Karsten Piepjohn

Bio: Karsten Piepjohn is an academic researcher from Institute for Geosciences and Natural Resources. The author has contributed to research in topics: Arctic & Terrane. The author has an hindex of 19, co-authored 80 publications receiving 1200 citations.

The Eurekan deformation in the Arctic: an outline

Abstract: The evolution of the Eurekan deformation zones in the Arctic is closely related to the development of the circum-Greenland plate boundaries in Early Cenozoic times (53 – 34 Ma). Mostly, the Eurekan Orogeny or deformation has been interpreted as a predominantly compressive tectonic event, but the Eurekan deformational history in the Arctic was not the result of a single tectonic episode. It rather represents a complex sequence of successive tectonic stages, which produced a number of intra-continental deformation zones with changing, sometimes opposing, lateral, oblique and convergent kinematics in the Canadian Arctic Archipelago, north and NE Greenland, and Svalbard. The interaction between the continental plates, especially in combination with the development of transform faults, resulted onshore in the formation of several complex deformation zones and areas of Eurekan deformation. The Eurekan deformation can be divided into two major tectonic stages: the first phase in the Early Eocene was dominated by orthogonal compression in the West Spitsbergen Fold-and-Thrust Belt along the west margin of the Barents Shelf and contemporaneous sinistral strike-slip tectonics along the Wegener Fault and on Ellesmere Island, whereas the second phase in the Late Eocene was characterized by dextral strike-slip and compression on Ellesmere Island and contemporaneous dextral transpression and transtension along the De Geer Fracture Zone or Hornsund Fault Complex between NE Greenland and Spitsbergen.

Progressive environmental deterioration in northwestern Pangea leading to the latest Permian extinction

Abstract: Stratigraphic records from northwestern Pangea provide unique insight into global processes that occurred during the latest Permian extinction (LPE). We examined a detailed geochemical record of the Festningen section, Spitsbergen. A stepwise extinction is noted as: starting with (1) loss of carbonate shelly macrofauna, followed by (2) loss of siliceous sponges in conjunction with an abrupt change in ichnofabrics as well as dramatic change in the terrestrial environment, and (3) final loss of all trace fossils. We interpret loss of carbonate producers as related to shoaling of the lysocline in higher latitudes, in relationship to building atmospheric CO2. The loss of siliceous sponges is coincident with the global LPE event and is related to onset of high loading rates of toxic metals (Hg, As, Co) that we suggest are derived from Siberian Trap eruptions. The final extinction stage is coincident with redox-sen- sitive trace metal and other proxy data that suggest onset of anoxia after the other extinction events. These results show a remarkable record of progressive environmental deterioration in northwestern Pangea during the extinction crises.

Eocene Compressive Deformation in Arctic Canada, N orth Greenland and Svalbard and Its Plate Teetonic Causes

Abstract: The compressive deformation in the Eurekau fold belt of Canada as weil as in the Wcst-Spitsbergen Fold-and-thrust bell is related to northward movement of the Greenland plate between anomalies 24 and 13, During this period, spreading systems Wand E of Greenland, eonverging at a RRR triplejunetion S of Greenland, were active simultaneously. It is proposed that sinistral strike-slip movement in Nares Strait occurred before this period, when spreading occurred in the Baffin Bay system W of Greenland only and the entire Eurasian plate (with Greenland attached) moved to the NE,

Tectonic Map of the Ellesmerian and Eurekan deformation belts on Svalbard, North Greenland and the Queen Elizabeth Islands (Canadian Arctic)

Abstract: The tectonic map presented here shows the distribution of the major post-Ellesmerian and pre-Eurekan sedimentary basins, parts of the Caledonian orogen, the Ellesmerian fold-and-thrust belt, structures of the Cenozoic Eurekan deformation, and areas affected by the Eurekan overprint. The present continental margin of North America towards the Arctic Ocean between the Queen Elizabeth Islands and Northeast Greenland and the present west margin of the Barents Shelf are characterized by the Palaeozoic Ellesmerian fold-and-thrust belt, the Cenozoic Eurekan deformation, and, in parts, the Caledonian orogen. In many areas, the structural trends of the Ellesmerian and Eurekan deformations are more or less parallel, and often, structures of the Ellesmerian orogeny are affected or reactivated by the Eurekan deformation. While the Ellesmerian fold-and-thrust belt is dominated by orthogonal compression and the formation of wide fold-and-thrust zones on Ellesmere Island, North Greenland, and Spitsbergen, the Eurekan deformation is characterized by a complex network of regional fold-and-thrust belts (Spitsbergen, central Ellesmere Island), large distinct thrust zones (Ellesmere Island, North Greenland), and a great number of strike-slip faults (Spitsbergen, Ellesmere Island). The Ellesmerian fold-and-thrust belt was most probably related to the approach and docking of the Pearya Terrane (northernmost part of Ellesmere Island) and Spitsbergen against the north margin of Laurasia (Ellesmere Island/North Greenland) in the earliest Carboniferous. The Eurekan deformation was related to plate tectonic movements during the final break-up of Laurasia and the opening of Labrador Sea/Baffin Bay west, the Eurasian Basin north, and the Norwegian/Greenland seas east of Greenland.

Cenozoic geodynamic evolution of the Aegean

Abstract: The Aegean region is a concentrate of the main geodynamic processes that shaped the Mediterranean region: oceanic and continental subduction, mountain building, high-pressure and low-temperature metamorphism, backarc extension, post-orogenic collapse, metamorphic core complexes, gneiss domes are the ingredients of a complex evolution that started at the end of the Cretaceous with the closure of the Tethyan ocean along the Vardar suture zone. Using available plate kinematic, geophysical, petrological and structural data, we present a synthetic tectonic map of the whole region encompassing the Balkans, Western Turkey, the Aegean Sea, the Hellenic Arc, the Mediterranean Ridge and continental Greece and we build a lithospheric-scale N-S cross-section from Crete to the Rhodope massif. We then describe the tectonic evolution of this cross-section with a series of reconstructions from ~70 Ma to the Present. We follow on the hypothesis that a single subduction has been active throughout most of the Mesozoic and the entire Cenozoic, and we show that the geological record is compatible with this hypothesis. The reconstructions show that continental subduction (Apulian and Pelagonian continental blocks) did not induce slab break-off in this case. Using this evolution, we discuss the mechanisms leading to the exhumation of metamorphic rocks and the subsequent formation of extensional metamorphic domes in the backarc region during slab retreat. The tectonic histories of the two regions showing large-scale extension, the Rhodope and the Cyclades are then compared. The respective contributions to slab retreat, post-orogenic extension and lower crust partial melting of changes in kinematic boundary conditions and in nature of subducting material, from continental to oceanic, are discussed.

Arc magmas sourced from melange diapirs in subduction zones

Abstract: At subduction zones, crustal material enters the mantle. Some of this material, however, is returned to the overriding plate through volcanic and plutonic activity. Magmas erupted above subduction zones show a characteristic range of compositions that reflect mixing in the magma source region between three components: hydrous fluids derived from the subducted oceanic crust, components of the thin veneer of subducted sediments and peridotite mantle rocks. The mechanism for mixing and transport of these components has been enigmatic. A combination of results from the fields of petrology, numerical modelling, geophysics and geochemistry suggests a two-step process. First, intensely mixed metamorphic rock formations—melanges—form along the interface between the subducted slab and the mantle. As the melange contains the characteristic three-component geochemical pattern of subduction-zone magmas, we suggest that melange formation provides the physical mixing process. Then, blobs of low-density melange material—diapirs—rise buoyantly from the surface of the subducting slab and transport the well-mixed melange material into the mantle beneath the volcanoes. Magma erupted at subduction-zone volcanoes contains mantle rocks and a mixture of fluids and sediments derived from the subducted slab. A synthesis of work over past years provides an integrated physico-chemical framework for subduction zones with mixing at the slab–mantle interface and transport towards the surface volcanoes by buoyant diapirs.