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El Niño Patterns and Sediment Flux to the Deep Sea

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

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

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  • 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 1NASA
  • 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 TimeAs 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) Surfacediagram from Romans & Graham (in prep)
  • 5. Sedimentary System Analysis in Deep TimeAs 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 systemdiagram 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 kaRomans 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 currentsRomans 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 deliveryof sediment to the basin •  The timing and distribution of large turbidity currents are investigated. Romans et al. (2009); GSA Bulletin
  • 45. Interacting controls on deliveryof 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 deliveryof 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 deliveryof 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 studyThe research summarized in this talkwas published in the journal GeologicalSociety 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