August 17, 2011
Geoscience BC Releases Report 2011-6 and Two Updates to Report 2009-3

 Geoscience BC is pleased to announce the release of the following three items:
  • Report 2011-6 "Ground testing of predicted geology based on stream and lake sediment geochemistry in the QUEST area, using previously undocumented bedrock exposures"
    by T. Bissig, J. Logan, D.R. Heberlein and F. Ma

  • Two addenda to Report 2009-3 "Using Geochemistry and Neural Networks to Map Geology under Glacial Cover" by C.T. Barnett and P.M. Williams
    • Addendum #1 - A Short Note on the Distribution of Geochemical Elements in Geological Formations of the QUEST Project Area
    • Addendum #2 - Supplementary Remarks on Pre-Processing the Geochemical Data

Both reports are available for download through Geoscience BC's website at www.geosciencebc.com/s/DataReleases.asp.


About Report 2011-6

Large parts of Central British Columbia are covered by fluvioglacial sediment which has prompted researchers to develop ways to constrain the geology under cover. One such study has predicted the geology undercover by applying a neural network approach to regional stream and lake sediment data (Geoscience BC Report 2009-3).

This report describes the results of a study aimed at ground-truthing the predicted bedrock geology map of Geoscience BC Report 2009-3. Exposures, largely of previously undocumented bedrock, have been mapped and sampled in 33 locations in the Prince George and Fort Saint James area. These samples have been analyzed for whole rock geochemistry. In addition, stream sediments were collected from six previously unsampled locations on first order streams within 1.2 km from sampled bedrock exposures. The new field exposures were mapped and then compared to the BC Geological Survey bedrock map.

The results presented are only applicable to areas with relatively thin overburden since no areas with deeply covered bedrock could be tested. However, the data show that the neural network was able to predict the bedrock geology well (i.e., most probable predicted bedrock matches the observed unit) in about 75% of the cases. In another 10% of the cases the observed geological unit matches the second or third most probable unit.

The new field exposures correlate well with the predicted geology map, thereby validating the neural network approach for predicting bedrock geology. This is also supported by the fact that, on the basis of empiric comparisons, the local rock geochemistry is reflected in the stream sediment samples collected nearby.

An earlier version of this report was presented by Thomas Bissig at the Kamloops Exploration Group Conference in April 2011. For more information on this report, go to www.geosciencebc/s/2011-06.asp.


About Addenda to Report 2009-3

Geoscience BC Report 2009-3 (C.T. Barnett and P.M. Williams) applied various clustering methods to the 42 element geochemical dataset in the QUEST Project. The results showed marked correlations with geology. This led to the idea of using a neural network to model the geochemistry in areas where the geology was known, and then to apply the model to infer the bedrock geology in the non-outcropping areas. The resulting inferred geology, wherever geochemical data was available, was almost identical to mapped geology in areas of outcrop, and blended well with mapped geology along the margins, where there was geochemical data available. The results showed that geochemistry combined with neural networks could provide a powerful tool for mapping bedrock geology concealed by a veneer of glacial overburden in the QUEST project area.

The two addenda released today provide additional detail on the data leveling and neural network processes used in the original report.

Addendum #1 ("A Short Note on the Distribution of Geochemical Elements in Geological Formations of the QUEST Project Area") explains how the neural network made its predictions, by examining the distribution of the 42 leveled elements for each of the 48 principal units that outcrop in the QUEST Project area and presenting a box and whisker plot for each unit.

Addendum #2 ("Supplementary Remarks on Pre-Processing the Geochemical Data" discusses the data leveling, gridding and imaging processes that were used in the original study.

The original report, maps and two addenda are available on the original report's webpage: www.geosciencebc.com/s/2009-3.asp.



Geoscience BC

Geoscience BC is an industry-led, industry-focused not-for-profit society. Its mandate includes the collection, interpretation and marketing of geoscience data and expertise to promote investment in resource exploration and development in British Columbia. Geoscience BC is funded through grants from the Provincial Government and works in partnership with industry, academia, government, First Nations and communities to attract mineral and oil & gas investment to BC.


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