Northern Extension Research Articles

DISTANCE TO THE SAGITTARIUS DWARF GALAXY USING MACHO PROJECT RR LYRAE STARS

We derive the distance to the northern extension of the Sagittarius (Sgr) dwarf spheroidal galaxy from 203 Sgr RR0 Lyrae stars found in the MACHO database. Their distances are determined differentially with respect to 288 Galactic Bulge RR0 Lyrae stars also found in the MACHO data. We find a distance modulus difference of 2.41 mags at $l$ = 5$^{\circ}$ and $b$ = -8$^{\circ}$ and that the extension of the Sgr galaxy towards the galactic plane is inclined toward us. Assuming $\rm R_{GC}$ = 8 kpc, this implies the distance to these stars is $(m-M)_0$ = 16.97 $\pm$ 0.07 mags, which corresponds to D = 24.8 $\pm$ 0.8 kpc. Although this estimate is smaller than previous determinations for this galaxy and agrees with previous suggestions that Sgr's body is truly closer to us, this estimate is larger than studies at comparable galactic latitudes.

Crustal seismic reflection measurements across the northern extension of the Taupo Volcanic Zone, North Island, New Zealand

A crustal seismic reflection profile across the offshore Taupo Volcanic Zone (OTVZ) has been reprocessed to improve the lower crust–upper mantle image. The OTVZ is underlain by several strong sub-horizontal crustal reflections that may correspond to shear zones or mafic sills. A reflector interpreted to correspond to Moho lies at a depth of about 8–8.5 s twt (seconds two-way-traveltime) – about 20 km – under the western margin of the Raukumara Peninsula and rises to a depth of about 6 s twt (about 16 km) under the active, eastern part of the OTVZ and can be traced at about this depth across most of the OTVZ. Underlying this inferred Moho are two diffuse zones of discontinuous reflectivity, one underlying the active eastern OTVZ and a less well defined one underlying the landward extension of the Havre Trough. They extend from about 15 to 35 km depth, within the mantle wedge, and are inferred to be imaging a zone of depleted upper mantle associated with crustal extension. A localised zone of deep (30–50 km) reflectivity and seismicity occurs under the eastern OTVZ margin and may relate to fluid flow from the Hikurangi plateau being subducted further east.

The marine algal (seaweed) flora of the Azores: additions and amendments 3

Abstract Thirteen species of benthic marine algae are reported as new to the mid Atlantic Azores archipelago, and the status is confirmed for five other species. Some of the new records fall within their overall distributional range. The discovery of seven species (Codium taylorii, Digenea simplex, Gelidiella tinerfensis, Gelidiopsis intricata, Laurencia microcladia, Papenfussiella kuromo, Phyllophora gelidioides) represents a northern extension in their Atlantic distributional range. The archipelago is the western limit of Papenfussiella kuromo and Phyllophora gelidioides in the Atlantic Ocean. Ascophyllum nodosum, common as drift, was found for the first time attached to rocks on Graciosa Island and Caulerpa webbiana is confirmed as a recent immigrant to the archipelago. Four species are removed from the flora.

UNDERUTILIZED PLANTS OF THE NORTHERN MARIANA ISLANDS

The Commonwealth of the Northern Mariana Islands, consisting of 14 islands, is located in the Western Pacific. Agriculture is relatively undeveloped in the Commonwealth, with farms mostly subsistence in nature. A variety of mixed vegetables, root crops, and tropical fruits, which form an important part of the local diet, are grown widely for family consumption and some for sale at local markets. These are grown mainly through backyard gardening. The Northern Marianas College Cooperative Research, Extension and Education Service is undertaking research on specialty crops, mainly food crops and minor cash crops for small-scale farmers, and promoting innovative agricultural development through scientific research. Several research and extension programs have been developed to promote awareness in underutilized crops in plant protection, crop production and improvement, and insect pests and diseases of major staple crops, such as sweet potato, taro, banana, corn and tropical fruits. These programs focus on a wide range Five-Year Plan of Work, which includes postharvest technology; marketing studies; value-added commodities; and food processing of staple crops, indigenous fruits, and nuts species. There is continuing emphasis on crops or varieties suitable for growth in the islands but are currently underutilized or neglected, such as Zingiber officinale (edible ginger), Curcuma longa (turmeric), Cananga odorata (ylang ylang), Calophyllum inophyllum (daok), Bixa orellana (annatto), etc. In the Commonwealth, thirty crops have been identified as underutilized or specialty crops with economic value, such as spices, staple, cosmetic oil, beverage, vegetable, timber, medicinal, fiber, dyes and crafts. Dwindling economy and foreign influences have changed social attitudes towards food production and consumption, such as the switch in food preferences from traditional foods to imported foods, e.g., rice, flour, sugar, and tinned food. However, a coherent agricultural research program could provide options that would help farmers to increase their food production capacity by cultivating underutilized crops.

Palaeomagnetic study of Tertiary volcanic domains in Southern Turkey and Neogene anticlockwise rotation of the Arabian Plate

Following collision with Eurasia, the Arabian Shield indenter has continued to deform into the weak Anatolian collisional collage that resulted from subduction of the Neotethyan Ocean. Differential movements have involved rotation and continuing northwards translation, and have been accommodated mainly by slip along major transforms including the northward extension of the Dead Sea Fault Zone (DSFZ) and the East Anatolian Fault Zone (EAFZ). To aid in evaluating post-collisional motions the palaeomagnetism of extensive volcanic domains at the northern margin of the stable shield in southern Turkey is reported here together with the timing of emplacement as constrained by K–Ar study. The age dating results indicate that volcanic activity occurred mainly during mid-late Miocene times corresponding to the final stages of suturing. Volcanic fields in the east of the investigated region are younger and correspond to Neotectonic volcanism in Brunhes and Matuyama chrons. Thermal and alternating field demagnetization of 399 cores from 83 sites in basaltic lavas identifies 29 units of normal and 43 of reversed polarity with 11 sites having transitional or random directions. Volcanic fields west of the Euphrates (Kilis–Gaziantep region) with ages in the range 7.0–20.3 Ma (average 14.9 Ma, SD = 4.3 Ma) have mean remanence D/ I = 353/52° (38 sites, 5.3°). Lava fields east of the Euphrates (Urfa region) are dated 10.4–12.1 Ma and yield a comparable mean remanence D/ I = 350/50° (17 sites, 6.0°). These collections are shown to have properly recorded palaeosecular variation with only minimal inclination shallowing and inferred anticlockwise rotations with respect to Eurasia since mid-Miocene times are 10.9 ± 4.3° and 14.0 ± 5.0° respectively. These contrast with clockwise rotation of 6.3 ± 4.3° derived from late Matuyama–Brunhes epoch volcanic rocks immediately to the north west of the Arabian margin where rotational impingement of the shield indenter into fault blocks within the Karasu Rift at the northern extension of the DSFZ interacts with left lateral motion at a rate of ~ 0.5 cm/year along this zone to produce small scale vertical axis rotations. Results from the volcanic suites sited on the stable shield are compared with other results from the Arabian Plate to conclude that it did not rotate significantly following closure of the Bitlis Suture until Late Miocene–Early Pliocene times since when it has rotated anticlockwise at a rate of ~ 1.0°/Myr. This is comparable to the present day rate of rotation deduced from GPS and correlates with crustal separation and sea floor spreading in the Red Sea. It also temporally links the rotation of the Arabian Plate to the initiation of the intracontinental transforms (North and East Anatolian fault zones) within Anatolia and to the subsequent extrusion of blocks within this accretionary domain by tectonic escape to the west.

Granitoid evolution in Sinai, Egypt, based on precise SHRIMP U–Pb zircon geochronology

Late-stage Pan-African granitoids, including monzogranite, syenogranite and alkali granite, were collected from four separate localities in Sinai. They were selected to represent both the calc-alkaline and alkaline suites that have been viewed as forming separate magmatic episodes in the Eastern Desert of Egypt, with the transition to alkali granite at ~ 610 Ma taken to mark the onset of crustal extension. Although intrusive relations were observed in the field, the emplacement ages of the granitoids cannot be distinguished within analytical uncertainty and they all formed within a restricted time span from 579 to 594 Ma. This indicates that the two suites are coeval and that some calc-alkaline rocks were also likely generated during the late extensional phase. These ages are identical to those recently obtained from similar rocks in the North-Eastern Desert, confirming that Sinai is the northern extension of the Eastern Desert Pan-African terrane of Egypt. Rare inherited zircons with ages of ~ 1790 and ~ 740 Ma are present in syenogranite from northeastern Sinai and indicate that older material is present within the basement. A few zircons record younger ages and, although some may reflect later disturbance of the main zircon population, those with ages of ~ 570 and 535 Ma probably reflect thermal events associated with the extensive emplacement of mafic and felsic dykes in both northeastern and southern Sinai.

The scattered debris of the Magellanic Stream

Abstract Searching the H i Parkes All-Sky Survey and its northern extension, we detected a population of very compact high-velocity clouds (HVCs) with similar velocities in the Galactic standard-of-rest frame which appear to be arranged in several filaments aligned with the nearby Magellanic Stream. A comparison with published O vi/Ca ii absorption and H i emission-line measurements suggests that the HVCs are condensations within an extended and mainly ionized component of the Magellanic Stream. They coincide in position with a faint gas stream predicted in numerical simulations of the Magellanic Clouds by Gardiner & Noguchi. Consequently, the Magellanic Stream could be much more extended than generally believed.

Ecological hindcasting of biogeographic responses to climate change in the European intertidal zone

Intertidal organisms are often assumed to live close to their thermal limits, and have emerged as potential early indicators of the effects of climate change. We compared our survey of the 2004–2006 geographic distribution of the barnacle Semibalanus balanoides to its distribution in 1872, 1955, 1963, 1971, and 1985, from surveys by Fischer, Crisp, Fischer-Piette, Barnes, Powell, and Southward. The southern geographic limit has retreated 300 km in France since 1872, at a rate of 15 to 50 km per decade. We compared our 2006 survey of the geographic distribution of the polychaete Diopatra neapolitana to its distribution in 1893–1923, from surveys by Saint-Joseph and Fauvel, and its distribution in 1969–1976 from surveys by Glemarec. The northern geographic limit of this species has advanced 300 km in France since 1893 at similar rates to Semibalanus. We used NOAA weather re analysis data and our mechanistic simulation model of intertidal animal body temperatures to hindcast the thermal environmental change near historical geographic limits in Europe for the past 55 years. Results indicate that changes in the southern limit of S. balanoides are due to intolerance of winter body temperatures above 10°C, leading to reproductive failure. Results for Diopatra are ambiguous: based on the northern extension of its range, either cold winters or cool summers limit its range, while gaps in its distribution are consistent with limitation by cooler summer conditions. The parallel shifts of D. neapolitana on sedimentary shores and Semibalanus on rocky shores suggest that similar climatic factors control the geographic limits of both species. The intertidal zone is a model system for examining the effects of climate change on biogeographic change both because of the rapidity of its response, and because the rich historical record allows direct tests of hypotheses.

THE ARECIBO LEGACY FAST ALFA SURVEY. V. THE H I SOURCE CATALOG OF THE ANTI-VIRGO REGION AT δ = +27°

We present a second catalog of HI sources detected in the Arecibo Legacy Fast ALFA Survey. We report 488 detections over 135 deg 2 , within the region of the sky having 22h 6:5, where the reliability of the catalog is better than 95% or (b) 5:0 < S=N < 6:5 and a previously measured redshift that corroborates our detection. Of the 488 objects presented here, 49 are High Velocity Clouds or clumps thereof with negative heliocentric recession velocities. These clouds are mostly very compact and isolated, while some of them are associated with large features such as Wright’s Cloud or the northern extension of the Magellanic Stream. The remaining 439 candidate detections are identied as extragalactic objects and have all been matched with optical counterparts. Five of the six galaxies detected with MHI < 10 7:5 M are satellites of either the NGC672/IC1727 nearby galaxy pair or their neighboring dwarf irregular galaxy NGC784. The data of this catalog release include a slice through the Pisces-Perseus foreground void, a large nearby underdensity of galaxies. We report no detections within the void, where our catalog is complete for systems with HI masses of 10 8 M . Gas-rich, optically-dark galaxies do not seem to constitute an important void population, and therefore do not suce at producing a viable solution to the void phenomenon. Subject headings: galaxies: distances and redshifts | galaxies: spiral | galaxies: photometry | radio lines: galaxies | catalogs | surveys

The recent northern introduction of the seaweed Caulerpa webbiana (Caulerpales, Chlorophyta) in Faial, Azores Islands (North-Eastern Atlantic)

Until recently, introduced species did not seem to have a significant adverse impact on the Azorean marine native flora and fauna. Nevertheless, one of the recent alien species listed for this region belongs to a genus with high invasive potential: Caulerpa (Caulerpales, Chlorophyta). Caulerpa webbiana was first detected in 2002 near the main yachting harbour of the Azores, Horta, in Faial. Through the years it has rapidly extended its colonized area and the density of colonies encountered have increased in the harbour and adjacent areas. The establishment of the seaweed represents a northern extension of its distribution and may have been facilitated by changes in climate. However, the actual pattern of C. webbiana distribution seems to indicate that this new species was possibly introduced by maritime traffic rather than reaching the island through natural rafting. There is an urgent need to address the issue of this seaweed in the Azores.

BASEMENT CONFIGURATION OF THE NORTHWESTERN SOUTH AMERICA - CARIBBEAN MARGIN FROM RECENT GEOPHYSICAL DATA

The oceanic nature of the crust in northern Colombia (underlying the Lower Magdalena Basins) has been postulated by different authors as a northern extension of the Cretaceous, mafic and ultramafic rocks accreted to the western margin of northwest Colombia (in the Western Cordillera and Baudo range). Localized, small outcrops of oceanic affinity rocks seem to support this hypothesis. However, geophysical data do not support this northern extension, but clearly mark the boundary between the collisional Panamá terrane with northern South America and the over thrusting of the latter on top of the obliquely convergent Caribbean plate. We produced maps to basement and Moho topography by integrated modeling of gravity, magnetics, seismic reflection surveys and well data from northwest Colombia and the southwestern Caribbean. In areas with good seismic coverage, the basement under the Lower Magdalena Basins (LMB) is represented by a clear reflector. In areas where seismic data shows poor imaging or is absent, we use a back stripping methodology to model first the sedimentary section, with known densities, composition and geometry controlled by oil wells and high quality seismic data, and then the deeper section. 2,5D gravity and magnetics modeling results in an initial Moho that can be extended to the entire region based on the control of available seismic refraction points. This controlled Moho provides the basis for basement modeling for the whole area and this sequence is iterated for several sections across the region. Our results indicate that the crust under northern Colombia is continental to thinned continental (transitional) in nature, with densities between 2,6 and 2,7 g/cm3. Our model also requires a dense wedge of sediments (density 2,5 g/cm3) at the base of the modern fold belt, which may represent a fossil sedimentary wedge attached to the continental margin. This wedge may have served as a backstop for the modern fold belt. The gravity modeling does not require oceanic crust to form the basement in the Sinú and San Jacinto fold belts as previously suggested. Discrete layers and thin slivers of oceanic sediments and basement could have been scrapped off the incoming plate and thrusted into an accretionary mélange, and eventually exposed at the surface, as seen in the Mulatos, Chalan and Cansona locations. The shape of the continental wedge / oceanic crust boundary resembles that of a very low angle/flat subduction zone (ß angle between 2º to 3º), and is interpreted here as a low angle over thrusting of northern South America riding in a highly oblique direction over the underlying Caribbean plate. The map to basement depth obtained during this study forms the basis for basin analysis, oil maturation and evolutionary studies of the region. As an example, we apply our map to a flexural analysis of the LMB.

The Northland Basin, New Zealand: Analysis of Gravity and Magnetic Data

The offshore Northland Basin, New Zealand, is the northern extension of the petroleum-producing Taranaki Basin. The basin has a complex history involving Mid- to Late-Cretaceous rifting, associated with the separation of the New Zealand micro-continent from the Australian/Antarctic plate, and early-Miocene thrusting and calc-alkaline volcanism, associated with the onset of plate convergence. 2-D seismic reflection data show that a sequence of Cretaceous to Recent sedimentary rocks up to 3-4 km thick occurs within the main depocentres. Gravity and magnetic data from the basin are complex and reflect the distribution of basement and volcanic rocks in the basin. Significant positive gravity anomalies, typically sub-circular, are associated with Miocene volcanics, whose upper surfaces are often evident in the seismic reflection data but whose overall geometries are poorly imaged. More linear, but less pronounced, gravity highs are attributable to up-thrown basement ridges whilst strong gravity lows mark the main depocentres. Strong magnetic anomalies are a characteristic feature of the basin and similarly mark the locations of the Miocene-Pliocene volcanics. In the northern part of the basin especially, more linear magnetic anomalies appear to be associated with structural units in the basement, however the nature of basement rocks in the region is poorly known. Gravity and magnetic data can therefore play a critical role in resolving some important features of basin development.

Trophic and environmental drivers of the Sechura Bay Ecosystem (Peru) over an ENSO cycle

Interannual environmental variability in Peru is dominated by the El Niño Southern Oscillation (ENSO). The most dramatic changes are associated with the warm El Niño (EN) phase (opposite the cold La Niña phase), which disrupts the normal coastal upwelling and affects the dynamics of many coastal marine and terrestrial resources. This study presents a trophic model for Sechura Bay, located at the northern extension of the Peruvian upwelling system, where ENSO-induced environmental variability is most extreme. Using an initial steady-state model for the year 1996, we explore the dynamics of the ecosystem through the year 2003 (including the strong EN of 1997/98 and the weaker EN of 2002/03). Based on support from literature, we force biomass of several non-trophically-mediated ‘drivers’ (e.g. Scallops, Benthic detritivores, Octopus, and Littoral fish) to observe whether the fit between historical and simulated changes (by the trophic model) is improved. The results indicate that the Sechura Bay Ecosystem is a relatively inefficient system from a community energetics point of view, likely due to the periodic perturbations of ENSO. A combination of high system productivity and low trophic level target species of invertebrates (i.e. scallops) and fish (i.e. anchoveta) results in high catches and an efficient fishery. The importance of environmental drivers is suggested, given the relatively small improvements in the fit of the simulation with the addition of trophic drivers on remaining functional groups’ dynamics. An additional multivariate regression model is presented for the scallop Argopecten purpuratus, which demonstrates a significant correlation between both spawning stock size and riverine discharge-mediated mortality on catch levels. These results are discussed in the context of the appropriateness of trophodynamic modeling in relatively open systems, and how management strategies may be focused given the highly environmentally influenced marine resources of the region.

Sm-Nd Isotope Technique as An Exploration Tool: Delineating the Northern Extension of the Thompson Nickel Belt, Manitoba, Canada

Application of Nd isotope mapping to aid mineral exploration has been tested successfully in areas north of the well-prospected, productive portion of the Thompson nickel belt in Manitoba, Canada. Economic nickel deposits in this main part of the belt are restricted to the Ospwagan Group cover sequence and ultramafic sills overlying Archean basement gneisses. Distinguishing some units in the Ospwagan Group from its basement and less prospective Paleoproterozoic paragneiss of the Burntwood Group in the area is difficult based on lithology, stratigraphy, geochemistry, and structure alone. However, the Ospwagan Group has a unique Nd isotope signature that allows it to be identified with certainty. A compilation of Nd isotope data from the main portion of the Thompson nickel belt and a new dataset from drill core and reconnaissance mapping clearly support early exploration indications that basement gneiss and narrow belts of the Ospwagan Group typical of the belt extend northeast of the main part of belt for at least 100 km. This confirms the presence of a large new area for nickel exploration, the limits of which are still unknown. In this poorly exposed, northern area, crustal-residence Nd model ages (T CR ) are instrumental in clearly separating (1) the Ospwagan Group supracrustal rocks (T CR = 2.8–3.2 Ga) that host the nickel deposits from (2) Neoarchean basement gneiss (T CR = 3.2–3.5 Ga), (3) juvenile, overthrust Burntwood (T CR = 2.2–2.6 Ga), Grass River, and Sickle (T CR = 2.0–2.4 Ga) Groups paragneisses, and (4) fragments of a Mesoarchean gneiss complex (T CR = 3.5–4.1 Ga), the latter being the host of precious metal prospects. The variation in Nd model ages not only distinguishes the different supracrustal successions, but the variable inheritance of ancient crustal material in units of Archean gneiss reflected in Nd model ages serves as a tool to unravelling the complexly interleaved structure of this crust and aids in tracing the potentially nickel-hosting Ospwagan Group in narrow structural keels. The robustness of the Nd isotope system under the conditions of high-grade metamorphism and migmatization attained in the Thompson nickel belt makes this an ideal tool for distinguishing between units of economically prospective and barren gneiss in frontier areas where other methods have failed, are difficult to apply, or have led to erroneous interpretations.

Petrology, geochemistry and geodynamic implications of Jurassic island arc magmatism as revealed by mafic volcanic rocks in the Mesozoic low-grade sequence, eastern Rhodope, Bulgaria

In the eastern Bulgarian Rhodope, mafic extrusive rocks and underlying greenschists are found in the Mesozoic low-grade unit, which represents the northern extension of similar sequences including the Evros ophiolites in Thrace (Greece). Both rock types define a suite of low-Ti tholeiitic basalts to transitional boninitic basaltic andesites and andesites and associated metapyroclastites (greenschists), intruded at its base by diorite dikes of a boninitic affinity. Mafic lavas and greenschists display large ion lithophile element (LILE) enrichment relative to high-field strength elements (HFSE), flat REE patterns of a slight light REE depletion, a strong island arc tholeiite (IAT) and weak MORB-like signature. All these rocks are characterized by negative Nb anomalies ascribed to arc lavas. They have positive ɛNd i values in the range of + 4.87 to + 6.09, approaching the lower limit of MORB-like source, and relatively high ( 207Pb/ 204Pb) i (15.57–15.663) at low ( 206Pb/ 204Pb) i (18.13–18.54) ratios. The Nd isotopic compositions coupled with trace element data imply a dominantly depleted MORB-like mantle source and a contribution of subduction modified LILE-enriched component derived from the mantle wedge. The diorite dike has a low ɛNd i value of − 2.61 and is slightly more Pb radiogenic ( 207Pb/ 204Pb) i (15.64) and ( 206Pb/ 204Pb) i (18.56), respectively, reflecting crustal contamination. Petrologic and geochemical data indicate that the greenschists and mafic extrusive rocks represent a magmatic assemblage formed in an island arc setting. The magmatic suite is interpreted as representing an island arc–accretionary complex related to the southward subduction of the Meliata–Maliac ocean under the supra-subduction back-arc Vardar ocean/island arc system. Magmatic activity appears to have initiated in the north during the inception of the island arc system by the Early–Middle Jurassic time in the eastern Rhodope that most likely graded to back-arc spreading southwards as represented by the Late Jurassic MORB-type Samothraki Island ophiolites. This tectonic scenario is further constrained by paleotectonic reconstructions. The arc–trench system collided with the Rhodope in the Late Jurassic times.

Late Paleoproterozoic to mid-Neoproterozoic history of northern Laurentia: An overview of central Rodinia

At the assumed core of reconstructed Rodinia, northern Laurentia, comprising the Canadian Shield (including Greenland) and its buried western and northern extensions beneath Phanerozoic cover, is considered in two parts. On its southeast side, the Grenville Province is part of a major late Mesoproterozoic orogen inferred to be related to the assembly of the Rodinia supercontinent. The remainder of northern Laurentia experienced a long period of crustal stability beginning at ca. 1.8 Ga, recorded for the most part by intracontinental and passive-margin sedimentation along with mafic igneous activity, mainly in the mid-Mesoproterozoic, related to limited extension. To the south, this stable part of northern Laurentia is overprinted by late Paleoproterozoic orogeny (Yavapai, Mazatzal, and Central Plains orogens) and early Mesoproterozoic magmatism (granite-rhyolite provinces). Deformed and metamorphosed rocks related to these form a major part of the interior of the Grenville orogen, where mid- to late Mesoproterozoic orogenic events led to accretion of terranes to Laurentia and subsequent terminal collision. The first manifestation of Rodinia breakup began in the west at ca. 0.8 Ga, some 0.2 Ga earlier than along the southeast side; the age of initial rifting along the northern margin is not known.

Seismic evidence for whole lithosphere separation between Saxothuringian and Moldanubian tectonic units in central Europe

The Bohemian Massif is part of the Variscan belt of central Europe. We carried out a high resolution mapping of lithospheric thickness beneath central Europe by investigating 264 teleseismic events recorded at 80 broad band stations in the western Bohemian Massif with the method of S receiver function analysis. A negative phase beneath the Saxothuringian and northeastern Teplá‐Barrandian units at about 9–10 s before the S onset is interpreted as caused by the lithosphere‐asthenosphere boundary (LAB) at 80–90 km depth. In the Moldanubian unit, the negative phase occurs at 13–15 s before the S onset, corresponding to lithospheric thickness of 120–130 km. The boundary between the domains is oriented E‐W and probably marks the northern extension of Moldanubian lithosphere. The Moho also deepens from the Saxothuringian to the Moldanubian unit. The observed crustal/lithospheric domains could represent two distinct microplates with a relatively sharp boundary cutting through the whole lithosphere.

Segmentation of the western Taiwan active fault zone inferred from its structural analogy to the Nankai trough region, southwest Japan

A west-facing active fold-and-thrust structure is typified by the three thrust sheets soled by the frontal Changhua, central Chelungpu and hindward Shuangtung faults in the Taichung area, central western Taiwan. The least deformed Changhua sheet comprises an N–S-trending frontal structural high and a parallel inner basin. The Chelungpu and Shuangtung sheets deform an N–S-trending syncline that originates from an older basin. The N–S-striking structures are traversed or overlain by ENE-WSW-trending structures, such as the ENE-striking Tuntzuchiao fault and adjoining eastward bends of the northern tips of the Chelungpu and Shuangtung faults. Such transverse structures are located in three other areas of western Taiwan: near Hsinchu, north of Chiayi and north of Tainan. The configuration of the island-parallel and transverse structures mimics structural features of the rupture units of interplate earthquakes off southwest Japan, which are produced by right-oblique subduction of the Philippine Sea plate along the Nankai trough. This suggests that the western Taiwan active fault zone can be divided into five rupture areas 60–80 km long, and may be controlled by left-oblique convergent tectonics at the northern extension of the Manila trench.

Inertial and tidal shear variability above Reykjanes Ridge

Yearlong 75 kHz acoustic Doppler current profiler (ADCP) data were obtained well above Reykjanes Ridge (northern extension of the Mid-Atlantic Ridge (MAR)). The area is characterized by relatively large semidiurnal tidal (‘ D 2’) currents that have (at lunar M 2) more than half a decade larger variance than inertial ( f) currents. However, despite the relatively weak near-inertial kinetic energy, its vertical current shear shows larger magnitudes than at M 2 in an otherwise flat f− D 2 band limited between frequencies 0.74 and 1.35 f, which equals the inertio-gravity wave bounds [ σ min, σ max]( N= f). N represents the buoyancy frequency. The shear in this band dominates all shear computed at 20 m effective vertical scale. As the kinetic energy spectrum peaks at M 2, but not (significantly) at S 2 and N 2, a difference in tidal (and inertial) scales and hence sources is observed. M 2-tides contribute mostly to large-scale coherent motions. The dominant incoherent f− D 2 shear is highly variable in time (∼2-day periodicity). Furthermore, inertial and tidal shear are more or less completely separated in space and time, each occurring in different layers in the vertical. The thin shear layers reflect the rapidly varying short vertical scale N s profile, to within the ∼20 m limitation of ADCP data, rather than the large-scale smooth N L. In each of large- N s layers Ri≈1, probably. The yearlong smoothed shear magnitude follows N L, but only as stable Ri≈5. The shear polarization is more circular than rectilinear, albeit varying with time, and highly symmetric around f. During transitions, e.g., between stratified and homogeneous layers and between waves from varying sources, near-circular motions can generate near-rectilinear shear in the direction of wave propagation (in the direction of the minor axis of the current ellipse). This contrasts with the possibility of near-rectilinear barotropic oscillatory motions generating near-circular shear under viscosity in shallow seas.

Holocene sedimentary evolution and palaeocoastlines of the Lower Khuzestan plain (southwest Iran)

The Holocene sequence of the Lower Khuzestan plain in southwest Iran has been investigated in the context of coastal evolution and relative sea-level change. A literature review about the coastal evolution of the Shatt-el Arab region with respect to relative sea-level changes is provided. The sedimentary succession in undisturbed hand-operated cores and temporary outcrops is described and facies are identified on the basis of lithology, sedimentary structures and macrofossils. Four main sedimentary environments are interpreted from the Holocene sedimentary record of the plain: brackish tidal flat, clastic coastal sabkha, brackish–freshwater marsh and fluvial plain. The study of the vertical and spatial distribution of sedimentary facies, their environmental interpretation especially with respect to the relationship to tide levels is done for five different zones in the plain. Chronological control is provided by radiocarbon dates. On the basis of this analysis, palaeogeographical reconstructions of the Lower Khuzestan plain, and the northern extension of the Persian Gulf were made for different points in time between 8000 and 450 cal BP. This study shows that during the early and middle Holocene, the Lower Khuzestan plain was a low-energy tidal embayment under estuarine conditions. During the initial sea-level rise of the early Holocene, the coastline rapidly transgressed across the shelf, and drowning of a major valley resulted in the development of extended tidal flats. Deceleration of sea-level rise after approximately 5500 cal BP, together with probably more arid conditions, allowed coastal sabkhas to extend widely and to aggrade while the position of the coastline remained relatively stable. Continued deceleration of sea-level rise initiated the progradation of the coastline from ca. 2500 cal BP. The effect of sediment supply by the rivers became more important than the effect of relative sea-level rise. The Karun megafan developed under a descelerating rate of sea-level rise, controlling the avulsive shifting of the rivers Karkheh and Jarrahi and their loci of sediment input. Moreover, in this study it is suggested that a Holocene RSL highstand, above the present-day sea level, as suggested by previous workers, did not occur.