Institute Of Geosciences

The Tharsis rise on Mars with a diameter of about 8000 km and an elevation up to 10 km shows extensive volcanism and an extensional fracture system. Other authors explained this structure by (I) an uplift due to mantle processes and by (II) volcanic construction. Gravity models of four profiles are in accordance with a total Airy isostatic compensation of the whole rise with mean crustal thicknesses of 50 km and 100 km. But two regions exhibit significant mass deficits: (i) the area between Olympus Mons and the three large Tharsis volcanoes and (ii) central Tharsis. This can be explained by (1) a heated upper mantle, (2) a chemically modified upper mantle, (3) a crustal thickening, or (4) a combination of these three processes. Crustal thickening is mainly a constructional process, but the mass deficit should contribute to a certain degree of uplift causing the extensional area of Labyrinthus Noctis. Gravity modelling results in a different isostatic state of the three Tharsis volcanoes. Pavonis Mons is not compensated, Ascraeus Mons is highly or totally compensated, and Arsia Mons is medium or not compensated. The large, flat volcanic structure Alba Patera has been explained by a hot spot with an evolution of a mantle diapir. The results have shown that the Tharsis rise is a very complex structure. The central and eastern part of the rise is characterized by extensional features and a mass deficit (Extensional Province). The western part is dominated by many volcanic features and a central elongated mass deficit (Volcanic Province). The northern part consists of Alba Patera. It seems unlikely that the whole rise has been generated by one stationary large axisymmetric plume or hot spot. There could have been one or more active hot spots with an evolution in space and time.

Various types of electrodes designed for the measurement of the electric field in the soil or in sea water at periods larger than one minute have been compared in a one-year experiment in Garchy, France. The experiment included more than fifty electrode pairs with liquid or absorbed electrolytes and Pb/PbCl2, Ag/AgCl, Cu/CuSO4 and Cd/CdC12 metal-ion couples. The electrode parameters were systematically measured in the laboratory and the electrodes were installed in the field to constitute 50-meter long parallel dipoles separated by 2 meters. Pairs of electrodes used for sea measurements were monitored in a salted water vessel. Fourtytwo potential differences were recorded with a sampling interval of 1 minute between May 1995 and April 1996. When electrodes are compared, large differences are observed in the long term stability as well as in the sensitivity to diurnal variations, rainfall and soil saturation. For measurements in soil, the installation method of the electrodes plays an important role. In salted water, the best performing electrode pair has a drift of the order of 0.1 mV per year. In soil, typical drifts for the best sensors are of the order of 0.2 mV per month in dry soil and 0.5 mV per month in soaked soil. Preferred electrode designs and installation methods, depending on the external conditions or the type of geophysical measurement, emerge from this experiment. In addition to the magneto-telluric field, potential variations which are not electrode or installation effects are observed and attributed to electrical sources in the soil.

Throughout mankind’s history, the need to secure and protect the home settlement was an essential one. This holds especially true for the city of Ainos (modern Enez) in Turkish Thrace. Due to its continuous settlement history since the 7th/6th century BC, several different types of city walls were built—sometimes even on top of each other—several of which have been preserved over time. To decipher the construction style, the course and the age of a buried city wall segment in the southern part of the former city, a geoscientific multi-proxy approach including magnetic gradiometer (MG) and electrical resistivity tomography (ERT) measurements in combination with granulometrical, sedimentological and microfaunistical investigations on sediment cores was applied. We were able to (1) present reasonable arguments for its Hellenistic age; (2) reveal the course of this wall segment and extrapolate it further north into a less studied area; and (3) demonstrate that in this near-coastal area,...

The monumental tumulus Yı gma Tepe is an important part of the cityscape of the ancient city of Pergamon. The tumulus construction is estimated in the Hellenistic period, the internal structure and exact purpose have been unknown so far. Its height of 32 m and diameter of 158 m make the deep interior of the tumulus practically inaccessible for excavations. Therefore, we applied a combination of geophysical

We present a case study of a bog showing how an integrated approach of multi-method geophysical sounding and local soil sampling can be used to identify, differentiate, and map organic sediments. Our study is based on ground-penetrating radar (GPR), electrical resistivity tomography (ERT) and shear-wave seismic (SH seismic) profiling applied to sediments of the former Lake Duvensee (northern Germany), nowadays a bog. This is a well-known locality for remains from the Mesolithic hunter-gatherers’ occupation that has been attracting archaeological and geoarchaeological research for100 years. The bog is embedded in low conductive glacial sand and is characterized by layers of different gyttja sediments (detritus and calcareous). The present study was conducted in order to identify the bog morphology and the thickness of the peat body and lake sediments, in order to understand the basin evolution. To validate the geophysical results, derived from surface measurements, drilling, soil ana...

We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude t...

The work of the Pergamon excavation in 2017 concentrated on the exploration of the Hellenistic residence city and its surroundings within the framework of the current research programme, whose field work could be completed. The focus was on geophysical prospections and stratigraphic trenches on the burial mound Yýðma Tepe. To test hypotheses on the development of the settlement history of the city hill of Pergamon, Bau X on the western slope was examined. The survey of the Kane-peninsula was finished; it provided unexpected insights into the importance of the site for traffic and trade in the microregion. The extensive monument preservation measures at Pergamon concentrated on the Gymnasion and the Red Hall. A detailed preliminary report, which contains also information about other fields of activity such as the study of elite burial practises, will be published in “Archäologischer Anzeiger” 2018/2.

Die Bestanderhaltung historischer Bauwerke bedarf grundlicher Voruntersuchung, Qualitatskontrolle und Bauwerksuberwachung, um die Eingriffe in die Denkmalsubstanz zu minimieren und Folgeschaden zu vermeiden. Zerstorungsfreie Prufmethoden und numerische Modellierungsverfahren bieten heute bewahrte und neue Moglichkeiten, gesicherte Kenntnisse uber die Bauwerke und die altersbedingten Veranderungen ihrer Baumaterialien zu erzielen und gleichzeitig die Eingriffe fur Materialentnahmen und Bauwerksoffnungen zu minimieren. Anhand von Fallbeispielen werden aktuelle Forschungsergebnisse prasentiert. Georadarmessungen werden mit theoretischen Modellierungen kombiniert, um gemessene Anomalien in Materialparametern zu begrunden. Moderne Anforderungen wie die energetische Sanierung historischer Gebaude werfen neue Problemfelder auf, fur die anhand von Modellierungen des Warme- und Feuchtetransports Antworten gefunden werden. Die Weiterentwicklung von Ultraschallmesstechnik und Signalauswertung ...

Der Schwerpunkt unserer geomagnetischen Messungen in Milet lag im Bereich eines vermuteten Hafengebiets östlich vom Humeitepe, im Bereich der Heiligen Straße sowie im Gebiet zwischen Kalabaktepe und der späthellenistischen Stadtmauer. Für die Arbeiten wurde ein DGPS gesteuerter Multisensor-Wagen mit acht Differenz-Fluxgate-Sensoren eingesetzt. Die Magnetik-Sensoren besaßen einen horizontalen Abstand von 500 mm. Im Osthafen liefert die Magnetik klare Hinweise auf Hafenbauwerke mit Landungsplätzen. Westlich der Heiligen Straße finden wir eine ausgedehnte Nekropole mit einem eigenen Wegesystem. Besondere Bedeutung gewinnt der Nachweis der kontinuierlichen Fortsetzung des archaischen Straßensystems über die späthellenistische Stadtmauer hinaus bis zum Kalabaktepe hin. Nördlich des Kalabaktepe finden wir eine bisher unbekannte frühchristliche Friedhofskirche. Geoelektrische Messungen können die Ergebnisse wesentlich vertiefen und erlauben so eine gezielte Ausgrabung mit optimierten Schni...

The city of Iznik, called Nikaia or Nicaea in ancient times, is located in northwest Anatolia, Turkey. Nicaea is renowned especially for the first Council of Nicaea convened by the Roman emperor Constantine in AD 325 in an attempt to unify the Church. During an international field course on the geophysical exploration of archaeological targets we detected the remains of a small previously unknown Byzantine church on a fallow lot of land inside the city. The church is oriented parallel to the ancient Hippodamian street grid that deviates from the modern street system of the quarter by~45°. We found the contours of the nave, two aisles and three apses as well as evidence of a partly refilled grave. The geophysical measurements indicate that the foundations of the church consist of low-porosity hard rock with a low magnetic susceptibility, probably limestone or sandstone embedded in fluvial sediments. The field study is based on ground-penetrating radar (GPR), magnetics, electric resistivity tomography (ERT) and microgravimetry. It highlights the strength and necessity of combining different geophysical methods in exploring and characterizing archaeological sites. In fact, the foundation walls of the church do not show any magnetic anomaly but could be delineated clearly only by GPR. The wall remains appear as highly resistive spots in ERT. By converting the three-dimensional GPR image into an electric resistivity model we could verify that the ERT results fully correspond to the ruins found by GPR. The structure interpreted as a loosely refilled grave is indicated mainly by a weak gravity anomaly (~9 μGal) and a diffuse reflection pattern in GPR. Electric forward modelling shows that this structure leads to an additional increase of a high resistivity anomaly, which is primarily caused by foundation rocks, but it cannot be resolved within the ERT pattern a priori.

The shift to the early Holocene in northern Europe is strongly associated with major environmental and climatic changes that influenced hunter-gatherers’ activities and occupation during the Mesolithic period. The ancient lake Duvensee (10,000–6500 cal. BCE) has been studied for almost a century, providing archaeological sites consisting of bark mats and hazelnut-roasting hearths situated on small sand banks deposited by the glacier. No method is yet available to locate these features before excavation. Therefore, a key method for understanding the living conditions of hunter-gatherer groups is to reconstruct the paleoenvironment with a focus on the identification of areas that could possibly host Mesolithic camps and well-preserved archaeological artefacts. We performed a 16-channel MALÅ Imaging Radar Array (MIRA) system survey aimed at understanding the landscape surrounding the find spot Duvensee WP10, located in a hitherto uninvestigated part of the bog. Using an integrated appr...

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The work of the Pergamon excavation in 2017 concentrated on the exploration of the Hellenistic residence city and its surroundings within the framework of the current research programme, whose field work could be completed. The focus was on geophysical prospections and stratigraphic trenches on the burial mound Yığma Tepe. To test hypotheses on the development of the settlement history of the city hill of Pergamon, Bau X on the western slope was examined. The survey of the Kane-peninsula was finished; it provided unexpected insights into the importance of the site for traffic and trade in the microregion. The extensive monument preservation measures at Pergamon concentrated on the Gymnasion and the Red Hall. A detailed preliminary report, which contains also information about other fields of activity such as the study of elite burial practises, will be published in "Archäologischer Anzeiger" 2018/2.

A cave underneath the theatre of Miletus in western Turkey contains a spring and can be identified as an ancient sanctuary. It underwent two main building phases, both of which appear to be linked to building phases of the theatre, one Hellenistic and the other Roman. The cave contained terracotta figures and limbs that might have been votive offerings. 44 late antique oil lamps may also have been votives; they were buried inside the spring when the spring was filled in at the turn of the fifth century A.D. or soon thereafter. The infill also contained marble heads from the stage building of the theatre that had previously been mutilated, probably by Christians and possibly in order to mar their beauty. The infill hid the spring as well as burying the lamps and marbles. This appears to have had the twofold function of closing the sanctuary – probably in response to the anti-pagan laws of the Theodosian emperors – and of protecting the sacred spring, the votive offerings, as well as ...

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