Sedimentology and ichnology of Neogene Coastal Swamp deposits in the Niger Delta Basin, Nigeria
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Date
2016-12
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Publisher
Instytut Geologii UAM
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Abstract
Often analyses of depositional environments from sparse data result in poor interpretation, especially in multipartite
depositional settings such as the Niger Delta. For instance, differentiating channel sandstones, heteroliths and mud-
stones within proximal environments from those of distal facies is difficult if interpretations rely solely on well log sig-
natures. Therefore, in order to achieve an effective and efficient interpretation of the depositional conditions of a given
unit, integrated tools must be applied such as matching core descriptions with wireline log signature. In the present
paper cores of three wells from the Coastal Swamp depositional belt of the Niger Delta are examined in order to achieve
full understanding of the depositional environments. The well sections comprise cross-bedded sandstones, heteroliths
(coastal and lower shoreface) and mudstones that were laid down in wave, river and tidal processes. Interpretations
were made from each data set comprising gamma ray logs, described sedimentological cores showing sedimentary fea-
tures and ichnological characteristics; these were integrated to define the depositional settings. Some portions from one
of the well sections reveal a blocky gamma ray well log signature instead of a coarsening-upward trend that characteris-
es a shoreface setting while in other wells the signatures for heteroliths at some sections are bell blocky in shaped rather
than serrated. Besides, heteroliths and mudstones within the proximal facies and those of distal facies were difficult to
distinguish solely on well log signatures. However, interpretation based on sedimentology and ichnology of cores from
these facies was used to correct these inconsistencies. It follows that depositional environment interpretation (especially
in multifarious depositional environments such as the Niger Delta) should ideally be made together with other raw
data for accuracy and those based solely on well log signatures should be treated with caution.
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Keywords
sandstones, heteroliths, ichnofossil, cores, depositional environment, Miocene
Citation
Geologos, 2016, 22, 3, pp. 191-200
ISBN
ISBN 978-83-232187-4-6