The geochemistry of residual soils as an aid to geological mapping: A statistical approach

Shepherd, A.; Harvey, P. K.; Leake, R. C.

doi:10.1016/0375-6742(87)90084-7

Cited by 8 publications

(6 citation statements)

References 10 publications

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“…New cluster centroids were calculated as the mean of all the points assigned to each cluster. The data points are then reassigned to their nearest group and the process is repeated until, (i) convergence (no re-assignment required) or (ii) a set number of iterations have been preformed (Shepherd et al 1987;Pelling et al 1989). Following this procedure 'natural' geochemical groups are sought within the dataset, the optimum number of groups to divide the Hole 504B data into was ten.…”

Section: Classification Of Basalts (M D and T) Frommentioning

confidence: 99%

The validity of whole-rock geochemistry in the study of the oceanic crust: a case study from ODP Hole 504B.

Brewer

Pelling

Lovell

et al. 1992

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Attempts to interpret the geochemistry of the oceanic crust are constrained by the representative nature, quality, and amount of material recovered from an individual site. The most effective sampling method has been that of continuous coring while drilling, although the amount of material recovered from a single hole can vary with depth from 0 to 100%, and is often, though not necessarily, low. Observations suggest there is inevitably a biasing towards the recovery of unaltered material. DSDP/ODP Hole 504B has been successfully drilled in a series of stages and a 1500 m section of the oceanic crust has been sampled. The core recovery in Hole 504B is, however, generally poor; consequently the study of both igneous and alteration processes at this site is limited. An alternative to this scenario is offered by down-hole geochemical (nuclear) measurements. The nuclear responses provide a limited but near-continuous geochemical dataset within this hole. The derived chemo-stratigraphy correlates well with that based upon conventional geophysical measurements. Alteration has played an important role in producing the observed chemical signatures and may partly explain the poor core recovery within the hole. Downhole nuclear measurements in the ocean crust provide a novel geochemical dataset in the study of both primary and secondary processes. This information must be integrated with lithological, petrological and geophysical data to produce the most complete appraisal yet of the oceanic crust.

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Section: Classification Of Basalts (M D and T) Frommentioning

confidence: 99%

The validity of whole-rock geochemistry in the study of the oceanic crust: a case study from ODP Hole 504B.

Brewer

Pelling

Lovell

et al. 1992

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“…Non-hierarchical cluster analysis has been available for some years, and its use in geological science is well known (Le Maitre, 1982; Davis, 1986;Shepperd et al, 1987). The method proved useful for interpreting different ODP well logging data (Brewer et al, 1990;Gonçalves, 1995).…”

Section: Non-hierarchical Cluster Analysismentioning

confidence: 99%

“…Logging data frequently represent gradational changes between lithofacies. The number of groups chosen is, therefore, not optimal, but represents convenient divisions within the data whose boundaries are gradational (Shepperd et al, 1987). On the other hand, subtle changes within the same lithofacies can lead to the classification of heterogeneities.…”

Section: Non-hierarchical Cluster Analysismentioning

confidence: 99%

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Lithologic interpretation of downhole logging data from the Côte d'Ivoire-Ghana Transform Margin: a statistical approach

Gonçalves

1998

Proceedings of the Ocean Drilling Program, 159 Scientific Results

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Downhole logging data determined during Ocean Drilling Program Leg 159 on the Côte d'Ivoire-Ghana Transform Margin correlate to a varying degree with lithological and structural features observed in core description. Statistical analysis, such as principal component analysis and non-hierarchical cluster analysis, has been employed to classify these data into lithologically similar groups to produce a statistically derived lithostratigraphy for the holes drilled. The derived logstratigraphy is in good agreement with the lithostratigraphy defined from the study of core specimens conducted by the Shipboard Scientific Party, but also highlights some apparently anomalous sedimentary regions in the holes, which should be the focus for further examination. These regions, defined here as zones, are related either to lithological or petrophysical variations within the sediments.

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“…Initially, 20 groups were fitted; a distinct break in the mean-squared deviation between groups occurs at Groups 11 (Hole 792E) and 12 (Hole 793B). Further details of the method are given in Lebart et al (1984), Shepherd et al (1987), and Harvey and Lovell (1989).…”

Section: Downhole Geochemistrymentioning

confidence: 99%

Chemical Stratigraphy of Boreholes in the Izu-Bonin Arc from In Situ Nuclear Measurements

Lovell¹,

Pézard²,

Harvey³

1992

Proceedings of the Ocean Drilling Program

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In situ nuclear measurements were made in open-hole sections of Ocean Drilling Program Holes 792E and 793B. They provide quantitative estimates of a limited range of formation elements. A comparison of core and geochemical log data indicates reasonable agreements between the two. Limited analyses of a wide range of core samples indicate that although the chalk and nannofossil-rich silts are distinct, the admixture of sands, clays, and volcanogenic debris provides a range of homogeneous sediment compositions. The chemical homogeneity does not allow detailed distinct zoning on a simple chemical basis. Statistical analysis of the log data, however, reveals distinct and recognizable patterns that enable a chemostratigraphy to be derived for both sites. This chemostratigraphy is in agreement with the shipboard-derived lithologic units. It reveals considerable detail that may act as the focus for further evaluation.

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The geochemistry of residual soils as an aid to geological mapping: A statistical approach

Cited by 8 publications

References 10 publications

The validity of whole-rock geochemistry in the study of the oceanic crust: a case study from ODP Hole 504B.

The validity of whole-rock geochemistry in the study of the oceanic crust: a case study from ODP Hole 504B.

Lithologic interpretation of downhole logging data from the Côte d'Ivoire-Ghana Transform Margin: a statistical approach

Chemical Stratigraphy of Boreholes in the Izu-Bonin Arc from In Situ Nuclear Measurements

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