Summary of part of my PhD research on sedimentary system evolution; published in GSA Bulletin in 2009.

1. Influence
of
millennial-­‐scale
El
Niño
pa4erns
on
sediment
delivery
from
land
to
the
deep
sea
Insights from the Holocene
Santa Monica Basin, CA
Brian Romans
Virginia Tech Geosciences
1
NASA

2. Using Quaternary ‘experiments’ to better understand deep time
• Marine sediment ‘sinks’ (basins that
accumulate sediment at the terminal
source
end of the system) can end up
preserved in the long-term geologic
record
• In deep time (>106 yr), the source of
sediment (eroding uplands) are
inherently not preserved – that mass
is transferred
sink
• Relative to partially preserved ancient
systems, Quaternary sedimentary
systems can be investigated in their
entirety

3. Sedimentary System Analysis at Time Zero
• production and transport of sediment in net-erosional source areas
• transfer of mass to net-depositional sinks (sedimentary basins)
• spatial configuration of sediment routing on full display SOURCE
• emphasis on quantifying rates of erosion, transfer, and storage (101-103 yr)
TRANSFER ZONE / SINK
TERMINAL SINK
Examination of these systems permits robust
investigation of forcings: climatic fluctuation, sea-level
changes, oceanographic conditions, tectonics (activity/
geometry), etc.
diagram from Romans & Graham (in prep)

4. Sedimentary System Analysis in Deep Time
As We Scroll Back Through Geologic Time …
• source area modified; removed completely as mass is transferred
• sinks in transfer zone might be preserved in long-lived systems; terminal sinks
only segment remaining (if anything) when tectonic regime changes
• temporal resolution diminishes (degree of time-averaging increases)
• direct to inferential
Chronostratigraphic (Paleogeographic) Surface
diagram from Romans & Graham (in prep)

5. Sedimentary System Analysis in Deep Time
As We Scroll Back Through Geologic Time …
• source area modified; removed completely as mass is transferred
• sinks in transfer zone might be preserved in long-lived systems; terminal sinks
only segment remaining (if anything) when tectonic regime changes
• temporal resolution diminishes (degree of time-averaging increases)
• direct to inferential
Chronostratigraphic (Paleogeographic) Surface
In some cases, this is all that is left of an ancient S2S system
diagram from Romans & Graham (in prep)

6. I’m a geologist … I want to know what controls these patterns
Thin- and medium-bedded turbidites interbedded with siltstone, Paleocene
German Rancho Fm., northern California coast (photo taken by Brian
Romans)

7. I’m a geologist … I want to know what controls these patterns
Controls on stratigraphic patterns are
divided into two general categories:
Allogenic
Autogenic
Meter-scale turbidite beds in the Upper Cretaceous
Tres Pasos Formation, southern Chile (photo taken
by Brian Romans)

8. I’m a geologist … I want to know what controls these patterns
Controls on stratigraphic patterns are
divided into two general categories:
Allogenic
Forcings external to the
sedimentary system (e.g., sea
level, tectonic movement, climate)
Autogenic
Processes and dynamics internal to the
sedimentary system (e.g., channel/lobe
avulsion, bar growth, progradation)
Meter-scale turbidite beds in the Upper Cretaceous Tres
Pasos Formation, southern Chile

9. I’m a geologist … I want to know what controls these patterns
Controls on stratigraphic patterns are
divided into two general categories:
Allogenic vs. Autogenic?
One way to approach this
problem is to carefully
investigate ‘modern’ systems
where the controls are much
better constrained
Meter-scale turbidite beds in the Upper Cretaceous Tres
Pasos Formation, southern Chile

10. Why study sediment-routing systems in the California Borderland?
§ basins are small à data
coverage of an individual
system is good
§ relatively sand-rich
submarine fan systems
adjacent to nearby and
uplifting sediment sources
§ External forcings such as
climatic fluctuations, sea
level, and tectonism is well
constrained
NOAA

11. Why study sediment-routing systems in the California Borderland?
§ basins are small à data
coverage of an individual
system is good
§ relatively sand-rich
submarine fan systems
adjacent to nearby and
uplifting sediment sources
§ External forcings such as
climatic fluctuations, sea
level, and tectonism is well
constrained
NOAA

12. Sediment Transfer Across Continental Margins
Santa Barbara
Ventura
Los
Angeles
basemap made with GeoMapApp; annotations by authors

13. California Borderland Sediment-Dispersal System
source
sink
sink
basemap made with GeoMapApp; annotations by authors

14. California Borderland Sediment-Dispersal System
source
source source
sink sink
sink
source
sink
sink
sink
basemap made with GeoMapApp; annotations by authors

15. California Borderland Sediment-Dispersal System
source
source source
source
source
basemap made with GeoMapApp; annotations by authors

16. California Borderland Sediment-Dispersal System
source
source source
sink
sink sink
source
source
sink
sink
sink
sink
basemap made with GeoMapApp; annotations by authors

17. California Borderland Sediment-Dispersal System
source
source source
sink
sink sink
source
source
sink
sink
sink
sink
basemap made with GeoMapApp; annotations by authors

18. California Borderland Sediment-Dispersal System
A single watershed feeds
multiple sinks and one sink
receives material from multiple
watersheds
basemap made with GeoMapApp; annotations by authors

19. California Borderland Sediment-Dispersal System
The Santa Barbara littoral cell
moves coarse-grained sediment
laterally across the margin
basemap made with GeoMapApp; annotations by authors

20. Routing of Coarse-Grained Sediment (sand + gravel)
Santa
Clara Calleguas
River Creek
Hueneme
Canyon

21. California Borderland Sediment-Dispersal System
Vast majority of post-Last
Glacial Maximum sand
delivered to coast ends up
in Santa Monica Basin
basemap made with GeoMapApp; annotations by authors

22. Santa Monica Basin and Hueneme submarine fan
Hueneme canyon and fan is
dominant feature since post-
glacial transgression
SMB is a closed basin - no bypass
to other Borderland basins
fan divisions from Normark et al. (1998)

23. Santa Monica Basin and Hueneme submarine fan
fan divisions from Normark et al. (1998)

24. ODP Site 1015 – radiocarbon-dated core
0
2 • Interval of interest is from sea floor to
~12 m deep; interbedded sandy
turbidites and mud deposition
4
6
8
10
12
Romans et al. (2009); GSA Bulletin

25. ODP Site 1015 – radiocarbon-dated core
0
2 • Interval of interest is from sea floor to
~12 m deep; interbedded sandy
turbidites and mud deposition
4
• Eleven radiocarbon dates going back
6
to ~7,000 years ago
8
10
12
Romans et al. (2009); GSA Bulletin

26. ODP Site 1015 – radiocarbon-dated core
0
5
2 • Interval of interest is from sea floor to
~12 m deep; interbedded sandy
4 turbidites and mud deposition
4
• Eleven radiocarbon dates going back
3
6
to ~7,000 years ago
• Tied to seismic-reflection data à five
8 2 stratigraphic intervals mapped
10
1
12
Romans et al. (2009); GSA Bulletin

27. Mapping basinal sediment distribution
Romans et al. (2009); GSA Bulletin

28. Mapping basinal sediment distribution
area of sediment
volume calculations
Romans et al. (2009); GSA Bulletin

29. Volumes and rates of basinal sedimentation
Over the past 7,000 years, the average sediment accumulation rate in
Santa Monica Basin = 3.74 million tons/year
Romans et al. (2009); GSA Bulletin

30. Historical Santa Clara River sediment flux
Measured sediment flux at
modern river mouth averages
3.10 million tons/year
Warrick & Farnsworth (2009)
30

31. Historical Santa Clara River sediment flux
Measured sediment flux at
modern river mouth averages So, that’s an average
3.10 million tons/year over several millennia
Warrick & Farnsworth (2009)
…what about the
variability of flux at
shorter time scales?
31

32. Using the basin plain record to assess variability in flux
5
Changes in thicknesses among the five
stratigraphic intervals measured in the
basin plain are proportional to changes
4 among their volumes
3
2
1
Romans et al. (2009); GSA Bulletin

33. Using the basin plain record to assess variability in flux
5
Changes in thicknesses among the five
stratigraphic intervals measured in the
basin plain are proportional to changes
4 among their volumes
3
In this case, the basin plain is an
adequate representation of
2 sedimentation in Santa Monica Basin
as a whole for this time period.
1
Romans et al. (2009); GSA Bulletin

34. Timing and magnitude of turbidity-current events
Romans et al. (2009); GSA Bulletin

35. Timing and magnitude of turbidity-current events
What’s controlling the observed increase in
sand delivery to the basin plain?
Romans et al. (2009); GSA Bulletin

36. Climate influence on sediment delivery to the deep sea
Moy et al. (2002)
Romans et al. (2009); GSA Bulletin

37. Climate influence on sediment delivery to the deep sea
Moy et al. (2002)
Barron et al. (2003)
Romans et al. (2009); GSA Bulletin

38. Climate influence on sediment delivery to the deep sea
Moy et al. (2002)
Warrick & Farnsworth (2009)
Barron et al. (2003)
Romans et al. (2009); GSA Bulletin

39. Relationship to Holocene seismicity
Dolan et al. (2007)
paleoseismologic compilation
shows increased seismic activity
of LA region faults ~1-3 ka
Romans et al. (2009); GSA Bulletin

40. Relationship to record in adjacent Santa Barbara Basin
Santa Clara
River
Santa Barbara
Basin
Santa
Monica
Basin
event beds in ODP 893
(interpreted to be result of
Santa Clara River floods)
Rack & Merrill (1995)
Romans et al. (2009); GSA Bulletin

41. Relationship to record in adjacent Santa Barbara Basin
Santa Clara
River
Santa Barbara
Basin
Santa
Monica
Basin
event beds in ODP 893
(interpreted to be result of
Santa Clara River floods)
Rack & Merrill (1995)
history of beach accretion
and erosion along Santa
Barbara coast
Masters (2006)
Sand eroded from Santa Barbara beaches very likely made its
way into Santa Monica Basin via turbidity currents
Romans et al. (2009); GSA Bulletin

42. Linking River History to Changes in Basinal Deposition
avulsion of river
mouth ~2-3 ka
Hitchcock et al., 2000
How does the change from direct feed (river mouth
directly into canyon head) to indirect feed (littoral cell to head of Hueneme
canyon head) impact basinal sedimentation? submarine canyon

43. Shift in river recorded in basin plain stratigraphy?
littoral cell
input
direct river
input
Romans et al. (2009); GSA Bulletin

44. Interacting controls on delivery
of sediment to the basin
• The timing and distribution of large
turbidity currents are investigated.
Romans et al. (2009); GSA Bulletin

45. Interacting controls on delivery
of sediment to the basin
• The timing and distribution of large
turbidity currents are investigated.
• Increase in magnitude and frequency
of ENSO cycles à increased
sediment flux to deep sea.
Romans et al. (2009); GSA Bulletin

46. Interacting controls on delivery
of sediment to the basin
• The timing and distribution of large
turbidity currents are investigated.
• Increase in magnitude and frequency
of ENSO cycles à increased
sediment flux to deep sea.
• Shift in sediment routing from direct
river-input to indirect littoral-input.
Romans et al. (2009); GSA Bulletin

47. Interacting controls on delivery
of sediment to the basin
• The timing and distribution of large
turbidity currents are investigated.
• Increase in magnitude and frequency
of ENSO cycles à increased
sediment flux to deep sea.
• Shift in sediment routing from direct
river-input to indirect littoral-input.
• Increased earthquake activity may
have been important trigger for large
turbidity currents.
Romans et al. (2009); GSA Bulletin

48. Using Quaternary ‘experiments’ to better understand deep time
• From a geological perspective,
Quaternary sedimentary system
analysis allows us to test our conceptual
models of how basins fill with sediment source
• These models inform/constrain
numerical models of system evolution
that are important for:
• predicting how sedimentary systems will
respond to environmental change
• understanding transfer of other sink
materials from land to sea (pollutants,
terrestrial carbon, etc.)
• predicting distribution/heterogeneity of
subsurface fluid reservoirs (hydrocarbon
extraction, CO2 injection, etc.)

49. More details about this study
The research summarized in this talk
was published in the journal Geological
Society of America Bulletin in 2009
Link:
http://gsabulletin.gsapubs.org/
content/121/9-10/1394.abstract
PDF:
https://sites.google.com/site/
romansbrian/2009Romansetal-
SantaMonicaBasinHoloceneflux.p
df?attredirects=0