bluuebunny/crossref_metadata_2025 huggingface dataset:
Stratigraphic traps in the Tertiary rift basins of Indonesia: case studies and future potential
Authors: Atkinson Christopher , Renolds Michael , Hutapea Oskar
Published: April 2008

Stratigraphic traps are often regarded as one of the most risky exploration targets and are frequently the most difficult trap type to secure management support for drilling. This is despite their frequent occurrence in many basins, in particular the mature onshore basins of North America. The critical factors required for the development of stratigraphic traps are the presence of a fully charged petroleum system, favourable basin and reservoir architectures, low dips in the accumulation zone and good seal integrity. These factors commonly occur in the Palaeogene rift basins of Indonesia and consequently, since the early 1990s stratigraphic traps have often accounted for the majority of recently discovered fields.

The Palaeogene rifts of Indonesia are prone to the stratigraphic trapping of hydrocarbons simply because they possess an almost perfect petroleum system in which traps of this type can form. Every rift has a similar history beginning with a syn-rift phase, which primarily provides source rocks of various types as well as reservoir sandstones. This is followed by a thermal sag phase (‘early post-rift’) where better quality reservoir sandstones and sometimes reef carbonates are found. The ensuing transgressive phase (‘late post rift’) guarantees a marine shale regional seal. This seal is most impressive at the Minas Field in Central Sumatra where 6 billion barrels of oil are trapped at only 600 metres depth with no surface oil seeps. The various late Tertiary ‘orogenic’ phases trigger migration of hydrocarbons generally up the flanks of the rifts as well as creating structures at shallower levels. Sometimes this structural activity is so intense that the regional seal is breached causing hydrocarbons to migrate into these shallower structures where major accumulations have been found. However, where the seal is not breached the hydrocarbons must still be trapped below it on the flanks of the rift. The giant Widuri and Kaji Semoga fields are perfect case history examples.

There is no doubt that in Indonesia the ‘easy oil’ has already been found in large 4-way dip closures or classic Sunda Fold inversion structures. However, it is contended that there is still a huge potential for finding large reserves in stratigraphic traps in basins with the right characteristics. In this context, two largely unexplored basins within the Asahan Offshore PSC, North Sumatra and the Biliton PSC, West Java are discussed. Both these areas exhibit all the ingredients required for successful stratigraphic trap discoveries but both remain at the present day undrilled for this play type.
The importance of stratigraphic plays in the undiscovered resources of the UK Continental Shelf
Authors: Stoker S. J. , Gray J. C. , Haile P. , Andrews I. J. , Cameron T. D. J.
Published: April 2008

This paper analyses the statistics of existing United Kingdom Continental Shelf (UKCS) fields and discoveries as a means of assessing which plays are likely to contain the greatest untapped potential for stratigraphic traps. Current Department of Trade and Industry (DTI) estimates put the maximum discovered ultimate recovery of the UK at 50 billion (× 10
9
) barrels of oil equivalent (BBOE); estimated technically recoverable undiscovered resources are between 4.1 to 21.3 BBOE, based on a prospect mapping approach.

As of end 2003, 82% of the oil and gas fields and discoveries on the UKCS have been found in structural traps; 12% have been found in combination structural/stratigraphic traps and only 6% in stratigraphic traps. The majority of stratigraphic traps and combination traps occur in association with syn-rift (Upper Jurassic) and post-rift deep-water plays. There has been relatively little direct exploration for stratigraphic traps until recently, and a number of the major discoveries in stratigraphic traps were found by chance. Few substantial untested structural traps remain in the UK North Sea except at considerable depth with associated risks. We estimate that perhaps 50% of the UKCS undiscovered resources are located in stratigraphic or combination traps, principally within syn- and post-rift deep-water sandstone plays.
Lower Cretaceous deep-water sandstone plays in the UK Central Graben
Authors: Milton-Worssell R. J. , Stoker S. J. , Cavill J. E.
Published: April 2008

Up to the present, exploration of the UK Lower Cretaceous deep-water sandstone play has been confined largely to the Moray Firth basins. The Lower Cretaceous of the Central Graben area has been modelled previously as predominantly shale-prone, and hence unattractive to exploration. There is a growing realization that this may not be the case. Since seismic imaging of Lower Cretaceous sandstones is known to be poor whether hydrocarbon-bearing or water-wet, a robust depositional model must be constructed from well and regional geological data in order to predict sandstone distribution and geometry, and hence to aid identification of potential hydrocarbon traps. Of the hundreds of wells drilled in the Central Graben area that targeted deeper Jurassic-Triassic reservoirs, virtually all have been located on the flanks of the graben, or on intra-graben highs. However, 71 of these wells have proved sandstones or traces of sandstone within the Lower Cretaceous, giving grounds for optimism that more substantial deep-water sandstone developments may be present within the graben depocentres. Twenty-six leads have been identified within these depocentres; most of these are located within stratigraphic traps in interpreted detached basin floor fans.
Extrusive sandstones (extrudites): a new class of stratigraphic trap?
Authors: Hurst Andrew , Cartwright Joseph A. , Huuse Mads , Duranti Davide
Published: April 2008

Extrusive sandstone bodies are identified as entirely stratigraphic traps associated with sand injectites. They may be difficult to recognize but have four-way dip closure and are invariably connected through underlying lower permeability strata to parent sandbodies by sandstone dykes or transgressive sills that belong to sand injectite complexes. Extrusive sandstones (extrudites) constitute an immature exploration target, which is largely untested by deliberate exploration wells. Using seismic data alone, the distinction between extrudites and intrusive sills, and between extrudites and depositional sands, may be problematic. Sedimentological criteria may make differentiation possible when core is available. Extrudites are likely to have been drilled and misinterpreted as conventional deep-water turbidites within deep-water systems affected by sand injection.
Rhodalgal/bryomol assemblages in temperate-type carbonate, channelized depositional systems: the Early Miocene of the Sarcidano area (Sardinia, Italy)
Authors: Bassi Davide , Carannante Gabriele , Murru Marco , Simone Lucia , Toscano Francesco
Published: April 2008

During Aquitanian-Burdigalian times, temperate-type carbonate-siliciclastic successions were deposited in basins located on the graben and half-graben along the Oligo-Miocene Sardinia Rift Basin (Sardinia, Italy). In one of these basins, the Isili Basin, rhodalgal/bryomol limestone was deposited in a temperate-type carbonate depositional system in which a shallow carbonate factory, a marginal tributary belt and a main channel were identified. In this paper, the Isili Limestone is described in terms of biogenic components and taphonomic characterization. To understand the palaeoecology of the depositional settings and the related palaeoceanographic controls, the coralline algal assemblages were differentiated according to coralline growth forms, rhodolith shapes, rhodolith inner structure and taxonomic composition. In addition, a first analysis was carried out in order to discriminate among the different bryozoan and mollusc assemblages present in different localities corresponding to different palaeoecological settings. The results obtained provide fundamental support for palaeoenvironmental reconstruction that combines palaeobiological analyses (i.e. rhodolith characteristics, bryozoan growth forms, taphonomic features) with previous physical (sedimentological and geometrical) observations. This allows a more detailed reconstruction of the complex relationships between the different sectors of the sedimentary system: the carbonate factory, the smaller erosive tributary channels and the deeper main channel.
Models of temperate carbonate deposition in Neogene basins in SE Spain: a synthesis
Authors: Braga Juan C. , Martín José M. , Betzler Christian , Aguirre Julio
Published: April 2008

Upper Miocene (Tortonian-Messinian) to Lower Pliocene (Zanclean) temperate bioclastic limestones occur in the Betic intermontane basins mixed with diverse proportions of siliciclastics. Components are mostly originally calcitic skeletons of invertebrates (especially bryozoans and bivalves) and coralline algae. Carbonate mud content is usually low and cementation is generally weak. These temperate carbonates formed in ramps. The depositional surface profile and local hydrodynamic conditions in each example controlled the occurrence of diverse facies at similar positions within the ramp. Shallow-water facies are well represented and formed in beaches and backshore lagoons, spits, rocky shores and submarine cliffs. Shoals developed seawards of shore deposits; the relatively quiet environments basinwards of the shaosl were the areas of maximal carbonate production (factory facies). The lack of early lithification favoured mobilization of skeletal particles. Waves and currents during storms transported carbonate grains landwards from the factory areas to shoals, spits and beaches. Skeletal grains were also transported downslope along the ramp. Re-deposited carbonates occur within basinal marls in submarine lobes and channels fed by channels cross-cutting and excavating the platform sediments. The absence of hermatypic corals and calcareous green algae in shallow-water deposits suggests cool surface water temperatures during carbonate formation. Large benthic foraminifers and oxygen stable isotope values indicate winter surface water temperatures of 16–17°C.
Oceanography, sedimentology and acoustic mapping of a bryomol carbonate factory in the northern Gulf of California, Mexico
Authors: Halfar J. , Strasser M. , Riegl B. , Godinez-Orta L.
Published: April 2008

Bryomol carbonates, composed of bryozoans and molluscs, are found in non-tropical shelf and upper slope settings where they are sensitive indicators of oceanographic conditions. Few modern bryomol carbonate settings have been investigated to date, despite their importance in the Phanerozoic rock record. Furthermore, no detailed facies mapping and long-term oceanographic observations have been undertaken in modern bryomol settings, even though this is important for accurately interpreting facies, climate and oceanography from fossil bryomol carbonates. A bryomol carbonate factory on the western margin of the northern Gulf of California, Mexico was selected for an integrated high-resolution
in situ
oceanographic monitoring, acoustic seafloor mapping, sediment and bryozoan growth morphology study. Molluscan- (28%), bryozoan- (25%) and barnacle- (14%) dominated carbonate production takes place under normal saline warm-temperate eutrophic conditions, with average near sea surface temperatures of 20°C. Even though temperatures are unusually warm for the formation of bryomol carbonates, they develop as a result of prevailing eutrophic conditions (average chlorophyll-
a
contents of 2.2 mg chl-
a
m
−3
). Eutrophic conditions provide ample food to heterotrophic calcifiers and largely exclude faster-growing phototrophic organisms by drastically restricting the depth of the euphotic zone and, therefore, water clarity. Thus, the presence of high amounts of nutrients can generate cool-water-type carbonate assemblages at temperatures where a warm-water association would be expected.
Carbonate sedimentation, climate change and stratigraphic completeness on a Miocene cool-water epeiric ramp, Murray Basin, South Australia
Authors: Lukasik Jeff , James Noel P.
Published: April 2008

Lower to Middle Miocene warm temperate-water carbonates of the Murray Supergroup, comprising both fossiliferous heterozoan and foraminifer photozoan facies, accumulated on a low-energy, marine, mesotrophic epeiric ramp in a broad, shallow, intracratonic basin. Depositional conditions ranged from temperate-water with abundant nutrients supplied from the surrounding hinterland under a cool, moist climate regime in the early Miocene, to warm-temperate and subtropical seas with reduced levels of trophic resources associated with an increasingly arid regional climate in the middle Miocene. The succession is separated into three, metre-scale, 1.25–2.75 Ma, transgressive-regressive sequences, or stratigraphic packages. Transgressive carbonates range from Lower Miocene, heterozoan, open-marine echinoidal and bryozoan facies to Middle Miocene, bryozoan-rich, open-marine foraminifer-photozoan facies. Regressive deposits are mainly heterozoan, varying from restricted nearshore marine clays to molluscan seagrass meadow facies, all of which are interpreted to represent highly mesotrophic water conditions. The turn-around from transgression to regression, the transition zone, is variably preserved depending upon the ability of the depositional system to track changes in falling sea-level and is critical to the completeness of the succession. Stratigraphic completeness dramatically increases from the Lower to Middle Miocene stratigraphic packages as rates of sediment production and accumulation increased in conjunction with higher water temperatures and climatic aridity set against a background of increasing eustatic amplitudes. The result is a greenhouse-style succession generated in an evolving icehouse world. This highlights the principle that while allogenic repetition is produced by eustatic forcing, the nature and completeness of the ‘cool-water’ carbonate stratigraphic record can vary significantly due to subtle changes in the nature of the carbonate factory, which are, in turn, determined by sea-water temperature and trophic resources related to climate.
Epitaxial calcite cements in Earth history: a cooler-water phenomenon during aragonite-sea times?
Authors: Knoerich Andrea C. , Mutti Maria
Published: April 2008

Epitaxial calcite overgrowths on echinoderm fragments are important contributors to the rock record during specific time intervals in Earth history (so-called ‘calcite-sea’ times). Such overgrowths also occur throughout the Phanerozoic in heterozoan carbonate associations, where, these cements often form the volumetrically most important cement type. The origin and environment in which this cement forms are controversially debated, reaching from early marine, meteoric, burial to emergence. The formation of epitaxial overgrowth in calcite sea shallow-water carbonates is reported from early diagenetic environments (marine, marine burial and meteoric), whereas for aragonite sea shallow-water heterozoan carbonates generally a later, burial diagenetic environment of epitaxial cement precipitation is stated. Data from the central Mediterranean area (Maltese Islands and Sicily) show that also in heterozoan shallow-water carbonates the main phase of epitaxial cement precipitation can occur early, in the marine, meteoric and marine burial environment. Cementation was not sourced by pressure solution of calcitic grains, which clearly postdates epitaxial cement growth, but by the early dissolution of aragonitic biota. These findings underline the importance of aragonitic components as an early cement source in aragonite-sea time non-tropical/heterozoan carbonates and emphasize the similarity of the diagenetic evolution of these rocks with calcite-sea time tropical carbonates.
The history of meteoritics — overview
Authors: McCall G. J. H. , Bowden A. J. , Howarth R. J.
Published: April 2008

This volume was proposed after Peter Tandy and Joe McCall organized a 1-day meeting of the History of Geology Group, which is affiliated to the Geological Society, at the Natural History Museum in December 2003. This meeting covered the History of Meteoritics up to 1920 and nine presentations were included, the keynote talk being given by Ursula Marvin. There was an enthusiastic audience of about 50, who expressed the view that this meeting should lead to a publication. Dr Cherry Lewis, the chairperson of the group, discussed this with Joe McCall, who said that the material was too small for a Special Publication, but it could be developed by expanding it, taking the history through the 20th century, when there was a revolution and immense expansion both in the scope of meteorite finds and the application of meteoritics to scientific research on a very broad front with the advent of the Space Age. This was agreed and a format of about 24 articles was designed, approaches being made to selected authors.

The sections of this Special Publication relate to the early development of meteoritics as a science; collecting and museum collections; researches establishing the provenance of meteorites; and impact craters and tektites.
The Neolithic pottery of Abri Pendimoun (Castellar, France): a petro-archaeometric study
Authors: Basso E. , Binder D. , Messiga B. , Riccardi M. P.
Published: April 2008

Middle and Late Neolithic ceramics from Abri Pendimoun (Castellar, France) and their geological raw materials have been investigated to characterize the ceramic bodies and to determine the possible provenance of raw materials. Petrographic, mineralogical and energy-dispersive spectrometry analyses were undertaken to define the compositional parameters of sherds and to clarify the relationship between Square Mouthed Pottery-phase I (VBQ I) and Chassey Culture. The ceramic bodies were generally made from glauconite-rich layers and terra rossa, unprocessed or mixed in variable proportions. Different kinds of temper, such as carbonates and/or aplite fragments, were added to the mixtures. Although most of the analysed ceramics were produced locally, a few mixtures show the addition of exogenous rocks. Although these ceramics could be interpreted as imported, we demonstrate that local clayey materials were used at Abri Pendimoun. The hypothesis that pottery was imported can therefore be ruled out. A small amount of crushed calcite (5%) was added to some glauconitic pellet mixtures. Pots made with this mixture are normally referred to the VBQ I. This combination of mixture and shape indicates that there was an important link between the VBQ I and Chassey Cultures.
Late La Tène pottery from western Switzerland: one regional or several local workshops?
Authors: Maggetti Marino , Galetti Giulio
Published: April 2008

A total of 203 pieces of fine ceramic and four clays from seven sites of western Switzerland (Bern, Genève, Grotte du Four, La Tène, Marin, Saint-Triphon — Massongex and Yverdon) were studied chemically and mineralogically to determine if there was local production at each site and if trade links existed between the sites. Firing wasters from Bern and the region of Genève indicate local ceramic production. The sherds are often contaminated with secondary phosphorus and, in the case of Bern, copper. Most of the fine ceramic is CaO-poor, contrasting with the CaO-rich clays. Based on the chromium and nickel concentrations, it can be subdivided into two distinct groups. The majority of the sherd populations from Genève, Saint-Triphon and Massongex, as well as a few specimens from Bern, La Tène and Yverdon, have high Cr and Ni values. The remaining sherds have low Cr and Ni concentrations. The analyses show that: (1) the fine ceramic from each of the seven sites forms an often inhomogeneous and widely dispersed group, distinct from the others; consequently, it is most probably a local or regional product; (2) ceramic import is probable for one piece from Grotte du Four (provenance Yverdon); (3) the Late La Tène fine ceramic was manufactured mainly from silicate or silicate-carbonate, fat to lean clays.
Chemical-mineralogical characterization of historical bricks from Ferrara: an integrated bulk and micro-analytical approach
Authors: Bianchini Gianluca , Marrocchino Elena , Moretti Alessandro , Vaccaro Carmela
Published: April 2008

In this paper we present bulk X-ray fluorescence-X-ray diffraction (XRF/XRD) and microanalytical scanning electron microscope-electron microprobe analysis (SEM-EMPA) data on historical bricks from Medieval or Renaissance buildings of Ferrara (NE Italy) to provide insights into the nature and provenance of the raw material as well as clues on the sintering techniques. Chemical data indicate that the starting materials were obtained by mixing high Cr-Ni clay and subordinate sand (both quarried from the P
o
river alluvial deposits) with the possible introduction of a Na-rich flux component. Thin-section observation, XRD and micro-analytical data indicate the presence of key accessory phases such as pyroxene, amphibole, epidote and rare olivine in the pre-fired mineral assemblage, confirming the utilization of the Po river sediments. Recognition of neo-formation firing phases (e.g. melilite, wollastonite), together with composition of micas, amphiboles and interstitial glasses, indicate kiln temperatures between
c.
800 and 1000 °C. This provides guidelines for making new compatible and durable bricks to be utilized for restoration, and contributes to the preservation of historical masonry.
Pre-industrial glassmaking in the Swiss Jura: the refractory earth for the glassworks of Derrière Sairoche (ct. Bern, 1699–1714)
Authors: Eramo G.
Published: April 2008

Fragments of the melting furnace and several crucibles of the glassworks of Derrière Sairoche are compared with local raw materials. Principal component analysis (PCA) based on the chemical composition and on the grain-size distribution of the archaeological and natural materials demonstrates that the analysed samples were made from the same raw material and that local clayey sands (Hupper, Sidérolithique) were exploited. Availability
in situ
of good raw materials made tempering unnecessary. Their high melting point (
c.
1600 °C) allowed good performance in service conditions at temperatures up to 1500 °C. Moreover, because of low Fe
2
O
3tot
concentrations, batch-glass contamination was avoided.
Petrographic features and thermal behaviour of the historically known ‘pietra ollare’ from the Italian Central Alps (Valchiavenna and Valmalenco)
Authors: Antonelli Fabrizio , Santi Patrizia , Renzulli Alberto , Bonazza Alessandra
Published: April 2008

Thermal and porosimetric properties of different lithotypes of ‘pietra ollare’ (magnesite-bearing talc-shists, chlorite-schists, tremolite-bearing chlorite-schists and serpentine-schists) from the Italian Central Alps (Valchiavenna and Valmalenco) have been investigated. Some cross-correlations are established among the main mineral—petrographic and textural features, thermal behaviour and historical utilization of these lithotypes for the production of stoves and cooking pots during the Middle Ages. All the analysed samples show (1) low total open porosity (0.73–2.85%) with meso- and micropores prevailing over macropores; (2) regular linear expansion up to
c.
700 °C, good thermal stability up to 1200 °C and negligible weight loss (< 1%) to
c.
500 °C; (3) high thermal expansion (5.57 × 10
−6
°C
−1
< α
25–100 °C
< 8.89 × 10
−6
°C
−1
). The results indicate that, under the thermal conditions typical of the traditional medieval ‘open fire system’ (
T
≤ 600 °C), the Italian ‘pietra ollare’ from the Central Alps was an excellent fire-resistant geomaterial, which did not undergo any significant transformation as a result of thermal shocks.
Prehistoric polished stone artefacts in Italy: a petrographic and archaeological assessment
Authors: D’Amico Claudio , Starnini Elisabetta
Published: April 2008

The paper illustrates the results of an archaeometric project on the raw material characterization of some collections of prehistoric polished stone tools, dated from the Early Neolithic to the Bronze Age, from sites located in Northern Italy. The petrographic analyses (surface and thin-section microscopy, X-ray powder diffraction, scanning electron microscopy-energy-dispersive spectrometry, X-ray fluorescence, atomic absorption spectrometry) revealed a raw material circulation network involving the whole of Northern Italy. Here occur the outcrops of high-pressure (HP) meta-ophiolites, which were widely utilized from the Early Neolithic onwards for the manufacture of polished cutting-edged tools, which are represented by axes, adzes and chisels. Other raw materials, such as serpentinites, seem to have been preferred for the production of other types of artefacts, including stone rings used as bracelets. The analyses revealed that the prehistoric polished stone artefacts were made from uncommon lithologies such as Alpine eclogites, jades and other HP meta-ophiolites. These rocks were exploited from primary and secondary sources, mainly located in Piedmont, the Aosta Valley and Liguria. During the Neolithic these lithologies are the dominant raw material for the polished stone tools in Northern Italy and southeastern France. In the same period, in other European countries the same lithologies occur less frequently as axe or adze blades; in NW Europe they were frequently used for manufacturing long ceremonial axes, which have a typology that does not appear to belong to the Italian tradition.
The stone of the inscribed Etruscan stelae from the Valdelsa area (Siena, Italy)
Authors: Gandin A. , Capezzuoli E. , Ciacci A.
Published: April 2008

The results of an archaeometric study on five inscribed Etruscan funerary stelae, produced during the second half of the sixth century
BC
, in the Valdelsa area (NW of Siena, Italy), are reported. The style of the inscriptions suggests the presence of a local culture and a common language. The stone used to make the stelae is a laminated limestone consisting of the alternation of more or less compact bands whose petrographic features can be compared to those of travertines (continental carbonates deposited from hot springs). The fabric of the stone of these stelae implies provenance from a thermal deposit, in the Valdelsa area, where calcareous tufa dominates; however, hot water deposits are probably to be found in the Gracciano Val d’Elsa area, not far from the localities where the stelae were found.
Geochemical and petrographic approaches to chert tool provenance studies: evidence from two western USA Holocene archaeological sites
Authors: Morgenstein Maury
Published: April 2008

Chert (flint, jasper and agate) from a late Holocene site in Elko, northern Nevada, USA, and a Mid-Holocene site east of Seattle, Washington, USA, represents a wide range of geological source environments for microcrystalline polymorphs of quartz. Potential chert source material and lithic artefacts from these two archaeological sites are utilized to develop laboratory approaches to provenance studies. Chert paragenesis determined by petrographic analysis and geochemical cluster fingerprinting using inductively coupled plasma (ICP) and ICP-mass spectrometry analyses accompanied by scanning electron microscope-energy dispersive X-ray fluorescence analysis provides compelling source to artefact correlations.
Mid-Cretaceous stratigraphy of the James Ross Basin, Antarctica
Authors: Crame J. A. , Pirrie D. , Riding J. B.
Published: April 2008

The extensive Cretaceous sedimentary sequence exposed within the James Ross Basin, Antarctica, is critical for regional stratigraphic correlations in the Southern Hemisphere, and also for our understanding of the radiation and extinction of a range of taxonomic groups. However, the nature and definition of Cenomanian-Turonian strata on the NW margins of James Ross Island has previously been difficult, due both to marked lateral facies changes and to stratigraphical discontinuities within the extensive Whisky Bay Formation. Facies variation and local unconformities were the result of fault-controlled deep-marine sedimentation along the basin margin. In this study the Albian-Cenomanian boundary is defined for the first time in the upper levels of the Lewis Hill Member of the Whisky Bay Formation. However, there is a Cenomanian-late Turonian unconformity between the Lewis HIll and Brandy Bay members of the Whisky Bay Formation. Equivalent lithostratigraphical units exposed further to the SW on James Ross Island appear to be more complete with the early Cenomanian-late Turonian interval represented by the upper parts of the Tumbledown Cliffs and the lower part of the Rum Cove members of the Whisky Bay Formation. The Turonian-Coniacian boundary is provisionally placed at the junction between the Whisky Bay and Hidden Lake formations. The revised stratigraphic ages for this section show that the Late Cretaceous radiations of a number of major plant and animal groups can be traced back to at least the Turonian stage. This raises the possibility that their dissemination might be linked to the global Cretaceous thermal maximum.
Late Cretaceous Antarctic fish diversity
Authors: Kriwet J. , Lirio J. M. , Nuñez H. J. , Puceat E. , Lécuyer C.
Published: April 2008

New material from the Santa Marta Formation (late Coniacian-?early Maastrichtian) of James Ross Island contributes significantly to the current knowledge of Late Cretaceous Antarctic fish diversity. The taxon list for the Santa Marta Formation is extended, and new records of neoselachians and teleosts are reported. The stratigraphic ranges of some previously known taxa are enlarged, and the palaeobiogeography and palaeoecology of Late Cretaceous Antarctic fishes are discussed. Top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the Santa Marta and López de Bertodano formations. The only fish adapted to crushing hard-shelled invertebrates were the chimeroids. Rays, an important component of marine fish associations, as well as fish from lower trophic levels, remain unknown from the Late Cretaceous of Antarctica.
Late Eocene penguins from West Antarctica: systematics and biostratigraphy
Authors: Tambussi C. P. , Acosta Hospitaleche C. I. , Reguero M. A. , Marenssi S. A.
Published: April 2008

Penguins are by far the most dominant group of marine vertebrates in the Eocene La Meseta Formation (Seymour Island, Antarctica). We analysed the penguin fauna recovered there from both a systematic and a biostratigraphic point of view. We have added two new species (
Tonniornis mesetaensis
and
T. minimum
) and have defined a biostratigraphic unit, the
Anthropornis nordenskjoeldi
Biozone. This interval of strata, easily distinguishable by the numerous occurrence of penguin bones and the phosphatic brachiopod
Lingula
, is located nearly 30–35 m below the top of the 145 m-thick Submeseta Allomember. The highest morphological and taxonomic penguin diversity living sympatrically (organisms that live simultaneously in the same place), including giant and tiny species, is documented in this interval. Fossil penguins bones studied in this paper, recovered from rocks interpreted as shallow-marine deposits, accumulated between 34.2 and 36.13 Ma (late Late Eocene).
The late Middle Eocene terrestrial vertebrate fauna from Seymour Island: the tails of the Eocene Patagonian size distribution
Authors: Case Judd A.
Published: April 2008

The Middle Eocene Antarctic terrestrial vertebrate palaeofauna from the La Meseta Formation on Seymour Island (= Isla Marambio), Antarctic Peninsula has a U-shaped, bimodal distribution of body sizes. This palaeofauna includes a wide range of body sizes from small insectivorous, omnivorous and granivorous marsupials, a rodent-like non-therian gondwanathere, large-sized ungulates, a sloth and cursorial birds (a ratite and a phororachoid). Medium-sized, homeothermic animals in the size range represented by rabbit to small ungulate-sized animals have not been found.

For comparison, the Early Eocene Casamayoran (Vacan ‘subage’) mammalian palaeofauna from Patagonia has a reasonably normal distribution of body sizes, with the modal class represented by medium-sized mammals, a distribution that is the direct opposite of the Antarctic palaeofauna. A comparison of the Middle Eocene Antarctic palaeofauna from the La Meseta Formation to the early Eocene Vacan-aged mammal palaeofauna is appropriate, due to the taxonomic affinities of the Antarctic palaeofauna to Riochican (latest Palaeocene) and Vacan-aged palaeofaunas of Patagonia. If these Patagonian mammalian palaeofaunas (PMP) were the source for the La Meseta palaeofauna (LMP), then a similar normal distribution with less taxonomic diversity would be expected. However, the LMP does not meet this expectation or even a distribution where all size classes are equally represented. Thus, the pattern of size distribution is quite different from the PMPs.

Floral data for the Early Eocene of Patagonia indicate subtropical conditions with mean annual temperatures (MAT) of 15.6 °C and equable winter temperatures (>10 °C) generating high taxonomic diversity at the species level. Floral data from the La Meseta Formation of equivalent age to the mammalian fauna indicate a cooler MAT of 11–13 °C with a highly seasonal climate, where the mean winter temperature could have ranged from −3 to 2 °C. There is also a significant drop in floral taxonomic diversity, which is dominated by
Nothofagus
.

A bimodal body size distribution pattern is not an unusual pattern for higher latitude mammalian faunas. Modern boreal mammalian faunas of North America have a low frequency of species in the medium body size range in response to cold winter temperatures in these higher latitudes. The smaller-sized mammals have adapted their physiology to the cold winter temperatures. The larger animals have adapted to the cold winter conditions by conserving heat through small surface-area-to-volume ratios as a result of their greater bulk. The low frequency of medium-sized animals is due to the fact that neither of these thermal strategies is available to them and thus they are at a selective disadvantage.
The geological development of the Balkan Peninsula related to the approach, collision and compression of Gondwanan and Eurasian units
Authors: Karamata Stevan
Published: April 2008

The Balkan Peninsula includes the margins of both Eurasia (the Moesian microplate) and Gondwana (the Adria microplate as a promontory); it also includes ophiolitic belts that represent remnants of Tethys and its marginal seas. Various terranes docked to larger crustal units and were incorporated to form new units. Most units within the Balkan Peninsula moved northwards to their present positions, jointly or independently, from positions around, or south of, the Equator from the end of the Palaeozoic to the present day. The assembly of these units was associated with generally northeastward subduction of Tethys. The first main period of docking was in the Carboniferous. Later, from the Permian to the Maastrichtian, marginal seas opened and later closed. Island arcs formed within the northwestern part of Tethys, and parts of continental margins were detached and relocated, or were transported along transcurrent faults. In the Maastrichtian the entire oceanic area was closed and the main units sutured. The resulting assemblage later underwent additional compression, rotation and transcurrent displacement of some units.
Biochronology of Jurassic and Early Cretaceous radiolarites from the Lycian Mélange (SW Turkey) and implications for the evolution of the Northern Neotethyan ocean
Authors: Danelian T. , Robertson A. H. F. , Collins A. S. , Poisson A.
Published: April 2008

New radiolarian ages for blocks of radiolarian cherts associated with other blocks of distal pelagic facies and ophiolitic lithologies within the Lycian Mélange, SW Turkey, indicate deposition during Mid-Jurassic to Early Cretaceous time. Radiolarites overlying pink pelagic limestones of an allochthonous carbonate unit accumulated during the Mid- to Late Jurassic. On the basis of structural evidence the Lycian Mélange is inferred to have been rooted within the Northern Neotethys, to the north of the Tauride-Anatolide microcontinent. The Lycian radiolarites can be compared with other dated radiolarites from the Izmir-Ankara suture, the root zone of the Northern Neotethyan ocean. Based on all the available radiolarian data it is inferred that radiolarites accumulated within the Northern Neotethys in western Turkey from Late Triassic (Mid-Carnian to Late Norian) to Mid-Cretaceous (Cenomanian) time. The radiolarites were later detached from their inferred oceanic basement and accreted within a subduction complex during the Late Cretaceous (Turonian-Maastrichtian) and emplaced over the northern margin of the Tauride-Anatolide continent together with slices of continental margin and ophiolitic lithologies.
Cumulates and gabbros in southern Albanian ophiolites: their bearing on regional tectonic setting
Authors: Koller F. , Hoeck V. , Meisel T. , Ionescu C. , Onuzi K. , Ghega D.
Published: April 2008

The western belt of the southern Albanian ophiolites consists of six major ophiolite massifs (Voskopoja, Rehove, Morava, Devolli, Vallamara, Shpati) and two smaller ones (Luniku and Stravaj). Each massif has a distinct sequence of mantle tectonites, ultramafic cumulates (plagioclase-bearing peridotites and wehrlites), cumulate gabbros, troctolites and isotropic gabbros. Voskopoja, Rehove and Morava have predominantly lherzolites as mantle tectonites, Shpati lherzolites and harzburgites, and Devolli and Vallamara almost exclusively harzburgites. A volcanic section together with volcanogenic sediments occurs only in the Voskopoja and Rehove massifs as well as in the smaller Luniku and Stravaj massifs. Whole-rock geochemistry and mineral chemistry suggest a mid-ocean ridge setting for the origin of the cumulates and gabbros from the Voskopoja, Rehove and Morava massifs, with only a minor suprasubduction zone (SSZ) influence. The Shpati massif and the small Luniku massif show mid-ocean ridge (MOR) and SSZ signatures in their plutonic sequences. Cumulates and gabbros from Devolli and Vallamara formed in an SSZ setting. The predominance of MOR-generated crustal rocks and the relatively minor occurrence of SSZ-generated plutonic rocks together with the volcanogenic sediments in the Voskopoja and Rehove massifs are indicative of a back-arc basin origin of the western belt ophiolites above a westward-dipping subduction zone.
Palaeomagnetic insights into the evolution of Neotethyan oceanic crust in the eastern Mediterranean
Authors: Morris Antony , Anderson Mark W. , Inwood Jennifer , Robertson Alastair H. F.
Published: April 2008

A synopsis of palaeomagnetic data from three Late Cretaceous eastern Mediterranean Tethyan ophiolites (Troodos, Hatay and Baër-Bassit) and their sedimentary cover sequences is presented. These data provide valuable insights into the role of regional- and local-scale tectonic rotations in the geodynamic evolution of Neotethyan oceanic crust. The geologically earliest phases of tectonic rotation are documented in the Troodos ophiolite, where rotations around both subvertical and subhorizontal axes are readily related to the development of the spreading fabrics and structures during crustal genesis. Subsequent
c.
74° antickockwise intra-oceanic rotation of a ‘Troodos microplate’ has been quantified through analysis of the
in situ
sedimentary cover of the Troodos ophiolite. Results indicate that bulk anticlockwise rotation began soon after the cessation of spreading and ended by the end of the Eocene, with
c.
50–60° of microplate rotation being over by the Maastrichtian, the time at which ophiolite thrust sheets were emplaced onto the Arabian continental margin to the east of Troodos. Recent results from the emplaced, structurally dismembered Baër-Bassit ophiolite indicate extreme anticlockwise rotations of ophiolitic thrust sheets varying on a kilometre scale. New data from the post-emplacement sedimentary cover confirm that only a small component of these rotations is due to post-emplacement tectonism. Baër-Bassit represents the leading edge of the emplaced ophiolitic sheet. New data from the more coherent section preserved in the Hatay ophiolite to the north demonstrate significant anticlockwise rotation. This is equivalent to the rotation of the most northerly part of the Baër-Bassit units to the south, and is of the same sense and magnitude as the pre-Maastrichtian phase of microplate rotation documented in the Troodos. This suggests a common, intra-oceanic origin for the majority of the Troodos and Hatay rotations, and a significant component of the more variable rotations observed in Baër-Bassit. Overall, therefore, the data support a model involving: (1) intra-oceanic rotation of a coherent region of crust within the southern Neotethyan basin; this rotated unit is more areally extensive than has previously been inferred from consideration of data from the Troodos ophiolite alone; (2) emplacement of part of the rotated unit onto the Arabian platform; (3) subsequent localized post-emplacement modification, related to the development of the current plate configuration.
The wide distribution of HP-LT rocks in the Lycian Belt (Western Turkey): implications for accretionary wedge geometry
Authors: Rimmelé Gaëtan , Oberhänsli Roland , Candan Osman , Goffé Bruno , Jolivet Laurent
Published: April 2008

In SW Turkey, Fe-Mg-carpholite has recently been recognized in the basal metasediments of the Lycian Nappes, which overthrust the Menderes Massif on its southern flank. This high-pressure-low-temperature (HP-LT) metamorphic index mineral was widely found in the Bodrum peninsula region. Our new metamorphic and structural data on similar carpholite-bearing rocks found farther north in several klippen of the Lycian Nappes located on top of the Menderes Massif show that HP-LT rocks in SW Turkey occur over a distance of >200 km in both north-south and east-west directions, thus indicating a wide HP-LT metamorphic belt. The deformation pattern from the Bodrum peninsula to Çivril, all along the contact between the Lycian Nappes and the Menderes Massif, reveals the role played by major top-to-the-NE shear zones contemporaneous with exhumation of the Lycian HP-LT rocks. This deformation shows an oblique direction of opposite shear sense relative to the earlier southward translation of the Lycian Nappes over the Menderes Massif, for which top-to-the-south displacements are preserved in the upper units of the Lycian Nappes on the Bodrum peninsula, as well as at the base of the Lycian nappe klippen located farther north. The widespread distribution of well-preserved Fe-Mg-carpholite-bearing rocks in the Lycian Nappes has implications for the geometry of the accretionary wedge responsible for HP-LT metamorphism in SW Turkey.
A new orogenic model for the External Hellenides
Authors: Doutsos T. , Koukouvelas I. K. , Xypolias P.
Published: April 2008

In the context of the External Hellenides, ‘pro’-lithosphere, corresponding to the Apulian microcontinent, converges on ‘retro’-lithosphere, corresponding to the Pelagonian microcontinent. Structural and stratigraphic data in the External Hellenides suggest that the convergence at this margin is fairly well described by the conceptual doubly vergent accretionary wedge model. This new orogenic model for the External Hellenides differs from the classical west-verging assumption and emphasizes that the retro-mass flux is critical for the pro-mass flux. Our model is primarily 2D, and is described in terms of three system components: an accretionary wedge (or pro-wedge), an uplifted plug and a retro-wedge. Three ‘isopic’ zones (Pindos, Gavrovo-Tripolitsa and Ionian) are included in the pro-wedge. The uplifted plug in the north (Epirus area) includes the Pindos ocean ophiolitic rocks and the Pindos zone, the Parnassos zone in central Greece, and the HP belt of the External Hellenides in the Peloponnese. The retro-wedge includes the Mesohellenic Trough in the north and the Argos plain in the south.
Evidence for late Holocene activity along the seismogenic fault of the 1999 Izmit earthquake, NW Turkey
Authors: Pavlides S. B. , Chatzipetros A. , Tutkun Z. S. , Özaksoy V. , Doğan B.
Published: April 2008

During the strong 1999 Izmit (Kocaeli) earthquake, 100 km long east-west-striking (N80°–100°), right-lateral, fault traces were formed. In the epicentral area the seismic ruptures did not follow any known or mapped fault traces, but morphology and tectonostratigraphic evidence from trenches reveal pre-existing earthquake-related features, e.g. elongated valleys, shutter ridges, high-angle slopes, scarplets and stream offsets. In the Gölcuk Peninsula a characteristic NW-SE-trending extensional fault segment emerged at the surface with a 1.5–2 m maximum vertical displacement and a 0.30 m right-lateral component. The resulting coseismic fault scarp was mapped in detail, and two trenches were excavated at the Dëniz Evler site. The 1999 displacement at this site was 1.50 m, whereas the penultimate event displaced the same sediments by 0.70 m, and a previous event by 0.20 m. Displacement is not characteristic, as fault-associated soft (recent) deltaic deposits, and the fault itself, are typically not coseismic, but rather a secondary accommodation structure in geometric consistency with the right-lateral main displacement zone. The data were compared with similar results from the Aşãgı Yuvacik, Kular Yaylacik and Acisu sites between Izmit and Sapanca Lake. The same fault segment seems to have been activated and produced surface ruptures including during the earthquakes of
AD
1509,
AD
989 and
AD
554, plus two prehistoric events. The palaeoseismological results provide clear evidence for repeated reactivation of the same fault or fault segments during historical seismic events.
Flow in multiscale fractal fracture networks
Authors: Davy P. , Bour O. , De Dreuzy J.-R. , Darcel C.
Published: April 2008

The paper aims at defining the flow models, including equivalent permeability, that are appropriate for multiscale fracture networks. As a prerequisite of the flow analysis, we define the scaling nature of fracture networks that is likely quantified by power-law length distributions whose exponent fixes the contribution of large fractures versus small ones. Despite the absence of any characteristic length scale of the power-law model, the flow structure appears to contain three length scales at the very maximum: the connecting scale, the channelling scale, and the homogenization scale, above which the equivalent permeability tends to a constant value. These scales, including their existence, depend on the fracture length distribution and on the transmissivity distribution per fracture. They are basic in defining the flow properties of fracture networks.