A Factor Model of the Relationship between Stream Sediment Geochemistry and Adjacent Drainage Basin Lithology, Medvednica Mt., Croatia

Josip Halamić,Zoran Peh,Slobodan Miko,Lidija Galović,Dragan Bukovec

doi:10.4154/gc.2001.04

Josip Halamić, Zoran Peh + Show 3 more

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https://doi.org/10.4154/gc.2001.04

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Abstract

A mathematical model is constructed to relate the geochemical composition of recent stream material in a number of catchments on Medvednica Mt. to a broadely defined bedrock lithology which represents the parent material for the former. It is a system based factor model, which synthesizes eight lithological and 25 geochemical variables (major, minor and trace elements), reducing their relationships to six geologically meaningful factors. Five of these divulged a definite relationship between geochemistry and lithology. These are labelled as follows: factor of metamorphic rocks; factor of igneous rocks; factor of Tertiary carbonate rocks; factor of parametamorphic rocks and factor of Mesozoic carbonate rocks. Two lithologies; the Mesozoic clastic rocks and Quaternary sediments showed no clear association to any of the factors. Alternatively, one of the factors (F2) can be identified as “non-lithologic” indicating other, perhaps anthropogenic, contributions to the stream sediment geochemical composition.

Highlights

As a convenient medium for geochemical mapping the stream sediment represents a silty fraction transported and deposited in a recent stream channel
In order to reconcile these extremes and elucidate the relationships between geochemical composition of the stream sediment samples and bedrock lithology underlying the sampled drainage basins we offered an approach based on multivariate statistics: the factor analysis with a series of factor score maps of the investigated area
Inasmuch as the factor analysis had been used as an exploratory method in geochemical investigations, the number of factors essential to the interpretation of the factor model was specified during the analysis

Summary

Introduction

As a convenient medium for geochemical mapping the stream sediment represents a silty fraction (clay to finegrained sand) transported and deposited in a recent stream channel. This sampling medium is still mostly preferred, in areas with temperate climate and a dense drainage network because its geochemical composition is regarded as the most informative for regional reference purposes, in the domain of mineral exploration, and in the area of pollution assessment (DARNLEY et al, 1995). Some authors (e.g. OTTESEN et al, 1989) draw atttention to the opposite effect in the case of long and narrow valleys without tributaries, when stream sediment samples taken at intervals along the valley are no more than replicas of the same material from the same source, with no new geochemical information

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