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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.

News & Views

News Archive

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...

November 9, 2016

International Volcano Scientists Unite

For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...

October 4, 2016

USGS Assesses Mineral Potential for Sagebrush Habitats in Six Western States

USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...

October 3, 2016

Uganda Targets Up to U.S.$100 Million for Mineral Exploration

Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...

September 9, 2016

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...

September 1, 2016

Scientists take to the skies to track West African pollution

Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...

August 17, 2016

New IGS Xplore prospectivity maps for Botswana

International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.

August 11, 2016

NexGen Makes New High Grade Discovery

NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...

August 10, 2016

Rampion UXO Disposal to Take Place This Week

E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...

August 9, 2016

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...

August 8, 2016

Northern Shield Identifies High Quality VTEM Targets at Séquoi

Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...

August 3, 2016

Rio Tinto tailors big data drive to copper

Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...

August 1, 2016

Tetra Tech Awarded $200 Million Navy CLEAN Contract

Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...

May 3, 2016

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...

April 11, 2016

Medgold Resources: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...

April 8, 2016

De-carbonizing our energy sector

Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...

March 15, 2016

N-Sea Expands into the French Offshore Wind Industry

Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...

March 9, 2016

PDAC 2016 Convention Exceeds 22,000 Attendees

Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...

March 3, 2016

6 Alpha Launches EOD Contracting Division

6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...

A 4,000-year-old necropolis in Turkey

Ground magnetic survey has proved a boon to archaeologists studying the Middle Bronze Age period in Anatolia

By Graham Chandler

When archaeologists undertaking surface surveys at a site near Afyon in western Turkey about five years ago unexpectedly came across a grave on the surface, they knew they were on to something. It was near an area already known for an ancient necropolis and had several similarities to it, but with limited funding to excavate the entire research area they couldn’t be sure what lay beneath.

Aydin Buyuksarac was at the time an associate professor in the Department of Geophysical Engineering at Cumhuriyet University in the Turkish city of Sivas and a member of the team. “They started to excavate but could not decide where the start point was and where they could stop,” he recalls. Buyuksarac had a suggestion. “Geophysical investigations could give an idea, and limitations about the area,” he says. It worked. Sure enough, the site was revealed and confirmed as a necropolis; and now called the Dedemezari Necropolis.

Buyuksarac is, as are most archaeologists, sold on the use of geophysical methods, such as the magnetic survey they used at Dedemezari, to find elusive underground cultural remains that could otherwise entail extensive costs and still only provide hit-or-miss solutions. “Some classic archaeological exploration methods such as trenching and drilling require an enormous expenditure of human energy and engender high costs,” he says. “Moreover, these classic methods are destructive for archaeological sites. Developments in image processing and graphic representation of geophysical data provide high-speed, non-destructive reconnaissance surveys.”

Magnetic surveys in particular have proven useful. Underground cultural and archaeological features usually harbor remnant magnetization that can in a local sense bend the Earth’s magnetic field. These disturbances can be accurately and precisely measured with today’s highly sensitive magnetometers. The method’s effectiveness is a function of the level of contrast between the buried features and their local environment.

Some of the most common artifacts that produce measurable magnetic anomalies are items of fired clays. The reason for this is simple: objects such as kilns, bricks, tiles, pottery and grave jars have remnant magnetization which was induced in the firing process—these show up as contrasts with local magnetic fields. Measuring these, processing and correcting the magnetic data, then using sophisticated digital image processing techniques to sharpen and enhance the magnetic anomalies formed around the buried items can paint a grand picture of what lurks beneath.

Which is particularly useful and applicable when used to assist archaeologists’ searches for buried graves. Most very ancient graves, cemeteries and necropolises are devoid of telltale surface indications; and often contain buried artifacts harboring remnant magnetizations.

Buyuksarac and his colleagues from Selcuk University along with two researchers from Ankara University first proved out this magnetic technique investigating another necropolis, the Harmanoren Necropolis. The Harmanoren dates to around 2500 BC and is the third largest necropolis in southwestern Anatolia. They surveyed at a sampling frequency of two metres in three adjacent areas. They then applied linear transformations, horizontal planar removal, and reduction of the pole and analytic signal to transform the signals to readable subsurface images. This outlined several attractive locations of potential burials. Based on these determined locations, excavations then easily revealed several ceramic grave jar burials exactly as predicted. To ensure it wasn’t just luck, magnetic susceptibility measurements of samples from the excavated jars showed that the observed magnetic anomalies could have been caused by them.

Other archaeological researchers have had good success with the magnetic method too. Buyuksarac and his colleagues write of Gaffney and his team who in 2008 reported using a magnetometer with a three-probe cart system at the Cyrenaica Archaeological Project in northern Libya. Another reported, also in 2008, using a rapid and sensitive magnetometer with SQUID (Superconducting Quantum Interference Device—a sensitive magnetic flux detector) to survey a Neolithic double-ring ditch at Niederzimmernnear Weimar, Germany. All showed how large areas can be mapped accurately and in short order.

And so it was at the Dedemezari Necropolis, which archaeologists believe was initially built around 2000 BC and belongs to what they term the Middle Bronze Age. “The Dedemezari Necropolis was used between 1900 and 1550 BC,” says Buyuksarac. “So we can say it is from the pre-Hittite period.”  This period in southwestern Anatolia is when the Luwians established themselves. The Luwians were an Indo-European-speaking peoples thought by historians to be responsible for some rather violent destruction of existing settlements when they invaded the region and may have been the earliest wave of the better-known Hittites to the area. One of their dialects was in fact incorporated into many Hittite hieroglyphs.

Buyuksarac headed up the magnetic survey of the Dedemezari Necropolis, which was supported by TÜBİTAK (The Scientific and Technological Research Council of Turkey). Over 3,600 square metres were surveyed using a sensitive proton magnetometer (Scintrex Envimag System with 0.1 nT sensitivity at 2-second sampling rate). This provided the total intensity of the magnetic field. His team used a method referred to as the tie-point correction for magnetic diurnal variations instead of the conventional base station method. He explains that tie-point corrections involve the use of one magnetometer and the repeated measurement of magnetic values at a single survey station throughout the day’s survey operations. Data were collected sequentially in the continuous mode at 0.2m sample intervals along profiles with 0.5m profile intervals; the sensor height was 0.5m above the surface. Recorded data sets were gridded using the kriging method (an interpolation technique). To avoid skewed magnetic anomalies, data were corrected for the non-verticality of the magnetization and ambient field by the reduction to pole (RTP) method.

The resulting map of analytic signal-transformed anomalies was then put to the practical test: excavation. Trench locations were chosen based on the magnetic survey and excavations undertaken. Archaeologists were thrilled: three types of grave were found. One made of clay, one carved into the rock and the other a simple grave. Not only were locations accurate but grave shapes were predictable. Shapes of the anomalies associated with the buried graves were mainly cylindrical and elliptical; the elliptical anomalies had negative magnetic values with no positive poles. The circular anomalies with positive and negative poles indicated either carved rock or simple graves. Generally, low magnetic anomalies indicated grave jars and the higher ones were produced by supporting stone that formed the sides of a grave. Because empty grave jars have very low magnetism, the susceptibility contrasts were also low. “The magnetic method was very sensitive to these kinds of archaeological materials due to heated kiln features,” says Buyuksarac.

Buyuksarac attributes much of the interpretation success to the use of magnetic field derivatives, both vertical and horizontal. He reckons interpretation of magnetic field derivatives, separately or together, provide good images of shallow bodies from magnetic data while at the same time reducing the field from deeper sources. Horizontal derivatives of the total magnetic field were computed in the space domain using finite-difference relationships; vertical derivatives were computed in the frequency domain using fast Fourier transform (FFT) filtering.

The other major contributor to the project’s success was the use of Geosoft software for the data processing, mapping and analysis. “The gridding capabilities within Oasis montaj were very useful and highly sensitive,” says Buyuksarac. “That’s why we firstly gridded the magnetic data. And then RTP transformations were applied to the gridded data. For analytic signal transformation, all magnetic maps were processed by computation of their horizontal-x, horizontal-y and vertical-z derivatives using Geosoft’s Oasis montaj gravity and magnetics interpretation extension software. It provided a good solution for our project needs, and produced the results we required.”

Overall Buyuksarac extols the advantages of using the magnetic method to search for graves. “The magnetic method was very successful,” he says. “Locating the graves was very fitting and excavations verified the suggested locations on the site.” Some proved highly interesting, especially one in particular which appeared to be in a close grouping. “We interpreted these as a family grave group,” he says. 

One of the settlements thought to have been invaded by the Luwians was Hissarlik, a fortified Bronze Age settlement site on the south shore of the Dardanelles which has been identified with the Homeric city of Troy. Coincidentally, nearby Canakkale has now become Buyuksarac’s new home. “I changed my university at the beginning of 2010,” he says. “I am now head of the department of geophysical engineering at Canakkale Onsekiz Mart University.” He may well have several new potential magnetic survey opportunities right in his backyard. “There were a lot of civilizations [throughout] the history of this city,” he says.


Principal source:
“Determination of Grave Locations in Dedemezari Necropolis (Western Turkey) using Magnetic Field Derivatives”, by A. Buyuksarac, M. O. Arisoy, O. Bektas, O. Kocak and T. Cay. Published in Archaeological Prospection (15), 2008: online in Wiley InterScience (