Paha

u

Kawek

aPa

hauKaw

eka

C) N

100 km

Previously published literature indicates apaleo-flow that runs parallel along the ECB, but whether flow direction was Northward or Southward is still debated.

Young zircon grains deposited onlyin the Northern Raukumara sub-basinfrom Middle Miocene to Early Plioceneindicate that flow direction may have limited dispersal of young volcanic sediment to the Southern Wairarapa sub-basin.

Paha

u

Kawek

aPa

hau

Kawek

a

N

100 km

A & B)

A & B both inhibited volcanic sediment flow to the Wairarapa sub-basin.

Kawek

a

Paha

u

N

100 km

We conclude that contribution of Pahau terrane sedimentto both sub-basins 23- 3.6 Ma indicate that the Pahau basement terrane was above sea level by at least Early Miocene.

Kawek

aPa

hau

B) N

100 km

B. There were reverse thrust fault barriers between the sub-basins that blocked sediment dispersal from the Raukumara to Wairarapa sub-basin.

Depositional Age

Rela

tive

Prob

abili

ties

Detrital Zircon Age (Ma)

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

Probability Density Plots (PDPs)

Early Pliocene(~5-3.6 Ma)

Late Miocene(~12-5 Ma)

Middle Miocene

(~16-12 Ma)

Early Miocene(~23-16 Ma)

42 mm/yr

48 mm/yr

Hikurangi Tre

nch

A)1(a)

Taupo Volcanic Zone

Axial Ranges

ForearcBasin

(km) 100 km

Subduction

Young grains Old grains b

C)

a

1(c)

Taranaki

WairarapaRegion

RaukumaraRegion

HIK

URA

NG

I TRE

NCH

A)

Taupo

Kaweka

basement

terra

ne

Pahau basement terrane

b

a

1(b)

Figure 1- Present-day NewZealand (NZ). a) Geographic location and key for map. b) North Island of NZ; Yellow region is East Coast Basin (ECB). c) Cross-section, from a to b, of figure 1(b) map. Adapted from maps and cross-section made by N. Nieminski.

Subduction Wedge

Pacific plate

Indo- Australianplate

Detrital Zircon Provenance of Neogene Forearc Sub-basin Sandstone: East Coast Basin of New Zealand TEXASTHE UNIVERSITY OF

AT AUSTINWHAT STARTS HERE CHANGES THE WORLD

Laura N. Dafov1, Nora M. Nieminski2, Lauren E. Shumaker2, Stephan A. Graham21

The University of Texas at Austin, Jackson School of Geosciences, Austin, TX, 78712, US 2

Stanford University, School of Earth, Energy, & Environmental Sciences, Stanford, California, 94305, US

Interpretations

Acknowledgements

Results

Geologic Setting and Background

Introduction and Purpose

Southern sub-basin Northern sub-basin

Probability Density Plots (PDPs)

Rela

tive

Prob

abili

ties

Detrital Zircon Age (Ma)

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

0

1

0 200 400 600 800

Depositional Age

Early Pliocene(~5-3.6 Ma)

Late Miocene(~12-5 Ma)

Middle Miocene

(~16-12 Ma)

Early Miocene(~23-16 Ma)

The East Coast Basin (ECB) of the North Island, New Zealand, is an active forearc basin that features sub-basins segregated by low-angle reverse faults. The purpose of studying the ECB:1) Understand the spatial and temporal contribution of sediment from distinct source terranes to Neogene deep-water deposits in the ECB may constrain the degree of basin segregation during evolution of the modern tectonic regime, permit delineation of active source areas, and constrain source-to-sink boundaries between terrestrial and marine deposition. 2) Elucidate the far-field effects of west-directed subduction along the Pacific-Australian plate boundary and onset of slip on the plate-bounding transgressional Alpine Fault.3) Study the dynamics of basin-fill and how sediment is transported to deep-water sub-basins (i.e. is it a fill-and-spill system or a stepped ponded/partial-ponded system?) to facilitate prediction of where to drill Neogene reservoirs.

Key for age bins of interest:

Cretaceous (~145-66 Ma)

Jurassic (~199-145 Ma)

Triassic (~251-199 Ma)

Permian (~299-251 Ma)The authors would like to thank AGU for the opportunity to present this research. Funding for this project has been provided by Stanford’s SummerUndergraduate Research in Geosciences and Engineering program (SURGE) and the Stanford Project On Deep-water Depositional Systems (SPODDS) consortium.

Raukumara Wairarapa

0 100 200 300 400 500

10 100 200 300 400 500

1

Rela

tive

Prob

abili

ties

Basement Terrane PDPsPahau

Kaweka

Detrital Zircon Age (Ma)Modi�ed �gure from Adams et al., 2013

KEYVolcanowithin Taupovolcanic zone

Paleo-flow direction

Raukumarasub-basin

Wairarapasub-basin

Rivers

Uplifted basementterrane/ mountainrange

Reverse thrust fault

BoundaryseparatingKaweka basement terranefrom Westernbasement terranes

BoundaryseparatingPahau basement terranefrom Kawekabasement terrane

Ocean

A through C are separate interpretations of sediment dispersal patterns that can explain why the young detrital zircon age signatures found in the Northern Raukumara sub-basin are not present in the Southern Wairarapa sub-basin during Middle Miocene to Early Pliocene time.

We hypothesized that the Pahau terrane uplifted sometime during the Pliocene to present time, but the results show that Pahau age signatures are already present in our oldest samples.

The biggest surprise in our data is that the Raukumara sub-basin contains young volcanic age signatures which are not present in the Wairarapa sub-basin.

Paha

u

Kawek

aPa

hau

Kawek

a

A) N

100 km

A. The volcanic source contributing sedimentto the Raukumarasub-basin wasgeographically restrictedby the Kaweka and Pahau ranges.

C. Paleo-flow direction along the ECB was Northward.

N = 200

N = 200

N = 100

N = 200

N = 100

N = 200

N = 100

N = 200

N = 200

N = 100

N = 200

N = 200

N = 100

Number of grains analyzed (N) = number of grains plotted

242

475

118

217

317429 490

624

109126

153

246

387523

283

472

Volcanic ages- 15.5 ± .216.1 ± .616.5 ± .8

18.4 ± .3520.1 ± .29

21.2 ± .4

Volcanic ages- 12.2 ± 0.813.82 ± 0.7813.95 ± 0.64

15.5 ± 0.7916.2 ± 1.516.5 ± 1.117.3 ± 1.425.5 ± 1.927.6 ± 4.6

Volcanic ages- 10.6 ± 0.611.87 ± 0.81

17.4 ± 0.9

Volcanic ages- 4.5 ± 0.4 8.09 ± 0.464.96 ± 0.31 8.6 ± 0.75.09 ± 0.19 8.9 ± 0.55.42 ± 0.31 9.1 ± 0.8

5.8 ± 0.6 9.28 ± 0.436.85 ± 0.4 9.5 ± 1

7 ± 0.5 10 ± 0.77.36 ± 0.33 10.1 ± 0.77.66 ± 0.57 10.3 ± 0.9

7.7 ± 0.4 11.29 ± 0.728 ± 0.5 11.6 ± 1

119

245

516

116

222

315 488

120

230

480

107

246

500

125

237

441

16.8

30.8

119175

241

339 510

14.4

19.2

121

187

234

325 494

136

246

10.5

13.5120

231

323 453

4.5

9

125108

186243

Paleogeographic Re-constructions

Paleogeographic re-constructions (Present, 10 Ma, and 20 Ma) of New Zealand from King 2000. Bold line depicts paleo-coastline. Colour coding: white = terrestrial non-deposition; green = terrestrial deposition; yellow = marginal marine sand-dominated facies; pale blue-grey = shelf; mid-blue = slope or submarine rise; dark blue = deep ocean. Basins depicted include: Taranaki (TB), East Coast (ECB), Canterbury (CB), Great South (GSB), and Western Southland (WS). ChP = Challenger Plateau, CP = Campbell Plateau, CR = Chatham Rise; NCB = New Caledonia Basin; NB = Norfolk Basin; PT = Puysegur Trench; EB = Emerald Basin. Faults, subduction zones, and sea�oor spreading centres shown in red. Pink circles = active volcanism.

20 Ma

Present

10 Ma

70 Ma

Figure above (70 Ma) from- E. McSaveney and R. Sutherland, New Zealand adrift. 2nd ed. Lower Hutt: Institute of Geological & Nuclear Sciences, 2005Drifting of New Zealand from Gondwana after breakup 85 Ma.

Conclusions