uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
uAbstract
u Types of data
uKey questions
uSand delivery
uFigures 2-5
uText
uShelf-transit time
uFigures 6-8
uText
uProcess change
uFigures 9-15
uText
uSea-level change
uShelf-edge deltas
uFigures 17-24
uText
u Tracts
/ trajectory
uFigures 25-27
uText
uReferences
|
Types of Data
Figure
1. Examples of the three types of data utilized in this study:
seismic data (upper left--seismic line courtesy
Statoil), large outcrops (middle right), and well transects (lower left,
well data courtesy A2D/Devon Energy).
This study of shelf –transiting shoreline
systems and generation of stratigraphic sequences in shelf-break basins,
as opposed to ramp basins, has utilized seismic data, large outcrops,
and well transects (Figure 1).
1. How are shelves constructed and how easily
can shorelines reach the shelf edge?
2. What is the significance of shelf-transit
time for the generation of sequences?
3. Are there changes in shoreline ‘type’
during the transit?
4. Is amplitude of fall/rise of sea level
important?
5. Is the presence of deltas at the shelf
edge a guarantee for deepwater sands?
How is sand delivered to the shelf edge and beyond?
Figures 2-5
Return to top.
-Sand to the
Shelf Edge
-
Waves, tides and
currents can bring sand to shelf edge (Figure 2A and
2B), but
difficulty increases with width of shelf.
-
Deltas are probably
the most efficient mechanism (Figure 2C).
-‘Shelf’
successions are built from repeated shelf transits by shorelines (Figure
3).
-In shelf
construction, controls on shelf-transit time and deltas attaining shelf
edge (Figure 4) are:
-Auto-retreat tends to prevent deltas from
reaching the shelf edge. Shoreline regression can turn to transgression
without any change in rate of sediment supply or sea-level rise (Figure
5).
 |
Figure 6. Transit times for deltas to
reach shelf edge (after Burgess and Hovius, 1998; Muto and
Steel, 2002). |
 |
Figure 7. A. Cross-section, Columbus
basin: 4th order sequence between maximum flooding
surfaces below and above sand-rich interval defined by a basal
unconformity (58) (from Sydow et al., 2003, with kind permission
of GCSSEPM Foundation, Norman C. Rosen, Executive Director).
Interval demonstrates growth across faults, with the largest at
or near the shelf edge.
B. Seismic Line A, East Venezuela shelf / Columbus basin
(location in Figure 8):
shelf-edge trajectory of the SEG
reservoir interval shows lateral (progradation) and vertical
(aggradation) components (from Sydow et al., 2003,
with kind permission of GCSSEPM Foundation, Norman C. Rosen,
Executive Director). |
 |
Figure 8. A. Composite log of SEA area records repeated
transgressive-regressive shelf transits on the East Venezuela
shelf (from Sydow et al., 2003, with kind permission of GCSSEPM
Foundation, Norman C. Rosen, Executive Director). B. Index map,
also illustrating eastward advancement of shelf edge (from Sydow
et al., 2003, with kind permission of GCSSEPM Foundation, Norman
C. Rosen, Executive Director). |
Regressive
transit of shelf is necessary for delivery system to reach shelf edge.
Auto-retreat
prevents many deltas from attaining a shelf-edge location, when seal
level (SL) is rising.
For stable or
falling relative sea level, even for wide shelves, transit time rarely
exceeds 100,000 years.
Orinoco
transiting the east Venezuela shelf (Figures 7 and
8)
Is There
Process Change during the Regressive-Transgressive
Transit?
(Figures 9,
10,
11, 12,
13, 14, and
15)
 |
Figure 9. A.
Schematic cross-section illustrating the relation of the various
systems tracts to shelf edges and to changes of relative sea
level. B-D. Influence of dominant shoreline process (tide,
river, wave) on shoreline configuration. B. Irrawaddy delta
(Myanmar [Burma]). C. Yellow River delta, D. Niger delta. |
 |
Figure 10.
Schematic sections illustrating changes in influence of
processes with changes in relative sea level: A. Open shelf
setting. B. Ramp setting in shallow basin). |
 |
Figure 11.
Process change on shorelines with sea-level change (and within a
sea-level cycle): examples of tidal influence and variation of
it with time, change of relative sea level, and systems tract. |
 |
Figure 12.
Hogsnyta, Spitsbergen, characterized by shelf-edge
river-dominated delta during lowstand and shelf-edge
wave-dominated deltas at highstand. |
 |
Figure 13. At
Storvola, Spitsbergen, flat trajectory angle with different
shoreline type than where the trajectory angle is rising. |
 |
Figure 14. Seismic line (courtesy
Statoil), showing expression of deltaic deposits during falling
base level and during rising base level. Inset: Delta position
and type on shelf in relation to sea level (F=fluvial-dominated;
W=wave-dominated; T=tide-dominated). |
 |
Figure 15. Sketch of important outcrop localities (Pallfjellet,
Brogniartfjellet, Storvola, and Hyrenstabben) in Spitsbergen
where the lower Eocene section shows relationships between
shelf-edge trajectory and facies changes (after Steel and Olsen,
2002, with kind permission of GCSSEPM Foundation, Norman C.
Rosen, Executive Director). |
Return to top.
-Shelf transit
and shoreline type (Figure 10)
A. Open shelf
setting
B. Ramp setting
in shallow basin
-Process change
on shorelines with sea-level change (Figure 11)
-Ancient example
of change in delta regime with RS (Figure 12)
-Shoreline
trajectory angle (reflecting sea-level behavior) affects shoreline type
(Figure 13).
-Delta type
varies with relative sea-level change (Figure 14).
-Spitsbergen
database (of lower Eocene facies) has provided ideas on relationships
between trajectory and facies changes (Figure 15)
Figure
16. Sediment distribution under two conditions of sea level change. A.
With small changes in sea level due to limited glaciation. B. widespread
glaciation with high amplitude in sea level changes. (From Galloway,
2001.)
-It is becoming accepted that Icehouse
amplitudes (>100m) are greater than Greenhouse ones (few 10s of m).
-It has been
suggested that Icehouse shelf transits would, therefore, partition more
of the sediment budget directly into deepwater areas.
-Greenhouse
transits would allow more redistribution of the budget along the shelf,
preserving more strandplain successions.
Galloway (2001)
has shown contrasting sediment patterns under limited glaciation and
associated sea-level change, as opposed to high-amplitude
“glacioeustasy” (Figure 16).
Is the Presence of
Deltas at the Shelf Edge a
Guarantee for Deepwater Sands?
 |
Figure 17. A. Delta barely reaching
shelf edge. B. Incision during sea level fall. C. Shelf-edge
progradation during rise. D. Shelf-margin wedge without
incision. |
 |
Figure 18. Stratigraphic cross-section
of regressive facies, transgressive and tidal facies, and
sequence stratigraphic surfaces from Spitsbergen outcrop area
(from Schellpeper and Steel, 2001; Steel et al., 2003, with kind
permission of GCSSEPM Foundation, Norman C. Rosen, Executive
Director). Inset same as
Figure 17. |
 |
Figure 19. Stratigraphic cross-section,
Brogniartfjellet, Spitsbergen, showing architecture of incised
shelf-edge to slope-canyon clinoforms: facies associations (from
Mellere et al., 2003, with kind permission of GCSSEPM
Foundation, Norman C. Rosen, Executive Director). Inset same as
Figure 17.
|
 |
Figure 20. Delta-front sands below
fluvial channelized sand on outcrop.
|
 |
Figure 21.
Montage of sedimentary structures on outcrop, representing
deposits from hyperpycnal flows, and stratigraphic cross section
from Spitsbergen outcrop area with interpretation of processes,
and upslope from channelized hyperpycnal flows, thin-bedded
turbidites and initial lowstand wedge (courtesy Andy Petter,
University of Texas). |
 |
Figure 22. Outcrop at Storvola and
Hyrnestabben, Spitsbergen, illustrates delivery of sands from
deltas (D) through slope (BS) to basin-floor fans (BFF). |
 |
Figure 23. Shelf edges on seismic line
(courtesy Statoil) and on outcrop at Storvola (inset, which is
same as outcrop illustration in
Figure 1). |
 |
Figure 24. Late prograding wedge is
formed by shelf-edge delta during late lowstand. |
Return to top.
-Shelf-edge delta
types (Figure 17)
-Shelf-edge delta
without much sand by-pass into deep water (Figure 18)
-Deep fluvial
erosion of the delta is necessary to produce significant sand by-pass
(Figures 19, 20, and
22).
-Type B deltas
deliver sands through slope to basin-floor fans (Figure 22).
-How is the
incised shelf edge setting recognized (Figure 23)?
-Shelf-edge
deltas are established for a second time in late lowstand (Figure 24).
Process Changes, Systems Tracts ,
Shelf Trajectory, and Reservoir
Prediction
-Shelf
Trajectories (Figure 25)
Generally strong
tide influence
General fluvial
dominance, but clear wave and tide influence
General wave
domination
-Models clothed
with process information will aid greatly in reservoir prediction
(Figures 26 and 27).
Fluvial-wave-tide interaction with increasing fluvial influence to shelf
edge
Apparent fluvial
domination, with great slope disruption
Fluvial-dominant
in deeper reaches; wave influence in shallow reaches
Flood-dominant
tidal currents in channels of shelf-edge estuaries
Dalrymple, R.W., B.A. Zaitlin, and R. Boyd, 1992, Estuarine facies
models: Conceptual basis and stratigraphic implications: Perspective:
Journal Sedimentary Petrology, V. 62, p. 1130-1146.
Galloway, W.E., 2001, Cenozoic evolution of sediment accumulation in
deltaic and shore-zone depositional systems , Northern Gulf of Mexico
Basin: Marine and Petroleum Geology, v. 18, p. 1031-1040.
Martinsen, Randi S., 2001, Wave
dominated versus current dominated shorelines in the Cretaceous Western
Interior Seaway (abstract): AAPG Bulletin, v. 85, no. 13. (Supplement).
Return to top.
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