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1

The ammonite faunas of the Callovian-Oxfordian boundary interval in Europe and their relevance to the establishment of an Oxfordian GSSP

Page K., Melendez G., Wright J.

Volumina Jurassica

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2009

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Vol. 7, no. 1

89-99

EN

At Moenkopi Wash along the Ward Terrace escarpment of northern Arizona strata of the upper Dinosaur Canyon Member of the Moenave Formation contain sedimentary structures we interpret as casts of tetrapod burrows. Sandstone casts and in situ burrows occur concentrated in two horizons that extend several hundred meters along the Ward Terrace escarpment. The structures, hosted in beds of eolian sandstone, form interconnecting networks of burrows that branch at right angles. Individual burrow casts have sub-circular cross sections and consist of nearvertical tunnels and horizontal to low-angle galleries that connect to larger chambers. Most burrow casts measure 5 to 15 cm in diameter, are filled by sandstone of similar grain size as the host rock, and have walls that are unlined and lack external ornamentation. Bedding plane exposure of the lower horizon reveals that the density of burrows exceeds 30 vertical tunnels per square meter. One exposure in the upper horizon reveals burrows concentrated in a mound-like structure with 1 m of relief. Rhizoliths, distinguished from burrows by their typical smaller diameters, calcareous infilling, and downward branching, co-occur with these burrows in the upper horizon. The fossil burrows in the Moenave Formation appear to have been constructed by a fossorial tetrapod with social behavior similar to the modern Mediterranean blind mole-rat. Although no skeletal remains are associated with the burrows, the fossil record suggests that the most likely producers of the Moenave burrows were tritylodontid cynodonts.

2

Integrated stratigraphical study of the candidate Oxfordian Global Stratotype Section and Point (GSSP) at Redcliff Point, Weymouth, Dorset, UK

Page K., Melendez G., Hart M., Price G., Wright J., Bown P., Bello J.

Volumina Jurassica

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2009

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Vol. 7, no. 1

101-111

EN

Ham Cliff near Redcliff Point, Weymouth, Dorset (SW England) exposes one of Europe's most complete Callovian-Oxfordian boundary sequences and has consequently been identified as a potential candidate GSSP for the base of the Oxfordian Stage. The boundary sequence lies within the thick mudrock facies of the Oxford Clay Formation and is abundantly fossiliferous, cardioceratid ammonites in particular being conspicuous. By convention, the stage boundary is drawn at the first occurrence of the genus Cardioceras here represented by C. redcliffense Page, Melendez and Wright at the base of the Scarburgense Subchronozone of the Mariae Chronozone. Associated Perisphinctoidea (including Peltoceras, Alligaticeras and Euaspidoceras) provide additional biostratigraphical information. Other macrofossil groups show less discernible changes, although frequent belemnites (Hibolithes) provide new highresolution carbon and strontium isotope data which are consistent with global curves and continuous sedimentation across the boundary interval. Magnetostratigraphic information is also available. Foraminiferal assemblages are dominated by epistominids but include a flood of early planktonic forms, including ?Globuligerina oxfordiana (Grigelis) immediately above the boundary. Well-preserved nannofloras are dominated by Watznaueria with conspicuous Zeugrhabdotus, podorhabdids and Stephanolithion indicating the NJ14 Biozone. Ostracoda and holothurian spicules are also recorded. These results are synthesised to provide a multidisciplinary, integrated review of the suitability of Redcliff Point for the definition of an Oxfordian GSSP. Correlations with the French candidate site in Haute-Provence are discussed and proposals made for formally establishing a GSSP for the base of the Oxfordian Stage in Europe.

3

Jurassic Global Stratotype Section and Points (GSSPs)-a potential serial World Heritage Site?

Page K., Melendez G., Henriques M.

Volumina Jurassica

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2008

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Vol. 6, no. 1

155-162

EN

The Operation Guidelines for the UNESCO World Heritage Convention state that proposed areas should: “..be outstanding examples representing major stages of Earth’s history, including the record of life”, “..contain all or most of the key interrelated and interdependent elements in their natural relationships”, “..have a management plan…” and “..have adequate long-term legislative, regulatory, institutional or traditional protection..”. By definition, Global Stratotype Sections and Points (GSSPs) should satisfy all these criteria, although in isolation, the proposal of any single GSSP is unlikely to succeed, however, as an individual site may lack a broader context. Nevertheless, combining a suite of GSSPs sites for a System within a ‘serial’ World Heritage site proposal would satisfy such a concern and could be an ultimate goal for the International Subcommission on Jurassic Stratigraphy.

4

Updated Middle Oxfordian biostratigraphy in the Central Iberian Chain (Spain) and state of progress of perisphinctid systematics

Bello J., Melendez G., Page K., Ramajo J.

Volumina Jurassica

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2006

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Vol. 4, no. 1

230-230

EN

Middle Oxfordian deposits in the Central Iberian Range (E Spain) are generally developed in biohermal to biostromal sponge limestones (Yatova Fm.). A major stratigraphic gap at the Callovian/Oxfordian boundary typically omits most of the Lower Oxfordian - excepting a few ephemeral sedimentary episodes - and the basal Middle Oxfordian Plicatilis Biozone. Despite being locally incomplete, however, the Transversarium and Bifurcatus biozones are well developed throughout the basin and display a remarkably complete ammonite succession. Perisphinctids are the key-group for biostratigraphic purposes and research carried out over the last 25 years has significantly contributed to refining the zonal scale for this interval. New information on this sequence indicates the following key points: 1. Recent progress includes the widespread recognition and correlation, including outside of Iberia, of the Rotoides Subbiozone at the top of the Transversarium Biozone and its further subdivision into two well-defined biohorizons: a lower, Universalis Biohorizon (Index: Per. universalis Bello, sp. nov. =Per. jelskii Siemiradzki, 1899, non 1891) and an upper Wartae Biohorizon. The latter is important as the direct forerunner of true representatives of Per. (Dichotomoceras) of the stenocycloidesbifurcatoides group. In addition, the identification of a Malinowskae Biohorizon with Per. malinowskae Br-Lewifski at the top of Bifurcatus Biozone (=Upper Grossouvrei Subbiozone) provides a valid name and level for specimens long misinterpreted as Per. bifurcatus (Quenstedt). 2. Taphonomic analysis of ammonite associations has provided an important tool for interpreting the sedimentary processes and the palaeogeographic evolution of the basin, including establishing the duration and reconstructing the processes associated with stratigraphic gaps. Similarly, taphonomic features shown by ammonite internal moulds across the Middle-Upper Oxfordian boundary (Bifurcatus-Hypselum chronozones) has facilitated the interpretation of this interval as a deepening stage on the platform, and therefore highly relevant for sequence and palaeogeographic analysis. 3. Finally, substantial progress achieved on the Perisphinctinae indicates the benefits of "re-shapeing" the systematics of the group in terms of modern, biological nomenclature. An open proposal is made considering the possibility of a unified taxonomy combining dimorphic pairs and a classification of the subfamily at the genus level, either a succession of genera as evolutionary links or perhaps a succession of species under a unique genus Perisphinctes (M & m).

5

The ammonite faunas of the Callovian/Oxfordian boundary interval in Europe and their relevance to the establishment of an Oxfordian GSSP

Melendez G., Page K., Wright J., Atrops F.

Volumina Jurassica

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2006

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Vol. 4, no. 1

185-185

EN

The latest Callovian and Early Oxfordian represent one of the most dynamic intervals in the history of Jurassic Ammonoidea and is characterized by one of the highest levels of mixing of Boreal, Submediterranean and even Mediterranean faunas. In particular the massive expansion of Boreal Cardioceratidae from their original “home” in Arctic areas as far south as South East France, brings them into contact with Mediterranean-style faunas rich in Phylloceratidae. This so-called “Boreal Spread” (after J. H. Callomon) provides the framework within which high-resolution inter-bioprovincial correlations are possible and hence the context for a sucessful GSSP designation for the base of the Oxfordian Stage within Europe (and hence the beginning of the Upper Jurassic). Associated with the Cardioceratidae, however, is a great variety of Perisphinctina, including Aspidoceratidae, Periphinctidae, Grossouvridae and rarer Pachyceratidae as well as frequent Hecticoceratidae and rarer Phylloceratidae. The latter groups are much more abundant in southern areas (Tethyan Realm), but the Aspidoceratidae do persist well into the Boreal Realm. Crucially, several groups of the Perisphinctina persist beyond Europe and therefore provide tantalising indications that a truly global correlation of any GSSP established in Europe will ultimately be possible. The current paper will review the stratigraphical, taxonomic and palaeobiogeographical context and significance of the trans Callovian/Oxfordian boundary faunas within Europe, building on recent results from the UK and France. Conclusions will be drawn concerning the appropriate – or convenient – level at which the place the Callovian-Oxfordian in Europe and its potential interpretation elsewhere. Such conclusions are highly relevant to the eventual establishment of an Oxfordian GSSP.

6

Protecting the Jurassic invertebrate collections in the museums: the “Museo Geominero” (Geo-mining Museum, IGME, Spain)

Delvene G., Melendez G., Menendez S.

Volumina Jurassica

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2006

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Vol. 4, no. 1

251-251

EN

The "Museo Geominero" ("Geo-mining Museum", Madrid) is one of the best examples of geological museums in Spain, promoting the protection conservation, as well as social and educational diffusion of geological and palaeontological heritage. As a research institution the museum contains a large number of geological and palaeontological samples with a great heritage value. The origin of the Museum collections were the samples collected by geologists and mining engineers of the so-called: "Comision del Mapa Geologico de Espana" (Commission for the Geological Map of Spain) created by Queen Elizabeth II in 1849. The collections, hence, came from many successive missions carried out by researchers of the "Instituto Geologico y Minero de Espana" (IGME) during the last 150 years in all Spain. At the moment, the permanent palaeontological exhibitions comprise the following collections: Spanish fossil invertebrates and flora, Spanish vertebrate fossils, foreign fossils and invertebrate taxonomy. Within the Jurassic invertebrate collections housed in the museum, representatives of Bivalvia (Mollusca) are the most significant group in both abundance and diversity. A still ongoing taxonomic review of the collections shows a total number of 44,307 specimens. The number of Jurassic elements is 5858. The bivalve collections comprise 810 specimens from Spain, 161 specimens from elsewhere in Europe and 25 specimens of uncertain origin, included in the collection of invertebrate taxonomy. Heritage value is underlined by the presence of many specimens from classical outcrops known since 1850. Most of them come from well-known Lower Jurassic outcrops in the Iberian Range: Anchuela del Campo, Maranchon (province of Guadalajara), Albarracin (province of Teruel) and Barahona (province of Soria). The origin of the samples of Guadalajara is very old: some of them were collected by the eminent scientists Lucas Mallada (1850-1885) and Jose de la Revilla (1955, 1959). Spanish Jurassic bivalve collections clearly reflect the rich palaeontological heritage of the country, according to bibliographic and recent field data. On the other hand, the bulk of the specimens from foreign fossil collections come from France, and are housed in the Museum since 1950. As a public research institution the collections are totally available to the members of scientific community. The taxonomic review of these collections has increased their heritage value. Almost all samples were collected and housed in the building before 1985, i.e. the year of the approval of the National Historical Heritage Law, hence forming a rich and diverse collection, representative of all areas of Iberia, despite their geographic origin and location still uncertain. This is a point of utmost importance today, since at the present moment it would be practically impossible to do so, due to the serious limitations to fossil collection imposed to researchers by the new heritage laws appeared in the autonomous communities of Spain.

7

Palaeogeographic evolution of the eastern Iberian carbonate ramp during the Middle Oxfordian

Ramajo J., Bello J., Melendez G., Page K.

Volumina Jurassica

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2006

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Vol. 4, no. 1

103-104

EN

Sedimentation on the East Iberian carbonate platform during the Middle and early Late Oxfordian represents the onset of subtidal marine conditions after a long period (Middle Callovian - Early Oxfordian) where extremely shallow to temporarily emerged environments predominated, favouring the development of condensed deposits. A progressive deepening during the Middle Oxfordian led to the development of sponge and microbiolite buildups alternating with biostromes. Levels with inverted or fragmented sponges and bioclastic storm deposits mark the most energetic events. Ammonite assemblages comprise mainly drifted shells from open-marine areas with only short-lived episodes of colonisation. Five stages are distinguished in this Middle Oxfordian sequence. 1. Parandieri Subchronozone - Middle Oxfordian deepening begins. In deeper areas to the NW, carbonate sediments contain abundant, well-preserved sponges occasionally in upright position. In shallower distal areas (SE) across a palaeogeographic swell, sedimentation is limited to thin, condensed levels of iron-oolite limestones and sponge spicules. 2. Luciaeformis-Schilli Subchronozone interval - a widespread deepening event leads to the development of sponge limestone facies throughout the platform. Sponge biostromes and buildups are developed in the NW, and in distal areas (SE) biostromic levels with inverted sponges and tempestite levels with broken sponges are common. A brief ammonite colonisation event took place in the NW during the middle Schilli Subchronozone. 3. Rotoides Subchronozone - lower part forms a condensed sequence (representing a storm deposit interval) formed by bioclastic limestones with sponge fragments and ammonite internal moulds. In the SE this interval is represented by a centrimetic level of bioclastic and ferruginous pelloids, which grade laterally into layers with fragmented sponges and pellets. The upper, Wartae Horizon, is represented in NW areas by a more expanded sequence of well-bedded micritic sponge limestones. 4. Stenocycloides Subchronozone - a micritic limestone sequence containing fragmented and broken sponges occasionally in upright position develops in the NW. In the SE more condensed, pelloidal, glauconitic limestones with packed, inverted sponge fossils are present. Ammonite assemblages comprise mainly reelaborated moulds. 5. Grossouvrei Subchronozone - the lower part in the NW forms a homogeneous interbedding of micritic limestones and marls with an increasing quartz content upwards; sponges are generally inverted or fragmented. In the SE, pelloidal and glauconitic limestones are dominant. Facies analysis and taphonomic features of ammonites indicate that maximum depths were reached at around the Grossouvrei-Hypselum zone boundary.

8

On the origin and palaeobiogeographic spread of Oxfordian ammonite genus Passendorferia and Tethyan subfamily Passendorferiinae Melendez

Melendez G., Atrops F., Bello J., Brochowicz-Lewiński W., D'Arpa C., Fozy I., Perez-Urresti I., Sequeiros L.

Volumina Jurassica

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2006

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Vol. 4, no. 1

240-241

EN

Oxfordian ammonite group Passendorferiinae (known as "Mediterranean Perisphinctids") form a lateral divergent branch of the main stem of Perisphinctidae, originating probably from Late Callovian Grossouvriinae (Alligaticeras) and spreading mainly in the Mediterranean (Tethyan) Province during the Early, Middle and Late Oxfordian. This morphologically homogeneous group is characterized by the evolute serpenticone coiling with sub-circular to subquadrate whorl section. Ribbing "simple" radial, is formed by mostly single and symmetrically bifurcate ribs, turning into thicker, straight, "columnar" ribs, slightly elevated on the ventral margin in adult stage of macroconchs. All these features make them strongly homoeomorphic with Tethyan Kimmeridgian Nebrodites, with which they have been often mistaken. The phyletic link might be represented by the genus Geyssantia Melendez, from Late Oxfordian Planula Chronozone. Microconchs, 80 to 120 mm Dm are isocostate, densely ribbed, lappeted and, show typically the development of parabolic nodes at the final part of adult phragmocone. Macroconchs 240 to over 320 mm Dm, slightly variocostate, show thick uniform columnar ribs in adult stage. Two main genera are so far recognized, evolving independently during Early and Middle Oxfordian: Passendorferia Brochwicz Lewiński, known from Lower Oxfordian early Cordatum Chronozone to Upper Oxfordian, Bimammatum-(?)Hauffianum Chronozone, characterized by extremely evolute serpenticone inner whorls with subcircular whorl section leading to subquadrate middle and outer whorls, and Sequeirosia Melendez, known mainly from the Middle Oxfordian characterized by more involute serpenticone coiling with subquadrate whorl section from early inner whorls. Passendorferiinae colonised and spread mainly on the southern margin of Tethys, being autochthonous in epioceanic carbonate platforms of western Tethys, from Hungary to southern Alps, Sicily, North Africa or Betic ranges, and reaching occasionally the external deeper areas of shallow epicontinental platforms at the northern margin of Tethys. This separate biogeographic distribution with respect to Perisphinctinae probably reflects a progressive extensional block differentiation of western Tethys at the Callovian-Oxfordian boundary and at the onset of Middle Oxfordian Transversarium Chronozone. Their rapid evolution provides them a biostratigraphic value similar to that of Perisphinctinae. At the turn of Middle-Late Oxfordian they gave rise to early Ataxioceratinae (Orthosphinctes), which would replace the Perisphinctinae and colonise the marginal epicontinental blocks of northern Tethys.

9

New biostratigraphic data on the Oxfordian from Roccapalumba (Western Sicily)

D'arpa C., Melendez G., Di Stefano P.

Volumina Jurassica

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2006

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Vol. 4, no. 1

144-144

EN

The small locality of Roccapalumba, in western central Sicily, is one of the most classical Jurassic localities described by G. G. Gemmellaro in his numerous monographs on the Jurassic faunas of Sicily. The Jurassic sequence by the village, crops out along an overturned carbonate succession overthrusting clastic deposits of Neogene age. Within this sequence the white massive limestones of Tithonian age form a characteristic escarpment on the landscape, which gives the name (“The Rock”) to the village. The earliest deposits cropping out at this point are Middle Jurassic, Bajocian to Early Callovian in age. Bathonian to Lower Callovian deposits are represented by light grey, micritic massive limestones. A sharp irregular surface marks the Middle/Upper Jurassic boundary level: a centimetric irregular limestone bed contains scarce Callovian ammonites, preserved as fragmented internal moulds showing evidence of taphonomic reelaboration (Paralcidia, Hecticoceras, Grossouvria). The Upper Jurassic sequence above this level comprises a first, lower succession of well defined grey-brownish, somewhat nodular limestone intervals (c. 20 m) of Oxfordian-Kimmeridgian age, and a second, upper succession of light grey massive micritic limestones (over 30 m) of presumably Tithonian age. A first lithological interval 7 to 7.5 m thick may be assigned to the Middle Oxfordian Transversarium Chronozone, Luciaeformis Subchronozone: some 1.5 to 2 m above the Middle/Upper Jurassic boundary level, the age of the deposits is evidenced by the presence of several specimens (fragmented shells) of Gregoryceras close to the G. riazi (Grossouvre) group. This first recorded association is followed by a second one including few specimens of Gregoryceras closer to G. transversarium (Quenstedt) group. This interval is topped by a clear discontinuity surface underlined by a yellow limestone level. The next interval, 3 m thick, may represent the middle-upper Transversarium Chronozone Schilli Subchronozone, by the record just above this level of a well preserved, resedimented (i.e. non-reelaborated) incomplete specimen of Sequeirosia (M) cf. brochwiczi (Sequeiros) and several fragmentary specimens of Passendorferia (m) erycensis Meléndez. Phylloceratina (Holcophylloceras, Sowerbyceras) are also common, whilst Lytoceratina are slightly scarcer. Above a new discontinuity marked by a second yellow limestone level, the next interval (about 3 m thick) has yielded few incomplete specimens of early Ataxioceratinae (Orthosphinctes) and Epipeltoceras gr. bimammatum (Quenstedt) that indicate Late Oxfordian, Bimammatum Chronozone age. Above a sharp, irregular truncational discontinuity surface, the sequence forms a 10-12 m thick interval of grey-brownish bioclastic, slightly nodular, well bedded limestones stratified in massive banks 40 to 50 cm thick. The Early Kimmeridgian age of this interval is evidenced by the frequent record of Ataxioceratinae (Lithacosphinctes spp.), “Aspidoceras” and a well preserved specimen of Nebrodites (M) close to the N. peltoideus (Quenstedt) group.

10

Jurassic Global Stratotype Section and Points (GSSPs) – a potential serial World Heritage Site?

Page K., Melendez G., Henriques M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

253-253

EN

The Operation Guidelines for the World Heritage Convention include the following criteria for the selection of natural heritage sites, which states that they should: "…be outstanding examples representing major stages of Earth's history, including the record of life, significant ongoing geological processes in the development of land forms, or significant geomorphic or physiographic features" [Criteria a (i)]; "The sites listed in a (i) should contain all or most of the key interrelated and interdependent elements in their natural relationships…" [Criteria b (i)]; "The site described in paragraph (a) should have a management plan…" [Criteria b (v)]; "A site described in paragraph (a) should have adequate long-term legislative, regulatory, institutional or traditional protection..." [Criteria b (vi)]. Global Stratotype Sections and Points (GSSPs) represent, by definition, the most stratigraphically complete and globally important stage-boundary sections known. They therefore fully satisfy the World Heritage criterion a (i). Crucially, their identification and ratification is regulated globally by the International Union of Geological Sciences (IUGS) which also advises UNESCO on the selection of World Heritage Sites for geological features - such a ratification can be taken as confirmation of global significance in more than just a technical or scientific sense. In addition, as part of the GSSP selection process aspects of the site's conservation status and safeguard for future study are also taken into consideration, Criterion b (vi) and be satisfied, if not b (v) as well. The proposal of any single GSSP in isolation as a World Heritage site is unlikely succeed, however, as individually such sites may lack a broader context. Combining a suite of GSSPs sites in a "serial" World Heritage site proposal - a well established approach in other contexts - is however, conceptually much more likely to succeed. In particular a proposal incorporating all the applicable GSSPs for a single system could certainly satisfy Criterion b (i), especially as all key interrelated and interdependent elements would then be included, i.e. all component stages of that system. Such a proposal could be an ultimately goal for the ISJS, as a celebration of decades of intensive work by many colleagues from many countries. Such a project would require a high degree of international agreement and already five countries are implicated in the process: Portugal, Spain, England, Scotland and France. Nevertheless, the close working relationships between specialists in different nations established through the Working Groups of the Subcommission can offer a marvellous opportunity for such collaboration.

11

Integrated stratigraphical study of the candidate Oxfordian Global Stratotype Section and Point (GSSP) at Redcliff Point, Weymouth, Dorset, UK

Page K., Melendez G., Hart M., Price G., Wright J., Bown P., Bello J.

Volumina Jurassica

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2006

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Vol. 4, no. 1

200-201

EN

Redcliff Point near Weymouth, Dorset (SW England) exposes one of Europe’s most complete Callovian-Oxfordian boundary sequences and has been the subject of a rigorous multidisciplinary assessment. The boundary sequence lies entirely within the clay facies of the Oxford Clay Formation, the relatively high carbonate content of which facilitates the excellent preservation of both macro- and microfaunas (and floras) as well as geochemical information. Ammonites, in particular, are conspicuous, and partly retain an aragonitic shell. By convention, the stage boundary is drawn at the first occurrence of the genus Cardioceras, which has been interpreted as corresponding to the transition between “Quenstedtoceras” paucicostatum (Lang) and Cardioceras ex gr. scarburgense (Young and Bird), specifically at the first occurrence of C. woodhamense Arkell sensu Callomon (non Marchand). This transition is well seen at Redcliff and provides the primary means through which the boundary can be correlated. Associated Perisphinctina (including Peltoceras, Alligaticeras, Properisphinctes and Euaspidoceras) provide additional biostratigraphical information. Other macrofossil groups show less discernible changes, although the end of the Callovian in England marks the local, virtual disappearance of Boreal cylindroteuthid belemnites with the persistence of Tethyan hibolithids into the Early Oxfordian. Isotopic studies of recovered belemnites record important information on carbon and strontium isotopes and provide new, high resolution data for the refinement of the global curves. The isotope data are also consistent with continuous sedimentation across the boundary. Foraminiferal assemblages are dominated by poorly preserved epistominids. Planktonic Foraminifera are recorded, mainly as pyrite steinkerns. This makes identification difficult although a flood close to the boundary appears to be Globuligerina oxfordiana. Other planktonic taxa are present, including one species that may be new. Nannofloras are well preserved, common to abundant and dominated by Watznaueria britannica with conspicuous Zeugrhabdotus erectus, podorhabdids and Stephanolithion bigotii. The presence of Stephanolithion bigotii maximum throughout, places the samples within the NJ14 biozone. Ostrocoda and holothurian spicules are also recorded. These results are synthesised to provide a multidisciplinary, integrated review of the suitability of Redcliff Point for the definition of an Oxfordian GSSP. Correlations with the French candidate site in Savournon, Haute-Provence are discussed and proposals made for formally establishing a GSSP for the base of the Oxfordian Stage in Europe.

12

Depositional sequences and ammonite fossilization on deep carbonate platform environments (Upper Oxfordian, Iberian Range, Spain)

Fernandez-Lopez S., Melendez G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

87-88

EN

The uppermost deposits of the Yatova Formation in the Ricla area represent a condensed section, 1.5 m thick, developed during the Semimammatum and Berrense subchronozones. This interval is composed of grey-reddish wackestone to packstone and boundstone beds alternating with marly intervals, bearing common sponges, ammonites and bioturbation textures. Terebratulid and rhynchonellid brachiopods, belemnites, bivalves, gastropods, serpulids, bryozoans, crinoids and echinoids are very scarce. Small sponge mud mounds, some few metres wide and less than 50 cm high, are locally developed. Limestone beds, 10 to 40 cm thick, show sharp base, but gradual size-increase or inverse grading of fossils and gradational upper boundary. Marly intervals, under 40 cm thick, display planar fabric, being normal grading of fossils more common than inverse grading. Hardground surfaces, ferruginous crusts and glauconite grains are common on the limestone beds. In contrast, hardground surfaces are not developed within marly intervals, although reworked concretions and remobilization surfaces are common, often capping the underlying argillaceous sediments. Parasequences show a less distinct development than in underlying intervals. Thickening and coarsening upwards sequences of metric thickness are common. Thinning and fining upwards sequences are scarce, generally developed between the last sponge mounds and associated with the thickest intervals of condensed deposits. This condensed interval is interpreted as formed in an open marine, moderately deep carbonate platform, below effective wave base, showing generally low-energy conditions with extremely low rates of carbonate and terrigenous sedimentation. Marly deposits represent background sedimentation, with very low rates of sediment accumulation, which may be due to sedimentary starving as well as to winnowing action on the seafloor. In contrast, limestone beds correspond to event sedimentation, with relatively high rates of sediment accumulation, probably distal tempestites. Lasting episodes of background sedimentation give rise to clay deposits showing no evidence of basal discontinuity, whereas brief events of turbulence lead to carbonate deposits with sharp base. The low diversity of the benthic fauna, scarce development of sponge bioherms and microbial crusts, as well as ammonite populations inhabiting the platform are all palaeobiological criteria confirming these deep and distal palaeoenvironments. Taphonomic features of ammonite assemblages indicative of sedimentary starving are the occurrence of: 1 - high concentrations of reelaborated ammonites showing very low values of taphonomic condensation; 2 - taphonic populations of type-2; 3 - predominant internal moulds of phragmocones completely filled with homogeneous sediment up to the innermost whorls; and 4 - reworked fossils bearing no signs of abrasion, bioerosion or dense encrusting. These condensed deposits characterize the last phase of a deepening half-cycle, attaining the maximum deepening environments during Upper Jurassic, within a 3rd order deepening/shallowing cycle developed in the Iberian platform system.