Deta Gasser

Western Norway University of Applied Sciences | HVL · Institute for Natural Sciences

The study of accessory phases, including trace element concentrations and radiogenic isotopes, provides powerful information for a better understanding of geological processes such as crustal anatexis. These accessory minerals are the primary carriers of many incompatible elements and Rare Earth Elements (REE) in crustal rocks. In this contribution...

Through the Phanerozoic eon, the trace fossil Macaronichnus—made by sediment-burrowing polychaetes—appears to be restricted to intermediate- and high-latitude shallow-marine habitats with cold to temperate waters or coastal areas closer to the equator with cold-water upwelling. We present records of such trace fossils in Ordovician (Darriwilian−San...

The post‐Caledonian thermal and geomorphological evolution of onshore Western Norway is poorly understood, including the formation and age of the high‐elevation low‐relief surfaces seen across the Norwegian landscape. We present new apatite fission track (AFT) and (U‐Th‐Sm)/He analyses from an elevation transect (ET) covering ∼1,800 m vertical dist...

The opening and closure of the Paleozoic Iapetus Ocean, leading to the collision of Laurentia and Baltica forming the Caledonian orogen, is one of the prime examples of a Wilson Cycle. In this perspective article, we summarize and discuss the content of 10 new research articles within a 5-stage framework of the Caledonian Wilson cycle from a North...

The opening and closure of the Paleozoic Iapetus Ocean, leading to the collision of Laurentia and Baltica forming the Caledonian orogen, is one of the prime examples of a Wilson Cycle. In this perspective article, we summarize and discuss the content of 10 new research articles within a 5-stage framework of the Caledonian Wilson cycle from a North...

We employ U–Pb calcite dating of structurally-controlled fracture fills within crystalline Caledonian basement in western Norway to reveal subtle large-scale tectonic events that affected this rifted continental margin. The ages (15 in total) fall into four distinct groups with ages mainly ranging from latest Cretaceous to Pleistocene. (1) The thre...

The Hølonda area of the central Scandinavian Caledonides is a key for models of the Caledonian orogen due to its Ordovician fauna of Laurentian affinity, now stranded on the Baltic side during opening of the North Atlantic. Here, we present a revised stratigraphic and tectonomagmatic model based on remapping, sedimentology, igneous geochemistry, Nd...

The late Early to early Middle Ordovician Fjellvollen Formation, Central Norwegian Caledonides, is a part of the Ilfjellet Group volcano-sedimentary succession formed in a rift basin that opened along the Laurentian margin. Depositional facies and trace fossils indicate the Nereites ichnofacies, typically found in distal turbidites and deep marine...

Basement fracture and fault patterns on passive continental margins control the onshore landscape and offshore distribution of sediment packages and fluid pathways. In this study, we decipher the spatial-temporal evolution of brittle faults and fractures in the northern section of the passive margin of Western Norway by combining field observations...

Arc-continent collision, followed by subduction polarity flip, occurs during closure of oceanic basins and contributes to the growth of continental crust. Such a setting may lead to a highly unusual association of ultrapotassic and mid-ocean ridge basalt (MORB)-type volcanic rocks as documented here from an Ordovician succession of the Scandinavian...

The late Neoproterozoic–Paleozoic Iapetus Ocean developed between Laurentia, Baltica, Siberia and Gondwana. Its Paleozoic closure history is recorded by volcano-sedimentary successions within the Caledonian orogen of Scandinavia, the British Isles and Newfoundland. We present new lithological, geochemical and geochronological data relevant for the...

Shoshonitic to ultrapotassic, mantle-derived volcanic rocks found within certain accretionary and collisional settings have trace element patterns comparable to those of common arc-related rocks, but with extreme enrichments in highly incompatible elements. Such rocks, previously unknown in the Scandinavian Caledonides, have been discovered in the...

This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and press...

This study investigates the Caledonian metamorphic and tectonic evolution in northern Norway, examining the structure and tectonostratigraphy of the Reisa Nappe Complex (RNC; from bottom to top, Vaddas, Kåfjord and Nordmannvik nappes). Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the...

The study presents data from a geochemical till survey conducted in the Oppdal/Berkåk area of Central Norway. Using a 1 × 2.5 km grid, 877 samples were taken to cover a 2000-km ² survey area (one site per 2.2 km ² ). The samples were air dried, sieved to <2 mm and analysed for 51 elements following an aqua regia extraction. A number of geochemical...

A geochemical surfacewater survey, focused on 2nd and 3rd order streams, was carried out in the Oppdal/Berkåk area in Norway. Stream water was collected at 168 sample sites, covering a 1500-km ² survey area. Electrical conductivity, pH, alkalinity and temperature were recorded in the field. Electrical conductivity and pH were also determined once m...

We present new structural, geochemical and U–Pb zircon data from syn- to late-orogenic sedimentary–volcanic basins in the southwestern part of the Trondheim Nappe Complex, central Norwegian Caledonides. In this area, a succession of enriched mid-ocean ridge basalt type metabasalt, jasper, ribbon chert with associated sandstone and conglomerate, and...

Structural data combined with U–Pb zircon and 40Ar/39Ar biotite and muscovite ages from the Rolvsnes granodiorite in western Norway show that: (1) the granodiorite intruded at ~466 Ma, cooled quickly and escaped later viscous deformation; and (2) brittle top-to-the-NNW thrust faults (Set I) and WNW–ESE-striking dextral strike-slip faults (Set II) f...

Manual extraction of topographic features from Light Detection and Ranging (LiDAR) images is a quick, cost effective and powerful tool to produce lineament maps of fractured basement areas. This commonly used technique, however, suffers from several biases. In this contribution, we present the influence of (1) scale, (2) illumination azimuth and (3...

This study investigates the behaviour of the geochronometers zircon, monazite, rutile and titanite in polyphase lower crustal rocks of the Kalak Nappe Complex, Northern Norway. A pressure-temperature-time-deformation path is constructed by combining microstructural observations with P-T conditions derived from phase equilibrium modelling and U-Pb d...

Thirty years of research, and especially the refinements of many geological, geochemical and geophysical techniques, have uncovered many new facets of the geology of the Scandina- vian Caledonides, also correcting some fundamental misconceptions. Our present understanding is that of a sequence of allochthons, some derived from Baltica, but others o...

Isotope dilution thermal ionization mass spectrometry U-Pb dating and coupled Lu-Hf solution inductively coupled plasma mass spectrometry analyses of zircon were acquired from magmatic rocks along two transects across the Scandinavian Caledonides in the Troms-Ofoten region of Norway to explore possible correlations and gain insight into the evoluti...

The Greenland and Svalbard Caledonides make up an important part of the Palaeozoic Caledonian orogen, and preserve a complex history of Palaeoproterozoic arc accretion, Proterozoic to Palaeozoic sedimentation within various basins and extensive magmatism, metamorphism and deformation during the Caledonian orogeny. In this summary, the current under...

The Caledonian orogen in Scandinavia is characterized by large-scale crustal nappe stacks which were emplaced east-/southeast-wards onto the Baltica shield. Whereas original thrust relationships are generally obscured by syn- to post-collisional extensional deformation in the southern and central Scandinavian Caledonides, several large-scale thrust...

The Chugach Metamorphic Complex (CMC) is a large high-grade metamorphic complex that developed in the Eocene within the Chugach accretionary complex along the southern margin of Alaska where subduction is still ongoing. The CMC has a conspicuous asymmetric structure with a migmatitic zone flanked in the north and west by amphibolite facies schists...

We present sensitive high-resolution ion microprobe (SHRIMP) U-Pb geochronology and trace-element chemistry of zircons from the Chugach metamorphic complex, southern Alaska, which allow us to precisely constrain the age and duration of peak metamorphism. Zircons separated from migmatitic metasedimentary gneisses show thin (5-30 mu m) overgrowths wi...

The tectonic origin of pre-Devonian rocks of Svalbard has long been a matter of debate. In particular, the origin and assemblage of pre-Devonian rocks of western Spitsbergen, including a blueschist-eclogite complex in Oscar II Land, are enigmatic. We present detrital zircon U-Pb LA-ICP-MS data from six Mesoproterozoic to Carboniferous samples and o...

Monazite is a common accessory mineral in various metamorphic and magmatic rocks, and is widely used for U-Pb geochronology. However, linking monazite U-Pb ages with the PT evolution of the rock is not always straightforward. We investigated the behaviour of monazite in a metasedimentary sequence ranging from greenschist facies phyllites into upper...

A 600km long metabasite belt is exposed at the southern border of the Chugach terrane in southern Alaska, south of the Eocene Chugach Metamorphic Complex (CMC). In this contribution, we present petrologic and geochemical results for parts of this metabasite belt. The metabasites studied are amphibolite grade and their PT conditions are evaluated wi...

This study documents the structural and metamorphic evolution of middle to lower crust along an oblique convergent curved continental margin during a time span of ∼60 Myr. Our study documents the importance of variable obliquity during convergence which led to the development of overprinting fabrics and distinct exhumation histories along strike of...

Metamorphic complexes occur at the Earth's surface in many places all over the world. The combined application of different geochronological and thermochronological techniques may help to constrain the rates of geological processes which led to the formation of such metamorphic belts. In this contribution we present the results of a multi-method ap...

The Chugach Metamorphic Complex (CMC) is an Eocene high temperature- low to medium pressure complex located in an accretionary prism (Southern Alaska). This complex is more than 300 km long, made up of metasediments associated with an amphibolite layer (~ 10m to several km width) in its southern part. Based on the study of some part of this amphibo...

The Paleozoic of Graz is an isolated nappe complex of about 1,500 km2 size and belongs to the Austroalpine units of the eastern European Alps. Despite more than 500 publications on stratigraphy, paleontology and local structure, many aspects of the internal geometry of this complex as a whole remained unclear. In this contribution, we present integ...

The Chugach Metamorphic Complex (CMC, Alaska) is a 200 km long and 10-50 km wide complex and is part of an active accretionary prism. According to the sparse existing literature, the complex is believed to be a low-pressure high-temperature terrain (400-650°C and ~3kb) with a migmatitic inner core (~5-10 km) and schist rims surrounded by phyllite (...

Exhumation mechanisms for metamorphic rocks include (a) erosion, (b) extension, (c) extrusion by channel flow, simple or pure shear, and - recently suggested - (d) slab extraction. Distinguishing in a particular case of a metamorphic complex between the different exhumation mechanisms is a much discussed subject in modern geodynamics. In order to a...

The Helvetic nappes in the Swiss Alps form a classic fold-and-thrust belt related to overall NNW-directed transport. In western Switzerland, the plunge of nappe fold axes and the regional distribution of units define a broad depression, the Rawil depression, between the culminations of Aiguilles Rouge massif to the SW and Aar massif to the NE. A co...

We present a geological map, profiles and the results of a detailed structural analysis of the Early Oligocene Engi Slates southwest of the village of Engi in the Sernft Valley in canton Glarus (Switzerland). In this area, the Engi Slates are folded on a deca- to hectometer scale into tight NW-vergent folds with sharp hinges. This took place during...

Den Brok & Jagoutz (2000) proposed that the Glarus Thrust would possibly have fol-lowed a pre-existing Miocene age erosional angular unconformity (Fig. 1; German: "Reliefüberschiebung"). Field work carried out in 2005 and 2006 in the area around the Landesplattenberg in Engi (Kanton Glarus) reveals that this angular unconformity may be found at the...