bluuebunny/crossref_metadata_2025 huggingface dataset:
Passage of debris flows and turbidity currents through a topographic constriction: seafloor erosion and deflection of flow pathways
Authors: Gee Martin J. R. , Masson Douglas G. , Watts Anthony B. , Mitchell Neil C.
Published: March 2003

Some of the Earth's largest submarine debris flows are found on the NW African margin. These debris flows are highly efficient, spreading hundreds of cubic kilometres of sediment over a wide area of the continental rise where slopes angles are often <1°. However, the processes by which these debris flows achieve such long run‐outs, affecting tens of thousands of square kilometres of seafloor, are poorly understood. The Saharan debris flow has a run‐out of ≈700 km, making it one of the longest debris flows on Earth. For its distal 450 km, it is underlain by a relatively thin and highly sheared basal volcaniclastic layer, which may have provided the low‐friction conditions that enabled its extraordinarily long run‐out. Between El Hierro Island and the Hijas Seamount on the continental rise, an ≈25‐ to 40‐km‐wide topographic gap is present, through which the Saharan debris flow and turbidites from the continental margin and flanks of the Canary Islands passed. Recently, the first deep‐towed sonar images have been obtained, showing dramatic erosional and depositional processes operating within this topographic `gap' or `constriction'. These images show evidence for the passage of the Saharan debris flow and highly erosive turbidity currents, including the largest comet marks reported from the deep ocean. Sonar data and a seismic reflection profile obtained 70 km to the east, upslope of the topographic `gap', indicate that seafloor sediments to a depth of ≈30 m have been eroded by the Saharan debris flow to form the basal volcaniclastic layer. Within the topographic `gap', the Saharan debris flow appears to have been deflected by a low (≈20 m) topographic ridge, whereas turbidity currents predating the debris flow appear to have overtopped the ridge. This evidence suggests that, as turbidity currents passed into the topographic constriction, they experienced flow acceleration and, as a result, became highly erosive. Such observations have implications for the mechanics of long run‐out debris flows and turbidity currents elsewhere in the deep sea, in particular how such large‐scale flows erode the substrate and interact with seafloor topography.
Sub‐wavebase cross‐bedded grainstones on a distally steepened carbonate ramp, Upper Miocene, Menorca, Spain
Authors: Pomar Luis , Obrador Antonio , Westphal Hildegard
Published: March 2003

Cross‐bedded grainstones on carbonate ramps and shelves are commonly related to the locus of major wave energy absorption such as shorelines, shoals or shelf breaks. In contrast, on the Early Tortonian carbonate platform of Menorca (Balearic Islands), coarse‐grained, cross‐bedded grainstones are found at a distance from the palaeoshoreline where they were deposited below the wavebase. Excellent exposures along continuous outcrops on the sea cliffs of Menorca reveal the depositional profile and three‐dimensional distribution of the different facies belts of the Tortonian ramp depositional system. Basinward from the palaeoshoreline, fan deltas and beach deposits pass into 5‐km‐wide gently dipping bioturbated dolopackstone (inner and middle ramp), then into 12–20°‐dipping dolograinstone/rudstone clinobeds (ramp slope) and, finally, into subhorizontal fine‐grained basinal dolowackestone to dolopackstone (outer ramp). In this Miocene example, coarse‐grained grainstones exist in five different settings other than beach deposits: (1) on the middle ramp, where cross‐bedded grainstones were deposited by currents roughly parallel to the shoreline at 40–70 m estimated water depth and are interbedded with gently dipping bioturbated dolomitized packstones; (2) on the upper slope, where clinobeds are composed mostly ofin siturhodoliths and red‐algae fragments; (3) on the lower slope, as small‐scale bedforms (small three‐dimensional subaqueous dunes) migrating parallel to the slope; (4) at the transition between the lower slope and the outer ramp, where mollusc‐rich and rhodolithic rudstones and grainstones, interbedded in dolomitized laminated wackestones containing abundant planktonic foraminifera, infill slide/slump scars as upslope‐backstepping bodies (backsets); (5) at the toe of the slope, where coarse skeletal grainstones indicate bedform migration parallel to the platform margin, induced by currents at more than 150 m estimated water depth. This Late Miocene example also illustrates how changes in intrabasinal environmental conditions (nutrients and/or temperature) may produce changes in stratal patterns and facies architecture if they affect the biological system. Two depositional sequences compose the Miocene platform on Menorca, where a reef‐rimmed platform prograded onto an earlier distally steepened ramp. The transition from the ramp to the reef‐rimmed platform was effected by an increase in accommodation space caused by ecological changes, promoting a shift from a grain‐ to a framework‐producing biota.
The Polonez Cove Formation of King George Island, Antarctica: stratigraphy, facies and implications for mid‐Cenozoic cryosphere development
Authors: Troedson Alexa L. , Smellie John L.
Published: March 2003

The middle to late Oligocene Polonez Cove Formation, exposed on south‐eastern King George Island, South Shetland Islands, provides rare evidence of mid‐Cenozoic West Antarctic cryosphere evolution. A revised lithostratigraphy and facies analysis and a review of the palaeoenvironmental significance of the formation are presented here. The diamictite‐dominated basal member of the formation (Krakowiak Glacier Member) records the presence and retreat of marine‐based ice on a shallow continental shelf. Five overlying members are recognized. These consist of basaltic‐sourced sedimentary rocks and lavas and represent a variety of shoreface and shallow continental shelf environments in an active volcanic setting. These units contain diverse reworked and ice‐rafted exotic clasts that become sparse towards the top of the formation, suggesting a continuing but waning glacial influence. New 40Ar/39Ar dates from interbedded lava flows indicate a late Oligocene age (25·6–27·2 Ma) for the Polonez Cove Formation, but are slightly younger than skeletal carbonate Sr‐isotope ages obtained previously (28·5–29·8 Ma). There is evidence for wet‐based subice conditions at the base of the Polonez Cove Formation, but no sedimentary facies to suggest substantial meltwater. This may reflect a subpolar setting or may result from lack of preservation or a high‐energy depositional environment. A northern Antarctic Peninsula/South Shetland Islands provenance is probable for most non‐basaltic clasts, but certain lithologies with possible origins in the Transantarctic and Ellsworth Mountains also occur sparsely throughout the formation. There is evidence to suggest that the presence of such far‐travelled clasts within subglacially deposited facies at the base of the formation reflects the advance of a local ice cap across marine sediments containing the clasts as ice‐rafted material. The presence of these clasts suggests that extensive marine‐based ice drained into the southern Weddell Sea region and that a strong Weddell Sea surface current operated both before and during deposition of the Polonez Cove Formation.
Grainfall processes in the lee of transverse dunes, Silver Peak, Nevada
Authors: Nickling W. G. , Neuman C. Mckenna , Lancaster N.
Published: March 2003

Grainfall deposition and associated grainflows in the lee of aeolian dunes are important in that they are preserved as cross‐beds in the geological record and provide a key to the interpretation of the aeolian rock record. Despite their recognized importance, there have been very few field, laboratory or numerical simulation studies of leeside depositional processes on aeolian dunes. As part of an ongoing study, the relationships among grainfall, wind (speed and direction), stoss sand transport rates and dune morphometry (height and aspect ratio) were investigated on four relatively small, straight‐crested transverse dunes at Silver Peak, Nevada. Between 55% and 95% of the total grainfall was found to be deposited within 1 m of the crest, and 84–99% within 2 m, depending primarily on dune size and shape. Grainfall decay rates on high dunes of large aspect ratio were observed to be very consistent, with a weak positive dependence on wind speed. For small dunes with low aspect ratios, grainfall deposition was more varied and decreased rapidly within 1 m of the dune crest, whereas at increased distance from the dune crest, it eventually approached the smaller decay rates observed on the large dunes. No dependence of grainfall on wind speed was observed for these small dunes. Comparison of field data with predictions from Anderson's (1988) saltation model of grainfall, based on the computation of saltation path lengths, indicates lack of agreement in the following areas: (1) deposition rate magnitude; (2) variation in decay rate with wind speed; and (3) the magnitude and location of the localized lee‐slope depositional maxima. The Silver Peak field results demonstrate the importance of dune aspect ratio and related wake effects in determining the rate and pattern of grainfall. This work confirms earlier speculation by McDonald & Anderson (1995) that temporary, turbulent suspension (or `modified saltation') of relatively large grains does occur within the dune wake, so that transport distances generally are larger than predicted by numerical simulations of `true' saltation.
Electrical resistivity ground imaging (ERGI): a new tool for mapping the lithology and geometry of channel‐belts and valley‐fills
Authors: Baines Dave , Smith Derald G. , Froese Duane G. , Bauman Paul , Nimeck Grant
Published: March 2003

Efforts to map the lithology and geometry of sand and gravel channel‐belts and valley‐fills are limited by an inability to easily obtain information about the shallow subsurface. Until recently, boreholes were the only method available to obtain this information; however, borehole programmes are costly, time consuming and always leave in doubt the stratigraphic connection between and beyond the boreholes. Although standard shallow geophysical techniques such as ground‐penetrating radar (GPR) and shallow seismic can rapidly obtain subsurface data with high horizontal resolution, they only function well under select conditions. Electrical resistivity ground imaging (ERGI) is a recently developed shallow geophysical technique that rapidly produces high‐resolution profiles of the shallow subsurface under most field conditions. ERGI uses measurements of the ground's resistance to an electrical current to develop a two‐dimensional model of the shallow subsurface (<200 m) called an ERGI profile. ERGI measurements work equally well in resistive sediments (‘clean’ sand and gravel) and in conductive sediments (silt and clay). This paper tests the effectiveness of ERGI in mapping the lithology and geometry of buried fluvial deposits. ERGI surveys are presented from two channel‐fills and two valley‐fills. ERGI profiles are compared with lithostratigraphic profiles from borehole logs, sediment cores, wireline logs or GPR. Depth, width and lithology of sand and gravel channel‐fills and adjacent sediments can be accurately detected and delineated from the ERGI profiles, even when buried beneath 1–20 m of silt/clay.
Sedimentology of magmatically and structurally controlled outburst valleys along rifted volcanic margins: examples from the Nuussuaq Basin, West Greenland
Authors: Dam Gregers
Published: March 2003

ABSTRACT After a period of early Palaeocene faulting and uplift of the Nuussuaq Basin, West Greenland, two valley systems were incised into the underlying sediments. Incision of the older Tupaasat valley took place during a single drainage event of large water masses, which resulted in catastrophic deposition. The valley was cut along early Palaeocene NW‐ to SE‐trending normal faults, clearly showing that the trend and the relief of the valley were structurally controlled. The valley fill is up to 120 m thick and consists of a lower part of sandstones and conglomerates deposited from catastrophic flows characterized by very high concentrations of suspended coarse‐grained sediment load. Catastrophic deposition was followed by rapid decrease in flow discharge and the establishment of a lacustrine environment within the valley characterized by the deposition of heterolithic sediments. The younger Paatuutkløften valley system was mainly cut into the Tupaasat valley fill, which was completely or nearly completely eroded away in many places. The younger valley is 1–2 km wide and up to 190 m deep. Incision of the Paatuutkløften valley probably reflected renewed tectonic activity and uplift of the basin. This phase was shortly followed by rapid major subsidence. The valley‐fill deposits comprise a uniform succession of fluvial and estuarine sandstones. The valley fill is topped by shoreface sandstones, which are succeeded abruptly by offshore mudstones deposited shortly before and during the initial extrusion of a thick hyaloclastite succession. The Paatuutkløften valley fill is attributed to a very rapid rise in relative sea level contemporary with extensive volcanism. It is suggested that this sequence of events coincided with the arrival of the North Atlantic mantle plume. In several respects, the early Palaeocene valley‐fill deposits of the Nuussuaq Basin are different from idealized facies models for incised valley systems and represent very special cases of incised valleys. Major differences from published examples include the dominance of catastrophic deposits and indications of large changes in relative sea level of several hundreds of metres taking place rapidly in less than 1 Myr. These changes were governed by the rise of the North Atlantic mantle plume.
Carbonate platform evolution: from a bioconstructed platform margin to a sand‐shoal system (Devonian, Guilin, South China)
Authors: Chen Daizhao , Tucker Maurice E. , Zhu Jingquan , Jiang Maosheng
Published: March 2003

ABSTRACT The depositional organization and architecture of the middle–late Devonian Yangdi rimmed carbonate platform margin in the Guilin area of South China were related to oblique, extensional faulting in a strike‐slip setting. The platform margin shows two main stages of construction in the late Givetian to Frasnian, with a bioconstructed margin evolving into a sand‐shoal system. In the late Givetian, the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies (mostly Renalcis and Epiphyton). These grew upwards and produced an aggradational (locally slightly retrogradational) architecture with steep foreslope clinoforms. Three depositional sequences (S3–S5) are recognized in the upper Givetian strata, which are dominated by extensive microbialites. Metre‐scale depositional cyclicity occurs in most facies associations, except in the platform‐margin buildups and upper foreslope facies. In the latest Givetian (at the top of sequence S5), relative platform uplift (± subaerial exposure) and associated rapid basin subsidence (probably a block‐tilting effect) caused large‐scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups. Subsequently, sand shoals and banks composed of ooids and peloids and, a little later, stromatoporoid buildups on the palaeohighs, developed along the platform margin, from which abundant loose sediment was transported downslope to form gravity‐flow deposits. Another strong tectonic episode caused further platform collapse in the early Frasnian (at the top of sequence S6), leading to large‐scale breccia release and the death of the stromatoporoid buildups. Siliceous facies (banded cherts and siliceous shales) were then deposited extensively in the basin centre as a result of the influx of hydrothermal fluids. The platform‐margin sand‐shoal/bank system, possibly with gullies on the slope, persisted into the latest Frasnian until the restoration of microbial buildups. Four sequences (S6–S9), characterized by abundant sand‐shoal deposits on the margin and gravity‐flow and hemipelagic deposits on the slope, are distinguished in the Frasnian strata. Smaller‐scale depositional cyclicity is evident in all facies associations across the platform–slope–basin transect. The distinctive depositional architecture and evolution of this Yangdi Platform are interpreted as having been controlled mainly by regional tectonics with contributions from eustasy, environmental factors, oceanographic setting, biotic and sedimentary fabrics.
Complex bedding geometries and facies associations of the turbiditic fill of a confined basin in a transpressive setting (Castagnola Fm., Tertiary Piedmont Basin, NW Italy)
Authors: Felletti Fabrizio
Published: March 2003

ABSTRACT This paper details the influence of syndepositional tectonics in controlling the architecture of a well‐exposed confined turbiditic sandbody, which crops out in the eastern part of the Tertiary Piedmont Basin (Castagnola Basin, northern Italy). The Castagnola Basin was tectonically active during sedimentation of the sandbody, and the lateral distribution of turbidity‐current deposits has been used to constrain both how the basin subsided and the impact of basin topography on flow behaviour and deposition. The sandbody occurs in the lower member of an Upper Oligocene–Lower Miocene turbidite system (the Castagnola Formation). The sandbody is ≈30 m thick and can be followed laterally for ≈1·8 km; it shows onlap terminations onto both northern and southern basin margins. The outcrop is sufficiently large to allow a detailed analysis of the facies and geometrical heterogeneity, as viewed approximately parallel to the average palaeocurrent trend (SW–NE). Correlation between 41 sedimentological logs reveals the diachronous development of a succession of sandstone packages (subunits). Nine vertically stacked and laterally juxtaposed packages have been recognized (subunits B to I from oldest to youngest), which reflect changes in basin floor accommodation as a result of synsedimentary tectonism. Each package shows the development of different vertical stacking patterns with thinning‐ and ‐fining‐upward small‐scale sequences and variable lateral facies arrangements, as a consequence of the position relative to the basin margins. The geometry, stratigraphic relationships, facies distribution and palaeocurrent directions indicate that turbidite deposition during accumulation of most of the sandbody was controlled by (1) synsedimentary tilting of the basin slopes; (2) the distribution of structural and depositional relief within the basin; (3) the thickness and volume of the turbidite flows; and (4) the angle of impingement of turbidity currents against the basin slopes.
A comprehensive approach to the study of methane‐seep deposits from the Lincoln Creek Formation, western Washington State, USA
Authors: Peckmann J. , Goedert J. L. , Thiel V. , Michaelis W. , Reitner J.
Published: March 2003

ABSTRACT A comprehensive approach using palaeontology, petrography, stable isotope geochemistry and biomarker analyses was applied to the study of seven small methane‐seep carbonate deposits. These deposits are in the Oligocene part of the Lincoln Creek Formation, exposed along the Canyon and Satsop Rivers in western Washington. Each deposit preserves invertebrate fossils, many representing typical seep biota. Authigenic carbonates with δ13C values as low as −51‰ PDB reveal that the carbon is predominately methane derived. Carbonates contain the irregular isoprenoid hydrocarbons 2,6,11,15‐tetramethylhexadecane (crocetane) and 2,6,10,15,19‐pentamethylicosane (PMI), lipid biomarkers diagnostic for archaea. These lipids are strongly depleted in 13C (δ13C values as low as −120‰ PDB), indicating that archaea were involved in the anaerobic oxidation of methane. Small filaments preserved in the carbonate may represent methanotrophic archaea. Archaeal methanogenesis induced the formation of a late diagenetic phase, brownish calcite, consisting of dumbbell‐shaped crystal aggregates that exhibit δ13C values as high as +7‰ PDB. Clotted microfabrics of primary origin point to microbial mediation of carbonate precipitation. Downward‐directed carbonate aggregation in the seeps produced inverted stromatactoid cavities. Large filaments, interpreted as green algae based on their size, shape, arrangement and biomarkers, imply that deposition occurred, in places, in water no deeper than 210 m.
Aeolian/fluvial interactions and high‐resolution sequence stratigraphy of a non‐marine lowstand wedge: the Avilé Member of the Agrio Formation (Lower Cretaceous), central Neuquén Basin, Argentina
Authors: Veiga Gonzalo D. , Spalletti Luis A. , Flint Stephen
Published: March 2003

Abstract Accumulation within the unconformity‐based Hauterivian Avilé Sandstone of the Neuquén Basin, Argentina, was characterized by a close interaction between fluvial and aeolian processes developed after a major relative sea‐level drop that almost completely desiccated the entire basin and juxtaposed these non‐marine deposits on shallow‐ and deep‐marine facies. Aeolian deposits within the Avilé Member include dune (A1) and sand sheet (A2) units that characterize the lower part of the unit. Fluvial deposits comprise distal flood units (F1) interbedded with aeolian dune deposits in the middle part of the succession, and low‐ (F2) and high‐sinuosity (F3) channels associated with floodplain deposits (F4) towards the top. The internal characteristics of the aeolian system indicate that its accumulation was strongly controlled by water‐table dynamics, with the development of multiple horizontal deflation super surfaces that truncate dune deposits and form the basal boundary of flood deposits and sand sheet units. A long‐term wetting‐upward trend is recorded throughout the entire unit, with an increase in fluvial activity towards the top and the development of a more permanent fluvial system overlying a major erosion surface interpreted as a sequence boundary. The upward increase in water‐table influence might be related to relative sea‐level rise, which controlled the position of the water table and allowed the accumulation of tabular aeolian units bounded by horizontal deflation surfaces. This high‐frequency, eustatically driven process acted together with a long‐term climatic change towards wetter conditions.
Lateral variations in sediment composition and bedding in Middle Triassic interplatform basins (Buchenstein Formation, southern Alps, Italy)
Authors: Maurer Florian , Schlager Wolfgang
Published: March 2003

ABSTRACTHemipelagic deposits are widespread in Triassic sequences of the Alpine belt and provide important data for stratigraphy and the study of bedding rhythms. The area of the western and central Dolomites of northern Italy escaped strong alpidic deformation and preserves such deposits in their original palaeogeographic setting. The Buchenstein Formation, the object of this study, was deposited in up to 1000 m deep, Middle Triassic interplatform basins, which extend over an area of 500 km2within the Dolomites. Excellent outcrops and volcaniclastic markers allow a detailed correlation of the formation in both laminated (anoxic) and bioturbated facies down to a bed scale, and show its relationship to coeval carbonate platforms. Correlation of lithostratigraphically well‐constrained intervals in the bioturbated facies reveal that lateral thickening and thinning of the deposits depends on the amount of shallow‐water debris in the succession and is a function of the distance to coeval carbonate platform sources. In the laminated background deposit, thickness variations in limestones and marls parallel the thickness variations in ash layers, and were caused by local redeposition of sediment on the basin floor. Lateral persistence of laminae indicates that bottom currents were weak in the Buchenstein basin, but were able to redeposit mud in a significant way. In the area around Seceda and Geisler (western Dolomites), a lateral transition from dark‐grey laminated to grey bioturbated to red bioturbated facies is observed, which is probably linked to local relief with different oxygenation conditions on the sea floor. A comparison shows that decimetre‐scale bedding is preserved in all facies types and that the bedding rhythm is partly the result of different cementation of the sediment during early diagenesis. Correlation of individual layers in the bioturbated facies reveals that beds are thicker and enriched in lime mud in the western part of the basin, and decrease in thickness and contain less micrite towards the east, further away from the main shallow‐water areas. Nearslope calciturbidites change gradually from distinct layers into lateral arrays of micrite nodules and bands further out in the basin. These observations point to a platform source of lime mud in the Buchenstein basin.
Turbidites in the Upper Carboniferous Ross Formation, western Ireland: reconstruction of a channel and spillover system
Authors: Lien Trond , Walker Roger G. , Martinsen Ole J.
Published: March 2003

ABSTRACT The Upper Carboniferous deep‐water rocks of the Shannon Group were deposited in the extensional Shannon Basin of County Clare in western Ireland and are superbly exposed in sea cliffs along the Shannon estuary. Carboniferous limestone floors the basin, and the basin‐fill succession begins with the deep‐water Clare Shales. These shales are overlain by various turbidite facies of the Ross Formation (460 m thick). The type of turbidite system, scale of turbidite sandstone bodies and the overall character of the stratigraphic succession make the Ross Formation well suited as an analogue for sand‐rich turbidite plays in passive margin basins around the world. The lower 170 m of the Ross Formation contains tabular turbidites with no channels, with an overall tendency to become sandier upwards, although there are no small‐scale thickening‐ or thinning‐upward successions. The upper 290 m of the Ross Formation consists of turbidites, commonly arranged in thickening‐upward packages, and amalgamated turbidites that form channel fills that are individually up to 10 m thick. A few of the upper Ross channels have an initial lateral accretion phase with interbedded sandstone and mudstone deposits and a subsequent vertical aggradation phase with thick‐bedded amalgamated turbidites. This paper proposes that, as the channels filled, more and more turbidites spilled further and further overbank. Superb outcrops show that thickening‐upward packages developed when channels initially spilled muds and thin‐bedded turbidites up to 1 km overbank, followed by thick‐bedded amalgamated turbidites that spilled close to the channel margins. The palaeocurrent directions associated with the amalgamated channel fills suggest a low channel sinuosity. Stacks of channels and spillover packages 25–40 m thick may show significant palaeocurrent variability at the same stratigraphic interval but at different locations. This suggests that individual channels and spillover packages were stacked into channel‐spillover belts, and that the belts also followed a sinuous pattern. Reservoir elements of the Ross system include tabular turbidites, channel‐fill deposits, thickening‐upward packages that formed as spillover lobes and, on a larger scale, sinuous channel belts 2·5–5 km wide. The edges of the belts can be roughly defined where well‐packaged spillover deposits pass laterally into muddier, poorly packaged tabular turbidites. The low‐sinuosity channel belts are interpreted to pass downstream into unchannellized tabular turbidites, equivalent to lower Ross Formation facies.
Phylogenetic revision of the parasitoid wasp family Trigonalidae (Hymenoptera)
Authors: CARMEAN DAVID , KIMSEY LYNN
Published: March 2003

A phylogenetic analysis of generic relationships and revised generic concepts for the Trigonalidae is presented. The Trigonalidae is divided into two subfamilies, the Orthogonalinae and the Trigonalinae. Orthogonalinae consists of a single primitive genus, Orthogonalys, sharing many generalized apocritan characters, but lacking advanced trigonalid characters including antennal tyloids and female metasomal armature. No synapomorphies have been detected for the Orthogonalinae. Trigonalinae are characterized by the presence of tyloids. The Trigonalinae were originally defined by the absence of female armature, and were therefore polyphyletic because armature has been lost several times. Within the revised concept of Trigonalinae, the tribe Trigonalini is characterized by the presence of elongate parameres and an intertorulus distance subequal to the distance between the torulus and the eye. A second tribe, Nomadinini, is based on the secondary loss of tyloids, and comprises the previous subfamilies Seminotinae, Nomadininae, Bareogonalinae and Lycogastrinae. The two tribes Trigonalini and Nomadinini share the presence of female armature, although in some Trigonalini it has been secondarily lost. The genera Labidogonalos Schulz, Lycogastroides Strand, Lycogonalos Bischoff, Nanogonalos Schulz, Poecilogonalos Schulz and Taiwanogonalos Tsuneki are synonymised under Taeniogonalos Schulz. The species Lycogaster zimmeri Bischoff, Tapinogonalos maschuna Schulz, and Trigonalys pictifrons Smith (placed in Lycogaster by Schulz, 1906a) are transferred to Taeniogonalos. The genera Discenea Enderlein and Stygnogonalos Schulz are synonymised under Trigonalys Westwood. The species Labidogonalos flavescens Bischoff, L. sanctaecatharinae Schulz, Trigonalys lachrymosa Westwood (placed in Lycogaster by Bischoff, 1938), T. maculifrons Cameron (placed in Labidogonalos by Bischoff, 1938) and T. rufiventris Magretti (placed in Lycogaster by Schulz, 1907a) are transferred to Trigonalys.Trigonalys costalis Cresson is synonymised with Taeniogonalos gundlachii (Cresson). Xanthogonalos fasciatus Bertoni and X.severini Schulz are synonymised with Trigonalys sanctaecatharinae (Schulz). Mimelogonalos partiglabra Riek and M. punctulata Riek are synonymised with M. bouvieri Schulz. Lectotypes are designated for Trigonalys melanoleuca Westwood and Taeniogonalos fasciatipennis (Cameron). The author of Trigonalys maculifrons is Sharp (1895), not Cameron (1897), and the author of Taeniogonalos enderleini is De Santis (1980), not Schulz 1906. Viereck (1914) designated Trigonalys pulchella Cresson as type of the genus Tapinogonalos Schulz, preceding Bischoff's (1938) designation, making Tapinogonalos a synonym of Orthogonalys. A new genus, Afrigonalys, is proposed for the three species that were described in ‘Tapinogonalos’sensu Bischoff, nec Viereck.
Afrochlus Freeman: an African gondwanan midge and the phylogeny of the Podonominae (Diptera: Chironomidae)
Authors: CRANSTON  , EDWARD
Published: March 2003

The immature stages and male adult of Afrochlus harrisoni Freeman are described for the first time, from the type locality, a granite outcrop in Zimbabwe. A phylogenetic position within the subfamily Podonominae as sister to South African‐western/central Australian genus Archaeochlus Brundin, suggested in 1966 by Brundin from the adult female alone, is confirmed by cladistic analysis of all life history stages combined. Within the Podonominae, the tribes Boreochlini and Podonomini erected by Brundin are monophyletic only if Trichotanypus Kieffer is transferred from the former to the latter. Little or none of the structure provided by the combined evidence from all stages is retrieved by cladistic analyses of characters derived solely from the adult stage. The implications of erection of monotypic genera for adult‐only taxa are discussed.
A phylogeny of the families of Scarabaeoidea (Coleoptera)
Authors: Browne Jonathan , Scholtz Clarke H.
Published: March 2003

Abstract.A study, based on examination of thirteen scarabaeoid families, was made of 134 adult and larval characters from the following character suites: 105 adult characters of the antennae, eye, epipharynx, mandible, maxillae, labium, tentorium, trochantin, procoxae, mesocoxae, mesothoracic spiracles, hind wing articulation, hind wing base, hind wing venation, hind wing folding, abdominal sternites, abdominal spiracles, male genitalia, ovarioles and karyotype; twenty larval characters of the antennae, fronto‐clypeal suture, stemmata, labial palpi, maxillae, mandibles, legs, stridulatory apparatus, spiracles and ecdysial process; and nine adult and larval biological characters. In order to assess the reliability of different characters in resolving scarabaeoid family relationships, six data sets were subjected to cladistic analysis: the total evidence character set (134 characters), restricted adult character set (thirty‐two characters, not including those of the wings), wing character set (seventy‐three characters), larval character set (twenty characters), biological character set (nine characters) and re‐codedHowden (1982)character set (thirty‐nine characters). The complete character set and wing character set both produced phylograms with all nodes resolved; the restricted adult data set, larval data set,Howden (1982)data set and biological data set produced phylograms with diminishing levels of node resolution. The reconstructed phylogeny, from the preferred phylogram of the total evidence character set, shows that the Scarabaeoidea comprises three major lineages; a glaresid, passalid and scarabaeid lineage. The glaresid lineage consists only of the Glaresidae. The passalid lineage comprises two major lines; a glaphyrid line (containing Glaphyridae, Passalidae, Lucanidae, Diphyllostomatidae, Trogidae, Bolboceratidae and Pleocomidae) and a geotrupid line (containing Geotrupidae, Ochodaeidae, Ceratocanthidae and Hybosoridae). The scarabaeid lineage contains those taxa traditionally included within the Scarabaeidae (Aphodiinae, Scarabaeinae, Orphninae, Melolonthinae, Acoma, Chasmatopterinae, Hopliinae, Oncerinae, Rutelinae, Dynastinae, Trichiinae, Cetoniinae and Valginae).
Systematic revision of the yucca moths in the Tegeticula yuccasella complex (Lepidoptera: Prodoxidae) north of Mexico
Authors: Pellmyr Olle.
Published: March 2003

The yucca moths (TegeticulaandParategeticula) are of great importance in studies of coevolution because of their obligate mutualism with their yucca hosts. Historically, three species ofTegeticulahave been recognized. One of them,T. yuccasella, has been regarded as the pollinator of all but two yucca species, but morphological, molecular and biological data show that this is a large complex of monophagous and oligophagous species that differ greatly in their biology. It also includes derived ‘cheater’ species that do not pollinate their hosts and oviposit into fruits rather than flowers. Here theyuccasellacomplex north of Mexico is revised. The nominotypic pollinator speciesyuccasellais redescribed, and ten new pollinator species described:altiplanella,baccatella,carnerosanella, cassandra, elatella,maderae,mojavella,rostratella,superficiellaandtreculeanella. Two non‐pollinating cheater species are recognized. One such species originally misidentified as aProdoxusspecies, then synonymised withyuccasella,is re‐erected as the non‐pollinatingintermedia. In addition, the new non‐pollinator speciescorruptrixis described.
Phylogeny of Neotropical Lepidocyrtus (Collembola: Entomobryidae): first assessment of patterns of speciation in Puerto Rico and phylogenetic relevance of some subgeneric diagnostic characters
Authors: Soto‐Adames Felipe N.
Published: March 2003

A phylogenetic analysis of the Neotropical members of genusLepidocyrtuswas conducted to assess the pattern of speciation in Puerto Rico while testing the phylogenetic information content of two characters used to diagnose subgenera. The analysis included twenty‐two species ofLepidocyrtusfrom the Neotropical Region for which information on the tergal chaetotaxy of the trunk was available, two species of HolarcticLepidocyrtus, three species ofPseudosinella, two species ofMetasinellaused in outgroup analysis and ninety‐two informative characters. The results do not support a monophyletic origin for the Puerto RicanLepidocyrtus, suggesting the current fauna originated through repeated invasions from abroad. Three instances of endemic speciation can be inferred from the cladograms. The geographical distribution and diversity of colour forms suggest thatL. caprilesi and L. paracaprilesispeciated sympatrically, whereas vicariance can explain speciation forL. lepargusandL. maldonadoi. The mode of speciation forL. dispar and L. biphasisremains unclear because the proportion of morphological variation between these species does not fit the proportions expected under the sympatric model suggested by their geographical distribution. The results support an early conclusion regarding appendicular scale distribution as a poor indicator of phylogenetic relationships. Taxa defined using this character are likely to be polyphyletic. The results disagree with a previous study in documenting low levels of homoplasy for the dental tubercle, implying that this character contains phylogenetic information useful in defining subgenera. However, the presence or absence of a dental tubercle is not diagnostic and should be used in combination with other characters. Comparisons of levels of homoplasy in Neotropical and HawaiianLepidocyrtussuggest that the relative position of two setae on the second abdominal tergum may be a better subgeneric character than other characters currently in use.
Revision and phylogenetic analysis of the New World genus Neoclypeodytes Young (Coleoptera: Dytiscidae: Hydroporinae: Bidessini)
Authors: Miller Kelly B.
Published: March 2003

The western North American and northern Central American genusNeoclypeodytesYoung is revised. Twenty‐five valid species are recognized in the genus. One additional name,N. luctuosus(Guignot) is treated as species of uncertain status. Eleven new species are described:N. amybethae,N. anasinus,N. astrapus,N. challeti,N. edithae,N. haroldi,N. megalus,N. nanus,N. roughleyi,N. similisandN. tumulus. Six new synonymies are established:N. centralis(Sharp) = N. cinctellus(LeConte);N. substriatus(Sharp) = N. discedens(Sharp);N. americanus(Guignot),N. decoratus(Fall) andN. quadrisignatus(Sharp) = N. fryii(Clark); andN. rugulosus(Guignot) = N. obesus(Sharp). Lectotypes are designated forN. curtulus(Sharp),N. discedens,N. discretus(Sharp),N. lynceus(Sharp),N. obesus,N. ornatellus(Fall),N. pictodes(Sharp),N. plicipennis(Crotch),N. quadrinotatus(Sharp),N. quadripustulatus,N. quadrisignatusandN. substriatus. A key is provided for the known species ofNeoclypeodytes. Distribution maps, illustrations of important morphological features and natural history notes are provided for each species. A single possible synapomorphy was found supporting the monophyly ofNeoclypeodytes, a pattern of two maculae on each elytron. The perplexing and unresolved relationships ofNeoclypeodytesto other bidessine genera are discussed. A cladistic analysis using twenty‐two characters of adult morphology is presented for twenty‐five species ofNeoclypeodytes, withUvarus lacustris(Say) andLiodessus affinis(Say) as outgroup taxa (rooted atU. lacustris). A single most parsimonious cladogram was obtained.
Phylogeny of Anophelinae (Diptera: Culicidae) based on nuclear ribosomal and mitochondrial DNA sequences
Authors: SALLUM M. A. M. , SCHULTZ T. R. , FOSTER P. G. , ARONSTEIN K. , WIRTZ R. A. , WILKERSON R. C.
Published: March 2003

Abstract Phylogenetic relationships among thirty‐two species of mosquitoes in subfamily Anophelinae are inferred from portions of the mitochondrial genes COI and COII, the nuclear 18S small subunit rRNA gene and the expansion D2 region of the nuclear large subunit 28S rRNA gene. Sequences were obtained from the genera Anopheles, Bironella and Chagasia. Representatives of all six subgenera of Anopheles were included: Anopheles, Cellia, Kerteszia, Lophopodomyia, Nyssorhynchus and Stethomyia. Using parsimony and maximum likelihood methods, various combinations of these DNA sequence data were analysed separately: 18S, 28S, combined 18S and 28S, combined COI and COII, and combined 18S, 28S, COI and COII (‘total evidence’). The combined rDNA data contain strong phylogenetic signal, moderately to strongly supporting most clades in MP and ML analyses; however, the mtDNA data (analysed as either nucleotide or amino acid sequences) contain little phylogenetic signal, except for relationships of very recently derived groups of species and, at the deepest level, for the monophyly of Anophelinae. The paraphyly of Anopheles relative to Bironella is confirmed by most analyses and statistical tests. Support for the monophyly of subgenera Anopheles, Cellia, Kerteszia and Nyssorhynchus is indicated by most analyses. Subgenus Lophopodomyia is reconstructed as the sister to Bironella, nested within a clade also containing Nyssorhynchus and Kerteszia. The most basal relationships within genus Anopheles are not well resolved by any of the data partitions, although the results of statistical analyses of the rDNA data (S‐H‐tests, likelihood ratio tests for monophyly and Bayesian MCMC analyses) suggest that the clade consisting of Bironella, Lophopodomyia, Nyssorhynchus and Kerteszia is the sister to the clade containing Cellia and Anopheles.
Phylogeny of the death's head hawkmoths,Acherontia[Laspeyres], and related genera (Lepidoptera: Sphingidae: Sphinginae: Acherontiini)
Authors: Kitching Ian J.
Published: March 2003

Abstract.Adult death's head hawkmoths (Acherontiaspecies) have a unique feeding biology as cleptoparasites of honeybees, stealing honey from the combs, rather than imbibing nectar from flowers. The moths have a range of features, both morphological and behavioural, that enable them to successfully enter, feed and escape from the colonies. These adaptations may vary among the threeAcherontiaspecies and allow them each to target different species of honeybee. A cladistic analysis is presented of the hawkmoths of tribe Acherontiini. The study aims to resolve the relationships of the genera and species of Acherontiini, with a particular focus on the three species ofAcherontia. The dataset comprises sixty‐five characters derived from adult, larval and pupal morphology, and larva host‐plant biology. These data are analysed using equal weighting and implied weighting. Acherontiini and each constituent genus are recovered as monophyletic. However, withinCoelonia, there is ambiguity in that the sister‐species relationshipsC. brevis+C. fulvinotataandC. fulvinotata + C. solaniare equally parsimonious under both weighting schemes. Furthermore, under equal weightingAgriusis placed equally parsimoniously as the sister group of eitherAcherontia + CoeloniaorCallosphingia. Under implied weighting, however, only the latter relationship is most parsimonious (fit). WithinAcherontia,A. atroposandA. styxare always recovered as sister species to the exclusion ofA. lachesis. The results of the phylogenetic analysis provide an objective basis for future studies of the unique cleptoparasitic association of these moths.
Phylogeny of the bee genusAgapostemon(Hymenoptera: Halictidae)
Authors: Janjic Jessica , Packer Laurence
Published: March 2003

Abstract. A phylogeny for genusAgapostemon(Hymenoptera: Halictidae) is reconstructed from morphological characters, using all species, with four representatives of Agapostemonini as outgroup taxa. Parsimony analysis using 150 unordered characters resulted in eighteen equally parsimonious trees, a strict consensus of which is highly resolved forAgapostemon. Based on this analysis,AgapostemonoidesRoberts & Brooks is returned to generic status, and a new subgenus is described:Notagapostemon, which includes therhopalocerus,heterurus,atrocaeruleus,erebus,kohliellus,nasutusandintermediusgroups of Moure & Hurd. Species groups are proposed forNotagapostemonand revised inA. (Agapostemon).Agapostemon cockerelliCrawford is synonymized withA. obliquus(Provancher),A. epichryseus(Morelos) withA. leunculusVachal,A. incaRoberts withA. heterurusCockerell,A. hispaniolicusRoberts female withA. centratus(Vachal) andA. hispaniolicusRoberts male withA. alayoiRoberts. Optimization of known behaviours suggests communal ancestry for the genus and infers the prevalence of this behaviour inAgapostemon. Optimization of geographical range suggests a Central American or Caribbean origin ofAgapostemon, with one invasion of North America and multiple invasions of South America and the Caribbean. One invasion of the Caribbean suggests arrival from North America via Florida.
Isotopic closure
Authors: Villa
Published: March 2003

The closure of isotopic chronometers to loss or exchange of radiogenic daughters is best analysed in terms of phenomena that induce recrystallization, i.e. fluid circulation and strain. In the presence of these fast phenomena, temperature is not a rate‐controlling parameter for isotope transport. Only in those rare instances where no fast mechanism can be petrographically documented, do minerals survive very high temperatures without appreciable modification of their isotopic record. For these (admittedly unlikely) rocks, a self‐consistent upward recalibration of the ‘closure temperature’ is defined.
Infra‐arc mantle–crust transition and intra‐arc mantle diapirs in the Kohistan Complex (Pakistani Himalaya): petro‐structural evidence
Authors: Burg  , Bodinier  , Chaudhry  , Hussain  , Dawood
Published: March 2003

The Jijal and Chilas Complexes have been interpreted previously as the lower levels of the layered Kohistan Island Arc, in Pakistan. We provide petro‐structural evidence for melt‐consuming reactions between mantle rocks and infiltrated, volatile‐rich magmas in both complexes. Precipitated minerals in Jijal and Chilas suggest that melt‐rock reaction occurred at higher pressure in Jijal than in Chilas. The early appearance of orthopyroxene in Chilas and the spatial relationship of the ultramafic rocks with quartz‐bearing norites indicate that the reactant melt was more silicic. We argue that the Jijal Complex includes the infra‐arc crust/mantle boundary and that ultramafic associations of the Chilas Complex are apices of possibly younger, intra‐arc mantle diapirs.
Evidence from U–Pb zircon and 40Ar/39Ar muscovite detrital mineral ages in metasandstones for movement of the Torlesse suspect terrane around the eastern margin of Gondwanaland
Authors: Adams C.J. , Barley M.E. , Fletcher I.R. , Pickard A.L.
Published: March 2003

New U–Pb detrital zircon ages from Triassic metasandstones of the Torlesse Terrane in New Zealand are compared with 40Ar/39Ar muscovite data and together, reveal four main source components: (i) major, Triassic–Permian (210–270 Myr old) and (ii) minor, Permian–Carboniferous (280–350 Myr old) granitoids (recorded in zircon and muscovite data); (iii) minor, early middle Palaeozoic, metamorphic rocks, recorded mainly by muscovite, 420–460 Myr old, and (iv) minor, Late Precambrian–Cambrian igneous and metamorphic complexes, 480–570 Myr old, recorded by zircon only. There are also Proterozoic zircon ages with no clear grouping (580–1270 Myr). The relative absence of late Palaeozoic (350–420 Myr old) components excludes granitoid terranes in the southern Lachlan Fold Belt (Australia) and its continuation into North Victoria Land (East Antarctica) and Marie Byrd Land (West Antarctica) as a potential source for the Torlesse. The age data are compatible with derivation from granitoid terranes of the northern New England Orogen (and hinterland) in NE Australia. This confirms that the Torlesse Terrane of New Zealand is a suspect terrane, that probably originated at the NE Australian, Permian–Triassic, Gondwanaland margin and then (200–120 Ma) moved 2500 km southwards to its present New Zealand position by the Late Cretaceous (90 Ma). This sense of movement is analogous to that suggested for Palaeozoic Mesozoic terranes at the North American Pacific margin.