Robert Scholger

Magnetic susceptibility as indicator of environmental pollution of soils in Tallinn

Abstract Low-field magnetic susceptibility (κ) and concentration of 40 elements were determined for 531 samples collected from top-soils on the territory of the biggest industrial centre of Estonia. This study was carried out during a small-scale geochemical mapping and monitoring of soils in the frame of the project “Urban geochemistry of Tallinn” supported by NATO. The main purpose was to establish the sources of pollution and to study applicability of κ for determining geochemical anomalies. Relationship between κ and element concentrations in the topsoil was studied by means of correlation and factor analyses. Higher than average κ values were observed in soils on the territory of phosphorite deposits at Maardu. The susceptibility anomaly is caused by particular geological circumstances and can be related to high contents of ferromagnetic minerals in the host rocks. Strong positive correlation of magnetic susceptibility with Cr, Pb, Zn and Cu observed in soils from the central part of the city are conditioned by industrial contamination mainly by metal-working factories and by traffic. These heavy metals, known as the most hazardous elements, are easily extracted by plants from the soils in the studied area. In addition to traditional geochemical mapping, the magnetic susceptibility was successfully applied in determining heavy metal pollution of soils on the city territories.

Permian–Triassic boundary magnetostratigraphy from the Southern Alps (Italy)

Palaeomagnetic investigations of Permian–Triassic boundary sections in the Dolomites provided a magnetostratigraphy for the uppermost part of the Permian Bellerophon Formation to the Lower Triassic Werfen Formation. Magnetite was the dominant magnetic component in most of the samples, while the presence of hematite was characteristic for the Tesero horizon, which is regarded as the immediate Permian–Triassic boundary layer. The palaeomagnetic results are consistent with earlier studies of Permian and Triassic sediments and volcanites in the Southern Alps. The mean characteristic remanence directions indicate deposition and remanence acquisition at a shallow northerly palaeolatitude and a counterclockwise rotation. A zone of reversed polarity occurs at the top of the Permian sequence and a polarity change from reverse to normal polarity shortly above the base of the Werfen Formation. The onset of a tectonically controlled sedimentary cycle marks the beginning of the basal Triassic normal polarity zone, which corresponds to most of Griesbachian time. The record of geomagnetic polarity across the Permian–Triassic boundary confirms the apparent continuity as found by sedimentologic biostratigraphic investigations which emphasise a gradual lithic transition with no evidence for a time gap at the boundary.

Palaeomagnetic results from southern Albania and their significance for the geodynamic evolution of the Dinarides, Albanides and Hellenides

Abstract Mesozoic and Cenozoic rocks were studied in three tectonic units in southern Albania. The area belongs to the Ionian Zone, Outer Albanides. Rock magnetic investigations, comprising alternating field and thermal cleaning, stepwise acquisition of isothermal remanent magnetization and hysteresis experiments were carried out. They established magnetite and titanomagnetite as the main carriers of the natural remanent magnetization. In the high field behaviour, haematite and goethite can also be seen. Several fold tests on the site and on a regional scale indicate that the directions are characteristic. These directions prove a general clockwise rotation of about 40° since the Tortonian. Using all available palaeomagnetic data from Albania, individual movements of the different tectonic units within the Inner and Outer Albanides can be deduced. This is also valid for the Albanian Alps, which are understood to be the southernmost part of the Dinarides.

Stratigraphic re-evaluation of the stratotype for the regional Ottnangian stage (Central Paratethys, middle Burdigalian)

The Ottnangian stage represents the middle Burdigalian (c. 18.1-17.2 Ma) within the regional stratigraphic concept for the Central Paratethys. The section Ottnang-Schanze in the North Alpine Foreland Basin of Upper Austria has been defined as its stratotype by Rogl et al. (1973). We present an updated strati- graphic evaluation of the section based on biostratigraphy of foraminifers, dinoflagellate cysts and calcare- ous nannoplankton as well as magnetostratigraphy. In agreement with earlier studies, assemblages of benthic foraminifers (co-occurrence of Amphicoryna ott - nangensis and Sigmoilopsis ottnangensis, mass-occurrences of Lenticulina inornata) document a late early Ottnangian age. Dinoflagellate cyst Exochosphaeridium insigne is recorded for the first time in the early Ott- nangian and its occurrence together with Apteodinium spiridoides, Cordosphaeridium cantharellus and Glaphyrocysta reticulosa s. l. extends the regional dinoflagellate zone Ein from the middle to the early Ott - nangian. On a global scale, the revealed marker species indicate zone D17a (middle-late Burdigalian). Cal- careous nannoplankton assemblages with the very rare occurrence of Sphenolithus cf. belemnos and S. aff. heteromorphus show remarkable affinities to Mediterranean nannoplankton zone MNN3b. Together with the frequent occurrence of Helicosphaera ampliaperta and the absence of Triquetrorhabdulus carinatus an assignment to standard nannoplankton zone NN3 (early-middle Burdigalian) is indicated. Magnetostratigraphy revealed an inverse polarisation for the outcrop. In combination with the biostrati- graphic age constraints and the present correlation of the Ottnangian to the Bur3 sea-level cycle the section belongs to polarity chron C5Dr.2r. For the first time, an absolute age between 17.95-18.056 Ma for the stra- totype can be inferred.

Reconstruction of the geodynamic evolution of the Northern Calcareous Alps by means of paleomagnetism

Abstract We review the paleomagnetic studies published on the Northern Calcareous Alps (NCA) and also include data from two theses that were not published yet. Moreover, we present new data from upper Santonian to Maastrichtian Gosau deposits from the Neue Welt Area in the easternmost part of the NCA (D = 325.8. I = 37.1, α 95 = 8.3, positive fold test, thus indicating counterclockwise rotation and inclination flattening). Although several of the recently published studies provide valuable data, presently the paleomagnetic data base of the NCA does not provide a sufficient frame work for a quantitatively backed paleogeographic model. By thus documenting the state of research, we want to outline major problems regarding the paleomagnetic characterization of the NCA and also specify the kind of paleomagnetic future work that is particularly needed within this mountain range.

New paleomagnetic results from the Aegean extensional province

Various Oligocene formations from NE Greece (ignimbrites from the Medousa area, rhyolites from Zagradenia, granodiorites from Elatia) show discordant paleomagnetic signatures, in each case indicating small cw (clockwise) rotation and also inclination flattening. Marls from Pithion were partly remagnetized in a present-day field. Samples that contain ancient magnetization components also indicate small cw rotation and inclination flattening. However, the magnetization of andesites from Peplos reflects a considerably larger rotation, likely owing to local tectonics. In the context of previous work in the area, these results are used to propose a subdivision of NE Greece into four structural zones of distinctive rotational behaviour (from east to west): sites in zone 1, east of the Kavala-Xanthi-Komotini fault (KXK), show various cw and ccw (counterclockwise) rotation angles owing to complex kinematics resulting from the interaction of the KXK and the north-Anatolian fault zone. However, zone 2, between the KXK and the Strymon valley, is structurally homogeneous (∼ 10° cw rotation). The paleomagnetic signature of the Vertiskos massif (zone 3) implies a larger (> 30°) cw rotation, whereas sites in the Vardar basin (zone 4) contain a paleomagnetic signature similar to that of zone 2. This suggests a motion of the Vertiscos massif, a meta-ophiolitic nappe, relative to underlying strata. Indeed, zones 2 and 4 may be parts of the same structural unit which underlies this nappe.

Palaeomagnetic investigations in Northern Albania and their significance for the geodynamic evolution of the Adriatic-Aegean realm

Abstract Palaeomagnetic results from the Inner and Outer Albanides south of the Shkoder-Pec line have established a clockwise rotation of about 45° for all tectonic units investigated so far. In Northern Albania, different tectonic zones surrounding the Shkoder-Pecline were sampled at 56 sites consisting of about 400 samples. Less than 50% of the samples had sufficiently high NRM intensities for thermal demagnetization and magnetization vector analysis. Fold and reversal tests support the results. The palaeomagnetic directions demonstrate a strong tectonic disturbance in the central part of the study area. The northernmost sites in the Albanian Alps show counterclockwise rotation (with respect to present north) in agreement with results from the Southern Dinarides. The pattern favours the idea that the Shkoder-Pec line is the transition zone between the counterclockwise rotation in the north and the clockwise rotation in the south.

Cretaceous/Tertiary boundary sections on the coast of the Black Sea near Bjala (Bulgaria)

Abstract Cretaceous/Tertiary boundary sections in Bulgaria on the coast of the Black Sea near Bjala, 35 km south of Varna have been identified by biostratigraphic, mineralogical, geochemical and magnetostratigraphic methods. The undisturbed hemipilagic sediments of Profile 2b (Bjala) show a mass extinction of Cretaceous nannoplankton species as well as a bloom of survivors at the K/T boundary and the first occurrence of new nannoplankton species after the K/T event. A comparison of biostratigraphic and magnetostratigraphic results provides a time scale for the evolution of these new nannoplankton species.

Geomagnetic and Geoelectric Prospection on a Roman Iron Production Facility in Hüttenberg, Austria (Ferrum Noricum)

Geophysical prospection has been applied in the Hüttenberg area (Carinthia, Austria), where important parts of the Roman iron production in the province of Noricum between the first century bc and the fourth century ad are located. A combination of geomagnetic, geoelectric and electromagnetic measurements at different scales yielded information about the extent of the industrial complex and the location of yet undiscovered subsurface monuments in the surrounding area of the Semlach-Eisner archaeological site. The vertical and lateral extension of a slag deposit from the smelting activities could be determined by means of geomagnetic mapping and multi-electrode geoelectric profiles. For the prediction of the continuation of walls in the subsurface outside the excavated area, the total horizontal derivative of the magnetic anomaly as well as geoelectric measurements were most suitable, whereas electromagnetic measurements were not successful owing to the high conductivity of widely spread pieces of slag. Copyright

Finding the invisible smelt: using experimental archaeology to critically evaluate fieldwork methods applied to bloomery iron production remains

Few critical evaluations of fieldwork methods applied to iron production and ironworking remains exist. This paper demonstrates how an experimental smelt can be a proxy for testing and evaluating methods used to detect, record and excavate a bloomery furnace and smithing hearth. In this investigation, a series of smelting and smithing experiments were recorded and compared to the results obtained from an archaeological analysis into their heavily disturbed remains (topographical survey, geophysical prospection, magnetic survey collection and excavation). Non-invasive techniques confirmed the presence of pyrotechnology. Invasive methods, however, highlighted the importance of examining micro-residues in providing a greater insight into the metallurgical activities that had taken place. The methods used and the results of the experiment are assessed in comparison to known archaeological examples from a Roman iron smelting complex in Hüttenberg (Austria) to demonstrate how a proxy can be effective in better understanding archaeological remains. Some of the broader issues relating to fieldwork methods and guidelines are also discussed.