bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Cretaceous Serra Geral igneous event on the temperatures and heat flow of the Paraná Basin, southern Brazil
Authors: Hurter SUZANNE J. , Pollack HENRY N. 
Published: November 2007

AbstractWe investigate the effects of the cooling of intrusive and extrusive igneous bodies on the temperature history and surface heat flow of the Paraná Basin. The Serra Geral igneous event (130–135 Ma) covered most of this basin with flood basalts. Associated with this event numerous sills and dykes intruded the sediments and basement, and extensive underplating may have occurred in the lower crust and upper mantle beneath the basin. We develop an analytical model of the conductive cooling of tabular intrusive bodies and use it to calculate temperatures within the sediments as a function of time since emplacement. Depending on the thickness of these igneous bodies and the timing of sequential emplacement, the thermal history of a given locus in the basin can range from a simple extended period of higher temperatures to multiple episodes of peak temperatures separated by cooling intervals. The cooling of surface flood basalts, sills and dykes is capable of maintaining temperatures above the normal geothermal gradient temperatures for a few hundred thousand years, while large‐scale underplating may influence temperatures for up to 10 million years. We conclude that any residual heat from the cooling of the Serra Geral igneous rocks has long since decayed to insignificant values and that present‐day temperatures and heat flow are not affected. However, the burial of the sediments beneath the thick basalt cap caused a permanent temperature increase of up to 50°C in the underlying sediments since the beginning of the Cretaceous.
Experimental modelling of forearc basin development during accretionary wedge growth
Authors: Larroque CHRISTOPHE , Calassou SYLVAIN , Malavieille JACQUES , Chanier FRANK 
Published: November 2007

AbstractWe present results of three sand‐box experiments that model the association between tectonic accretion and sedimentation in a forearc basin. Experimental sedimentation occurs step by step in the forearc basin during shortening of the sand wedge.In each experiment, the development of the accretionary wedge leads to the formation of a major backthrust zone. This major deformation zone accounts for the thickening in the rear part of the wedge. In natural settings this tectonic bulge dams sediments that are transported toward the trench from mountainous terrain behind the forearc.We test the variation of friction along the déollement and note the following: (1) shortening of a low‐friction wedge involves a mechanical balance between forethrusts and backthrust propagation and this balance is recorded by the sedimentary sequence trapped in the forearc basin. Indeed, if most of the movement occurs along the backthrust, the deepening of the basin will be larger and consequently the thickness of the sedimentary sequence will be greater. (2) Such balance does not exist in the case of a high‐friction wedge. (3) Variation of friction along the décollement during shortening of the sand wedge leads to modification in the forearc basin filling. Thus, for similar increments of convergence, the sequence deposited in the forearc basin shows relatively larger thickness when the wedge is shortened above a high‐friction décollement.We suggest that contraction and thickening in the rear part of the wedge is an efficient mechanism to, initiate and develop a forearc basin. Thus, this kind of basin occurs in convergent settings, without collapse related to local extension or tectonic erosion. They represent a sedimentary trap on a passive basement, bounded by a tectonic bulge.The Quaternary Hikurangi forearc basin, southeast of the North Island of New Zealand, is bounded by two actively uplifting ridges. Thus, this basin is considered to be a possible example of the basins modelled in our experiments, and we suggest that the limit between the basin and the wedge could be a complex backthrust zone.
The blanketing effect in sedimentary basins
Authors: Wangen Magnus 
Published: November 2007

AbstractThe deposition of cold sedimerlts, called thermal blanketing, is studied when the sedimentary basin is considered as part of the lithosphere. A general one‐dimensional temperature equation is obtained which accounts for blanketing, the movement of the lower boundary of the lithosphere, and the eventual stretching of the sediments and the lithosphere. These processes appear explicitly as convective terms in the model, which is a generalization of a previous temperature equation. The description of these processes b!‐means of convective terms is a major result in the paper; it makes these processes more amenable to quantitative investigations. The temperature equation is studied in two different settings; one where the lithosphere remains unstretched, and another where the lithosphere is subjected to constant strain rate stretching. The parameter controlling thermal blanketing in these models is the Peclet number. The transient period towards a stationary state, and the stationary state representing maximal blanketing are studied. Analytical expressions for various stationary states are obtained. When the lithosphere remains unstretched it is concluded that a necessary condition for strong blanketing is a sedimentation rate of the order of 250mMyr‐1. Where the sediments contribute to the heat flow by decay of radioactive isotopes, the radioactive heat production divided by the sedimentation rate should be at least 10‐9 (Wm‐3)/(mMyr‐1) for the heat production to compete with blanketing. During stretching of the lithosphere it is shown that for stretching factors (p) larger than 2, the convective effect of stretching the sediments contributes more to the reduction of the heat flow than the blanketing effect. Blanketing counteracts the increased heat flow caused by the stretching of the lithosphere, and the upwelling hot asthenosphere. With sedimentation rates inferred from isostatic calculations it is found that the strain rate times the initial crust thickness should be more than 0.25 km Myr‐1 for the blanketing effect to be noticeable. It is also shown that sediment infill which follows thermal subsidence, after a period of stretching, is not capable of blanketing.
Oligocene to early Miocene tectono‐sedimentary history of the Alicante region (SE Spain): implications for Western Mediterranean evolution
Authors: Geel T. 
Published: November 2007

AbstractThe Alicante region, situated at the intersection of major Western Mediterranean structural units, is unique in possessing a complete marine Oligocene to early Miocene record of both platform and slope deposits. Detailed analysis of three selected platform areas in the north of the region, each showing a different tectono‐sedimentary history, and comparison with coeval slope deposits in the south of the region shows that: (a) during the Rupelian to early Chattian the region formed part of the Iberian microplate and can be considered the south‐eastern continuation of the NW‐SE‐trending Iberian Chain (folding phase between 36 and 33 Ma, updoming event at 31–29 Ma, both induced by Pyrenean collision); (b) during the late Chattian to Aquitanian it was linked to the extensional, SW‐NE‐orientated Valencia Trough forming part of its western margin (rifting phases at 28 and 25 Ma); (c) from the Aquitanian‐Burdigalian boundary (20 Ma) onward, the region underwent NW‐directed compression due to Betic collision (folding phases at 20 and 17 Ma); (d) a foreland basin formed in the late Burdigalian (18–17 Ma), continuous from the Betic Cordilleras over the Alicante region to the Balearics; (e) a purely compressive regime was superseded by strike‐slip tectonics at the Langhian—Serravallian boundary.The previously formulated hypotheses of coeval compression and extension with inferred hypothetical strike‐slip or other faults in or near the Alicante region is rejected on the basis that compress ional and extensional tectonics are separated in time in the Alicante region.
The interior rifts of the Yemen ‐ analysis of basin structure and stratigraphy in a regional plate tectonic context
Authors: Redfern Phillip , Jones Julie A. 
Published: November 2007

AbstractThe full extent of Mesozoic rift basins within interior Yemen has only recently been established. This work presents a detailed documentation of the stratigraph)., structure and basin development of the Marib‐Shabwa and Sirr‐Sayun basins, and the Jeza Trough.Yemen is located at the south‐western margin of the Arabian Plate, which for most of its early geological history formed part of the northern passive margin of Gondwanaland. Mesozoic break up of the super‐continent was associated with major rifting in the Late Jurassic (main phase) and Early Cretaceous. Orientation of the rift basins reflects an inheritance from deep‐seated Precambrian structural trends which cross the Arabian Plate.The resultant structure of basement highs, tilted fault blocks, marginal terraces and central graben highs is illustrated in a series of detailed cross‐sections. A comprehensive stratigraphic framework has also been established for the Jurassic and Cretaceous basin‐fill, enabling thickness and facies variations to be analysed. This reveals a clear shift in the main period of fault‐related, high sediment accumulation rates, both within and across the three interior basins of Yemen.In the western Marib‐Shabwa Basin, the fill is dominantly Late Jurassic, whilst the eastern Shabwa Basin and Sirr‐Sayun Basin exhibit a progressively increased, and younger, Early Cretaceous fill. The main period of fault‐related sedimentation in the most easterly basin, the Jeza Trough, is wholly Cretaceous.Plate tectonic reconstructions of the area for this period have documented the separation and subsequent north‐eastward movement of the Indian Plate, away‐ from Africa‐Arabia. We believe this may have been the causal mechanism in the progressive eastward migration of rift activity in the Yemen.
Regular spacing of drainage outlets from linear mountain belts
Authors: Hovius NIELS 
Published: November 2007

Abstract Straight sections of many actively uplifting mountain belts have simple patterns of drainage, transverse to their main structural trend. Streams rising near or beyond the topographic ridgepole of these sections are spaced at seemingly regular intervals. To test whether this regularity exists, morphometric aspects of drainage networks were measured in 11 mountain belts. The spacing of drainage basins can be expressed using a spacing ratio, which in effect is the ratio of the length and the width of the catchments under consideration. Average spacing ratios for most linear mountain belts are within a narrow range of values between 1.91 and 2.23. A linear relationship exists between the spacing of catchment outlets and the distance between the main divide and the front of the mountain belt in which they have developed. The Nepalese Himalaya form an exception to this regular pattern. In this mountain belt drainage is blocked and diverted by structures that have developed in relation to the Main Boundary Thrust. Structural complications cause drainage patterns to become less regular, introducing important non trans verse components.The linear relationship between spacing of catchment outlets and half‐width of the mountain belt may be expressed in an equation of the same general form as Hack's law of stream length and drainage basin area. It seems likely that the mechanism underlying Hack's law also explains the consistent regularity of drainage spacing in active mountain belts. However, no generally accepted explanation for Hack's law has been offered. The narrow range of spacing ratios found for drainage networks in active orogens may represent an optimal catchment geometry that embodies a ‘most probable state’ in the uplift‐erosion system of a linear mountain belt.The linear relationship between the half‐width of a mountain belt and spacing of catchment outlets has profound implications for the modelling of erosion of orogenic topography, and for the formation and filling of foreland basins.
The relationship between basin and margin thermal evolution assessed by fission track thermochronology: an application to offshore southern Norway
Authors: Rohrman MAX , Andriessen PAUL , van der Beek PETER 
Published: November 2007

Abstract We use a quantitative model of apatite fission track (AFT) annealing to constrain the thermal evolution of a sedimentary basin and its margin. Apatites deposited in a basin contain several types of information. Provided temperatures remained below ≅70°C, they retain much of their provenance thermal signatures and mainly record the thermal evolution of their source area. Above 70°C, the fission tracks in apatite rapidly fade, reflecting the thermal evolution of the basin. Therefore, downhole AFT dates in a well section can in principle be used to assess both the provenance detail (from shallow/cool samples) and the subsequent thermal history in the basin (from the deeper samples).We apply this concept to the south Norwegian offshore and onshore using AFT and ZFT (zircon fission track) data; the latter constrain maximum palaeotemperatures and provide additional provenance information. AFT and ZFT data from three offshore wells in the northern North Sea are shown to contain a record of palaeogeographical and tectonic evolution, closely associated with the Norwegian basement. ZFT data from Middle Triassic sediments suggest a Permian volcanic source. Modelling of AFT data from Jurassic sediments presently residing at temperatures below 70°C indicate rapid cooling during the Late Triassic to Early Jurassic, similar to onshore AFT data. During the Cretaceous minor sediment supply was derived from the Norwegian basement, as evidenced by ZFT ages that do not correlate to the onshore, suggesting that parts of southern Norway were covered with sediments at this time. At the end of the Palaeogene and during the Neogene, the south Norwegian basement again became a major source of elastics.AFT and ZFT data indicate that all wells are presently at maximum temperatures. No significant (> 500 m) erosion events are indicated in the three wells since the Jurassic. AFT data have not yet effectively equilibrated to present‐day temperatures as nonzero fission track ages are maintained in sediments currently at temperatures of > 120°C. This implies that the present‐day thermal regime has only recently been installed. Probable causes include rapid subsidence and an increase in the geothermal gradient during the last 5 Myr.
Modelling sedimentation in ocean trenches: the Nankai Trough from 1 Ma to the present
Authors: Mountney NIGEL P. , Westbrook GRAHAM K. 
Published: November 2007

Abstract Sediment accumulation within ocean trenches located at actively accreting convergent margins is determined by an interplay between sediment supply, sediment subduction/accretion at the toe of the overriding accretionary complex and the rate of subduction. Modelling trench sedimentation provides insight into the principal controlling factors, and a means of deriving, from the pattern of sedimentation, how factors, such as the rates of sediment supply and subduction, have varied over the period of accumulation of the trench sediments. Two DSDP‐ODP drill sites within the Nankai Trough reveal a coarsening‐upward megasequence, indicating a progressive facies transition from abyssal muds to outer‐trench silts to inner‐trench sands. The changing geometry of the trench‐wedge over the past 1 Myr has been determined by modelling variations in net sediment flux for two trench‐perpendicular profiles. The models were constrained to fit the stratigraphy at the drill sites, and the simulated present‐day geometries of the trench were matched with those shown on seismic reflection profiles by successive adjustment of the model. Results from both sites confirm a ‘slow’ subduction rate of <20 km Myr‐1. At the south‐western site (582), the width of the trench‐wedge has ranged from 13 to 21 km over the past 1 Myr. To the north‐east, at Site 808, the width has ranged from 7 to 13 km over the past 0.5 Myr. These changes in trench‐wedge width are primarily the result of large changes in sediment supply rate. The subduction of the Shikoku Ridge, a fossil spreading centre adjacent to Site 808, has had a major influence on the style of sedimentation within the trench.The style of accretion from the trench to the toe of the accretionary complex has important implications for geometrical adjustment of the trench‐wedge. Thrust displacement lifts the protothrust region out of the trench, resulting in a decreased width. This is followed by a phase of increasing width as the trench‐wedge adjusts towards a new equilibrium. The cyclical, episodic accretion process results in a periodic second‐order variation in trench‐fill size that is superimposed on primary trends determined by variations in sediment supply rates and subduction rates over time.
Molecular mechanisms of virstatin resistance by non‐O1/non‐O139 strains of Vibrio cholerae
Authors: Shakhnovich Elizabeth A. , Sturtevant Derek , Mekalanos John J. 
Published: November 2007

SummaryVirstatin is a previously described small molecule inhibitor of Vibrio cholerae virulence. We have demonstrated that the molecule inhibits the activity of the transcriptional activator ToxT, thereby preventing elaboration of the toxin co‐regulated pilus (TCP) and cholera toxin in vitro and in vivo in O1 strains of V. cholerae. While strains of the O1 and O139 serogroups are the cause of most epidemic and endemic cholera currently seen globally, sporadic disease caused by strains of non‐O1/non‐O139 serogroups suggests that understanding the pathogenic mechanisms of these unusual strains is relevant for disease. Although some non‐O1/non‐O139 strains have acquired the pathogenicity island that encodes the TCP, the role that this essential colonization factor of O1/O139 strains plays in the virulence of non‐O1/non‐O139 strains has not been determined. In this study, we utilize virstatin in a ‘chemical genetic approach’ to examine the role of ToxT, and thus by inference TCP, in the colonization of a panel of predominantly non‐O1/non‐O139 tcp+ strains. We identified nine strains whose colonization was resistant to virstatin inhibition in the infant mouse model. These strains presumably colonize by a TCP‐independent mechanism or contain a naturally occurring virstatin‐resistant ToxT. Four strains contained the typical toxT gene found in O1/O139 strains (toxTEPI) isolated from cholera epidemics. Interruption of toxT in one of these strains did not affect colonization of the infant mouse small intestine. The remaining five strains were found to contain a sequence divergent toxT gene that has been previously designated toxTENV because of its occurrence in isolates of V. cholerae from the environment. We show that ToxTENV is resistant to virstatin in two separate heterologous systems and is necessary for efficient colonization of the infant mouse small intestine. These results support the new concept that chemical genetic probes for the in vivo function or expression of virulence genes can be used to identify strains that express alternative virulence factors or novel regulatory systems that are functional in vivo.
Solution structure of the novel dispersin protein of enteroaggregative Escherichia coli
Authors: Velarde Jorge J. , Varney Kristen M. , Inman Keith G. , Farfan Mauricio , Dudley Edward , Fletcher Jonathan , Weber David J. , Nataro James P. 
Published: November 2007

SummaryEnteroaggregative Escherichia coli (EAEC), increasingly recognized as an important cause of infant and travelers' diarrhoea, exhibits an aggregative, stacked‐brick pattern of adherence to epithelial cells. Adherence is mediated by aggregative adherence fimbriae (AAFs), which are encoded on the pAA virulence plasmid. We recently described a highly prevalent pAA plasmid‐borne gene, aap, which encodes a protein (nicknamed dispersin) that is secreted to the bacterial cell surface. Dispersin‐null mutants display a unique hyper‐aggregating phenotype, accompanied by collapse of AAF pili onto the bacterial cell surface. To study the mechanism of this effect, we solved the structure of dispersin from EAEC strain 042 using solution NMR, revealing a stable beta‐sandwich with a conserved net positive surface charge of +3 to +4 among 23 dispersin alleles. Experimental data suggest that dispersin binds non‐covalently to lipopolysaccharide on the surface of the bacterium. We also show that the AAF organelles contribute positive charge to the bacterial surface, suggesting that dispersin's role in fimbrial function is to overcome electrostatic attraction between AAF and the bacterial surface.
Dissection of a type VI secretion system in Edwardsiella tarda
Authors: Zheng Jun , Leung Ka Yin 
Published: November 2007

SummaryBacterial pathogens use different protein secretion systems to deliver virulence factors. Recently, a novel secretion system was discovered in several Gram‐negative bacterial pathogens, and was designated as the type VI secretion system (T6SS). In Edwardsiella tarda, a partial E. tardavirulent protein (EVP) gene cluster was implicated in protein secretion. Here, we identified the entire EVP cluster as a T6SS and two additional secreted proteins (EvpI, a homologue of VgrG, and EvpP) were found. We systematically mutagenized all the 16 EVP genes and found that the secretion of EvpP was dependent on 13 EVP proteins including EvpC (a homologue of Hcp) and EvpI but not EvpD and EvpJ. All EVP mutants except ΔevpD were attenuated in blue gourami fish. The 16 EVP proteins can be grouped according to their functions and cellular locations. The first group comprises 11 non‐secreted and possibly intracellular apparatus proteins. Among them, EvpO, a putative ATPase which contained a Walker A motif, showed possible interactions with three EVP proteins (EvpA, EvpL and EvpN). The second group includes three secreted proteins (EvpC, EvpI and EvpP). The secretion of EvpC and EvpI is mutually dependent, and they are required for the secretion of EvpP. The interaction between EvpC and EvpP was demonstrated. Lastly, two proteins (EvpD and EvpJ) are not required for the T6SS‐dependent secretion.
Dimerization or oligomerization of the actin‐like FtsA protein enhances the integrity of the cytokinetic Z ring
Authors: Shiomi Daisuke , Margolin William 
Published: November 2007

SummaryIn bacteria, the actin‐like FtsA protein interacts with the tubulin‐like FtsZ protein, helping to assemble the cytokinetic Z ring, anchor it to the cytoplasmic membrane and recruit other essential divisome proteins. FtsA also interacts with itself, but it is not clear whether this self‐interaction is required for its full functionality. Here we describe new dominant negative missense mutations in Escherichia coli ftsA that specifically inhibit FtsA homodimerization and simultaneously cause disruption of Z rings. The negative effects of one mutation, M71A, were suppressed by altering levels of certain division proteins or by additional mutations in ftsA that promote increased integrity of the Z ring. Remarkably, when FtsA, FtsA‐M71A, and other mutants of FtsA that compromise self‐interaction were connected in a tandem repeat, they were at least partially functional and suppressed defects of an ftsZ84(ts) mutation. This gain of function by FtsA tandems further suggested that FtsA monomers cause deleterious interactions with FtsZ and that increased dimerization or oligomerization of FtsA enhances its ability to promote Z‐ring integrity. Therefore, we propose that FtsZ assembly is regulated by the extent of FtsA oligomerization.