The MARGINS Program “To understand the complex interplay of processes that govern the evolution of continental margins”

Rupturing Continental Lithosphere (RCL) The driving forces for rift initiation, propagation and evolution Deformation variation in time & space Physical and chemical evolution of crust and mantle as rifting proceeds to spreading The role of magmatism and fluids in continental extension Gulf of Calif. / Salton Trough

Seismogenic Zone (SEIZE) Controls on seismic energy release during earthquake The temporal relationships among stress, strain, pore fluid pressure thru seismic cycle Controls on locked, unlocked regions on subduction interface; energy release during earthquake Propagation and slip rates of earthquakes and distribution of fast, slow, tsunamigenic earthquakes Nankai Costa Rica

Subduction Factory (SF) How do subduction parameters act as forcing functions, regulate production of magma and fluid from the Subduction Factory? How does the volatile cycle (H 2 O and CO 2 ) impact chemical, physical and biological processes from trench to deep mantle? What are the energy, mass and chemical balances across the Subduction Factory, and how do they affect continental growth and evolution? Central America Izu-Bonin- Mariana

"The Ties that Bind Source to Sink, within and between New Guinea and New Zealand"

NSF MARGINS Source-to-Sink Program Fly River, Papua New Guinea Waipaoa River, New Zealand Two dynamic systems Contrasting characteristics More mechanistic insight from comparison

Courtesy of Steve Kuehl Waipaoa Basin

COMPARISON OF DISPERSAL SYSTEMS FlyWaipaoa Settingwet tropicaltemperate Sediment Dischargelarge (10 8 t/y)moderate (10 7 t/y) Manipulationsmall (+30% t/y)large (+300%? t/y) Fluvial settinglowland floodplainno lowland floodplain (long tidal reach) Discharge timingunrelated to oceancorrelated to ocean Gravity flowssaltwateralso freshwater (fluid mud)(hyperpycnal) Shelf sedimentationclinoform progradebasin infill Offshelf loss~5%>20% Offshelf sedsmostly CaCO 3 mostly siliciclastic

Courtesy of Steve Kuehl Waipaoa Basin – hillslope erosion after major rain storm

Basin size 2205 km 2 Precipitation 1000 – 2500 mm/yr Sediment discharge 15 Mt/yr Waipaoa River Courtesy of Steve Kuehl

Waipaoa mouth discharging sediment to shelf

10 cm Waipaoa shelf X-radiograph of core Showing multiple flood deposits Courtesy of Steve Kuehl

Basin infill on Waipaoa shelf (modified after Foster & Carter, 1997)

Submarine canyons and fans on Waipaoa slope and rise Courtesy of Clark Alexander

Dispersal pathways on Waipaoa slope and rise Courtesy of Clark Alexander

Fly Strickland Basin size 75,000 km 2 Precipitation 1000–10,000 mm/yr Sediment discharge 115 Mt/yr Courtesy of Bill Dietrich

THREE MECHANISMS FOR ACCUMULATING FLUVIAL SEDIMENT Growth of river bank - e.g., point bars, scroll plains Overbank flow - during flood seasons, including flow through crevasses Flow through tie channels – associated with oxbows

High flow in the swamp grass reach: tie channels pour into lakes

Bia Lagoon Tie channel Low flow in swamp grass reach: tie channels drain lakes

Calculating accumulation rates Strickland – Pb and Ag Fly – Cu Courtesy of Bill Dietrich

Strickland – mean 1-3 cm/yretention ~10% Fly – mean 6-9 cm/yretention ~40% Courtesy of Bill Dietrich

10 m contour interval topographic map from NASA Shuttle Radar Topographic Mission Data (SRTM data). Hypothesis: due to the much higher sediment load on the Strickland, the floodplain is more evolved in response to sea level rise and less sediment is lost to its floodplain than the Fly. Strickland River Fly River Courtesy of Bill Dietrich

Strickland ~70 x 10 6 tons/y, and steeper gradient Fly ~10 x 10 6 tons/y Courtesy of Bill Dietrich

4 Fly River Alluvial Valley (Strickland tributary) Courtesy of Bill Dietrich

Lateral migration causes about 24 Million tons of sediment to be eroded from and added to the floodplain per year This suggests that lateral exchange for Strickland exceeds overbank deposition (by about 3 times). Courtesy of Bill Dietrich

Strickland versus Fly Summary (Dietrich et al.) Strickland: Receives more sediment Filled floodplains more rapidly Remobilizes floodplain sediment more effectively Has a lower net retention Strickland 10% Fly 40%

Fly River Tidal River – The Missing Link Courtesy of Bill Dietrich

Rapid fluctuations of uplands discharge are attenuated downstream due to channel and floodplain such that El Nino drought causes the largest signal variation to the delta

AA’ Fly River Clinoform

Shear Stress on seabed Courtesy of Andrea Ogston

Fluid muds can occur – spring tides of trade-wind season Thickest, greatest SSC during flooding tides

Flood tide impedes fluid muds from flowing seaward Ebb tide enhances fluid-mud flows

Clinoform accumulates ~40% of fluvial sediment discharge

Higher concentration of data points documents heterogeneity in clinoform sedimentation Greatest accumulation rates along foreset

Kiwai Valley now a partially filled valley on the continental shelf Path of ancestral Fly River

Courtesy of Bill Dietrich

From Liu et al. (2003)

Ancient delta? Ancient tidal river?

19.7 mm/y Accumulation near head of Kiwai Valley

Infilled shelf valleys (along-shelf view) 400 m Courtesy of Slingerland and Driscoll accumulation rates are greater in central Gulf of Papua

Modern Sedimentation over old clinoform (across-shelf view) 400 m Courtesy of Slingerland and Driscoll

Mixed sediment input to Gulf of Papua slope and rise Courtesy of Andre Droxler

MV MC MV MC Courtesy of Sam Bentley Some sediment escapes to slope in eastern GOP

63JPC Hemipelagic 66JPC Turbidites Courtesy of Larry Peterson Mixed sedimentation on Gulf of Papua slope and rise

de Garidel-Thoron et al, 2004 Courtesy of Larry Peterson

Final Comments Source-to-sink approach is providing new insights Should be extended to other margin systems, e.g.: glacial-marine, carbonate Future Insights Papuan Continuum – JGR special issue in March Waipaoa studies – Marine Geology special issue