Distal Sectors Research Articles

Synrift and post-rift thermal evolution of rifted margins: a re-evaluation of classic models of extension

Abstract The thermal evolution of continental rifted margins is key to understanding margin subsidence and hydrocarbon prospectivity. Observed heat-flow values, however, do not always comply with classic rifting models. Here, we use 2D numerical models to investigate the relationship between rifting, sedimentation and thermal history of margins. We find that during the synrift, the basement heat-flow and temperature are not only controlled by extension factor, but also by synrift sediment thickness and the evolution of deformation. As this progressively focuses oceanward, the proximal sectors thermally relax, while the distal sectors experience peak temperatures. In the post-rift, the lithosphere under the hyperextended margins does not return to its original state, at least for c. 100 Myr after break-up. Instead, it mimics that of the adjacent oceanic plate, which is thinner than the original continental plate. This results in heat-flow increasing oceanward at post-rift stages, when classic rifting theory predicts complete thermal relaxation. Our models also predict slightly increased heat-flows in the adjacent oceanic crust, potentially extending hydrocarbon plays into distal margins and oceanic crust, previously discarded as immature. Finally, our models indicate that commonly used temperature approximations to calculate heat-flow during rifting may strongly differ from those occurring in nature.

Flow transformations, mud partitioning and the variable stratigraphic architecture of basin-floor fan fringes

Highly efficient sediment gravity flows can bypass mid fan channels and lobes and deposit significant volumes of sand, mud and particulate organic matter in outer fan and basin plain settings. The Serpukhovian to Bashkirian fill to the Shannon Basin, western Ireland, includes deep-water fan deposits (Ross Sandstone Fm) that gradationally overlie basin floor shales (Clare Shale Fm). As part of a broader progradational succession, the upward transition from muddy basin floor to sandy fan preserves the stacked deposits of settings present prior to and outboard of mid-fan channels and lobes. Three fully cored boreholes and associated wireline data constrain the facies tracts in an 18 km long panel orientated oblique to original depositional dip. Two distal successions dominated by hybrid event beds (HEBs) are recognised, separated by a prominent condensed section. The lower Cosheen system includes m-thick, tabular HEBs with prominent linked debrites that pass down dip into much thinner sandstones overlain by sand-speckled mudstone caps that thicken distally before thinning. The latter are interpreted as secondary mudflows released following reconstitution of more thoroughly mixed sections of the up-dip linked debrites. Significant bypass and accumulation of mud by this mechanism helped heal local topography and maintain a relatively flat sea floor promoting an overall tabular geometry for the deposits of larger volume hybrid flows reaching the distal sector of the basin. The overlying distal Ross system fringe is characterised by very fine to fine-grained sandstones and is lateral to compensationally-stacked lobes further to the west. It has a progradational (at least initially) stacking pattern, facies transitions developed over shorter length scales, and includes outsized event beds but these are thinner than those in the Cosheen system. Common banding and evidence for turbulence suppression by dispersed clay rather than entrained mud clasts indicate these were transitional flows. In this case, event beds are inferred to taper distally, with significant mud emplaced by plug flow retained as caps to sandy event beds rather than bypassing down-dip. Different flow transformation mechanisms thus impacted how mud was partitioned across the fringe of the two systems and this influenced bed geometries, larger scale bed stacking patterns and stratigraphy. Whereas the flow efficiency concept stresses the ability of flows to carry sand in a basinward direction, it is also imperative to consider the variable efficiency of mud transport given the operation of clay-induced flow transformations. These can either promote bypass or trigger premature fallout of mud with implications for how systems fill accommodation, bed -scale facies transitions and the burial and preservation of particulate organic carbon fractionated along with the clay in deep-water system fringes.

Benthic foraminiferal morphogroups and their response to relative sea-level changes in the upper Hauterivian-lower Barremian Agua de la Mula Member of the Agrio Formation (Patagonia, Argentina)

A morphogroup analysis of the upper Hauterivian-lower Barremian foraminiferal assemblages from the Agua de la Mula Member of the Agrio Formation (Neuquén Basin, Argentina) reveled six associations based on benthic foraminiferal morphogroups identified by means of cluster analysis and treated with multivariate methods. In order to assess the paleoenvironmental significance of the morphogroup associations, they were evaluated in relation to sampled geographic localities, ammonite biozones, sedimentary facies, and position into depositional sequences of the five sections analyzed. For this purpose, the statistical techniques of RDA, partial-RDA, PERMANOVA, and PCoA were applied. The morphogroup associations MgFA1, MgFA4, MgFA5 and MgFA6 revealed high percentages of planoconvex, biconvex and conical forms, with an inferred epifaunal habit and active herbivorous feeding strategy. The remaining MgFAs2 and 3 are mainly represented by planispiral tests with lenticular, flattened and elongated forms, attributed to shallow infaunal lifestyle and detrital and bacterial scavenger feeding habit. Sedimentation rates and associated food availability were considered the main controlling factors in the distribution of morphogroups across the analyzed tract of the basin, revealing differences between proximal and distal sectors. In the sections characterized by higher terrigenous input, in a most proximal position of the basin, food increases downward in the sediments and so shallow infaunal morphogroups prevail (MgFAs2–3). At the same time, shallow infaunal-dominated associations are distributed throughout 3rd-order regressive systems tracts that commonly are associated with high sedimentation rates. Associations mostly represented by epifaunal morphogroups (MgFAs1, 4–6) recur at 3rd-order transgressive systems tracts where low sedimentary input characterizes the sequences, favoring long exposure of organic matter at the seafloor. Moreover, epifaunal forms with grazing herbivorous and detritivorous habits increase throughout the distal sector of the basin, following the decreasing supply of organic matter in settings farther from sedimentary input.

Heat flow modelling of the Punta del Este Basin (offshore Uruguay) and its correlation with structural crustal domains

The Punta del Este Basin is located at the offshore of Uruguay, and it is considered an underexplored basin with a high potential for holding hydrocarbon plays. Geologically, it constitutes an aborted rift related to the Gondwana fragmentation process, and subsequent opening of the Atlantic Ocean (Upper Jurassic - Lower Cretaceous). The stratigraphic and tectonic evolution comprises four phases from the Paleozoic pre-rift stage to present-day post-rift stage (Neogene/Quaternary). Due to the estimated hydrocarbon potential of this basin, exploratory activities have been intensified in the last decades, based on the acquisition of a significant amount of geophysical data which allowed a better comprehension of the basin's geology. Previous studies related to this basin were mainly oriented to the stratigraphy, structural framework, and petroleum systems comprehension. This research is focused on the thermal evolution of the Punta del Este Basin and its correlation with the crustal geological structure. For this purpose, a heat flow model was developed in order to understand thermal evolution through geological time. A 2D heat flow modelling based on pseudo wells was carried out to research and reconstruct the paleo heat flow. Bottom-hole temperatures (BHTs), seabed heat flow measurements, and Moho discontinuity depth interpretations have been employed in the reconstruction of heat flow evolution through time. A structural analysis based on seismic interpretation allowed to identify the Moho discontinuity and define four crustal domains in the study area: proximal (unattenuated crust), necking, hyperextended (stretched and thinned transition crust), and oceanic crust. The thermal model shows a strong correlation between heat flow and crustal thickness. In this way, the proximal domain develops low heat flow values while the distal sector shows higher values, due to the strong influence of the rifting event in crust thinning.

Hydrodynamics of karst aquifers in metamorphic carbonate rocks: results from spring monitoring in the Apuan Alps (Tuscany, Italy)

During the last 40 years, extensive research has characterized the hydrogeology of many karst aquifers, as they are important water resources. Despite that, a systematic investigation on metamorphic karst aquifers is still lacking. The present study investigates the functioning of marble karst aquifers by means of spring hydrological monitoring, coupled with storm-hydrograph, thermograph, and chemograph (HTC) analysis and lag time analysis. Renara and Equi springs (Apuan Alps, Italy) were selected for this investigation. These springs drain catchments that have different degrees of structural complexity. Piston flow is the common hydrodynamic response of Renara spring to infiltration. Strong dilution effects were observed only during the heaviest rainfall events. Prolonged dry conditions after a sustained recharge phase showed the delayed arrival of infiltration water about a month later. Equi spring has a more complex behaviour due to its wider and more hydrologically heterogeneous catchment but the comparison of HTC graphs during the winter dry phase helped to recognize the differential contributions of proximal and distal sectors. Both springs show a rapid discharge increase in response to impulse infiltrative events. Conversely, water temperature and specific electrical conductivity increase only slightly during floods, indicating limited chemical and thermal exchanges between the rock and the water stored in these aquifers. The hydrodynamic behaviour of these karst springs suggests that the Apuan metamorphic aquifers are characterized by the predominance of conduit porosity over fissure and matrix porosities. This is explained by a reduced interstitial porosity and fracturing of the metamorphic carbonate rocks.

Geology, geomorphology and geochronology of the coseismic? Emad Deh rock avalanche associated with a growing anticline and a rising salt diapir, Zagros Mountains, Iran

This work documents for the first time the prehistoric, but morphologically pristine, Emad Deh rock avalanche of the Zagros Mountains. The ca. 420 Mm3 rock avalanche was initiated as a rockslide on a dip slope affecting a weak unit of marls with interbedded limestones overlain by a thick and competent limestone formation. The slope is located on the northern limb of the growing Gavbast Anticline and at the edge of the inflating Gavbast Dome, related to a buried salt diapir of Hormuz salt. The unconfined rock avalanche deposits, covering 32 km2, were accumulated on coalescing alluvial fans and a floodplain environment. The depositional lobe shows sectors with distinctive morphological features attributable to the variable flow-depositional behavior of the debris stream, controlled by the nature of the substrate: (1) proximal continuous breccia flanked by levees; (2) intermediate depression; and (3) flat-topped polygonal hills and conical hills. A morphometric and spatial distribution analysis has been performed with the 550 conical hills (hummocks) mapped in the distal sector. The rock avalanche, with 914 m of maximal height drop (H) and 9280 m of runout (L), displays an extraordinarily high mobility (H/L index of 0.09), that can be attributed to the combined effect of dynamic rock fragmentation and basal lubrication by the soft substrate in the floodplain. Relief rejuvenation and slope over-steepening related to the growth of the anticline and the inflation of the Gavbast Dome are considered the main long-term preparatory factors that shifted the slope to a state of marginal stability. The slope failure was likely triggered by a large M ≥ 6.5–7 earthquake at ca. 5.4 ka, as indicated by OSL ages obtained from folded alluvium situated just beneath the rock avalanche deposit. The source of the earthquake was probably a blind reverse fault situated beneath the asymmetric Gavbast Anticline, as support the structural and geomorphic features of the fold. The identification and dating of large coseismic landslides in the Zagros Mountains, where large earthquakes are rarely accompanied by primary surface ruptures, could help to improve both landslide and seismic hazard assessments.

Factors driving sediment compositional change in the distal area of the Ria de Vigo (NW Spain): oceanographic processes vs. paleopollution.

We analyze potential Late Holocene metal contamination along a sediment core collected in the distal zone of Ria de Vigo (North Spain). Statistical treatment of the dataset based on a multiproxy approach enabled us to identify and disentangle factors influencing the depositional processes and the preservation of the records of this activity in the area over the last ≈3000years BP. Some layers of the analyzed core have significant enrichment in Cu and a moderate enrichment in Ag, Mo, As, Sb, S, Zn, Ni, Sn, Cd, Cr, Co, Pb, and Li. The enrichment of these elements in some layers of this core may be related to mining activities that have taken place since classical times in the region. Successive phases of pollution were identified along the core KSGX24 related to the Late Bronze Age (≈3000-2450years BP), Iron Age (≈2450-1850years BP), Roman times (≈1850-1550years BP), Middle Ages (≈1250-500years BP), and industrial and modern (≈250-0years BP) anthropic activities. The protection of the Cies Islands, the erosive and transport capacity of the rivers in the region, oscillations of the oceanographic and climatic regime, atmospheric contamination, and diagenetic sedimentary processes might have contributed to the accumulation and preservation of this record in the distal region of the Ria de Vigo. The studied core shows that the industrial and preindustrial anthropic impacts caused an environmental liability and contributed to the presence of moderate to heavy pollution of various metals in surface and subsurface sediment layers in the distal sector of the Ria de Vigo, which could be a hazard to biota.

Along-strike sedimentological variability and architectural patterns of the transgression of a “mid”-Cretaceous braidplain system (Iberian Basin, eastern Spain): A tool for depicting eustatic and tectonic signatures within the framework of a global transgression

The mid-Albian to lower Cenomanian Utrillas Group is interpreted as an arid braidplain system in the Serranía de Cuenca region (Iberian Basin, Spain). In its proximal locations, it consists of an interaction of alluvial facies and subordinate aeolian deposits, with the occurrence of tidally-influenced deposits that reflect a general transgressive trend to the top of the succession. However, the distal areas of this braidplain system, where there was a more intense interaction with the Tethys Ocean, have remained understudied to date.We present a sedimentological study of two outcrops (Pajaroncillo and Reíllo) located at the distal sector of the braidplain system and 12 km apart, defining an along-strike relative position. Both outcrops differ notably regarding the arrangement and distribution of the facies associations identified despite their relative closeness. Based on the sedimentological analysis, the main transgressive and regressive trends of the succession have been identified, along with several correlatable stratigraphic surfaces. This has permitted us to distinguish five stages (T1–T5), which reflect the overall transgressive evolution of the succession: a continental aggradational stage (T1), dominated by alluvial deposition; an initial transgression stage (T2) dominated by an open coast setting in Reíllo and a restricted mudflat system in Pajaroncillo; a regressive stage (T3), during which continental alluvial to supratidal environments deposited; a resumption in transgression (T4), characterised by an array of inter- to subtidal environments; and a deepening stage (T5), when the transgression advanced landward, giving rise to the most distal deposits of the studied succession.The studied outcrops, located at the basin edge, have been integrated within the regional sequence stratigraphy framework, which was originally devised for more central areas of the Iberian Basin (Valencia Domain) and the Prebetic. This regional approach has allowed us to interpret the studied deposits as third-order depositional sequences. Besides, the supra-regional implications of this research are discussed within the broader context of Iberia and the subtleties of its tectono-sedimentary evolution during the Albian to Cenomanian times.

‘Isolated base‐of‐slope aprons’: An oxymoron for shallow‐marine fan‐shaped, temperate‐water, carbonate bodies along the south‐east Salento escarpment (Pleistocene, Apulia, southern Italy)

AbstractThis paper regards the lower Pleistocene temperate‐water carbonate deposits disconformably overlying an escarpment made up of faulted Cretaceous to Miocene limestones of the Apulia Foreland (southern Italy). Study deposits discontinuously crop out along the present‐day eastern Salento sea cliff, and form isolated fan‐shaped bodies, up to 1 km wide and up to 40 to 50 m thick, each of them covering an area of a few square kilometres. The internal arrangement of beds is represented by up to 25° to 30° lobate, seaward dipping clinobeds thinning and onlapping onto a rocky foreslope in the proximal sector and passing to gently inclined to sub‐horizontal strata in the distal sector. Seven facies were distinguished, mainly composed of coarse‐grained skeletal carbonates made up of a heterozoan association including coralline algae, large and small benthic foraminifera, echinoids, molluscs, bryozoans and serpulids. Since clinobeds were formed thanks to hyperconcentrated density flows (grain flows) bypassing the upper part of the inherited escarpment, these skeletal grains represent ex situ deposits whose shallow‐marine factory was located upward (landward) with respect to the bypassed zone, likely in the almost flat area on top of the Salento Peninsula. Clinobeds are often affected by tens of metres wide and long channel‐like structures interpreted as landslide scars. Inside these gullies, contorted beds (slumps) or matrix‐supported intra‐bioclastic floatstone/rudstone (massive deposits) are present. The occurrence of supercritical‐flow structures (for example, backset‐bedded beds) indicates the development of hydraulic jumps along the steep slope of gullies. Since these clinostratified, fan‐shaped carbonate bodies represent carbonate slopes, and that the latter are known as aprons, normally related to linear sourced sediments, an acceptable oxymoron for studied fan‐shaped carbonate bodies is suggested: ‘isolated base‐of‐slope aprons’.

Stepping out across the Karoo retro-foreland basin: Improved constraints on the Ecca-Beaufort shoreline along the northern margin

The Karoo Supergroup of South Africa, internationally renowned for its almost continuous Carboniferous to Jurassic record of deposition in a foreland basin setting, hosts an unparalleled record of fossil tetrapods that provides unique insight into terrestrial biodiversity change over this extended period. Understanding of the litho-, bio- and chronostratigraphy of the Karoo Basin has greatly improved in recent years but most work has focused on the thicker and better-exposed rocks in the basinal foredeep. A core issue that has remained ambiguous is the stratigraphic placement of the diachronous Ecca-Beaufort contact, for which different criteria have been used during mapping in different parts of the main Karoo Basin. Comparison of biostratigraphy and contrasting lithological facies changes with those in the better-studied foredeep enabled us to revise the lithostratigraphy of the Ecca and Beaufort groups in the distal part of the main Karoo Basin. The presence of proximal marine facies associations in the distal sector conform with the definition of the Waterford Formation of the Ecca Group, so far recognised only in the southern foredeep. The upper contact of the Waterford Formation represents a change from a subaqueous to a subaerial delta plain depositional environment and marks the boundary between the Ecca and Beaufort groups, as in the south. This has consequences for Beaufort Group stratigraphic subdivision in the distal sector of the Karoo foreland basin.

The neogene of the Lower Tagus Basin (Portugal)

The Tertiary Lower Tagus Basin (LTB) occupies a large area in Portugal and constitutes a symmetric basin of the oriental huge Upper Tagus Basin, centered at Madrid (Spain). The LTB was an endorreic basin during the Paleogene. Marine connection occurred at the Lower Aquitanian; at the Lisbon – Setúbal Peninsula region the sedimentation was in the ocean/continent interface, with several changes in the coast line. Apparently, the first marine transgression came from South, originating a gulf with a N-S coral reef that attained the Lisbon area. Occidental communication to the sea was established after the Burdigalian.The sedimentary and palaeontologic record of the distal sector of the LTB (Lisbon–Setúbal Peninsula) is related to sea level changes. The fossil richness – dinoflagellates, spores, pollen, plant macrorremains, foraminifera, ostracoda, molluscs, echinids, fishes, reptiles, mammals – and O and C isotopes, constitutes a large source of information for environmental and palaeogeographical reconstitutions, as well as for the establishment of correlations between marine and continental deposits. The analysis and the integration of a large amount of lithological and biostratigraphical data joined with isotopic ages (K/Ar and 87Sr/86Sr), allow the establishement of a chronostratigraphic framework for the distal part of the Miocene of the LTB and the definition of 10 depositional sequences, in part agreeing with the Haq’s 3rd order eustatic cycles. Climatic evolution during the Miocene has been also characterized. At continental environments, the faunas and floras point out to an alternation of moist and dry episodes, the dryest one at the Langhian

Quantifying Multiple Erosion Events in the Distal Sector of the Northern Alpine Foreland Basin (North-Eastern Switzerland), by Combining Basin Thermal Modelling with Vitrinite Reflectance and Apatite Fission Track Data

This work quantifies the amount of erosion associated with the Cretaceous and Miocene erosional unconformities recognised in the distal part of the Northern Alpine Foreland Basin (NAFB), north-eastern Switzerland. To achieve this goal, the basin thermal modelling approach is applied, calibrated by two different sets of data collected in previous studies: vitrinite reflectance (%Ro) and the temperature estimated from apatite fission tracks (AFT) data modelling. The novelty of this approach is the possibility to constrain the timing and magnitude of multiple erosion events by integrating thermal modelling with thermochronologic data. Combining these two methods allows the erosional events to be separated which would not be possible using only irreversible paleothermometers, such as vitrinite reflectance data. Two scenarios were tested, based on the data of two published thermochronology studies. For the Cretaceous unconformity, similar results are obtained for the two scenarios, both indicating that the deposition and the subsequent complete erosion of Lower Cretaceous deposits, in the order of 500–1300 m, depending on the area, are necessary, in order to attain the temperatures estimated by the thermal history modelling of AFT data. Thus, a depositional hiatus for this period is not likely. For the Miocene-Quaternary unconformity, the magnitude of erosion calculated for the two scenarios differs by 300–1400 m, depending on the AFT data considered. The two scenarios lead to a different evaluation of the subsidence and uplift rate of the study area, thus to a different interpretation of the tectono-stratigraphic evolution of this distal sector of the NAFB.

Variables to predict spontaneous eruption of palatally displaced permanent canine after interceptive extraction of primary canine: A systematic review and meta-analysis

To evaluate the effectiveness of different diagnostic variables measured on panoramic radiographs (PAN) to predict spontaneous eruption of palatally displaced canine (PDC) after interceptive extraction in late mixed dentition. Digital databases (MEDLINE, CENTRAL (Cochrane), Scopus, clinicaltrials.gov, ISRCTN registry) and hand searches were performed up to March 2020. Both randomized and non-randomized controlled trials were considered for the review. Study selection, data extraction, risk of bias assessment (RoB2.0 and ROBINS-I), and the certainty of evidence evaluation (GRADE) were performed according to Cochrane Handbook for Systematic Reviews of Interventions. The random-effects method for quantitative synthesis of dichotomous as well as continuous data was used. Out of 767 retrieved records, 4 controlled trials fulfilled the eligibility criteria and were included in the review. Studies were assessed at low risk of bias except one. Overall certainty was strong to moderate. PDCs in distal sectors (RR: 1.621; 95%CI: 1.259 to 2.086; P<0.001) and alpha-angle <30° (SMD: -1.350; 95%CI: 1.924 to -0.776; P<0.001) were significantly benefited from interceptive extraction. However, Vertical distance of PDC cusp tip from occlusal plane had statistically insignificant (p: 0.855) roll on eruption prediction. Interceptive extraction at a younger age, initial horizontal localization (sector position), and alpha-angle (initial mesial inclination) are the most important variables predicting the spontaneous eruption of palatally displaced canines. Findings of this review can be utilized to make evidence-based decisions for managing PDCs with diverse sectors and mesial inclinations. However, well-designed clinical trials are recommended to strengthen the evidence.

Bushveld superplume drove Proterozoic magmatism and metallogenesis in Australia

Large-scale mantle convective processes are commonly reflected in the emplacement of Large Igneous Provinces (LIPs). These are high-volume, short-duration magmatic events consisting mainly of extensive flood basalts and their associated plumbing systems. One of the most voluminous LIPs in the geological record is the ~ 2.06 billion-year-old Bushveld Igneous Complex of South Africa (BIC), one of the most mineralised magmatic complexes on Earth. Surprisingly, the known geographic envelope of magmatism related to the BIC is limited to a series of satellite intrusions in southern Africa and has not been traced further afield. This appears inconsistent with the inferred large size of the BIC event. Here, we present new radiometric ages for alkaline magmatism in the Archean Yilgarn Craton (Western Australia), which overlap the emplacement age of the BIC and indicate a much more extensive geographic footprint of the BIC magmatic event. To assess plume involvement at this distance, we present numerical simulations of mantle plume impingement at the base of the lithosphere, and constrain a relationship between the radial extent of volcanism versus time, excess temperature and plume size. These simulations suggest that the thermal influence of large plume events could extend for thousands of km within a few million years, and produce widespread alkaline magmatism, crustal extension potentially leading to continental break-up, and large ore deposits in distal sectors. Our results imply that superplumes may produce very extensive and diverse magmatic and metallogenic provinces, which may now be preserved in widely-dispersed continental blocks.

Morphologic evaluation of root resorption after miniscrew assisted en mass retraction in adult bialveolar protrusion patients

BackgroundBialveolar protrusion is one of the most common chief complaints from the Asian orthodontic patients. Typical orthodontic treatment includes extraction of the bimaxillary premolars and en mass retraction of anterior tooth with maximum anchorage by placing miniscrews. However, excessive pursuit of profile improvement by retraction and intrusion of anterior teeth may result in root resorption, alveolar bone loss, even dehiscence. Thus this retrospective, analytical study was to evaluate the root resorption of anterior teeth after miniscrew assisted en mass retraction in adult bialveolar protrusion patients.Materials and methodsThirty six adult patients with bimaxillary protrusion had four first premolars extracted, and then miniscrews were placed to provide anchorage. CBCT scans were performed before (T1) and posttreatment (T2). A new improvement project introduced for 3D CBCT registration assessment of root morphology. The paired t-test was used to compare changes from T1 to T2. The relationship between the root resorption and the movement of anterior teeth were assessed by Pearson correlation coefficient analysis.ResultsThe significant differences were only found in apical third of root and the largest resorption in apical third of the root is always noted in the palatal and distal sectors. Significant correlations were observed in the loss of root in distal and palatal sectors, the root length and volume decrease with the amount of anterior teeth retraction and intrusion.ConclusionThe new 3D registration assessment of root morphology will be helpful for the clinicians. Pursuit of large retraction and intrusion leads to obvious anterior teeth root resorption.

Anatomy and facies distribution of terminal lobes in ephemeral fluvial successions: Jurassic Tordillo Formation, Neuquén Basin, Argentina

AbstractIn terminal fluvial‐fan systems, characteristic proximal to distal variations in sedimentary architectures are recognized to arise from progressive downstream loss of water discharge related to both infiltration and evaporation. This work aims to elucidate downstream trends in facies and architecture across the medial and distal zones of terminal‐fan systems, which record transitions from deposits of channel elements to lobe‐like and sheet‐like elements. This is achieved via a detailed characterization of ancient ephemeral fluvial deposits of the well‐exposed Kimmeridgian Tordillo Formation (Neuquén Basin, Argentina). The fine sand‐prone and silt‐prone succession associated with the medial to distal sectors of the system has been studied to understand relationships between depositional processes and resulting architectures. Facies and architectural‐element analyses, and quantification of resulting sedimentological data at multiple scales, have been undertaken to characterize sedimentary facies, facies transitions, bed types, architectural elements and larger‐scale architectural styles. Eight bed types with distinct internal facies transitions are defined and interpreted in terms of different types of flood events. Channelized and non‐channelized architectural elements are defined based on their constituent bed types and their external geometry. The most common elements are terminal lobes, which are composite bodies within which largely unconfined sandy deposits are stacked in a compensational manner; a hierarchical arrangement of internal components is recognized. Proximal feeder‐channel avulsion events likely controlled the evolution of terminal‐lobe elements and their spatiotemporal shifts. Stratigraphic relations between architectural elements record system‐wide trends, whereby a proximal sector dominated by channel elements passes downstream via a gradational transition to a medial sector dominated by sandy terminal‐lobe elements, which in turn passes further downstream to a distal sector dominated by silty terminal lobe‐margin and fringing deposits. This work enhances current understanding of the stratigraphic record of terminal fluvial systems at multiple scales, and provides insight that can be applied to predict the facies and architectural complexity of terminal fluvial successions.

Volcaniclastic sedimentation influenced by logjam breakups? An example from the Blanco River, Chile

The Blanco River drains the southern flank of the Chilean Chaitén volcano toward the Pacific Ocean. During 2008, much of the rhyolitic tephra erupted by the volcano was remobilized by this (and others) fluvial system. In the Blanco River, the sediments were temporarily stored upstream of the valley dammed by logs, epiclastic and pyroclastic detritus. The logjam generation was controlled by a complex combination of several factors including abundant tephra influx, rains, steep topographic gradients, forest vegetation, and widening of the fluvial course. Sediment-laden flows generated by logjam breakup or overflow severely affected the downstream-located Chaitén village. The resulting sedimentary record is remarkable by the important proximal-distal changes in sediment composition, grain-size and types of flow within specific depositional episodes. Exposures of fluvial deposits underlying those of the 2008 eruption in the upland sector of the Blanco River display a similar sedimentary record suggesting a comparable hydro-sedimentary dynamics during deposition.This contribution analyzed the sedimentary succession that underlies the 2008 eruption deposits, in order to: i) document in detail the sedimentary processes occurred in the Blanco River as consequence of the interaction with the Chaitén volcano tephra and analyze if this hydro-sedimentary behavior departs from the expected response in similar situations; and ii) contribute to the dating of generation and rupture of logjams and exploration of the associated volcanic hazard. Basic methodology included facies analysis, recognition and correlation of depositional episodes, and 14C dating of wood and charcoal in the deposits. Four depositional episodes (named A to D) were identified within the proximal and distal fluvial segments. The proximal sector is located along the current fluvial course and the distal sector is a lowland floodplain area. In the proximal fluvial segment, the depositional episodes representing syn-eruptive conditions are composed by volcaniclastic gravels and sands, formed by stream flows (with different sediment concentration) and debris flows; and reworked ash and lapilli strata generated by the dilute flow-debris flow continuum. In this fluvial segment, particularly in the depositional episodes B and C, there are downstream facies and compositional changes that suggest recurrent generation and rupture of logjams. Depositional episode B probably occurred between 1216 and 1294 cal AD and 1391–1438 cal AD as suggested by the radiocarbon dates, and is related with the widespread “Vilcún Tephra” from the Chaitén volcano. In the distal fluvial segment the depositional episodes record sedimentation of volcaniclastic mud in ponded zones or temporally flooded areas, with incorporation of abundant organic matter, associated with sediment (sandy)-laden dilute flows and scarce preservation of ash-fall beds. It is further proposed that downstream compositional changes in syn-eruptive fluvial deposits (volcaniclastic sediments that change downstream to pyroclastic sediments) can be indicative of the presence of former logjams in similar fossil fluvial volcaniclastic sequences.

GIS-Based Geomorphological Map of the Calore River Floodplain Near Benevento (Southern Italy) Overflooded by the 15th October 2015 Event

On 15 October 2015, the floodplain of the Calore River underwent a destructive flood, with a stream stage increase up to 10 m. In this paper, we describe the GIS-based, object-oriented geomorphological map of the overflooded sectors of the Calore River floodplain near Benevento. The map graphically represents the field-checked results of a detailed geomorphological study carried out by means of GIS analysis of historical and topographic maps and orthophotos. Particular attention was devoted to the analysis of the channel adjustments experienced by the Calore River since the end of the 19th century, which shaped most of the landforms in the floodplain. The results showed that the investigated floodplain is characterized by abandoned channels, anthropogenic landforms, and five orders of recent river terraces separated by gently-sloping inactive fluvial scarps, less than 2 m high. On the oldest and/or more distal sectors of the floodplain, landforms are badly preserved, probably due to the more prolonged reshaping by natural erosional processes and anthropogenic activities, and to the high erodibility of the loose sediments in which they are shaped. The proposed map could be a key tool for a correct flood hazard assessment in the Benevento area, permitting thematic maps that avoid or reduce the negative effects of events similar to the 15 October 2015 flood.

Cephalic duodenopancreatectomy resection: technique, morbidity and mortality

Background: Advances in recent decades in the massive form of diagnostic techniques for images, a better understanding of pancreatic diseases and management pre, intra, and postoperative patients has affected in some centres of reference, a significant reduction of mortality and an increase in the survival of the cephalic pancreaticoduodenectomy for the treatment of malignant and benign tumours of the confluent bile-duodenum-pancreatic today this surgery is performed with acceptable morbidity and mortality. The objective of this study is to evaluate the incidence of the disease, pancreatic resection technique, morbidity and mortality of the Pancreaticoduodenectomy. Methods: Between December 2000 and December 2014, 96 PDC have been operated. Of them, 54 male and 42 female, whose ages ranged from 27 to 79 years old (average of 59 years) In relation of symptoms, in 89 patients had weight loss which varied between 4 to 15 kg, 83 opportunities presented jaundice, in 82 cases looked for pain, 51 vomiting and fever in 14 cases. All the patients out an ultrasound of the abdomen, to detect 80 times allowed observing tumours, noting in addition in 82 cases the main bile duct dilatation. Likewise, was performed in all patients a CT scan of the abdomen, which showed in 86 opportunities dilatation of Wirsung duct and 89 cases bile duct dilatation hepatic intra and extra hepatic. Results: All patients underwent a PD and as it is our custom, trying to expand the pancreatic resection as much as possible to the left of the mesenteric-portal axis in patients with tumours of the head of pancreas and lymphadenectomy in the hepatic pedicle prolonged by the artery to the celiac trunk. In addition, we have extended lymphadenectomy to the superior mesenteric artery and tissue retro-portal. We rebuild by pancreatic-jejunostomy term-terminal invagination anastomosis with a tutor in the Wirsung duct in cases of pancreas mild. 10-15 cm from it makes the hepatico-jejunostomy anastomosis end-side. About 40 cm of pancreatic-jejunostomy anastomosis jejunum is sectioned to make a Y -shaped Roux, whose distal sector, previous close terminal, allow the gastro-jejunostomy With respect to mortality within 30 days, 5 patients (4, 80%) died. Subsequently, 5 more patients died within 90 days (9.3%). With respect to morbidity, we divide them into in two, clinics that were 17 patients (16.32%), which were 3 lung disease, 6 febrile syndromes, 4 diabetes, 1 arrhythmia, 1 IAM, respiratory failure and an atrial fibrillation last two died. 50 patients were surgical (48%). Within pancreatic fistula was in 32 patients (30, 72%), divided into type A: in 25 cases (24%) where there was no clinical impact, type B: 4 opportunities (3.84%) and finally type C: 3 (2.88%), which one of them after being intervened. C patient died. With respect to the gastric emptying was present in 19 (18.24%) who had more than 10 days the SNG. Finally 5 (4.80%) had intra peritoneal bleeding, which were re intervened and one of them died. In addition, 8 patients had a biliary fistula (7.62%). Conclusion: Finally, we would like to talk about strong evidence that high-volume centres have lower mortality than low-volume centres. There is evidence that patients treated at high-volume centres have reduced surgical mortality and morbidity, higher survival in the long term, greater number of lymph nodes in the surgical specimen, increased frequency of R0, less hospital stay, and generate lower costs. The Results of our work support the concept that surgeons with low volume of PDC annually, but with strict training in institutions with adequate infrastructure and a multidisciplinary team, can also get good results in the malignant and benign lesions of biliary-duodenum-pancreatic confluent.

Endosseous distal extension (EDE) blade implant technique useful to provide stable pillars in the ipotrophic lower posterior sector: 22 years statistical survey.

The aim of this issue is to describe endosseous distal extension (EDE) surgical technique. This implant technique was conceived and applied since 1993 by Dr Luca Dal Carlo, as an evolution of the classical ramus blade implant technique. With this technique, you attain great stability of the blade implant, due to the following difference compared with the classical blade implant technique: the hard and soft tissues lying behind implant abutment are not being destroyed at all. A slot is made on the upper side of the bone ridge, and the blade is inserted into it and pushed backwards, so that the implant is embedded under untouched tissues. Using blade implants specially drawn for this particular surgery, the slot’s length turns out to be about half of the implant’s length. Piezo bistoury is useful to facilitate surgical proceedings. If we compare the regenerated bone on the mesial part of the implant and the bone that had remained untouched on the distal side, we will see a difference in the tissue density even after a long time. EDE technique is suitable for those cases in which the lower distal sector is characterized by scarceness of cancellous bone. Data collected during 22 years of clinical practice (97.7% 5-year success rate) allow to suggest employing this technique with asymmetric blades to treat D3-D4 narrow ridges located in the posterior mandible. Soft tissue response results are very good.