanthropological research in over a century, raising some of the major issues of contemporary Upper Paleolithic studies.
Reworked fossils may contribute unique data to ichnology, stratigraphy, and paleoecology. Reworked Upper Cretaceous echinoids are found on Ocean Isle Beach, North Carolina, United States. Tests of Hardouinia sp. cf. H. mortonis were intensely bored by clionaid sponges (Entobia) and bivalves (Gastrochaenolites), with rare polychaete annelids (Caulostrepsis). Evidence for a high-energy environment in the Late Cretaceous is provided by the sandstone infill and a geopetal infill. Hardouinia were bored on all surfaces, largely lack surface detail and have been corraded, exposing the internal structure of some borings, indicating that these specimens were tumbled in a modern, high energy marine environment. Borers showed substrate preferences: Entobia is largely limited to the test, but do penetrate the sandstone infill in some specimens; Caulostrepsis mainly infested the crystalline calcite of the echinoid test; and Gastrochaenolites penetrated both tests and lithified sandstone infill. This Entobia-Gastrochaenolites assemblage in these echinoids differs from the Entobia-Caulostrepsis assemblage recognized from the approximately coeval, but spatially distant, tests of Upper Cretaceous Echinocorys ex gr. scutata found reworked on the North Sea coast of Norfolk, England. Unlike the Entobia-Gastrochaenolites association of North Carolina, the boring association in Norfolk is between Entobia and Caulostrepsis, which are found in both tests and chalk infill. Thus, the lithology of the infill is an important factor in determining these differences.
Lithostratigraphic and structural framework, chronology and geochemistry
of the Tertiary calc-alkaline volcanism of Cap-d'Ail (French Maritime
Alps) are specified according to the new data collected during the
earthworks of the recent railway tunnel built between Cap-d'Ail and
Monaco. Two different magmatic events were dated: the first one, to
Palaeogene, the other one, to Neogene. To cite this article: J.-P.
Ivaldi et al., C. R. Geoscience 335 (2003).
The Late Oligocene oyster Hyotissa antiguensis (Brown) is locally common in the Antigua Formation of Hughes Point, eastern Antigua, Lesser Antilles; it was not commonly bored at that time. Its valves and shells are robust, and reworked into the shallow water near-shore environment in Antigua; it could potentially be incorporated into younger rocks. Its neoichnology includes clues that would facilitate identification of these oysters as reworked fossils. The suite of modern borings found in these specimens includes common Caulostrepsis taeniola Clarke, Gastrochaenolites isp. cf. G. turbinatus Kelly and Bromley and Entobia isp., and rare Oichnus simplex Bromley and Rogerella? isp. The latter three taxa are limited to oyster shell substrates. Of the common ichnotaxa, Caulostrepsis and Gastrochaenolites are particularly prominent in limestone clasts and limestone cemented to oyster shells, which would be an indicator of reworking if found in a post-Oligocene lithified deposit. Caulostrepsis and Gastrochaenolites are relatively less common in oyster shells and valves, and in many specimens are seen to terminate against the shell. Entobia is the only common boring limited to the shell substrate. The fidelity of preservation of modern borings is also superior in limestone clasts. This suite of borings is comparable with those found in the Neogene of the Antillean region.
A new collection of tests of the Chalk (Late Cretaceous) holasteroid echinoid Echinocorys ex gr. scutata Leske, occurring as clasts on the beach between Overstrand and Cromer, north Norfolk, England, show a range of features that have not been discussed hitherto. Unlike the previous report of similar reworked tests from the same locality, specimens are commonly not bored; where bored, Entobia and Caulostrepsis are commonest, and a sinuous boring (?) or burrow (?) immediately beneath the test surface is left in open nomenclature. Encrusting episkeletozoans, both Recent (bryozoans, serpulids, spirorbidae) and Late Cretaceous (bivalve? or brachiopod?, crinoid) are present on some better preserved tests.
The present article illustrates a straightforward case of hydrothermal dolomitization, affecting Jurassic platform limestones of the Provençal and Subbriançonnais Domains (Maritime Alps, North-Western Italy). Dolomitized bodies are randomly distributed within the host limestone, and are commonly associated with dolomite vein networks and tabular bodies of dolomite-cemented breccias discordant with respect to bedding. Main dolomite types are a finely to medium-crystalline replacive dolomite and a coarsely-crystalline saddle dolomite occurring both as replacive and as cement. Stratigraphic constraints indicate that dolomitization occurred during the Cretaceous, in a shallow burial context, and was due to the circulation of hot fluids (temperature about 200. °C, as indicated by fluid inclusion microthermometry) through faults and related fracture networks. Hydrothermal dolomitization therefore indirectly documents a Cretaceous fault activity in the Maritime Alps segment of the European Tethyan passive margin.
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The numerous mineral distinctions of the various rocks composing the Alps, and their separation into more or less crystalline masses, were the chief objects of the researches of the illustrious De Saussure; and some time elapsed before it was thought possible to bring these mountains into anything like a comparison with the sedimentary deposits of other parts of Europe, the determination of which had been established by their normal order of position and their imbedded organic remains. As soon however as Brochant (1808) declared his belief, that large crystalline masses of the Central and Savoy Alps, which had previously been considered of primary age, belonged to the earlier sedimentary or transition period, a new field of research was prepared; and Dr. Buckland made a still more important step, in a very able essay, wherein he boldly synchronized, in a general manner, the so-called transition rocks of Brochant, with our secondary British types*. Stimulated by such examples, and also by the researches of Brongniart, Von Buch, É. de Beaumont, Boué, Lill von Lilienstein and others. Professor Sedgwick and myself published our views in a memoir in the Transactions of the Geological Society†, accompanied by a general geological map of the Eastern Alps. Since that period, however, much progress having been made, by applying to this chain the more accurate knowledge of the order of equivalent formations, I had the strongest desire to revisit my old ground, to compare it with those regions of the Alps formerly unexplored by me, yet rendered
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Having occasion to visit the neighbourhood of Nice in the spring of 1826, I am gratified to bear testimony to the accuracy of the description of that district given by Mr. De la Beche in the preceding paper, and beg to subjoin a few observations which I made in company with M. Risso along nearly fifty miles of the high road that runs north-east from Nice towards the Col di Tendi.
The hill, one mile south of the village of Scarena and twelve miles northeast of Nice, affords a section of the green-sand formation, the details of which I noted on the spot, and which coincide with those given by Mr. De la Beche in other localities nearer to Nice. The mass of the stratum is a blue and grey marlstone, like the chalk-marl or firestone of England; through this are dispersed, subordinately, beds of a coarse and gritty limestone, with large calcareous masses containing green earth, and nodules of chert and of coarse jasper resembling the chert and jasper of the green-sand formation at Lyme and Sidmouth. The beds near Scarena abound with Nummulites, Turrilites, Ammonites, and the usual shells of the English green-sand formation. All these characters, however, disappear in the compact grey limestone, which both covers and lies beneath the well defined beds of green-sand; and it deserves investigation, whether the superior compact limestone is a modified condition of chalk, or an equivalent to the sandy and argillaceous deposits that make up the great bulk of the
In the June Number (p 251), we gave Messrs. Pictet and Lory's most recent views on the disputed age of those beds which contain the Terebratula diphya or T. viator of Pictet. In order to complete thier views I now publish a letter recently received from M.Héberts, which he requests me to add to the present notes.
A sedimentological and stratigraphical analysis has been applied to the Early Cretaceous glaucony-rich deposits of the southeastern margin of the Vocontian Basin. Thin sections, X-ray diffraction on random powders analyses, and data from geochemical analyses, performed on pure disaggregated glauconite grains by wavelength dispersion spectroscopy (WDS), allow the distinction of two populations of highly evolved glauconite grains. The first population is interpreted to be autochthonous (i.e., grains that have not experienced any transport from their place of origin). The second is interpreted to be parautochthonous (i.e., grains that have been removed from their place of origin and concentrated landward and seaward within nearly coeval deposits). Palaeoenvironmental information has been deduced mainly from (1) the characteristics of glauconitic grains, (2) meso- and microscopic analyses performed on the named lithozones, and (3) their lateral changes on a kilometre scale. Basin palaeogeography implies a southern area belonging to an outer platform and a northern zone with the characteristics of a distal ramp (Hauterivian). This depositional setting changed during the Barremian–Aptian owing to tectonics; fault systems led to a drowning of the western segment, but the previous environmental pattern presented again during Albian–Early Cenomanian times. Four different depositional events have been distinguished in the Early Cretaceous, and the relative sea-level changes have been reconstructed. We have traced relative sea-level fall during the Late Valanginian, the Early Barremian and the Albian (the second and third of these corresponding to the tectonic uplift outlined by Wilpshaar et al. (Cretac. Res. 18 (1997) 457)), while the general subsidence is confirmed by the transgression that led to the formation of glauconitic minerals. During the Lower Cretaceous, two second-order cycles have been recognized; although of the second order, the first sequence (Late Valanginian–Barremian) is made up like a third-order depositional sequence where different system-tracts are enhanced. The compared relative sea-level change corresponds to the curve of the second-order cycles of Haq et al. (1988, SEPM Spec. Publ. 42, 71–108).
From north to south, the lower course of the Var River cuts through three tectonic units: (1) the Nice arc (“arc de Nice”), (2) the oriental part of the Castellane arc (“arc de Castellane”), and (3) the autochthonous Provençal substratum. The Nice and Castellane arcs are sub-Alpine overthrusts, emplaced near the end of the Miocene and reactivated in Plio-Quaternary times. During the Pliocene, the downstream section of the river was invaded by the sea and transformed into a ria. The Pliocene sedimentary succession (Tabianian in its oldest levels) fossilizes a deeply incised erosional relief.
In 1895, G.K. Gilbert suggested that rhythmical repetition of patterns in the sequences of strata correspond to orbital variations and could provide a chronology for Earth history. This suggestion remained a heuristic hypothesis in need of testing; in this, the Mediterranean region latterly played a crucial role. Its extended sequences of pelagic and lacustrine–paludal strata provide long time series of hierarchical rhythmic variations tied directly to biostratigraphy and to magnetic reversals. The latter provide historical control and links to astronomically calculated curves that have been extended progressively into the past. These comparisons verify the orbital origins of the major sedimentary rhythms and are serving to reduce the age uncertainties of the significant time stratigraphic levels (biostratigraphic and magnetostratigraphic zones) from an order of ca 500 kyr toward the precessional (20 kyr) level. This refinement has essentially been reached for the last 14 Myr of Earth history in the Mediterranean, and beyond in the Pacific Ocean. The cyclic structure of shallow-water platform carbonates is also hierarchical but here the identification with specific orbital cycles has been equivocal and complicated by conflicts with radiometric data. In the gap-riddled shallow-water successions showing hierarchical ‘sequences’, the identification of some third-order, fourth-order and fifth-order ‘sequences’ or ‘parasequences’ with orbital forcing is being explored but remains inferential. Beyond chronology, the orbital variations constitute an endless series of experiments: similar variations in insolation, which resulted in sedimentary patterns formed by a chain of responses extending through atmospheric and hydrospheric dynamics to geological processes and the dynamics of the biotic systems. The emerging patterns offer glimpses into the past, to reveal previously unexpected phenomena such as systematic oscillations in deep-water aeration and unexpected oscillations in composition of upper-water plankton: patterns that pose new challenges to the understanding of Earth history.
The holasteroid Echinocorys is a common, robust echinoid in the Upper Cretaceous–Danian Chalks and limestones of northern Europe. It formed hard substrates
that were infested by a variety of encrusters and borers during its life and after death. Echinocorys is also a durable fossil. Tests occur as clasts on the beach at Overstrand, and between Overstrand and Cromer, north Norfolk,
eastern England. Reworking from (mainly) coastal sections has reintroduced Chalk Echinocorys into the benthic environment over 70 million years after its death and inhumation, with rare specimens washing up on the
beach at these localities. Unsilicified Echinocorys tests form a taphonomic series. The oral surface is the stable resting surface which is commonly not bored unless the exposed
Chalk infill is strongly infested by Entobia isp. Clean, unbored tests grade through specimens where the test calcite is perforated by Entobia isp. to remnants where most of the apical surface of the echinoid has been lost by boring, and the Chalk infill is perforated
by Caulostrepsis cf. taeniola Clarke, Entobia isp. and rare Gastrochaenolites isp. In contrast, flint steinkerns and external moulds are not bored. Four principal lines of evidence are used to determine
the time of occurrence of these borings: (1) comparison with common Chalk borings known from Echinocorys; (2) tests are invariably infilled with well-lithified Chalk, but (with one exception) borings preserve no evidence of prior
infilling; (3) the suite of borings are typical of modern lithoclasts on the beach; and (4) flint echinoids preserve no evidence
of modern borings. Lack of Cretaceous encrusting organisms is further evidence that suggests most borings may be modern. There
is only a limited indication of a mix of modern and ancient (Oichnus isp., indeterminate U-shaped boring) borings as has been noted previously in a belemnite from Overstrand.
KeywordsBiostratinomy–Reworked fossils–Holasteroids–Beachcombing–Ichnology–Borings
Large benthic foraminifers are considered to be good indicators of shallow marine carbonate environments in fossil series. Over the last 50 years, the palaeoenvironment of Tertiary Nummulites accumulations has been a matter of debate, particularly because of difficulties in interpreting these deposits, and in this way, the absence of analogues in present-day seas does not help. The aim of this paper is to insight the different ways Nummulites tests and clasts may accumulate according to their hydrodynamic behaviour. Based on experimental measurements and on SEM observations, it appears that the high primary skeletal porosity of Nummulites made them easily transportable. The calculated threshold shear velocities confirm that large-sized Nummulites can be moved by weak wave-driven currents. This peculiar hydrodynamic behaviour of Nummulites could explain the diversity of depositional models. Depending on local hydrodynamic conditions, autochthonous Nummulites deposits can be preserved as in situ winnowed bioaccumulations or be accumulated offshore, onshore or alongshore, away from the original biotope.
In 1830-33, Charles Lyell laid the foundations of evolutionary biology with Principles of Geology, a pioneering three-volume book that Charles Darwin took with him on the Beagle. Lyell championed the ideas of geologist James Hutton, who formulated one of the fundamental principles of modern geology - uniformitarianism. This proposed that natural processes always operate according to the same laws, allowing us to understand how features of the Earth's surface were produced by physical, chemical, and biological processes over long periods of time. Volume 1 consists of 26 chapters, a comprehensive index and woodcut illustrations of various mechanisms of geological change. Lyell begins with a definition of geology and then reviews ancient theories of the successive destruction and renovation of the world. He mentions James Hutton's ideas in chapter four, and goes on to discuss the effects of climate change, running water, volcanic eruptions and earthquakes on the Earth's crust.
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