The passage of sediment from mountain source to ocean...

The passage of sediment from mountain source to ocean sink:

Results from the MARGINS S2S Waipaoa Sedimentary System, Hikurangi Margin

Alan Orpin & Source-to-Sink WSS Team

Photo: James Syvitski

Source-to-sink: a God’s-eye view

Canyon’s bypass slope

Intraslope sources

Closely-coupled catchment and

deep ocean sink e.g. Sepik, Var

Weak tectonic Dominant glacio-eustatic

Strong tectonic Weaker glacio-eustatic

Weakly-coupled catchment and deep ocean sink, shelf capture e.g. Amazon

Peak discharge

10x

Peak discharge 100-1000x

Submarine fans

Slope gradient and length

(Figure modified after Sømme et al., 2009)

Slopeward transfer driven by prograding clinoforms

4

Anthony the Anthropocene

Waipaoa, Waiapu

Waipaoa River mouth. Photo: James Syvitski

“… develop a quantitative understanding of margin dispersal systems and associated stratigraphy, so that we can predict their response to perturbations, such as climatic and tectonic variability, relative sea-level change, and land-use practices”. (Excerpt from MARGINS Source to Sink

Executive Summary)

►  Emphasis on quantification of processes and linkages ►  Terrestrial and marine

►  Limited to the last-glacial cycle, but emphasis on

Holocene and Anthropocene records

(Image courtesy Josh Mountjoy)

Taupo Volcanic Zone

NE rain

Poverty Bay study area

Southern Ocean swell

Why the Waipaoa?

Waipaoa because… 1. Dramatic landscape responses to drivers

2003

1958 1939 (Aerial photos C/- Landcare Research)

2008

(Photo Phaedra Upton, GNS Science)

Dramatic changes in catchment behaviour: millennial scale

Berryman et al. (2010) ► Up to 50% of the post-glacial

downcutting achieved between 10-8 ka ► Rapid upstream migration (~2 km/ka) of

several major knickpoints Upton et al. (2013) ► LGM conditions more erosive compared

to Holocene

(Figure modified after Berryman et al., 2010)

Waihuka tributary of upper Waipaoa

Strong climate and environmental signals: event scale (10-2 to 102 y)

Lake Tutira catchment Post-cyclone Bola, 1988 (photos courtesy of Noel Trustrum)

1988 (Cyclone Bola)

1985

1977

1960

1973

1938

LTF9 –frozen box core (after Page et al., 1994)

►  Gomez et al. (2011, 2013) - global climate teleconnections.

►  Orpin et al. (2010) - intra-lake deposits and non-climate triggers.

Event strata (10-3 y timescales)

Low density, fine-grained upper surface

Low density mottled, weakly bioturbated?

Laminae, hummocky cross-stratification

0 cm

5 cm

10 cm 40

30

20

10

0

Dep

th c

m

(X-radiograph courtesy Rose & Kuehl, 2010)

Bola-style event (Lila Rose Pierce & Steve Kuehl, PhD thesis)

Cyclone Bola event, shelf core

July 2010 storm, shelf core

Oceanographic tripods

36 m

55 m

48 m

Figure after Richard Hale et al. (submitted, Special Issue of CSR) Oceanographic data courtesy of UW

1 in 8 yr flood

Depositional events ~10 cm deposit

Erosion?

Coherence of event drivers: an annual view

(Image courtesy Josh Mountjoy)

MD063003 MD063002

MD063008 MD063009

TAN0810-9

TAN0810-5 TAN0810-2

TAN0810-3

Cores show loss of terrestrial event fidelity in deepest ocean, BUT a turbidite record

►  Cascadia Margin template (see Goldfinger et al., 2007)

►  Cores cross-correlated

► Demanding of sophisticated

age-models

► Synchronicity of events

►  73 synchrononous turbidites

► 5-fold reduction in slope

sedimentation since LGM

► Hyperpycnites and debris flows rare

►  Earthquakes most plausible trigger

► Poverty re-entrants return times c.

150-400 yrs

►  Subduction interface earthquakes c.

800 yrs

Characterising Hikurangi Margin turbidites since the LGM

Pouderoux et al. (2012a, b)

After Hugo Pouderoux et al. (2012a, b) - Marine Geology and Natural Hazards and Earth System Science.

(Figures modified after Gomez et al., 2007; 2013; and in prep)

Cores allow inter-basin millennial-scale correlation through system

Shelf Lower floodplain

Upper floodplain

►  Cycle of perturbations and landscape recovery

►  Importance of landscape pre-conditioning

► Instantaneous and century-length scales for

“events”

►  Human activity has had most profound impact on

late Holocene sedimentation

Catastrophic floods

>M7 earthquakes

Landscape recovery post-Taupo

Closure of shelf sediment budgets (pre-human)

Post-glacial basin geometry

Holocene accumulation

rates

(Figures after Gerber et al., 2010)

Last-century budgets and deposition on Poverty shelf

►  Supply climate driven (floods) ►  Big sediment signals ►  At 102 yr timescales, perhaps only 25-50%

stratigraphically complete (Sommerfield, 2006)

Century-scale Century-scale

“Goldilocks Zone Sausage” of strata preservation

Mid-slope basin

Trough

Basin capture and transfer across the Poverty margin

Mid-shelf basin

Lower-slope basin

Near complete shelf capture (pre-human)

Capture & loss

MSC seismic profile

Active uplift

Active uplift

Imbricate thrust faults

Deformation front

avalanche debris Quaternary

shelf fill

Quaternary basin fill

3 km

2 km

1 km

Holocene riverine supply

Small %

Holocene budget: Gerber et al., 2010; Alexander et al., 2010; Orpin et al., 2006. Slope structure: Pedley et al., 2010.

Waipaoa 66%, 15%?

Waiapu 77%

Inflection point around 100 km shelf width

Off-shelf sedimentation dominates <20 km

Have anthropogenic impacts overwhelmed margin morphology as the dominant control on off-shelf sediment transfer?

Influence of shelf width and supply on off-shelf dispersal: have we tipped the scales?

91% Var

(Figures modified after Walsh & Nittrouer, 2003)

(Figure from Paquet et al., 2009)

Tectonic-sediment interactions over 150 ka timescales, upper Hikurangi Margin

Depocentre location controlled by:

► Eustacy <20-30 kyr timescales

► Tectonic deformation >100 kyr timescales

From mountain source to ocean sink: Waipaoa Sedimentary System

Supply Move + store capture + move capture + move

► Interconnectedness of source and sink, lithological coherence ► Ephemeral preservation of events, both marine and terrestrial

► Inter-basin fidelity at 101+ y timescales

► Utility of budgets: rates, tectonic-sediment interactions, and unknowns

► Marine paleoearthquake record

Figure from “Mountain source to ocean sink”, Special Issue of Marine Geology vol. 270, 2010