FORAMINIFERAL BIOSTRATIGRAPHY, PALAEOENVIRONMENT AND SEQUENCE STRATIGRAPHY OF WELL-A, NIGER DELTA, NIGERIA
FORAMINIFERAL BIOSTRATIGRAPHY, PALAEOENVIRONMENT AND SEQUENCE STRATIGRAPHY OF WELL-A, NIGER DELTA, NIGERIA
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Date
2015-10
Authors
NWAEJIJE, EMMANUEL CELESTINE
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Abstract
Sixty seven ditch cutting samples were collected from Well-A (latitudes 5°31'34"N and longitudes 5°42'30"E) in the Niger Delta, Nigeria at depth intervals between 2441m to 3650m for this study. Lithologic description of the samples indicate seven lithofacies comprising shale, siltstone and sandstone corresponding to the Paralic Agbada Formation.Foraminiferal analysis was carried out on these samples, a total of fifty one species were recovered; thirty seven benthonic and fourteen planktonic species. The planktonic index recovered from the well (Praeorbulina glomerosa, Praeorbulina sicana, Orbulina suturalis and Catapsydrax dissimilis) revealed that the age of the penetrated well is Miocene. Three planktonic foraminiferal zones corresponding to the N6 – N7, N8 –N9 and N9 zones of Blow (1969) are proposed for the well. The planktonic zones are Catapsydrax dissimilis Partial-range zone, Praeorbulina glomerosa Interval zone, and Orbulina universa Taxon – range zone respectively.Sequence stratigraphic analysis of the studied well-A based on foraminiferal biofacies and lithologic characteristics revealed five systems tracts (two TSTs, two HSTs and one LST), two MFS (proposed at 3388m and 3557m - dated 15.9Ma and 17.4Ma respectively) and two sequence boundaries (proposed at 3301m and 3466m dated 15.5Ma and 16.7Ma respectively), as a result, three depositional sequences were established from the well intervals. This also revealed that the well interval was exposed to two local depositional cycles (cycle 6 and 7), two regional cycles (cycles 2.2 and 2.3) within the TB2 super cycles as illustrated in Haq et al (1988) chronostratigraphic chart. The sediments of the studied well were considered to be of normal marine depositional environment based on the triangular plot of the foraminiferal test type (arenaceous, porcelaneous and hyaline). The paleobathymetry of
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the well rangefrom non-marine to middle neritic setting based on lithologic and foraminiferal distribution.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF A
MASTERDEGREE IN GEOLOGY.
DEPARTMENT OF GEOLOGY
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
FORAMINIFERAL BIOSTRATIGRAPHY, PALAEOENVIRONMENT, SEQUENCE STRATIGRAPHY, NIGER DELTA, NIGERIA