Lateral and vertical changes of deformation style in the osen-røa thrust sheet,Oslo region

Changes in deformation style and amounts of shortening in the Osen-Røa thrust sheet of the Oslo Region occur vertically and laterally approaching the thrust front in the south. Deformation in the CambroMiddle Ordovician sequence passes laterally from closely spaced imbricates in the north (50–60% shortening), through triangle, pop-up and imbricate zones toward the south (20–37% shortening) to widely spaced zones of deformation (up to 20% shortening) approaching the thrust front. Changes in deformation style are attributed to changing boundary conditions across the Klekken thrust, declining end-of-orogenic forces and an increase in thickness of competent units in the Ordovician rocks to the south. Vertical changes in deformation style are attributed to the increasing percentage of competent units upward in the Cambro-Silurian sedimentary rocks. In the north, the accompanying decrease in shortening upwards requires a structurally necessary upper detachment horizon to separate folded late Middle Ordovician-Silurian sediments from imbricated early Cambro-Middle Ordovician sediments below; while southward in the Oslo area the upper detachment needs to be placed between Silurian and Cambro-Ordovician units. Finally, in Eiker, with less than 20% shortening, the whole CambroSilurian sequence appears to have deformed as a single unit. In the northern Oslo Region, the upper detachment probably has a backthrust sense of motion above an imbricate stack (passive roof duplex). Further south the upper detachment is probably directed toward the foreland.     

Magmatic and metamorphic controls on chemical variations within the Eiksunddal eclogite complex,Sunnmøre,western Norway

The Eiksunddal eclogite complex is one of the larger group B (“country-rock”) eclogites within the Western Gneiss Region (WGR) of Norway. Whole-rock chemical data suggest a magmatic origin for the rocks within the eclogite complex. The chemical variations among the eclogitic rocks were controlled by accumulation of olivine (Fo₈₀) and plagioclase (An₇₀) and probably magnetite. The composition of the interstitial (“trapped”) liquid is derived by linear regression methods and is a high-Al orthopyroxene normative basalt. The most likely conditions of crystallization are: T ≈ 1150°C, P < 10 kbar. The Al-rich nature of the interstitial liquid may have implications for the formation of anorthosites and leucogabbros associated with similar mafic rocks elsewhere in the WGR. Trace-element characteristics are compatible with a continental origin of these rocks.During the subsequent metamorphic history, the marginal parts of the complex have suffered variable degrees of contamination. Abundant amphibole inclusions in large garnets in garnet websterites suggest local hydration at pre-eclogitic stages. This may be associated with introduction of radiogenic Sr as previously reported by W.L. Griffin and H.K. Brueckner. During prograde metamorphism, alkali exchange occurred during growth of garnet, clinopyroxene and biotite at the expense of pargasitic amphibole and orthopyroxene. The most extensive metasomatism however, was probably associated with the introduction of fluid during amphibolitization (retrogression) of the eclogitic rocks. Three model reactions — eqs. 5–7 — qualitatively explain the relation between degree of retrogression and the observed metasomatic effects. Whether Si and Ca are gained or lost during retrogression seems to be controlled by the extent of amphibole growth in diopside + plagioclase symplectites initially formed by breakdown of omphacite.Alumina has behaved in a more or less immobile way during metasomatism. Low mobility of Al is also reflected by the formation of subsilic (Al-rich) amphiboles and Al-rich plagioclase during garnet breakdown. This demonstrates the importance of kinetic factors in controlling mineral chemistry.     

Geologic and U–Pb geochronologic evidence for early Paleozoic tectonism in the Dadeldhura thrust sheet,far-west Nepal Himalaya

The Dadeldhura thrust sheet inm western Nepal consists of Proterozoic–Lower Paleozoic sedimentary and plutonic rocks, and their metamorphic equivalents, that rest structurally on Proterozoic strata of the Lesser Himalayan sequence. Although regional metamorphism and ductile deformation were widespread during Tertiary thrust emplacement, relicts of early Paleozoic tectonism are preserved locally. New field and geochronologic studies, together with the findings of previous workers, indicate that this early Paleozoic tectonism included: (1) regional metamorphism to at least garnet grade, (2) regional folding of a thick metamorphic sequence into a broad east–west trending syncline, (3) outcrop-scale folding of metasedimentary rocks, (4) emplacement of Cambro–Ordovician granitic bodies during and after the metamorphism and deformation, (5) uplift and erosion of the metamorphic sequence, with garnet-grade rocks locally exposed at the surface, and (6) derivation of Ordovician conglomeratic sandstones from the early Paleozoic orogen. Similar records of metamorphism, deformation, and uplift/erosion have been found in other regions of the Himalaya, indicating that rocks of the Dadeldhura thrust sheet were originally involved in a regionally extensive orogenic system. Future tectonic models of Himalayan orogenesis must accommodate this early Paleozoic event.     

Investigating the kinematics of local thrust sheet rotation in the limb of an orocline: a paleomagnetic and structural analysis of the Esla tectonic unit, Cantabrian–Asturian Arc, NW Iberia

The Esla tectonic unit lies along the southern boundary of the Cantabrian–Asturian Arc, a highly curved foreland fold-thrust belt that was deformed during the final amalgamation of the Pangea supercontinent. Previous structural and paleomagnetic analyses of the Cantabrian–Asturian Arc suggest a two-stage tectonic history in which an originally linear belt was bent into its present configuration, creating an orocline. The Esla tectonic unit is a particularly complex region due to the interaction of rotating thrust sheets from the southern limb of the arc and the southward-directed thrusts of the Picos de Europa tectonic domain during late-stage north–south shortening and oroclinal bending. These structural interactions resulted in intense modification of early-phase thin-skinned tectonic structures that were previously affected by a deeper out-of-sequence antiformal stack that passively deformed the early thrust stack. A total of 75 paleomagnetic sites were collected from the Portilla and Santa Lucia formations, two carbonate passive-margin reef platform units from the middle Devonian. Similar to other regions of the Cantabrian–Asturian Arc, Esla Unit samples carry a secondary remanent magnetization that was acquired after initial thrusting and folding of Variscan deformation in the late Carboniferous. Protracted deformation during late-stage oroclinal bending caused reactivation of existing thrust sheets that include the Esla and younger Corniero and Valbuena thrusts. When combined with existing structural data and interpretations, these data indicate that the present-day sinuosity of the Esla Unit is the consequence of both secondary rotation of originally linear features in the western Esla exposures (e.g., frontal thrusts), and secondary modification and tightening of originally curvilinear features in the eastern Esla exposures (e.g., hanging-wall lateral/oblique ramps). Differences in structural style between the Esla and other tectonic units of the arc highlight the complex kinematics of oroclinal bending, which at the orogen-scale buckled an originally linear, north–south (in present-day coordinates) trending Cantabrian–Asturian thrust belt during the final stages of Pangea amalgamation.     

Textural variation in the pyrite-rich ore deposits of the Røros district, Trondheim Region, Norway: implications for pyrite deformation mechanisms

The Røros district is a pyrite-rich polymetallic sulfide orefield in the southeastern part of the Trondheim region, Central Norwegian Caledonides. All of the ore deposits at Røros are hosted within a Cambrian to Silurian succession that was deformed and metamorphosed at lower greenschist to lower amphibolite facies conditions during the Caledonian orogeny. Samples from five individual deposits across the orefield have been analyzed using a combination of reflected light petrographic observation, orientation contrast imaging, and electron backscatter diffraction. Results indicate that, whereas samples from each ore deposit have a variety of different textures, all of them preserve plastic deformation in pyrite grains that occurred at peak metamorphic conditions characterized by the development of internal lattice misorientation within pyrite grains and low-angle (～2°) dislocation walls. These observations indicate that the principal deformation mechanisms at peak metamorphic conditions were dislocation glide and creep. The preservation of brittle fracturing represents later overprinting events.     

Factors causing dynamic variations in the saltwater–freshwater transition zone in a beach aquifer, Mangsang, South Korea

Dynamic variation in the saltwater–freshwater transition zone below a seafront beach in South Korea was investigated with long-term monitoring of the groundwater in relation to the precipitation, wave height, and tide. Correlation, spectral analysis, and regression analysis of monitoring data were performed to deduce the relationships between these factors. The general shape of the transition zone was affected by the seasonal groundwater levels, but temporary fluctuations were predominantly affected by local rising-groundwater-level events. The distinct increases in the groundwater level were closely related to the wave height. Different patterns of electrical conductivity (EC) change were detected in the shallow and deep zones, and these differences indicated that the transition zone was highly dynamic. The EC values at shallow depths were temporarily increased by the wave setup and tidal fluctuations during the rising-groundwater events, but the EC at greater depths was reduced by the seaward or downward movement of the relative freshwater. In exceptional cases, during extreme increases in the groundwater level resulting from seawater flooding, the rapid downward flow of the flooding saltwater through the well bore caused synchronous EC fluctuations at all depths.     

Palaeoclimatic and regional implications of Older Dryas and Younger Dryas local glacier activity in the low-Arctic valley Finnkongdalen,Andøya,northern Norway

Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS ¹⁴C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances.     

Timing and maximum flood level of the Early Holocene glacial lake Nedre Glomsjø outburst flood,Norway

This study discusses the timing and maximum flood level of the Nedre Glomsjø outburst flood, Norway, based on sediment records retrieved from 15 bog and lake basins located close to the purported maximum flooded level. The sediment records in 12 of the basins consist of a distinct light-coloured silty bed that is correlated to the outburst-flood-deposited ‘Romerike Silt Bed’ identified elsewhere in the region. The silt bed is recorded in basins up to a certain elevation and is absent above this level. The new maximum flood level inferred from the basin sediment records exceeds the established landform-induced palaeostage indicators by 5–10 m. The data indicate a higher maximum flood level and larger inundation area than previously suggested and highlight the importance of acquiring a wide range of geological data when reconstructing palaeofloods. Radiocarbon dates of terrestrial macrofossils found stratigraphically above and below the Romerike Silt Bed suggest that the glacial lake Nedre Glomsjø outburst flood occurred between 10.5 and 10.3 cal. ka BP. The new and well-constrained timing of the outburst flood is beneficial for reconstructing regional deglaciation and provides a precise age for the Romerike Silt Bed chronostratigraphical marker, which is of value for studies in SE Norway and adjacent regions.     

Geochemical expressions of anoxic conditions in Nordåsvannet,a land-locked fjord in western Norway

The Nordåsvannet fjord in western Norway is a modern semi-enclosed basin suitable for studying sedimentary cycles as they occur under anoxic bottom conditions. It is characterized by strongly anoxic conditions in the water column and bottom sediments. Diagenetic pyrite formation occurs in the sediments, and syngenetic pyrite is formed in the lower water column. Organic matter burial in the fjord exceeds that of other environments with normal marine or upwelling conditions. This is due to the better preservation of organic matter. Organic matter composition appears to have changed over time with higher fractions of terrigenous organic matter being present in the most recent sediments. This may be a result of increased input of terrigenous organic matter, possibly due to sewage supply to the fjord over the last decades. Organic C and CaCO₃ contents of the sediments do not appear to reflect a productivity signal. Calcium carbonate content is influenced by chemogenic calcite formation. Biogenic opal content appears to reflect a productivity signal, but different degrees of dissolution may obscure its clear recognition.     

Magmatic evolution of the Karmøy Ophiolite Complex,SW Norway: relationships between MORB-IAT-boninitic-calc-alkaline and alkaline magmatism

The polyphasal magmatic evolution of the Caledonian Karmøy Ophiolite Complex includes: (1) formation of an axis sequence from island-arc tholeiitic (IAT) and more MORB-like magmas (493+7/-4 Ma); (2) intrusion of magmas of boninitic affinity (485±2 Ma); (3) intrusion of MORB- and IAT-like magmas; (4) intrusion and extrusion of calc-alkaline magmas (470+9/-5 Ma); (5) intrusion and extrusion of basalts with alkaline trace-element affinity. Repeated intrusion of MORB and IAT-like magmas may be explained by intermittent magmatism involving magma-chamber solidification and remelting of a source characterized by initial _Nd of approximately +6.5. The boninitic rocks may have formed from two LREE-depleted sources: the primary source of the axis-sequence magmas and the residual source left after extraction of these magmas. These sources have been enriched in LREE, Th and Zr from subducted material exhibiting a continental Nd-isotope signature with initial _Nd less than-8. Covariation between _Nd and Th, Zr, Nd, Y and Yb may be explained by metasomatic enrichment of a LREE-depleted mantle source by a LREE-enriched subduction component, followed by partial melting during which the degree of melting of the metasomatized mantle source increased linearly with the amount of subduction component added to the mantle source. The calc-alkaline magmas may have formed by remelting of a highly depleted source, which became enriched in some trace elements derived from the source of the subsequent alkaline magmatism. The geology and geochemistry of the Karmøy Ophiolite Complex suggest growth of an island-arc upon newly-formed oceanic crust, followed by arc-splitting and the development of a new basin.     

Relation between the variations in the global surface temperature,El Niño/La Niña phenomena,and the Atlantic Multidecadal Oscillation

We analyzed directed couplings between the variations in the global surface temperature and modes of the natural climatic variability: the El NiñoLa Niña (ENSO) quasi-periodical phenomena and the long-period Atlantic Mutidecadal Oscillation (AMO) based on the data for 1870–2014. According to the quantitative estimates based on the monthly and annual mean data, the initial data, and the 10-year mean remote data, the most pronounced impact of the ENSO on the global surface temperature and the AMO was found. A weaker bidirectional coupling between the global surface temperature and the AMO is also pronounced. The analysis using running windows revealed an alternating effect of the ENSO and AMO on the variations in the global surface temperature related to the AMO phases.     

Strain accumulation and fluid–rock interaction in a naturally deformed diamictite,Willard thrust system,Utah (USA): Implications for crustal rheology and strain softening

Structural and geochemical patterns of heterogeneously deformed diamictite in northern Utah (USA) record interrelations between strain accumulation, fluid–rock interaction, and softening processes across a major fault (Willard thrust). Different clast types in the diamictite have varying shape fabrics related to competence contrasts with estimated effective viscosity ratios relative to micaceous matrix of: ∼6 and 8 for large quartzite clasts respectively in the Willard hanging wall and footwall; ∼5 and 2 for less altered and more altered granitic clasts respectively in the hanging wall and footwall; and ∼1 for micaceous clasts that approximate matrix strain. Within the footwall, matrix X–Z strain ratios increase from ∼2 to 8 westward along a distinct deformation gradient. Microstructures record widespread mass transfer, alteration of feldspar to mica, and dislocation creep of quartz within matrix and clasts. Fluid influx along microcracks and mesoscopic vein networks increased westward and led to reaction softening and hydrolytic weakening, in conjunction with textural softening from alignment of muscovite aggregates. Consistent Si, Al, and Ti concentrations between matrix, granitic clasts, and protoliths indicate limited volume change. Mg gain and Na loss reflect alteration of feldspar to phengitic muscovite. Within the hanging wall, strain is overall lower with matrix X–Z strain ratios of ∼2 to 4. Microstructures record mass transfer and dislocation creep concentrated in the matrix. Greater Al and Ti concentrations and lower Si concentrations in matrix indicate volume loss by quartz dissolution. Na gain in granitic clasts reflects albitization. Large granitic clasts have less mica alteration and greater competence compared to smaller clasts. Differences in strain and alteration patterns across the Willard thrust fault suggest overall downward (up-temperature) fluid flow in the hanging wall and upward (down-temperature) fluid flow in the footwall.     

Hydrogeochemistry and Water Quality Evaluation along the Flow Path in the Unconfined Aquifer of the Düzce Plain,North-western Turkey

The Düzce Plain has a multi-aquifer system, which consists of a near surface unconfined aquifer, along with first and second deeper confined aquifers. Hydrochemical evolution and water quality are related to infiltration of the precipitation, recharge from the formations surrounding the plain, flow path of groundwater and the relationship between surface and groundwater. The groundwater in the unconfined aquifer flows towards the Efteni Lake and the Büyük Melen River. Surface waters are divided into two main hydrochemical facies in the study area: (a) Ca2+–HCO3?; and (b) Ca2+, Mg2+–HCO3-, SO42-. The groundwater has generally three main hydrochemical facies: (a) Ca2+–HCO3-; (b) Ca2+, Mg2+–HCO3-; and (c) Ca2+, Mg2+–HCO3-, Cl-. The hydrochemical facies a and b dominate within shallow depths in recharge areas under rapid flow conditions, while hydrochemical facies c characterizes shallow and mixed groundwater, which dominate intermediate or discharge areas (near Efteni Lake and Büyük Melen River) during low flow conditions and agricultural contamination. Calcium and bicarbonate ions, total hardness and electrical conductivity of total dissolved solids (EC–TDS) values increase along the groundwater flow path; but these parameters remain within the limits specified by the standards set for industrial and agricultural usages.     

Unique accessory Ti-Ba-P mineralization in the Kvalöya ultrapotassic dike,Northern Norway

Unusual ultrapotassic dikes were recently found on the Kvalöya Island in Northern Norway. The dikes crosscutting granites 1.8 Ga in age are 0.1–1.0 m thick and consist of phlogopite phenocrysts in a fine-grained groundmass of K-magnesioarfvedsonite, orthoclase, apatite, and secondary chlorite. According to the composition of the rock-forming minerals (4.5–6.0 wt % K₂O and 0.7–3.5 wt % TiO₂ in magnesioarfved-sonite, 1.6–3.6 wt % FeO in orthoclase, 9.2–10.7 wt % Al₂O₃ and 2.1–2.6 wt % TiO₂ in phlogopite) and its bulk chemical composition (K/Na = 2.3–2.9, K/Al = 1.0–1.2, (Na + K)/Al = 1.4–1.7, Mg# V = 65–73, (La/Yb) _n = 100–140, 3.2–4.0 wt % TiO₂, 0.55–1.47 wt % BaO, 2.5–3.0 wt % P₂O₅, 2650–3000 ppm Zr, 900–1260 ppm REE total, 2300–2500 ppm Sr), the rock corresponds to lamproite of the transitional type. The unique chemical composition of the rock resulted in uncommon Ti-Ba-P accessory mineralization, including baotite Ba₄(Ti,Nb)₈Si₄O₂₈Cl (up to 5 vol %), Sr-apatite (5–7 vol %), and previously unknown Na-Mg-Ba phosphate. Baotite forms anhedral elongated and isometric grains 10–500 μm in size. It is characterized by low Nb (0.03–0.05 f.c.); admixtures of K (0.04–0.12 f.c.) and Sr (0.04–0.07) replacing Ba and Fe (0.01–0.03 f.c.); and Al (0.03–0.04 f.c.) substituting Ti. Euhedral elongated zonal apatite crystals are extremely enriched in SrO (8–12 wt %) and REE₂O₃ + Y₂O₃ (6–9 wt %) in the marginal zone. Na-Mg-Ba phosphate occurs as prismatic grains 10–100 μm in size. The atomic ratio of its major cations Na: Mg: Ba: P ～ 2: 1: 1: 2 corresponds to the conventional formula Na₂MgBa(PO4)2; the mineral contains Sr, Mn, Fe, Ca, Si, and Al admixtures.     

Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria

Few well-dated, quantitative Holocene temperature reconstructions exist from high-altitude sites in the Central Eastern Alps. Here, we present a chironomid-based quantitative reconstruction of mean July air temperatures (T_July) throughout the Holocene for a remote high-mountain lake, Schwarzsee ob Sölden, situated above the treeline at 2796 m a.s.l. in the Austrian Alps. Applying a chironomid-temperature inference model developed from lakes of the Alpine region to a high-resolution chironomid record from the lake provides evidence for early Holocene (ca 10000–8600 cal yr BP) T_July of up to 8.5 °C, i.e. >4 °C above the modern (1977–2006) mean July temperature. The reconstruction reveals the so-called ‘8.2-ka cold event’ centered at ca 8250–8000 cal yr BP with temperatures ca 3 °C below the early-Holocene thermal maximum. Rather warm (ca 6 °C) and productive conditions prevailed during ca 7900–4500 cal yr BP. The chironomid record suggests a climate transition between ca 5200 and 4500 cal yr BP to cooler T_July. A distinct cooling trend is evident from ca 4500 until ca 2500 cal yr BP. Thereafter, the study site experienced its coldest conditions (around 4 °C or less) throughout the rest of the Holocene, with the exception of the warming trend during the late 20th century. Beside other factors, the Northern Hemisphere summer insolation seems to be the major driving force for the long-term trends in T_July at high altitudes in the Eastern Alps. Due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set, the chironomid-based temperature reconstruction fails to track phases of the late-Holocene climatic history with T_July cooler than 4 °C. Further chironomid-based palaeoclimate model and down-core studies are required to address this problem, provide more realistic T_July estimates from undisturbed high-altitude lakes in the Alps, and extract a reliable regional temperature signal.     

The petrology of a metamorphosed netveined acid-basic intrusion from the Østfold area,Southeast Norway

A 1325-1015 Ma old minor netveined acid-basic intrusion within the Sveconorwegian basement terrain of SE Norway is described. The intrusion is well preserved in spite of a superimposed Sveconorwegian amphibolite facies metamorphism (around 1015 Ma).In the netveined intrusion the acid and the basic material represent a potassic quartz monzonite of rapakivi type and a highly fractionated tholeiite enriched in FeO^x, TiO₂, K₂O, P₂O₅ and incompatible trace elements. These two materials have existed side by side as magmas of essentially the same temperature. Interaction between the materials is demonstrated, as there is evidence of: (1) selective element diffusion comprising Sr (and probably K and Rb), (2) phenocryst capturing, where the basic magma well above its solidus temperature at least captured alkali feldspar and quartz phenocrysts from the potassic quartz monzonitic magma, (3) formation of basic hybrids with an emulsion-like structure, and (4) formation of mechanical mixed hybrids. Based on Sr isotope mixing calculations it appears that the two melts existed side by side 1300 Ma ago.It is argued that the potassic quartz-monzonite magma was hot (> 1100°C) and dry (< 0.6% H₂O). It was possibly formed by total melting of a material of similar composition which could have been the basic member of the Moss-Filtvet augen gneiss (granite) which outcrops in the neighbourhood, or alternatively by partial melting of older intermediate or basic rocks at a deeper level in the crust. The heat necessary for the melting was presumably introduced by the injection of the tholeiitic magma that also was the source of the basic component of the netveined intrusion.The formation of the netveined structure of the intrusion has presumably been guided by development of curviplanar joints in the basic material, when the potassic quartz monzonite was still very mobile.     

Late Paleozoic low-angle southward-dipping thrust in the Züünharaa area,Mongolia: tectonic implications for the geological structures in the Sayan-Baikal and Hangai-Daur belts

International Journal of Earth Sciences - The Central Asian Orogenic Belt (CAOB) is key to understanding the Paleozoic–Mesozoic geodynamics of Eurasian continent. The geological structure of...     

Influence of Mussel Culture on the Vertical Export of Phytoplankton Carbon in a Coastal Upwelling Embayment (Ría de Vigo,NW Iberia)

The goal of this paper is to find out whether suspended mussel culture affects the vertical fluxes of biogenic particles in the Ría de Vigo on a seasonal scale. With this aim, vertical fluxes of particulate organic carbon (POC) and the magnitude and composition of vertical export of phytoplankton carbon (Cphyto) collected in sediment traps were examined by comparing data obtained inside a mussel farming area (RaS) with those found at a reference station (ReS) not affected by mussels. Our results indicate that mussel farming has a strong impact on sedimentation fluxes under the rafts, not only increasing POC flux but also altering the magnitude and composition of Cphyto fluxes. Average POC flux at RaS (2564?±?1936 mg m^?2 day^?1) was four times higher than at ReS (731?±?276 mg m^?2 day^?1), and much of this increase was due to biodeposit fluxes (Cbiodep) which accounted for large proportion of POC flux (35–60 %). Indeed, because of this high Cbiodep flux, only a small proportion of the POC flux was due to Cphyto flux (3–12 %). At the same time, we observed an increased sedimentation of phytoplankton cells at RaS that could be explained by a combination of mechanisms: less energetic hydrodynamic conditions under mussel rafts, ballast effect by sinking mussel feces, and diatom aggregates. Moreover, mussel farming also altered the quality of the Cphyto flux by removing part of the predatory pressure of zooplankton and thus matching diatom composition in water column and sediment traps.     

Structural geometry of a thick‐skinned fold‐thrust belt termination: The Olary Block in the Adelaide Fold Belt,South Australia

The Olary Block comprises a set of Palaeoproterozoic to Mesoproterozoic basement inliers that were deformed together with the Neoproterozoic sedimentary cover of the Adelaide Geosyncline during the ca 500 Ma Cambro‐Ordovician Delamerian Orogeny. Balanced and restored structural sections across this region show shortening of less than 20%. These basement inliers represent the interface between a region of thick‐skinned deformation bordering the Curnamona Craton to the north and a region of thin‐skinned deformation to the south and west in the Nackara Arc. The basement inliers represent upthrust segments of the subsided basin margin with the sedimentary package thickening to the south and to the west. Earlier formed extensional faults provided the major strain guides during Delamerian shortening. An early phase of east‐west shortening is interpreted to be synchronous with dextral strike‐slip deformation along basement‐relay structures (e.g. Darling River lineament). During progressive shortening the tectonic transport direction rotated into a northwest to north direction, coeval with the onset of the main phase of thin‐skinned fold deformation in the adjacent Nackara Arc.