Geophysical measurements of perennial snow patches in Pirin Mountain, Bulgaria

Perennial snow patches are considered as indicators of permafrost occurence. There are no large glaciers on the territory of Bulgaria but small patches of snow and firn have been observed in the high mountains in the end of the summer. Perennial snow patches are considered as indicators of permafrost occurrence. In this paper we present results from geophysical investigations of Snezhnika microglacier situated in the Golyam Kazan cirque, Pirin Mountain, Bulgaria. Ground penetrating radar (GPR) and 2D Electro Resistivity Tomography (ERT) were used to estimate the thickness of the perennial snow patch as well as its subsurface structure. Measurements started in 2018 and continued over the next three years in order to evaluate changes in the snow patches' size and thickness. The mean thickness of Snezhnika is about 4–6 m, reaching up to 8 m in some areas. ERT measurements of the deeper parts of the microglacier beds show high electrical resistivities reaching over 60000 Ωm at a depth of 4–10 m. An anomaly at this depth is likewise distinguishable on the GPR profiles. These anomalies are interpreted as frozen zones and are consistently observed on the ERT and GPR profiles in the next two years of the study. These results imply for the first time the existence of permafrost in Pirin mountain and respectively in Bulgaria.

Magnetometer surveys in archaeological research in Papua New Guinea: Keveoki 1, Gulf Province

A magnetometer survey was conducted on the abandoned village site of Keveoki 1, near the Vailala River, Gulf Province, PNG. The survey, using a single sensor proton precession magnetometer, was successful in locating and defining the boundaries of areas confirmed by excavation to contain dense assemblages of pottery. The combination of geophysical and excavation results allowed a broader understanding of the spatial distribution of human occupation at Keveoki 1 than would have been possible based on excavation or visual field walking alone. We suggest this technique should be applied more regularly. Archaeological geophysical prospection techniques have not previously been applied as part of archaeological investigations in Papua New Guinea (PNG), despite an extensive history of archaeological research in this area (e.g. Bulmer 1978; Frankel and Vanderwal 1985; White and O'Connell 1982). In part, this deficiency may be explained by the perceived high cost of geophysical survey as well as the difficulties associated with operating and transporting electronic equipment to the often remote, extremely rugged, wet tropical and inaccessible archaeological sites of the region. Nevertheless geophysical techniques have a demonstrated history of making an important contribution to archaeological investigations world-wide (e.g. Witten 2006; Conyers 2004; Gaffney and Gater 2003) and have the potential to answer important archaeological questions in PNG also. In particular, they have the potential to extend site information beyond the limited spatial extent usually obtained through excavation, and thus promise to enable understandings of village sites as spatially extensive landscapes rather than more restricted spatial nodes (Kvamme 2003). This is particularly apt for PNG where thick vegetation and swampy conditions can make site discovery through more conventional field walking very difficult.The archaeological record in many coastal parts of PNG is particularly amenable to geophysical investigations because here can be found extensive sites with dense ceramic deposits as well as numerous sub-surface structural features such as postholes, human burials and earth ovens. Since electromagnetic induction (EMI) and magnetic susceptibility in particular can directly detect pottery (Clark 1990) as well as the remnants of burning (Linford and Canti 2001) and anthropogenically-induced microbial activity (Linford 2004), geophysical prospecting evidently has great potential in such archaeological contexts. Other techniques, such as ground penetrating radar (GPR) (Conyers 2004) and direct current resistivity (Witten (2006) may find less regular application in this area, but could contribute where favourable site conditions exist.

Geophysical investigations at the Anuru Bay trepang site: A new approach to locating Macassan archaeological sites in Northern Australia

This paper presents the results of a magnetometer survey and initial archaeological excavations of Macassan and Indigenous features conducted at the Anuru Bay Macassan trepang processing site. The archaeology of this area is complex, containing both material reflecting the Indigenous utilisation of coastal resources and the periodic visits of the Macassan trepangers from Indonesia. Despite a history of archaeological investigations on Macassan period sites (i.e. Clarke 1994; McKnight 1976; Mitchell 1994), geophysical survey has not previously been applied as part of these investigations. While Macassan sites may contain features amenable to conventional archaeological geophysics (such as iron trepang processing pots), additional potential exists for the application of magnetometry to locate features created through burning, as has been applied to Australian Indigenous sites (Bonhomme & Stanley 1985; Fanning et al. 2009; Moffat et al. 2008 & 2010; Stanley & Green 1976; Wallis et al. 2008) and international Indigenous sites (Abbot & Frederick 1990; Batt & Dockrill 1998; Jones & Munson 2005). The results of this study demonstrate that this approach is equally applicable to Macassan sites, opening up a new and potentially fruitful avenue for exploring the archaeology of this trade system.

A new approach to investigating shipwreck sites in littoral envirornments: Multi-technique geophysical investigations of Port Elliot, South Australia

A bipartite geophysical survey methodology has been developed in order to locate archaeological sites in littoral environments and to gain precise information on their location, size and physical properties. The initial reconnaissance phase establishes the presence of prospective anomalies with limited time and budget. The second phase provides comprehensive information on the anomaly as context for further investigation if necessary. This approach was tested at Port Elliot, South Australia to locate the remains of the cutter Lapwing. An anomaly discovered during reconnaissance phase investigations proved inconsequential in phase two, and follow-up work was not carried out. This outcome demonstrates the benefits of using this approach in terms of money and time saved.

Geophysical investigations of the Tabernacle (Yilki) Cemetery, Encounter Bay, South Australia

Geophysical investigations were undertaken using ground penetrating radar (GPR) and electromagnetic induction (EMI) at the Congregational Tabernacle (Yilke) Cemetery, Encounter Bay. These yielded 25 probable and 16 possible grave locations, identified due to the presence of adjacent stratigraphic breaks in the soil profile on multiple GPR lines. Two larger areas of disturbance were identified in the GPR survey and an additional area by the EMI survey which may represent possible locations of the former Congregational Church, founded by Reverend Ridgeway Newland in 1846. While the results show no direct evidence of coffins and approximately half of the site was inaccessible to GPR survey, the results show that the currently accepted number of burials for this site (29) is probably too low.

GEOTECHNICAL INVESTIGATION OF THE PROPOSED IFE DAM SITE AT KAJOLA VILLAGE, ILE-IFE, SOUTHWESTERN NIGERIA

Geological and geophysical investigations were conducted to assess the competence and structural integrity of the foundation site of the proposed Ife-dam at Kajola Village, Ile-Ife, Southwestern Nigeria. Geological investigation along the two (2) proposed dam axes revealed that the overburden material is loose to dense with angular shearing resistance (ɸ) of 27o to 41o. The soils are predominantly elastic silts; cohesive with considerable strength and stability. Geophysical investigation involving the Schlumberger Vertical Electrical Sounding delineated four (4) lithologies namely: topsoil with resistivity of 69 – 558 Ωm and thickness between 1.5 and 4.0 m; weathered sandy layer with resistivity from 123 – 586 Ωm and thickness between 6.5 and 20.4 m; partially weathered/ fractured basement with resistivity from 60 – 220 Ωm and thickness between 6.5 and 14.0 m; and the fresh basement rock with resistivity from 1337 – 10683 Ωm. There are indications of fractures at a depth of 32 m beneath Axis B extending to Axis A at a depth of 35 m. The subsurface materials are suitable to host a dam. Axis B is more appropriate for the dam axis, although the fracture zone should be factored into the design of the dam to prevent water seepage.

Geophysical Investigations of the South-Western Wairarapa Region of New Zealand

<p>A model of the sub-surface structure of the south-western part of the Wairarapa sedimentary basin in central New Zealand was constructed from geophysical data obtained by the author during the period 1990-1991. A total of 122 new gravity observations, eight magnetotelluric (MT) stations and approximately two kilometres of seismic refraction lines were established in the study area. All methods complemented each other in the determination of the final result. The gravity data provided the depth for the basement layer of the basin, and determined the position of a fossil fault in the region of the Wharepapa River channel. The MT and seismic data confirmed the fossil nature of the fault. The results for the boundaries determined by the MT surveys were also shown to agree with the upper layers of the gravity model. The final model presented is of a sedimentary basin with thickness of approximately 2km, with a fossil fault dividing the basin near the vicinity of the Wharepapa River. To the west of the study area is a highly anomalous region which could not be fully modelled in this study because of lack of data in this particular area.</p>

Geophysical Investigations of the South-Western Wairarapa Region of New Zealand

<p>A model of the sub-surface structure of the south-western part of the Wairarapa sedimentary basin in central New Zealand was constructed from geophysical data obtained by the author during the period 1990-1991. A total of 122 new gravity observations, eight magnetotelluric (MT) stations and approximately two kilometres of seismic refraction lines were established in the study area. All methods complemented each other in the determination of the final result. The gravity data provided the depth for the basement layer of the basin, and determined the position of a fossil fault in the region of the Wharepapa River channel. The MT and seismic data confirmed the fossil nature of the fault. The results for the boundaries determined by the MT surveys were also shown to agree with the upper layers of the gravity model. The final model presented is of a sedimentary basin with thickness of approximately 2km, with a fossil fault dividing the basin near the vicinity of the Wharepapa River. To the west of the study area is a highly anomalous region which could not be fully modelled in this study because of lack of data in this particular area.</p>