ABSTRACT
Correctly identifying key variables associated with the temporal
and
spatial distribution of prolific marine petroleum source rock
(MPSR) units
is of critical importance towards the future development of models
accurately
predicting their existence and effective exploitation. The
geographic positioning
and prevailing paleoclimatic conditions on paleocontinental
reconstructions,
in combination with the processes controlling the drowning of
continental
margins and parameters associated with the establishment of high
biologic
productivity and long term anoxic conditions within the water
column, have
been pursued as first-order constraints controlling the
development of
some prolific marine petroleum source rock (MPSR) deposits. From
this,
a model has been developed that accounts for the enhanced
preservation
of regional type-II MPSR deposits on low
paleolatitudinally-positioned
continental margins and shelves that have undergone depression
with respect
to sea level. Two 'shelf-drowning' mechanisms, continental passive
margin
subsidence combined with eustacy, and tectonically-induced
subsidence by
the loading of continental margins, are presented as effective
processes
that contribute towards the more efficient accumulation and
preservation
of some extensive marine petroleum source rock (MPSR) units.
The potential utility of this model is examined by a comprehensive
analysis of an extensive active continental margin MPSR unit
deposited
within the late medial Ordovician Taconic Foreland Basin of
eastern New
York and a prolific late medial Cretaceous continental passive
margin MPSR
unit deposited within the Maracaibo Basin of northwestern
Venezuela. The
integrated use of organic geochemistry, programmed pyrolysis, and
geochemical
analyses of the Taconic Foreland Basin demonstrates that the Utica
Formation
was an organic-rich and a prolific, although now spent, MPSR unit.
The
existence of the Utica Formation is believed to have been the
result of
'channeled-flow upwelling', within a bathymetrically-constricted
collisional
foreland basin, which was spatially positioned at a subsiding
continental
margin entering a subduction zone. The penecontemporaneous
impingement
of the oxygen minimum zone of the water column at the drowned
continental
shelf caused the establishment of long-term anoxic conditions on
the outer
slope of the developing foreland basin. This consequently
increased the
potential for the preservation, subsequent burial and compaction,
and eventual
conversion of organic-rich muds into a regionally important source
rock
unit.
Geochemical analysis of the late medial Cretaceous derived
petroleum
oils of the Maracaibo Basin also requires the existence of one
regional
MPSR unit, the La Luna Formation. This is consistent with the
combination
of eustatic sea level rise, and thermal subsidence, of the
northern South
American passive continental margin and shelf during medial
Cretaceous
times being coincident with the development of high biologic
productivity
conditions within the overlying photic zone of the water column.
This was
a direct result of the low paleolatitudinal positioning of the
northern
coastline of South America during medial Cretaceous times. The
subsequent
movement of the Caribbean Plate through the Proto-Caribbean Seaway
in turn
controlled the timing and maturation of the MPSR unit, becoming
younger
as collision and foredeep sedimentation progressed eastwards.
Achong, C.M., 1993. Identifying key variables associated with the
temporal
and spatial distribution of prolific marine petroleum source rock
(MPSR)
units and its application to the Taconic Foreland Basin, eastern
New York.
Unpublished MSc. thesis, State University of New York at Albany.
196 pp.,
+xv
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 40 Z899 1993 A24
thesis (scanned text) - 9MB pdf file
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