Geological Society, London, Petroleum Geology Conference series
Vol. 7, 2010
Petroleum Geology: From Mature Basins to New Frontiers—
Proceedings of the 7th Petroleum Geology Conference
B. A. Vining, Baker Hughes, UK
and S. C. Pickering, Schlumberger, Gatwick, UK
Global petroleum systems in space and time
1. S. May1,
2. R. Kleist2,
3. E. Kneller1,
4. C. Johnson1 and
5. S. Creaney2
6.
Abstract
Each of the Earth's approximately 900 sedimentary basins is a unique result of geologic, hydrologic,
atmospheric and biologic processes. The interaction of these processes results in complex histories that
are palaeogeographically linked within tectonic provinces. Process-based genetic analysis provides the
fundamental framework for predicting the distribution and character of petroleum systems. New
technologies enable the exploitation of this predictability and are themselves the origin of new ideas
and improved systems understanding. Petroleum geoscience embraces both forward modelling of
processes as well as observation, calibration and inverse modelling. This approach of forward and
inverse modelling promotes a general scientific methodology of simulation, prediction, testing and
learning that allows us to describe the genetics of sedimentary basins. Genetic analysis can be applied
to the spectrum of resource types from hydrocarbon to groundwater to mineral systems and across the
range of scales from regional to play to prospect. Like the study of evolution through the fossil record,
fundamental characteristics of petroleum systems can be recovered from the patterns of their
distribution within the framework provided by plate motion, palaeogeography and palaeoclimate.
These fundamental drivers control regional tectonics, subsidence, fill history and deformation that
result in the phenotypic expression of individual basins and their fluid systems. Genetic analysis
results in a taxonomic hierarchy that facilitates prediction and guides resource exploration. Although
genetic analysis provides a framework for understanding the distribution and nature of petroleum
systems, that framework itself is insufficient to address the challenges now facing the petroleum
industry. New technologies are required to enable exploration in frontier settings, to identify new
opportunities in mature basins, to maximize recovery from existing fields, and to unlock the potential
of unconventional resources. Future success in all of these areas is fundamentally dependent on our
ability to conceptualize new ideas.
3.3. Tectonics of Rifting and Drifting: Pangea Breakup
3.3.1. Rift Basin Architecture and Evolution
Roy W. Schlische & Martha Oliver Withjack
Department of Geological Sciences, Rutgers University, Piscataway, NJ 08854-8066 U.S.A.
Rift basins have been increasingly the focus of research in tectonics, structural geology,
and basin analysis. The reasons for this interest include:
(1) Rift basins are found on all passive (Atlantic-type) continental margins and provide a
record of the early stages of (super)continental breakup.
(2) The architecture of these basins and the basin fill are strongly influenced by the
displacement geometry on the bounding normal fault systems (e.g., Gibson et al., 1989).
Thus, aspects of the evolution of these fault systems, including their nucleation,
propagation and linkage, can be extracted from the sedimentary record.
(3) Many modern and ancient extensional basins contain lacustrine deposits (e.g., Katz,
1990) that are sensitive recorders of climate. Milankovitch cycles (e.g., Olsen and Kent,
1999) recorded in these strata provide a quantitative test of the predictions of basin-filling
models (e.g., Schlische and Olsen, 1990) that can, in turn, be used to infer aspects of crustal
rheology during rifting (e.g., Contreras et al., 1997).
(4) Many of the major petroleum provinces of the world are associated with rift basins
(e.g., the North Sea basins, the Jeanne d'Arc basin, the Brazilian rift basins).
This section provides a brief overview of the rift basins related to Pangean breakup,
especially those along the central Atlantic margin (e.g., Olsen, 1997). In particular, we
examine:
(1) the structural architecture of rift basins;
(2) the interplay of tectonics, sediment supply, and climate in controlling the large-scale
stratigraphy of rift basins;
(3) how the sedimentary fill can be subdivided into tectonostratigraphic packages that
record continental rifting, initiation of seafloor spreading, basin inversion, and drifting; and
(4) how coring can be used to answer fundamental questions related to these topics.
Structural Architecture
A typical rift basin is a fault-bounded feature known as a half graben (Fig. 3.3.1.1a). In a
cross section oriented perpendicular to the boundary fault (transverse section), the half
graben has a triangular geometry (Fig. 3.3.1.1b). The three sides of the triangle are the
border fault, the rift-onset unconformity between prerift and synrift rocks, and the postrift
unconformity between synrift and postrift rocks (or, for modern rifts, the present-day
depositional surface). Within the triangular wedge of synrift units, stratal boundaries rotate
from being subparallel to the rift-onset unconformity to being subparallel to the postrift
unconformity. This fanning geometry, along with thickening of synrift units toward the
boundary fault, are produced by syndepositional faulting. Core from the Newark basin
confirms the thickening relationships (see Section 3.3.2). Synrift strata commonly onlap
prerift rocks. In a cross section oriented parallel to the boundary fault (longitudinal
section), the basin has a synclinal geometry (Fig. 3.3.1.1c), although more complicated
geometries are associated with segmented boundary fault systems (e.g., Schlische, 1993;
Schlische and Anders, 1996; Morley, 1999).
Figure 3.3.1.1. Geometry of a simple half graben. (a) Map-view geometry. (b) Geometry along a cross
section oriented perpendicular to the boundary fault, showing wedge-shaped basin in which synrift
strata exhibit a fanning geometry, thicken toward the boundary fault, and onlap prerift rocks. (c)
Geometry along a cross section oriented parallel to the boundary fault, showing syncline-shaped basin
in which synrift strata thin away from the center of the basin and onlap prerift rocks.
The half-graben geometry described above is directly controlled by the deformation
(displacement) field surrounding the boundary fault system (Gibson et al., 1989; Schlische,
1991, 1995; Schlische and Anders, 1996; Contreras et al. 1997). In a gross sense,
displacement is greatest at the center of the fault and decreases to zero at the fault tips (Fig.
3.3.1.2a); this produces the syncline-shaped basin in longitudinal section. In traverse
section, the displacement of an initially horizontal surface that intersects the fault is
greatest at the fault itself and decreases with distance away from the fault. This produces
footwall uplift and hanging-wall subsidence, the latter of which creates the sedimentary
basin (Fig. 3.3.1.2b). However, this geometry is affected by fault propagation and forced
folding (e.g., Withjack et al., 1990; Gawthorpe et al., 1997). As displacement accumulates
on the boundary fault, the basin deepens through time. Because the width of the hangingwall deflection increases with increasing fault displacement (Barnett et al., 1987), the basin
widens through time. Because the length of the fault increases with increasing displacement
(e.g., Cowie, 1998), the basin lengthens through time. The growth of the basin through time
produces progressive onlap of synrift strata on prerift rocks (Fig. 3.3.1.3).
Figure 3.3.1.2. Fault-displacement geometry controls the first-order geometry of a
half graben. (a) Perspective diagram before (left) and after faulting showing how
normal faulting uplifts the footwall block and produces subsidence in the hangingwall block. The yellow dashed line shows the outer limit of hanging-wall subsidence
and marks the edge of the basin. Displacement is a maximum at the center of the
fault (only the right half of the fault is shown) and decreases toward the fault tip. (b)
Traverse section before faulting (left) and after faulting and sedimentation showing
footwall uplift and hanging-wall subsidence. The latter produces a wedge-shaped
basin (half graben).
Figure 3.3.1.3. Simple filling model for a growing half-graben basin shown in map
view (stages 1-4), longitudinal cross section (stages 1-5), and transverse cross
section (stages 1-4). Dashed line represents lake level. The relationship between
capacity and sediment supply determines whether sedimentation is fluvial or
lacustrine. For lacustrine sedimentation, the relationship between water volume and
excess capacity determines the lake depth. Modified from Schlische and Anders
(1996).
The simple structural architecture described above may be complicated by basin inversion,
in which a contractional phase follows the extensional phase (e.g., Buchanan and
Buchanan, 1995). Typical inversion structures include normal faults reactivated as reverse
faults, newly formed reverse and thrust faults, and folds (Fig. 3.3.1.4, 3.3.1.5). Basin
inversion occurs in a variety of tectonic environments (e.g., Buchanan and Buchanan,
1995), including several passive margins related to the breakup of Pangea (e.g., Doré and
Lundin, 1996; Vagnes et al., 1998; Withjack et al., 1995, 1998; Hill et al., 1995; Withjack
& Eisenstadt, 1999). The causes of inversion on these passive margins is not well
understood. Section 4.2.1 describes how coring, in combination with other methods, may
help further our understanding of basin inversion on passive margins.
Figure 3.3.1.4. Examples of positive inversion structures. a) Cross section across
part of Sunda arc. During inversion, normal faults became reverse faults,
producing synclines and anticlines with harpoon geometries (after Letouzey,
1990). b) Interpreted line drawings (with 3:1 and 1:1 vertical exaggeration) of
AGSO Line 110-12 from Exmouth sub-basin, NW Shelf Australia (after Withjack
& Eisenstadt, 1999). During Miocene inversion, deep-seated normal faults
became reverse faults. In response, gentle monoclines formed in the shallow,
postrift strata.
Figure 3.3.1.5. Experimental models of inversion structures. Cross sections through three clay
models showing development of inversion structures (after Eisenstadt and Withjack, 1995). In each
model, a clay layer (with colored sub-layers) covered two overlapping metal plates. Movement of the
lower plate created extension or shortening. Thin clay layers are prerift; thick clay layers are synrift;
top-most layer is postrift and pre-inversion. Top section shows model with extension and no
shortening; a half graben containing very gently dipping synrift units is present. The middle section
shows model with extension followed by minor shortening; a subtle anticline has formed in the half
graben, and is associated with minor steepening of the dip of synrift layers. Bottom section shows
model with extension followed by major shortening. The anticline in the half graben is more
prominent, and is associated with significant steepening of the dip of synrift strata. New reverse faults
have formed in the prerift layers. Although the inversion is obvious in this model, erosion of material
down to the level of the red line would remove the most obvious evidence of inversion in the half
graben. Furthermore, the prominent reverse faults cutting the prerift units could be interpreted to
indicate prerift contractional deformation, as is common in the rift zones related to the breakup of
Pangea.
Stratigraphic Architecture
Numerous non-marine rift basins of varied geography and geologic age share a remarkably
similar stratigraphic architecture (Lambiase, 1990; Schlische and Olsen, 1990; Fig.
3.3.1.6). Known as a tripartite stratigraphy, the section begins with basin-wide fluvial
deposits overlain by a relatively abrupt deepening-upward lacustrine succession overlain by
a gradual shallowing-upward lacustrine and fluvial succession. The key to understanding
the significance of this tripartite stratigraphy rests in the relationships among basin capacity
and sediment and water supply (Schlische and Olsen, 1990; Carroll and Bohacs, 1999).
Tectonics creates accommodation space or basin capacity. Sediment supply determines
how much of that basin capacity is filled and whether or not lake systems are possible
(Figure 3.3.1.7). In general, fluvial deposition results when sediment supply exceeds
capacity, and lacustrine deposition results when capacity exceeds sediment supply.
Figure 3.3.1.6. Stratigraphic architecture of Triassic-Jurassic rift
basins of eastern North America. For tectonostratigraphic (TS)
package III, nearly all basins exhibit all or part of a tripartite
stratigraphy: 1, basal fluvial deposits; 2, "deeper-water" lacustrine
deposits; 3, "shallow-water" lacustrine and fluvial deposits. The
southern basins do not contain TS-IV. TS-I is only recognized in
the Fundy basin and may or may not be a synrift deposit. Where
TS-II is recognized, a significant unconformity (in terms of missing
time) commonly separates it from TS-III. Modified from Olsen
(1997), Olsen et al. (2000), and Schlische (2000).
Figure 3.3.1.7. [BELOW] Relationships among basin capacity, sediment supply, and
volume of water determine the large-scale depositional environments of terrestrial rift
basins. In example 1, basin-wide fluvial sedimentation is predicted. In example 2,
shallow-water lacustrine sedimentation is predicted. For the basin capacity and
available sediment supply shown in this example, no very deep lakes are possible
because the excess capacity of the basin (and thus lake depth) is limited. Thus, under
these conditions, climate is a relatively unimportant control on lake depth. In example
3, deep-water lacustrine sedimentation is predicted.
The relationships shown in Figure 3.3.1.7 allow us to interpret the large-scale stratigraphic
transitions observed in many non-marine rift basins. The fluvial-lacustrine transition may
result from an increase in basin capacity and/or a decrease in sediment supply. The
shallow-water lacustrine to deep-water lacustrine transition may result from an increase in
basin capacity, a decrease in sediment-supply, and/or increase in the available volume of
water. The deep-water lacustrine to shallow-water lacustrine transition may result from a
decrease or an increase in basin capacity (depending on the geometry of the basin's excess
capacity), an increase in the sediment supply, and/or decrease in the available volume of
water. How do we go about choosing the more likely interpretation? Interestingly, all of the
major stratigraphic transitions can be explained by an increase in basin capacity, for which
a simple basin-filling model is shown in Figure 3.3.1.3. Other basin filling models are
described by Lambiase (1990), Smoot (1991), and Lambiase and Bosworth (1995). As
discussed in Section 3.3.3, long cores from rift basins, combined with basin modeling (e.g.,
Contreras et al., 1997) and seismic reflection data (e.g., Morley, 1999), are required to test
the predictions of these basin-filling models.
Figure 3.3.1.8. Idealized rift basin showing unconformity-bounded
tectonostratigraphic packages. Thin black lines represent stratal truncation
beneath unconformities; red half-arrows represent onlaps. In eastern North
America, TS-I may not be a synrift deposit, and thus the geometry shown here
would be incorrect. TS-II is much more areally restricted and more wedgeshaped than TS-III. The transition between TS-III and TS-IV is likely related
to an increase in extension rate. An offset coring technique (vertical orange
lines), as used in the Newark basin coring project, does not sample TS-I and
most of TS-II. A deep core (vertical yellow line) is necessary to recover TS-I
and TS-II. Modified from Olsen (1997).
Tectonostratigraphic Packages and Basin Evolution
Olsen (1997) subdivided the synrift strata of central Atlantic margin rift basins into four
tectonostratigraphic (TS) packages (Fig. 3.3.1.6, 3.3.1.8). An individual TS package
consists of all or part of a tripartite stratigraphic succession, is separated from other
packages by unconformities or correlative conformities, and generally has a different
climatic milieu compared to other TS packages. TS-I is a Permian deposit that may or may
not be synrift, whereas TS-II, TS-III, and TS-IV are Late Triassic and Early Jurassic synrift
deposits (Olsen et al., 2000). The unconformities between TS-I, TS-II, and TS-III
represent significant geologic time. However, it is not yet clear if these unconformities are
related to regional tectonic changes (e.g., pulsed extension) (Olsen, 1997) or to relatively
local processes such as strain localization (a change from distributed extension on lots of
small faults to extension on a few large ones; e.g., Gupta et al., 1998) (Fig. 3.3.1.9). Given
their geometry and location in the rift basin, TS-I and TS-II can generally only be sampled
through deep coring and not the relatively shallow offset coring utilized in the Newark
basin (Section 3.3.3). The rift-onset unconformity between prerift rocks and various synrift
units should not be taken as evidence of regional uplift preceding rifting; rather, it more
likely reflects erosion and non-deposition occurring over a topographically elevated region
resulting from the assembly of Pangea.
Figure 3.3.1.9. Stages in the evolution of a rift basin. (a) Early rifting associated with
several minor, relatively isolated normal faults. (b) Mature rifting with through-going
boundary fault zone, widespread deposition, and footwall uplift and erosion.
TS-III and TS-IV were deposited in much larger basins or subbasins than was TS-II, and
the unconformity between them is small to non-existent (Olsen, 1997). TS-IV includes the
widespread CAMP basalts that were erupted in a geologically short interval at ~202 Ma
(e.g., Olsen et al., 1996; Olsen, 1999) (The CAMP basalts comprise a large-igneous
province or L.I.P.; see Section 3.1.3). Significantly, TS-IV is absent in all of the southern
basins of the central Atlantic margin. As discussed more fully in Withjack et al. (1998),
TS-IV was probably never deposited in this region, indicating that synrift subsidence had
ceased prior to TS-IV time. [A postrift basalt sequence, which may or may not be the same
age as CAMP, is present in the southern region and plausibly can be connected to a
seaward-dipping reflector sequence at the continental margin (Oh et al., 1995). The
temporal and spatial relationships of these igneous rocks is a critical coring target; see
sections 4.2.1 and 4.2.2.] Also significantly, basin inversion in the southern basins occurred
shortly prior to and during TS-IV time, while inversion in the northern basins occurred
after TS-IV time. (During TS-IV time, the northern basins underwent accelerated
subsidence; see Figure 3.3.2.7). Thus, the end of rifting, the initation of inversion, and
probably the initiation of seafloor spreading are diachronous along the central Atlantic
margin (i.e., during earliest Jurassic time in the southeastern United States and Early to
Middle Jurassic time in the northeastern United States and Maritime Canada) (Withjack et
al., 1998). Coring, field analysis, and seismic-reflection profiles of synrift and immediately
overlying postrift deposits and the structures formed in them, are necessary to clarify the
important events occurring at the rift-drift transition.
The inferred diachronous initiation of seafloor spreading along the present-day margin of
the central North America Ocean is part of larger trend that reflects the progressive
dismemberment of Pangea. As the North Atlantic Ocean continued to develop, seafloor
spreading propagated northward. For example, seafloor spreading between the Grand
Banks and southwestern Europe began during the Early Cretaceous (e.g., Srivastava and
Tapscott, 1986); seafloor spreading between Labrador and western Greenland began during
the early Tertiary (anomaly 27N) (e.g., Chalmers, et al., 1993); whereas seafloor spreading
between eastern Greenland and northwestern Europe began slightly later during the early
Tertiary (anomaly 24R) (e.g., Talwani and Eldholm, 1977; Hinz et al., 1993).
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3.3. Tectonics of Rifting and Drifting: Pangea Breakup
3.3.2. Extracting Tectonic Information from Cores in Rift Basins
Roy W. Schlische
Department of Geological Sciences, Rutgers University, Piscataway, NJ 08854-8066 U.S.A.
Rift basins are tectonic features. Thus, a goal of any large-scale study involving rift basins
should be a better understanding of the tectonic processes controlling basin formation and
infilling. The NSF-funded Newark Basin Coring Project (NBCP) demonstrated that it is
possible to extract tectonic information from cores in rift basins. This section reviews the
successes of NBCP in terms of tectonics and basin evolution and briefly highlights some of
the unanswered questions.
Figure 3.3.3.1. Schematic cross section
of the Newark basin showing offset
coring technique; marker unit at the
base of one core correlates with same
marker unit at top of adjacent core.
From Schlische (2000).
NBCP used an offset drilling technique (e.g., Olsen et al., 1996a) to take advantage of the
eroded half-graben geology of the Newark basin. Core sites were positioned so that the
bottom of one hole overlapped with the top of an adjacent hole in a distinctive stratigraphic
interval (Figure 3.3.2.1). Correlations are based on cyclostratigraphy and
magnetostratigraphy (Olsen et al., 1996a; Kent et al., 1995). The overlap sections allowed
construction of a composite stratigraphic section (Olsen et al., 1996a; section 3.2.2). In
addition, the overlap sections by themselves provide useful tectonic information. For
example, the overlap section between the Rutgers and Somerset cores shows that
stratigraphic units thicken by ~12% across the 10 km between these holes (Figure 3.3.2.2).
In addition, lake facies are deeper in Somerset than Rutgers. All overlap sections thicken
from the lateral edge of the basin toward the basin center (e.g., Rutgers-Titusville) and
from the hinged margin toward the intrabasinal faults and/or border fault system (e.g.,
Nursery-Titusville) (Figure 3.3.2.3). The simplest interpretation of these variations in
thickness and facies is variations in basin subsidence caused by syndepositional faulting
(see Figure 3.3.2.1).
Figure 3.3.3.2. Overlap section of the Rutgers and Somerset cores, showing
pronounced increase in thickness and proportion of deeper-water mudstones (gray
and black units) from Rutgers to Somerset. Based on data in Olsen et al. (1996a).
Click on the image at left to view a larger version.
Figure 3.3.3.3. Geologic map of
the north-central part of the
Newark basin showing the
locations of the seven NBCP drill
sites. Arrows indicate the amount
of thickening between overlap
sections of stratigraphically
adjacent cores based on
correlations in Olsen et al.
(1996a). Abbreviations for drill
holes are: M, Martinsville; N,
Nursery; P, Princeton; R,
Rutgers; S, Somerset; T,
Titusville; W, Weston. From
Schlische (2000).
Correlations of the NBCP cored sections to outcrop sections is also extremely useful (e.g.,
Silvestri, 1994, 1997; Olsen et al., 1996a; Schlische, 1999). The Perkasie Member of the
Passaic Formation extends across 125 km of the Newark basin (Figure 3.3.2.4). Variations
in thickness of the Perkasie Member indicate that the Newark basin is a large longitudinal
syncline, consistent with border-fault displacement being highest near its center and
declining towards its lateral ends (e.g., Schlische, 1992) (also see Figure 3.3.2.1).
Additional core-to-outcrop correlations, coupled with seismic-reflection profiles, indicate
that a hierarchy of fault-related folds along the border fault system and intrabasinal faults
formed, at least in part, syndepositionally (Jones, 1994; Schlische, 1992, 1995; Reynolds,
1994; Olsen et al., 1996).
Figure 3.3.3.4. Basinwide correlation of the
Perkasie Member of the Passaic Formation
showing variations in thickness and facies.
Inset sketch map of Newark basin shows
locations of sections. Modified from Olsen et
al. (1996a).
Click on the image at left for a larger
version.
The large-scale basin geometry outlined above, the large-scale stratigraphic architecture
present in the NBCP composite section (see Figures 2.4 and 3.3.1.5), and onlap
relationships revealed by seismic data can be reproduced in quantitative basin-filling
models (see Figure 3.3.1.3). Although these basin-filling models successfully explain
many aspects of the stratigraphy of the Newark basin and many other non-marine rift
basins (e.g., Lambiase, 1990; Schlische and Olsen, 1990; Olsen, 1997), this simply
indicates that the models are viable. The models are bolstered because they also make
quantitative predictions about accumulation rates. In the Newark basin, accumulation rates
are derived from Milankovitch lacustrine cycles in the NBCP composite section (Figure
3.3.2.5a; Contreras et al., 1997; Olsen and Kent, 1999). The most sophisticated numerical
basin filling models (which incorporate self-similar faulting, flexure, isostasy, and sediment
diffusion; Contreras et al., 1997) broadly account for observed trends in accumulation rates
in the NBCP data (Figure 3.3.2.5b). In addition, the basin-filling models place constraints
on the boundary conditions of the rifting process (constant strain-rate conditions are
favored over constant fault-lengthening rate), the rheology of the crust and lithosphere, and
the nature of fault growth (Schlische, 1991; Schlische and Anders, 1996; Contreras et al.,
1997).
Figure 3.3.3.5. Accumulation rate data derived from
NBCP cyclostratigraphy (a) and constant strain-rate
basin-filling model (b). The two accumulation rate data
sets were normalized by the maximum accumulation
rate in each data set to facilitate comparisons. The
numbered curves in (b) were derived from vertical drill
holes through the model rift basin shown in map view
on right. Curve 2 fits the Newark basin data reasonably
well, but fails to reproduce the marked increase in
accumulation rates at ~27.5 M.yr. since the onset of
extension (Early Jurassic extrusive interval). Modified
from Olsen (1997), Contreras et al. (1997), and
Schlische (2000).
Deviations from the predictions of the models are also important. The most notable
deviation in the Newark basin concerns the markedly higher accumulation rates (Figure
3.3.2.5) and deeper lake facies present in the Early Jurassic strata (tectonostratigraphic (TS)
package IV; see Figure 3.3.1.5) compared with those in TS-III (Olsen et al., 1996a, b).
Strata belonging to TS-IV are interbedded with a series of lava flows (CAMP flows) that
were emplaced in as little as 650 kyr (Olsen et al., 1996b). Schlische and Olsen (1990)
postulated that accelerated faulting and tilting would markedly increase basin asymmetry.
This would cause sediments and water to shift toward the basin depocenter, increasing
accumulation rates and average lake depths. This anomaly is not just limited to the Newark
basin: a plot of cumulative stratigraphic thickness versus age (Figure 3.3.2.6) shows
marked increases in accumulation rates for all of the eastern North American rifts
containing Early Jurassic strata (Schlische and Anders, 1996). Thus, tectonics is likely
responsible for this "anomaly", although the relationship of CAMP volcanism to this
tectonic anomaly is not clear.
Figure 3.3.3.6. Cumulative stratigraphic thickness versus
geologic age for various exposed rift basins in eastern North
America. The Culpeper (C), Deerfield (D), Fundy (F), Hartford
(H), and Newark (N) basins all show pronounced increases in
stratal thickness in earliest Jurassic time (extrusive interval).
Other abbreviations are DR, Deep River; DV, Danville; and R,
Richmond basins. Modified from Schlische and Anders (1996).
References:
Contreras, J., Scholz, C.H., King, G.C.P., 1997, A general model of rift basin evolution: constraints of
first order stratigraphic observations: Journal of Geophysical Research, v. 102, p. 7673-7690.
Jones, B.D., 1994, Structure and stratigraphy of the Hopewell fault block, New Jersey and
Pennsylvania: M.S. Thesis, New Bruswick, NJ, Rutgers University.
Kent, D.V., Olsen, P.E., and Witte, W.K., 1995, Late Triassic-earliest Jurassic polarity sequence and
paleolatitudes from drill cores in the Newark rift basin, eastern North America: Journal of Geophysical
Research, v. 100, p. 14,965-14,998.
Lambiase, J.J., 1990, A model for tectonic control of lacustrine stratigraphic sequences in continental
rift basins, in Katz, B.J., ed., Lacustrine Exploration: Case Studies and Modern Analogues: AAPG
Memoir 50, p. 265-276.
Olsen, P.E., 1997, Stratigraphic record of the early Mesozoic breakup of Pangea in the LaurasiaGondwana rift system: Annual Reviews of Earth and Planetary Science, v. 25, p. 337-401.
Olsen, P.E. and D.V. Kent, 1999, Long-period Milankovitch cycles from the Late Triassic and Early
Jurassic of eastern North America and their implications for the calibration of the early Mesozoic time
scale and the long-term behavior of the planets: Transactions of the Royal Society of London, series A,
in press.
Olsen, P.E., Kent, D.V., Cornet, B., Witte, W.K., and Schlische, R.W., 1996a, High-resolution
stratigraphy of the Newark rift basin (early Mesozoic, eastern North America): Geological Society of
America Bulletin, v. 108, p. 40-77.
Olsen, P.E., Schlische, R.W., and Fedosh, M.S., 1996b, 580 kyr duration of the Early Jurassic flood
basalt event in eastern North America estimated using Milankovitch cyclostratigraphy, in Morales, M.,
ed., The Continental Jurassic: Museum of Northern Arizona Bulletin 60, p. 11-22.
Reynolds, D.J., 1994, Sedimentary basin evolution: tectonic and climatic interaction: Ph.D. thesis,
New York, Columbia University.
Schlische, R.W., 1991, Half-graben filling models: new constraints on continental extensional basin
development: Basin Research, v. 3, p. 123-141.
Schlische, R.W., 1992, Structural and stratigraphic development of the Newark extensional basin,
eastern North America; Implications for the growth of the basin and its bounding structures:
Geological Society of America Bulletin, v. 104, p. 1246-1263.
Schlische, R.W., 1995, Geometry and origin of fault-related folds in extensional settings: AAPG
Bulletin, v. 79, p. 1661-1678.
Schlische, R.W., 1999, Progress in understanding the structural geology, basin evolution, and tectonic
history of the eastern North American rift system, in LeTourneau, P.M., and Olsen, P.E., eds., Aspects
of Triassic-Jurassic Rift Basin Geoscience: New York, Columbia University Press, in press.
Schlische, R.W., and Anders, M.H., 1996, Stratigraphic effects and tectonic implications of the growth
of normal faults and extensional basins, in Beratan, K.K., ed., Reconstructing the Structural History of
Basin and Range Extension Using Sedimentology and Stratigraphy: GSA Special Paper 303, p. 183203.
Schlische, R.W., and Olsen, P.E., 1990, Quantitative filling model for continental extensional basins
with applications to early Mesozoic rifts of eastern North America: Journal of Geology, v. 98, p. 135155.
Silvestri, S.M., 1994, Facies analysis of Newark basin cores and outcrops: Geological Society of
America Abstracts with Programs, v. 26, p. A-402.
Silvestri, S.M., 1997, Cycle correlation, thickening trends, and facies changes of individual paleolake
highstands across the Newark basin, New Jersey and Pennsylvania: Geological Society of America
Abstracts with Programs, v. 29, p. 80.
3.3.3. Large Igneous Provinces
Millard F. Coffin, Institute for Geophysics. The University of Texas at Austin, 4412
Spicewood Springs Rd., Suite 600, Austin, Texas 78759-8500
Plate tectonic theory has provided a breakthrough in understanding how the continuous
opening and closing of ocean basins reflects convection in the Earthís upper mantle.
Among the terrestrial planets and moons of our solar system, however, global plate
tectonics may well be unique to Earth. Even on Earth, current plate tectonic theory does not
predict major crustal growth events termed large igneous provinces, LIPs (Figure 3.3.3.1).
LIPs are a continuum of voluminous magmatic constructions which include continental
flood basalts and associated intrusive rocks, volcanic passive margins, oceanic plateaus,
submarine ridges, seamount groups, and ocean basin flood basalts. They form in massive
volcanic events that result from a mode of mantle convection different from that driving
plate tectonics on Earth. Furthermore, unlike the magmatism associated with plate tectonics
that creates new crust exclusively in the ocean basins or at ocean margins, LIPs form
independently of plate setting; they form on the continents, in the oceans, and along
margins between the two, and either wholly within plates or at plate boundaries. The
alternative mode of convection manifested by LIPs is probably how other terrestrial planets
and moons lose most, if not all, of their interior heat.
Figure 3.3.3.1: Global LIPs, including oceanic plateaus, volcanic passive margins, continental flood
basalts, submarine ridges, seamount groups, and ocean basin flood basalts. The CAMP is shown in red.
(Modified after Coffin and Eldholm, 1994).
LIPs represent enormous outpourings of predominantly basaltic magma that commonly
cover areas of 105 km2 or more. The largest appear to occur in ocean basins, where giant
plateaus such as the Ontong Java Plateau in the western Pacific and the Kerguelen Plateau
in the Indian Ocean have formed. Similarly, flood basalts were erupted along many
"volcanic passive margins" (e.g., Eastern North America, Greenland, Norway, Brazil,
Namibia, NW Australia) during continental breakup, as well as in continental settings (e.g.,
Columbia Plateau in the Pacific Northwest, Deccan in India, Karoo/Ferrar in South
Africa/Antarctica, Parana in Brazil, Siberian in Asia). Primarily because of ease of access,
continental flood basalts are the best sampled and documented type of LIP. Studies of
continental flood basalts illustrate the evolution in thinking regarding the importance of
such events for Earth evolution. Twenty years ago, when systematic studies of continental
flood basalts began, flood volcanism was largely viewed as produced by continental rifting
- a "standard" plate tectonic interpretation. Improvements in geochronology, however, have
demonstrated that all well-dated continental flood basalt provinces initially thought to have
formed over many tens of millions of years instead formed, for the most part, in a million
years or less. The rapid melt production rates documented by the eruption of huge volumes
of magma in such short time intervals implies a generation mechanism other than rifting,
since passive rifting cannot produce such high melting rates. This realization has led to
other models involving either the melting of a plume of hot, mantle that rises to the surface
from a deep thermal boundary layer, such as that between the core and mantle, or upflow of
deep upper mantle in areas where the plate thickness varies greatly. Neither the initial
phase of activity that produces the LIPs ("plume head") nor the subsequent volcanic
activity that commonly produces trailing volcanic ridges and island chains ("plume tail") in
the ocean basins (Figure 3.3.3.2, below) below are directly related to, or predicted by, the
standard cycle of plate formation, aging, and destruction described by plate tectonic theory.
Figure 3.3.3.2: Model of
Wilsonian periods and MOMO
(mantle
overturn,
major
orogeny) episodes. During
Wilsonian periods (left), the
normal mode of plate tectonics
prevails, with opening and
closing of oceans and mantle
convection with isolated upper
and lower mantle. Plumes
originate predominantly from
the base of the upper layer, and
continental
growth
is
dominated by arc accretion.
During
MOMO
episodes
(right),
accumulated
cold
material descends from the 660knm boundary layer into the
lower mantle, and multiple
major plumes rise from the
core-mantle boundary to form
large igneous provinces (LIPs)
at the surface, thus creating a
major overturn. (After Stein
and Hofmann, 1994)
The magnitude of such igneous events is perhaps best illustrated by oceanic plateaus. The
Ontong Java Plateau in the western Pacific, for example, consists of more than 50 million
km3 of mafic volcanic and plutonic rocks which form a ~30 km thick plateau encompassing
an area equal to one third of Australia. Events of this magnitude are unknown to human
experience, but the consequences are dramatic. For example, 1 million km3 of basalt, the
size of an average continental flood basalt province, would bury the area east of the
Appalachians from Maine to Florida under more than a kilometer of basalt. The release of
gases (CO2, SO2, Cl, F, H2O, etc.) accompanying such great eruptions must have had
tremendous consequences for the composition of the ocean and atmosphere, with dramatic
impact on climate and environment. Indeed, LIP formation correlates temporally with
ecological changes and extinction of life forms. For instance, the eruption of the Siberian
continental flood basalt province 250 million years ago at the Permian-Triassic boundary
coincided with the largest extinction of plants and animals in the geologic record. Ninety
percent of all species became extinct at the boundary. Similarly, eruption of the Central
Atlantic Magmatic Province (CAMP) correlates temporally with the Triassic-Jurassic
boundary mass extinctions. On Iceland, the 1783-84 eruption of Laki provides the only
human record of experience with the type of volcanism that constructs igneous provinces.
Although Laki produced a basaltic lava flow which represents only 1% of the volume of a
typical LIP flow, the eruptionís environmental impact resulted in the deaths of 75% of
Icelandís livestock and 25% of its population from starvation. If such a relatively small
eruption happened today, all air traffic over the North Atlantic would likely be halted for
three to six months.
Observational and modeling efforts to
understand LIP formation and development are
at an early stage and are comparable to
investigations of the mid-ocean ridge system
prior to development of the plate tectonics
paradigm, in that no one theory adequately
explains large-volume basaltic magmatism on
Earth and the other terrestrial planets and
satellites. Understanding the processes in the
Earthís mantle and crust, and the effects of LIPs
on the oceans, atmosphere, and biosphere (Fig.
Figure 3.3.3.3: Temporal correlations among 3.3.3.3), is of particular importance. Because
geomagnetic
the scientific problems associated with LIPs
polarity, crustal production rages, LIPs, sea
range widely, scientists from many disciplines
water Strontium
are involved in their study. These fields include
(Sr), sea level, climate, black shales, and mass
geochronology, marine geophysics, petrology,
extinctions.
geochemistry,
mineral
physics,
rock
(After Coffin and Eldholm 1994), Click on
deformation,
oceanic
and
atmospheric
image for a
chemistry,
physical
volcanology,
more legible figure.
paleomagnetics,
tectonics,
seismology,
geodynamics,
micropaleontology,
paleoclimatology,
paleoceanography,
sedimentology, remote sensing, and planetary
geology.
References:
Coffin, M. F., and Eldholm, O., 1994. Large igneous provinces: crustal structure,
dimensions, and external consequences, Reviews of Geophysics, 32, 1-36.
Stein, M., and Hofmann, A. W., 1994. Mantle plumes and episodic crustal growth, Nature,
372, 63-68.