bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre-collisional anastomosing shear zones in the Kohistan arc, NW Pakistan
Authors: Arbaret L. , Burg J.-P. , Zeilinger G. , Chaudhry N. , Hussain S. , Dawood H.
Published: April 2008

Ductile strain localization commonly forms a pattern of shear zones anastomosing around lenses of less deformed rock. Initiation and development of anastomosing shear zones are studied through description of the structures and deformation history of plutonic rocks that form the lower crust of the Kohistan arc. Structures and textures developed in these rocks result from primary magmatic to solid state regional strain, overprinted by anastomosing shear zones. The primary strain was mainly acquired during magmatic emplacement at 100-90 Ma. Strain localization took place continuously from magmatic emplacement to solid state deformation during cooling of the plutons and formed three successive sets of shear zones. Set 1 is composed of associated discrete Riedel and thrust shear zones developed above solidus conditions during southwestward thrusting. Continuous deformation from solidus to amphibolite facies conditions between 100 and 83 Ma formed the second set of shear zones. The lower amphibolite facies set 3 shear zones are diffeentiated by larger strains recorded in the thicker mylonitic zones and enlargement of the spacing between shear zones during cooling. The anastomosing pattern of shear zones described here probably represents arc-related deformation during subduction of the Tethys oceanic lithosphere below the Kohistan arc.
Isotopic constraints on the evolution of metamorphic conditions in the Jijal-Patan complex and the Kamila Belt of the Kohistan arc, Pakistan Himalaya
Authors: Anczkiewicz R. , Vance D.
Published: April 2008

Pressure-temperature data and Sm-Nd and Rb-Sr garnet ages are presented for retrogressed granulitic rocks of the Jijal-Patan complex and the Kamila Amphibolite Belt. Despite the retrogression and hydration, the two samples contain garnet and hydrous minerals that yield pressures and temperatures similar to previous estimates for pristine granulite facies rocks from the same area. The Sm-Nd and Rb-Sr garnet ages are concordant at 95–100 Ma for the two samples and for both isotopic systems. These ages are interpreted as dating cooling through 700–800 °C following magmatic crystallization and granulite facies metamorphism. In the case of the garnet amphibolites from the Kamila Belt, the garnets retain prograde major element zonation. In addition, the closure temperature for the Rb-Sr system is very close to the recorded temperature. For these reasons, the age of 100 Ma must represent a time close to that when the pressure and temperature preserved in the mineralogy and its chemistry was recorded. The isotopic equilibrium between garnet and paragonite at 90–100 Ma suggests that the regional hydration event that affected the lower crust of the Kohistan arc also occurred at this time. Cooling rates calculated from the Rb-Sr and Sm-Nd ages for the partially retrogressed granulite give a minimum of 3–6°C Ma
−1
and imply a different tectonic mechanism for the exhumation of the lower crust than is typical for granulites. This process may be related to early regional decompression following the collision of the Kohistan arc with Eurasia.
The Main Mantle Thrust in Pakistan: its character and extent
Authors: DiPietro J. A. , Hussain A. , Ahmad I. , Khan M. A.
Published: April 2008

The Main Mantle Thrust (MMT) represents the tectonic boundary between metamorphic shield and platform rock of the Indian plate hinterland, and dominantly mafic and ultramafic rock of the Kohistan-Ladakh arc complex in Pakistan. In some areas, this boundary is a sharp planar fault with development of mylonite; in other areas, it is a brittle-ductile imbricate zone; in still other areas, it contains large, discontinuous, slices of internally sheared and deformed ophiolitic mélange. The character of the MMT along its entire trace is discussed and it is concluded that there is no single continuous fault which marks the contact between the Indian plate and the Kohistan-Ladakh arc. On this basis, we propose a revised definition for the MMT that is consistent with both the original definition and with the usage of the term in literature. We suggest that the MMT fault contact be defined as the series of faults, of different age and tectonic history, that collectively define the northern margin of the Indian plate in Pakistan. On this basis, faults that define the MMT vary in age from Quaternary to possibly as old as Late Cretaceous. Discontinuous lenses of ophiolitic mélange that overlie the MMT fault contact, and which intervene between the Indian plate and the Kohistan-Ladakh arc, are considered to be part of an MMT zone that is equivalent with the Indus Suture Zone.
Crustal shortening estimates across the north Indian continental margin, Ladakh, NW India
Authors: Corfield R. I. , Searle M. P.
Published: April 2008

A structural and lithological map has been produced covering the Spontang ophiolite and the north Indian continental margin from the Indus Suture Zone in the north to the high-grade metamorphic rocks and granites of the High Himalaya in the south. Cross-section balancing techniques have been used to identify, quantify and sequentially restore three major phases of deformation (D1–3) affecting the north Indian continental margin resulting in > 85 km (280%) shortening.

D1 in the late Cretaceous involved obduction of the Spontang ophiolite, associated Neo-Tethyan thrust sheets and Mesozoic continental slope deposits onto the outer passive margin. D1 was responsible for 200% shortening by internal folding and duplex formation within stratigraphic units in the outer shelf, but did not affect the innermost parts of the Indian passive margin. Restoration of later structures suggests that the allochthonous thrust sheets were emplaced a minimum of 70 km onto the continental margin.

D2 from the early Eocene to Oligocene was the main phase of deformation associated with the collision of India and Asia. Re-thrusting places the Spontang ophiolite and associated mélanges over the Maastrichtian to Lower Eocene neo-autochthonous cover which accommodated 140–160% shortening in the hanging wall. D2 progressed with the propagation of thrusting down section and towards the foreland causing crustal thickening and Barrovian metamorphism. The thick, argillaceous late Cretaceous Kangi La Formation decoupled deformation in higher and lower structural levels in outer shelf areas.

D3 backthrusting and break-backthrusting in the late Tertiary formed a pop-up structure at the northern edge of the continental margin associated with a further 190–230% shortening and inversion of structures in the Indus Suture Zone. A major anticlinal structure also initiated across the southern edge of the Indus Suture Zone. South of Spontang reactivation of D2 thrusts as late D2/D3 normal faults was associated with gravitational collapse of the High Himalaya to the south. Extensional movement on these structures was probably concomitant with shortening in the pop-up structure to the north.

A reduction in present day and restored thickness of the Tethyan Himalaya and an increase in absolute shortening from east to west probably reflects a variation in the partitioning of deformation across the whole width of the orogen. This may be associated with the indentation of India into Asia to the northwest.
Glaucophane and barroisite eclogites from the Upper Kaghan nappe: implications for the metamorphic history of the NW Himalaya
Authors: Lombardo B. , Rolfo F. , Compagnoni R.
Published: April 2008

This paper presents the results of a petrographical and mineral chemical study of glaucophane- and barroisite-bearing eclogites from the Upper Kaghan nappe in the Higher Himalayan Crystallines of the Pakistan Himalaya, and discusses the implications of the
P-T
path recorded in such rocks for the tectonic and metamorphic history of the NW Himalaya. The eclogites described here come from a previously undescribed outcrop at Gittidas, but belong to the same suite as the garnet-omphacite-phengite-quartz-rutile eclogites previously described elsewhere in the Upper Kaghan nappe. The metamorphic peak assemblage is garnet-omphacite-rutile-quartz in glaucophane eclogite and garnet-omphacite-zoisite-rutile±kyanite±phengite±ankerite in barroisite eclogite. Most samples contain a significant amount of amphibole, white mica and quartz. White mica may be present either as part of the peak assemblage (phengite) or as a retrogressive phase after kyanite (paragonite). Amphibole is later than the metamorphic peak assemblage and is barroisite in most samples, but in relatively Fe-rich eclogite it is glaucophane with significant Na in the A site, Ca in the M4 site and tetrahedral A1. Garnet displays strong prograde zoning in the barroisite eclogites, with Mg increasing and Fe decreasing from core to rim. The iron-rich core is crowded with mineral inclusions of the peak assemblage, but inclusions of earlier paragonite, green and blue-green amphibole were also found. Peak metamorphic conditions in the barroisite eclogites have been estimated at
T
= 610 ± 30 °C and
P
= 24 ± 2 kbar from Fe/Mg partition in garnet-omphacite pairs, and from the garnet-omphacite-phengite barometer. These values are close to the equilibration conditions estimated for the eclogites of the North Himalayan Tso-Morari Dome. Strong similarities between metamorphic evolution of the Upper Kaghan nappe and metamorphic evolution of the eclogite-bearing units of the Neelum valley just to the east of the Kaghan valley indicate that the eclogite occurrences of the Kaghan-Neelum area define an eclogite-bearing terrane of regional extent, which was subjected to high pressure metamorphism in middle Eocene times. A comparison of the metamorphic evolution recorded in the eclogites of the NW Himalaya with that of the granulitized eclogites recently discovered in the E Himalaya suggests the possibility of a Himalaya-wide eclogitic metamorphism of pre-Miocene age. Therefore, the main difference between the Higher Himalayan Crystalline nappes of the NW Himalaya and those of the E Himalaya appears to lie less in the early part of their metamorphic evolution than in the different
P-T
paths they followed during exhumation.
Creation and destruction of travertine monumental stone by earthquake faulting at Hierapolis, Turkey
Authors: Hancock P. L. , Chalmers R. M. L. , Altunel E. , Çakir Z. , Becher-Hancock A.
Published: April 2008

The presence of travertines adjacent to the city and their value for construction was well known to the Greek, Roman and Byzantine residents of Hierapolis (modern Pamukkale). The travertines were mainly extracted from quarries on the outer slopes of a low plateau below the city. The distinctive attribute of most of the quarries is that they are narrow but deep vertical-sided trenches. Each trench is the site of a nearly vertical fissure that was filled by banded fissure travertine, one type of so-called
Phrygian marble
. Trench walls, formerly the contacts between vertical banded travertines and outward dipping bedded travertines, bear a well-defined herringbone pattern of tool marks identical to those on many of the stone blocks that were used for building Hierapolis. Deposition of the travertines in 21 major fissure-ridges was a consequence of precipitation following degassing of carbonate-rich hot waters emerging from springs aligned along active faults and associated fissures. Whereas the dense and attractively banded travertine in fissures was principally used as an ornamental stone, the bedded travertines of ridge sides were mainly employed as a dimension stone and for making columns. After many of the monuments at Hierapolis had been constructed from travertine, itself a faulting-related material, some of them were subsequently destroyed or damaged by earthquake fault reactivation, which caused them to be either shaken or displaced. The zone of greatest seismic damage coincides with the trace of the Hierapolis fault zone, whose location was detected from an alignment of offsets of walls and petrified irrigation channels. The kinematic class of this fault zone could be deduced because offsets of the linear archaeological features permitted opening directions to be determined, thus allowing the fault zone to be reinterpreted as a normal fault zone achieving a small downthrow to the southwest. The knowledge that the Hierapolis fault zone is a structure across which there is active stretching and increased hydrothermal flow helps to explain why the present-day area of hot pools and travertine deposition is situated immediately downslope of the fault trace. If this relationship between displaced features and recent travertine deposits occurs elsewhere it might be employed for finding the locations of earthquake faults.
Uses of volcanic products in antiquity
Authors: Griffiths D. R.
Published: April 2008

Since the advent of mankind many human societies have lived in volcanically active zones. The geological, archaeological and historical records provide a rich and diverse source of evidence for both archaeology and volcanology concerning the nature of volcanic processes and the effects of volcanism on the environment and on human society. To achieve a balanced understanding of the effects of volcanism on past cultures, it is important to consider the attractions as well as the hazards of life in an actively volcanic zone. This paper gives an overview of some of the ways in which a wide range of volcanic products were used by mankind in antiquity. These include the use of volcanic rocks as stone tools, as substrates for rock carvings, as materials for building and sculpture, as millstones, as additives to make cements that set under water, and, more indirectly, as precursors of fertile earths for agriculture and as sources of metals and semi-precious stones. The paper also considers some of the properties of volcanic products that may have made them attractive. Assessment of the interaction of past cultures with volcanism is highly relevant to the present: it can provide the temporal perspective needed to deal appropriately with the human aspects of contemporary and future volcanic hazards.
A critical reappraisal of the classical texts and archaeological evidence for earthquakes in the Atalanti region, central mainland Greece
Authors: Buck Victoria , Stewart Iain
Published: April 2008

Despite numerous damaging earthquakes in central Greece only the Atalanti Fault is considered to have ruptured successively, most recently in 1894 and in a historical event in 426 BC. Although the pre-Christian earthquake is now firmly entrenched in the tectonic literature, classical literary accounts are inconsistent and do not unequivocally tie the event to a particular time and place. Archaeological evidence from sites close to the Atalanti Fault similarly remains ambiguous, and fails to convincingly corroborate the rupture of the Atalanti Fault in 426 BC. In this paper, the main thrust of the argument is not to try to define the seismogenic source of the 426BCevent, but to illustrate the level of uncertainty that accompanies literary and archaeological information, and to highlight the need for caution when using interdisciplinary methods or datasets in earthquake seismology.
Santorini (Greece) before the Minoan eruption: a reconstruction of the ring-island, natural resources and clay deposits from the Akrotiri excavation
Authors: Friedrich Walter L. , Seidenkrantz Marit-Solveig , Nielsen Ole Bjørslev
Published: April 2008

Before the catastrophic eruption around 1640
BC
, Thera, Therasia and Aspronisi formed a ring-shaped island with a sea-flooded caldera in the middle. The so-called Pre-Kameni Island was situated in the centre of the caldera. This reconstruction is based on the study of stromatolites found in eruption products as well as other geological observations. The location of pre-eruption settlements or sites on the present rim of the Santorini caldera seems to support this reconstruction. Many of the rocks and minerals used in the Bronze Age culture are of local origin. Foraminiferal and mineralogical studies enable us to trace the source areas of a clay deposit found in a grave chamber in the Akrotiri excavation. This clay can be used for pottery making. The foraminiferal and mineralogical studies also help identify the natural drainage system and thus the freshwater supply, which may have been an important factor deciding the location of the Bronze Age settlement.
Late Minoan IB marine ware, the marine environment of the Aegean, and the Bronze Age eruption of the Thera volcano
Authors: Bicknell Peter
Published: April 2008

Late Minoan IB fine ware pottery includes a number of decorative styles. The most spectacular of these is characterized by motifs, hitherto only rarely deployed by Cretan vase painters, drawn from the marine world. Late Minoan IB marine ware turns up in ritual contexts, which include human sacrifice. The pottery style is likely to reflect, then, not simply a vagary of secular fashion, but a circumstance or circumstances requiring far-reaching religious attention. It is proposed that Late Minoan IB marine ware and the cult activities in which it was deployed were a response to negative effects of the Late Bronze Age Thera eruption on the marine environment of the Aegean.
The Johnston-Lavis collection: a unique record of Italian volcanism
Authors: Kirk W. L. , Siddall R. , Stead S.
Published: April 2008

Housed at University College London, the Henry James Johnston-Lavis collection of rocks, minerals, photographs, gouaches and engravings is extremely important in that it provides a record of volcanism in southern Italy, especially in the latter part of the 19th century. The collection of the intrepid Dr Johnston-Lavis also contains literature and materials relevant to earlier eruptions of the Italian volcanoes, and sample collections of both rocks and minerals from other world-wide locations of mineralogical and volcanological interest. Although regrettably now much depleted, a substantial part remains, and this continues to be a valuable resource for volcanologists, historical geologists and archaeologists.
Timing of the prehistoric eruption of Xitle Volcano and the abandonment of Cuicuilco Pyramid, Southern Basin of Mexico
Authors: Gonzalez Silvia , Pastrana Alejandro , Siebe Claus , Duller Geoff
Published: April 2008

The Cuicuilco pyramid was one of the first true urban centres in the Basin of Mexico. Its construction started a few centuries
BC
, during the Late Preclassic period. The pyramid is partially covered by a basaltic lava flow produced by the Xitle monogenetic volcano. New stratigraphic work around the pyramid and the volcano together with new radiocarbon dates indicate that the pyramid and nearby settlements were abandoned as a direct consequence of the volcanic activity of Xitle. The new dates, obtained from material which clearly is contemporaneous with the volcanic activity, suggest that the eruption took place around 1670 years
BP
, some 300 years later than previously thought.
‘A fire spitting volcano in our dear Germany’: documentary evidence for a low-intensity volcanic eruption of the Gleichberg in 1783?
Authors: Grattan J. P. , Gilbertson D. D. , Dill A.
Published: April 2008

This paper presents documentary evidence suggesting that the most recent volcanic activity in Germany may have occurred just over 200 years ago, rather than the 11 000 years held currently (Ulmener Maar, West Eifel). Several descriptions recounted here suggest that a mountain in Germany, the Gleichberg, may have erupted in the early summer of 1783. The reports of the volcanic event are laden with detail that would tempt the reader to accept them as genuine descriptions of an eruption, had the event been located in an historically active volcanic region. However, there are several reasons to suggest that the report of the Gleichberg eruption was a complex hoax, written to exploit the fear and panic generated by the dry fog present over much of Europe at the same time, which had its origins in the Laki fissure eruption. Geologically, the Gleichberg forms part of the Grabfeld, and is of Tertiary volcanic origin. There are no compelling geological reasons to suggest that this area has been tectonically active in recent times. The convincing detail of the report is used to illustrate the pitfalls waiting for geologists, historians and archaeologists who are using historical documents and folklore to explore the impact of volcanic eruptions upon ancient peoples and environments; time may lend weight to documents and folklore, which in reality may deserve none.
Seismic and volcanic hazards affecting the vulnerability of the Sana’a area of Yemen
Authors: Hughes Richard , Collings Adrian
Published: April 2008

The City of Sana’a is a World Heritage Site, renowned for its ancient tall and ornate domestic dwellings. Following a moderate, but locally destructive seismic event near Sana’a (Dhamar) in 1982 (
M
s
5.5–6.0), the seismic vulnerability of the city and its hinterland have been reviewed, using the extensive records of the Arab chroniclers, going back over 1500 years. A hazard study indicated that Yemen is a country of moderate seismicity rather than one of low seismicity as previously considered, as records indicated that moderate-sized earthquakes (
M
s
4.0–6.0), have occurred regularly over the last 1000–1500 years. It was determined that Sana’a is in a location where a damaging event could statistically occur every 200 years or so. Using a seismic character similar to that of the 1982 Dhamar event (shallow hypocentre, 40 s duration, peak ground acceleration 0.3
g
, and
M
s
5.5–6.0), the vulnerability of Sana’a was determined from condition surveys of some 250f the historical houses, which proved remarkable levels of active structural distress and fabric decay. It was estimated that nearly 680f the building stock in Sana’a would be severely damaged to totally damaged beyond repair by a similar earthquake, causing a significant loss of life and destruction of a World Heritage Site. Strategies and techniques for reducing the vulnerability of the urban fabric of Sana’a, ranging from simple upgrading within the owners’ means to significant engineering measures, sympathetic to the historical and archaeological fabric of the buildings, are considered. Also considered are volcanic hazards, as records indicate that closely related to the seismic activity in Yemen are occasional, generally small-scale, volcanic eruptions. Several eruptions are indicated to have occurred in the Sana’a area over the last 1500 years, and the area is vulnerable to future eruptions. An event in about
AD
200 is indicated by archaeological work to have overwhelmed several religious sites 20 km north of Sana’a.
Archaeological, geomorphological and geological evidence for a major earthquake at Sagalassos (SW Turkey) around the middle of the seventh century AD
Authors: Waelkens Marc , Sintubin Manuel , Muchez Philippe , Paulissen Etienne
Published: April 2008

The ancient city of Sagalassos, located 7 km north of the
ilçe
(centre of an administrative unit) of Ağlasun in the Turkish province of Burdur, was an important centre during the Roman period. The collapse and subsequent repairs of buildings may suggest that at least four distinct earthquakes struck this city. These could have occurred in the second half of the first century AD, the middle of the third century AD, the first quarter of the sixth century AD and the middle of he seventh century AD. The youngest of these four earthquakes could have been so destructive that the city was abandoned. The age of this earthquake is based on coins and pottery dated to the middle of the seventh century AD, overlain by the collapsed monuments. Additional evidence is provided by the fractures in a baked mosaic floor belonging to a library, set on fire in the third quarter of the fourth century AD and filled in with waste material and earth during the fire. A directional analysis of the fractures in the mosaic floor of the Library, on the pavement of the Upper Agora and on the Theatre steps gives some insight into the local stress field associated with this earthquake. The palaeostress field, inferred from this analysis, is similar to that created by a transtensional strike-slip activity on an E-W-trending tear fault, situated just north of the city. Although it cannot be proven that the earthquake was related to activity along this fault, the magnitude of the destruction suggests an epicentre in the proximity of the city.
The geological origins of the oracle at Delphi, Greece
Authors: De Boer J. Z. , Hale J. R.
Published: April 2008

Ancient authors from Plato to Pausanias have left descriptions of Delphi’s oracle and its mantic sessions. The latter were interpreted as events in which the Pythia (priestess) placed herself on a tripod over a cleft (fissure) in the ground below the Apollo temple. Here she inhaled a vapour rising from the cleft, and became inspired with the power of prophecy. French archaeologists who excavated the oracle site at the turn of the century reported no evidence of either fissures or gaseous emissions and concluded that the ancient accounts were myths. As a result, modern classical scholars and many archaeologists reject the ancient testimonies concerning the mantic sessions and their geological origin. However, the geological conditions at the oracle site do not
a priori
exclude the early accounts. A major WNW-ESE fault zone and a minor swarm of NNW-SSE fractures intersect below the site. These intersection(s) provided pathways for rising ground water, including a spring below the Apollo temple. The faults broke through a bituminous limestone formation at relatively shallow depth. Hydrocarbon gases that originated in this formation may have escaped during and after seismo-tectonic events. Such gases can induce mild narcotic effects. It is highly probable therefore that the Pythia’s inspiration resulted from the inhalation of light hydrocarbon gases, which rose along a fissure (fracture) in the adyton below the Apollo temple.
The falling stage systems tract: recognition and importance in sequence stratigraphic analysis
Authors: Plint A. Guy , Nummedal Dag
Published: April 2008

Until recently, sequence stratigraphic models have attributed systems tracts to periods of relative sea-level rise, highstand and lowstand. Recognition of a discrete phase of deposition during relative sea-level fall has been limited to a few studies, both in clastic and carbonate systems. Our work in siliciclastic ramp settings suggests that deposition during relative sea-level fall produces a distinctive
falling stage systems tract
(FSST), and that this is the logical counterpart to the transgressive systems tract. The FSST lies above and basinward of the highstand systems tract, and is overlain by the lowstand systems tract. The FSST is characterized by stratal offlap, although this is likely to be difficult or impossible to recognize because of subsequent subaerial or transgressive ravinement erosion. The most practical diagnostic criteria of the FSST is the presence of erosive-based shoreface sandbodies in nearshore areas. The erosion results from wave scouring during relative sea-level fall, and the stratigraphically lowest surface defines the base of the FSST. Further offshore, shoaling-upward successions may be abruptly capped by gutter casts filled with HCS sandstone, reflecting increased wave scour on the shelf during both FSST and LST time. The top of the FSST is defined by a subaerial surface of erosion which corresponds to the sequence boundary. This surface becomes a correlative submarine conformity seaward of the shoreline, where it forms the base of the lowstand systems tract. Differentiation of the FSST and LST may be difficult, but the LST is expected to contain gradationally-based shoreface successions because it was deposited when relative sea level was rising. Internally, the FSST may be an undifferentiated body of sediment or it may be punctuated by internal regressive surfaces of marine erosion and ravinement surfaces which record higher-frequency sea-level falls and rises superimposed on a lower-frequency sea-level fall. The corresponding higher-order sequences are the building blocks of lower-order sequences. The addition of a falling stage systems tract results in a significant reduction in the proportion of strata within a sequence that are assigned to the classical highstand and lowstand systems tracts.

Many outcrop and subsurface cross-sections use an overlying ravinement, or maximum flooding surface as datum. Those surfaces might be flat, but they are not horizontal. Both dip seaward at slopes that generally are steeper than the fluvial system responsible for creating the sequence boundary. When a section is restored to such a datum, the falling stage systems tract will appear to record stratigraphic climb, whereas in fact it does not.
Aspects of the stratal architecture of forced regressive deposits
Authors: Posamentier Henry W. , Morris William R.
Published: April 2008

Forced regression refers to the process of seaward migration of a shoreline in direct response to relative sea-level fall. Recognition criteria for forced regressive deposits include: (1) presence of a significant zone of separation between successive shoreface deposits, (2) the presence of sharp-based shoreface/delta front deposits, (3) the presence of progressively shallower clinoforms going from proximal to distal, (4) the occurrence of long-distance regression, (5) the absence of fluvial and/or coastal plain/delta plain capping the proximal portion of regressive deposits, (6) the presence of a seaward-dipping upper bounding surface at the top of the regressive succession, (7) the presence of increased average sediment grain size in regressive deposits going from proximal to distal and (8) the presence of ‘foreshortened’ stratigraphic successions.

The principal factors driving the stratal architecture of forced regressive deposits include: (1) the gradient of the sea floor progressively exposed by falling relative sea-level, (2) the ratio of the sediment flux to the rate of relative sea-level fall, (3) the ‘smoothness’ of relative sea-level fall, (4) the variability of sediment flux and (5) the changes of sedimentary process that occur as sea-level falls and progressively more of the shelf is subaerially exposed.

Forced regressive deposits are grouped into attached v. detached, and smooth-topped v. stepped-topped. Attached deposits are defined as successive downstepped stratigraphic units whose shoreface/delta front deposits are generally in contact with each other. In contrast, detached deposits are defined as successive downstepped stratigraphic units whose shoreface/delta front deposits are generally not in contact with each other. Rather, in this instance a zone of sedimentary bypass exists. Stepped-top forced regressive deposits are characterized by a succession of horizontally topped though downstepping stratigraphic units. In contrast, smooth-topped forced regressive deposits are characterized by a seaward-dipping, albeit smooth, upper bounding surface. The bounding surfaces of forced regressive deposits commonly are expressed as a ravinement surface at the top and an unconformity to correlative conformity at the base.
Carbonate megabreccias in a sequence stratigraphic context; evidence from the Cambrian of North Greenland
Authors: Ineson Jon R. , Surlyk Finn
Published: April 2008

In carbonate sequence stratigraphy, carbonate megabreccias have acquired particular significance, being deemed characteristic of the lowstand systems tract (LST) or the forced regressive systems tract (FRST). Large-scale mass-wastage can, however, result from factors other than sea-level change and it is rare that the sequence stratigraphic significance of megabreccias can be rigorously tested. In the Cambrian of North Greenland, erection of a robust sequence stratigraphic framework is facilitated by extensive fjord-wall exposures of the platform to deep shelf transect and by a well-developed carbonate-siliciclastic reciprocal sedimentation pattern within off-platform strata. On the basis of this independent framework, megabreccias are represented locally
within
the LST and the high-stand systems tract (HST), but occur systematically above the HST. These HST-capping megabreccias are composite sheets tens of metres thick that extend up to 50 km distally and flank the platform for up to 400 km along strike. They comprise debris derived from the highstand platform margin and slope and are directly overlain by mixed carbonate-siliciclastic sediments of the succeeding LST. The HST-capping megabreccias are assigned to the FRST; they record extensive failure of the platform margin and upper slope during relative fall of sea-level and prior to the onset of lowstand sedimentation. Although the LST megabreccias are compositionally distinctive, the sole example of an intra-HST megabreccia differs from those of the FRST only in terms of areal extent. In the absence of an independent framework, therefore, the sequence stratigraphic affinities of megabreccias may be ambiguous.
Sequence stratigraphy and architecture of the Late Pleistocene Lagniappe delta complex, northeast Gulf of Mexico
Authors: Kolla V. , Biondi P. , Long B. , Fillon R.
Published: April 2008

During the last fourth-order glacial-interglacial cycle (e.g. post oxygen isotope stage 5) the Lagniappe Delta system located in the northeast Gulf of Mexico, prograded several tens of miles seaward along two main NE-SW and N-S trending fairways. The delta complex is underlain by a well-developed calcareous shale-rich condensed section that was deposited during isotope stage 5. The delta complex comprises many progradational lobes that were deposited during fifth-order sea-level falls and during the fourth-order maximum lowstand and early rise of sea level associated with isotope stages 4 to 2. Each significant fifth-order sea level fall developed a sequence boundary with an unconformity updip and a correlative conformity downdip on which a delta lobe was deposited. Autocyclic processes also lead to deposition of numerous lobes through lobe switching. During the maximum sea-level lowstand, deep erosion related to the development of an extensive incised valley system occurred across the top of the prograding wedges that were deposited during relative sea-level fall (the falling stage systems tract) and modified all of the previous updip unconformities. The base of the incised valley system, and its correlative downdip conformity, form the main fourth-order sequence boundary. It is on this surface that the last part of the delta complex was deposited during the maximum lowstand and early rise of sea-level. Thus, during the last fourth-order cycle, several fifth-order ‘initial’ sequence boundaries and one fourth-order ‘final’ sequence boundary were formed. Infilling of the incised valley system occurred mainly during the early and late rise of sea-level (isotope stages 2 and younger), prior to a major landward shift of deltaic sedimentation in response to the rapid eustatic rise in sea level during isotope stage 1.
Tethyan oceans
Authors: Stampfli Gérard M.
Published: April 2008

Diachronous subsidence patterns of Tethyan margins since the Early Palaeozoic provide constraints for paleocontinental reconstructions and the opening of disappeared oceans. Palaeotethys opening can be placed from Ordovician to Silurian times and corresponds to the detachment of a ribbon-like Hun Superterrane along the Gondwanan margin. Neotethys opening took place from Late Carboniferous to late Early Permian from Australia to the eastern Mediterranean area. This opening corresponds to the drifting of the Cimmerian superterrane and the final closing of Palaeotethys in Middle Triassic times. Northward subduction of Palaeotethys triggered the opening of back-arc oceans along the Eurasian margin from Austria to the Pamirs. The fate of these Permo-Triassic marginal basins is quite different from areas to area. Some closed during the Eocimmerian collisional event (Karakaya, Agh-Darband), others (Meliata) stayed open and their delayed subduction induced the opening of younger back-arc oceans (Vardar, Black Sea). The subduction of the Neotethys mid-ocean ridge was certainly responsible for a major change in the Jurassic plate tectonics. The Central Atlantic ocean opened in Early Jurassic time and extended eastwards into the Alpine Tethys in an attempt to link up with the Eurasian back-arc oceans. When these marginal basins started to close the Atlantic system had to find another way, and started to open southwards and northwards, slowly replacing the Tethyan ocean by mountain belts.
Was the Late Triassic orogeny in Turkey caused by the collision of an oceanic plateau?
Authors: Okay Aral İ.
Published: April 2008

A belt of Late Triassic deformation and metamorphism (Cimmeride Orogeny) extends east-west for 1100 km in northern Turkey. It is proposed that this was caused by the collision and partial accretion of an Early-Middle Triassic oceanic plateau with the southern continental margin of Laurasia. The upper part of this oceanic plateau is recognized as a thick Lower-Middle Triassic metabasite-marble-phyllite complex, named the Nilüfer Unit, which covers an area of 120 000 km
2
with an estimated volume of mafic rocks of 2 × 10
5
km
3
. The mafic sequence, which has thin stratigraphic intercalations of hemipelagic limestone and shale, shows consistent within-plate geochemical signatures. The Nilüfer Unit has undergone a high-pressure greenschist facies metamorphism, but also includes tectonic slices of eclogite and blueschist with latest Triassic isotopic ages, produced during the attempted subduction of the plateau. The short period for the orogeny (< 15 Ma; Norian-Hettangian) is further evidence for the oceanic plateau origin of the Cimmeride Orogeny. The accretion of the Nilüfer Plateau produced strong uplift and compressional deformation in the hanging wall. A large and thick clastic wedge, fed from the granitic basement of the Laurasia, represented by a thick Upper Triassic arkosic sandstone sequence in northwest Turkey, engulfed the subduction zone and the Nilüfer Plateau.
Aspects of Jurassic Radiolarite Sedimentation in a Ramp Setting Following the ‘Mid-Late Jurassic Discontinuity’, Barla Dağ Area, Western Taurus, Turkey
Authors: Farinacci Anna , Fiorentino Andrea , Ridolfi Valerio
Published: April 2008

The Barla Dağ area of southwestern Turkey and its surroundings represent one of the most characteristic Tethyan regions in which the unique characteristics of the Jurassic radiolarite deposits permit detailed study of this enigmatic facies. Hitherto, radiolarites of Western Tethys have not been studied in sufficient detail to yield the information required for unequivocal interpretation of this siliceous sedimentary event. Moreover, few of the occurrences of Tethyan radiolarites during the Jurassic have been adequately explained by palaeoenvironmental causes deduced from facies analysis. In the Barla Dağ area, the main radiolarite episode began after the ‘main gap’ or mid-Late Jurassic discontinuity, a 25 Ma hiatus extending from the Early Bajocian to the Kimmeridgian. These radiolarites are interbedded with biocalcarenites characterized by shallow-water shells. They formed in a ramp environment subject to strong storm oscillatory movements and were deposited within, or just below, wave base.

Pre-existing platforms were converted into ramp settings by a widespread drowning episode, mainly following postulated regional warping that led to creation of the ‘main gap’. Coincident with this event, the differentiation of rimmed platform lagoonal organisms and typical ramp inhabitants, such as
Tubiphytes
, took place. Furthermore, nearby platforms, unaffected by the extensional faulting (e.g. the Davras Dağ), were sites of carbonate accumulation receiving only a few radiolarians. On the other hand, displaced shallow-water organisms of the same age (typical of the restricted lagoons flanking the rimmed platforms such as pfenderinas, kurnubias and
Clypeina jurassica
) are absent from the sequences of calcarenites interbedded with radiolarian cherts. Replacement of deep basins by ramps is indicated by the changing depositional bathymetry of some radiolarites. It is tentatively attributed to the extension of shallow seas and narrowing of the oceanic realm between Eurasian and African Plates in Western Tethys.
Geochemical Character and Tectonic Environment of Neotethyan Ophiolitic Fragments and Metabasites in the Central Anatolian Crystalline Complex, Turkey
Authors: Floyd Peter A. , Göncüoğlu M. Cemal , Winchester John A. , Yaliniz M. Kenan
Published: April 2008

The Central Anatolian Crystalline Complex (CACC) or Kırşehir Block is part of the metamorphosed leading edge of the Tauride-Anatolide Carbonate Platform. It contains oceanic remnants derived from the Neotethys Ocean (İzmir-Ankara-Erzincan branch) which separate it from the Sakarya microcontinent. Two tectonic units are distinguished: an amphibolite facies Mesozoic ‘basement’, dominated by platform marbles, over which is thrust a younger fragmented Upper Cretaceous ophiolite sequence. Three metabasite horizons were sampled to reconstruct the development of the oceanic components: (1) fragmented Upper Cretaceous (90-85 Ma) stratiform ophiolitic members comprising gabbros, sheeted dykes, basalt lavas and pelagic sediments thrust over all other units; (2) a tectonised admixture of basite, ultramafic and felsic blocks in an ophiolitic mélange (Upper Cretaceous matrix) thrust over the basement metamorphic rocks; and (3) amphibolites concordant with ‘basement’ marbles and minor pelagics of the largely (?)Triassic Kaleboynu Formation in the lower part of the carbonate platform.

Metabasalts and metagabbros from isolated fragments of the stratiform ophiolites form geochemically coherent groups and indicate the influence of a subduction component during their development. It is considered that the suprasubduction zone ophiolites record the association of a tholeiitic arc and an adjacent back-arc basin with more mid-ocean ridge basalt (MORB)-like compositions.

Metabasite blocks within the tectonised ophiolitic mélange slice are MORB like, together with minor ocean island basalt (OIB) and island arc basalts, and may be tectonically related to ophiolitic units within the accretionary wedge of the Ankara Mélange.

Concordant amphibolites of the Kaleboynu Formation are largely OIB types and reflect an early ensialic rifting stage of the Tauride-Anatolide Carbonate Platform. Small ocean basins also developed at this time, as recorded by the presence of MORB and associated pelagics.

The CACC block, together with parts of the Ankara Mélange, are considered to represent oceanic lithosphere (comprising both early spreading centre and latter subduction-influenced crust) and continental carbonate platform that were subsequently ejected from an accretionary-subduction complex on collision with the Sakarya microcontinent.
Geochemistry of Volcanic Rocks from the Çiçekdağ, Ophiolite, Central Anatolia, Turkey, and Their Inferred Tectonic Setting within the Northern Branch of the Neotethyan Ocean
Authors: Yaliniz Kenan M. , Floyd Peter A. , Göncüoğlu M. Cemal
Published: April 2008

The Central Anatolian Ophiolites (CAO) comprise a number of little studied Upper Cretaceous ophiolitic bodies that originally represented part of the northern branch of the Neotethyan ocean. The Çiçekdağ Ophiolite (CO) is an dismembered example of this ophiolite group that still retains a partially preserved magmatic pseudostratigraphy. The following units (bottom to top) can be recognized: (1) layered gabbro; (2) isotropic gabbro: (3) plagiogranite; (4) dolerite dyke complex; (5) basaltic volcanic sequence; and (6) a Turonian-Santonian epi-ophiolitic sedimentary cover. The magmatic rock units (gabbro, dolerite and basalt) form part of a dominant comagmatic series of differentiated tholeiites, together with a minor group of primitive unfractionated basalts. The basaltic volcanics mainly consist of pillow lavas with a subordinate amount of massive lavas and rare basaltic breccias. Petrographic data from the least altered pillow lavas indicate that they were originally olivine-poor, plagioclase-clinopyroxene phyric tholeiites. Immobile trace element data from the basalt lavas and dolerite dykes show a strong subduction-related chemical signature. Relative to N-mid-ocean ridge basalt the Çiçekdağ basaltic rocks (allowing for the effects of alteration) have typical suprasubduction zone features with similarities to the Izu-Bonin Arc, i.e. enriched in most large-ion lithophile elements, depleted in high field strength elements and exhibiting depleted light rare earth element patterns. The geochemical characteristics are similar to other eastern Mediterranean Neotethyan SSZ-type ophiolites and suggest that the CO oceanic crust was generated by partial melting of already depleted oceanic lithosphere within the northern branch of the Neotethyan ocean. The Çiçekdağ body, along with the other fragmented CAO, is thus representative of the Late Cretaceous development of new oceanic lithosphere within an older oceanic realm.
Tectonosedimentary Evolution of the Miocene Manavgat Basin, Western Taurides, Turkey
Authors: Karabiyikoğlu Mustafa , Çiner Attila , Monod Olivier , Deynoux Max , Tuzcu Sevim , Örçen Sefer
Published: April 2008

The Manavgat Basin is a northwest-southeast oriented basin that developed on the eastern side of the Isparta Angle, south of the Late Eocene thrust belt of the western Taurides. The Miocene fill of the basin lies unconformably on an imbricated basement, comprising a Mesozoic para-authocthonous carbonate platform overthrust by the Antalya Nappes and Alanya Massif metamorphics. The sedimentary fill is represented by clasticdominated deposits consisting of, in ascending order, a conglomeratic wedge, reefal shelf carbonates, limy mudstones, and calciturbidites with subordinate breccias and conglomerates.

Process-oriented facies analysis of the basin fill indicates a variety of depositional environments ranging from fluvial/alluvial fan and fan-delta complexes through reefal carbonate shelf and forereef slope to slope fan and basin floor. Fluvial/alluvial fan and fan-delta deposits are Burdigalian-Early Langhian in age and represent the initial conglomeratic valley-fill sedimentation during a relative sea-level rise balanced by important sediment supply from relief in the north-northeast hinterland. The continuous relative sea-level rise and a decreasing rate of sediment supply allowed the deposition of transgressive reefal shelf carbonates of Langhian age. Tectonic activity demonstrated by synsedimentary faults resulted in block faulting of the narrow carbonate shelf and foundering of the basin. The rest of the sedimentation consists of the fill of newly created accommodation space. The overall coarsening-upward succession consists of Upper Langhian-Serravallian limy mudstones-calciturbidites and debris flows, overlain by Tortonian coarse-grained fan-delta deposits. The gravity induced character of most of this progradational wedge implies a progressive uplift of the hinterland.