ª

ª

ª

ª

0

+

ª

+

=

174°E172°E170°E168°E

46

°S4

8°S

50

°S

0 25 50 75 100 km

Legend

Study area

Map boundary OMV

Map boundary DUN06

Map boundary M4-T4

Map boundary Hunt

Seismic lines used in study

Tara-1Tara-1

Toroa-1Toroa-1

Kawau-1AKawau-1A

Pukaki-1Pukaki-1

Hoiho-1CHoiho-1C

Pakaha-1Pakaha-1

Rakiura-1Rakiura-1

Takapu-1ATakapu-1A

Horseshoe-1Horseshoe-1

ª

ª

ª

ª

0

+

ª

+

=

Tara-1

Toroa-1

Kawau-1A

Pukaki-1

Hoiho-1C

Pakaha-1

Rakiura-1

Takapu-1A

Horseshoe-1

174°E

174°E

172°E

172°E

170°E

170°E

168°E

168°E

46

°S

46

°S

48

°S

48

°S

50

°S

50

°S

0 25 50 75 100 km

ª

ª

ª

ª

0

+

ª

+

=

Tara-1

Toroa-1

Kawau-1A

Pukaki-1

Hoiho-1C

Pakaha-1

Rakiura-1

Takapu-1A

Horseshoe-1

174°E

174°E

172°E

172°E

170°E

170°E

168°E

168°E

46°S

46°S

48°S

48°S

50°S

50°S

0 25 50 75 100 km

ª

ª

ª

ª

0

+

ª

+

=

Tara-1

Toroa-1

Kawau-1A

Pukaki-1

Hoiho-1C

Pakaha-1

Rakiura-1

Takapu-1A

Horseshoe-1

174°E

174°E

172°E

172°E

170°E

170°E

168°E

168°E

46°S

46°S

48°S

48°S

50°S

50°S

0 25 50 75 100 km

ª

ª

ª

ª

0

+

ª

+

=

Tara-1

Toroa-1

Kawau-1A

Pukaki-1

Hoiho-1C

Pakaha-1

Rakiura-1

Takapu-1A

Horseshoe-1

174°E

174°E

172°E

172°E

170°E

170°E

168°E

168°E

46

°S

46

°S

48

°S

48

°S

50

°S

50

°S

0 25 50 75 100 km

Beggs, J.M., 1993. Depositional and tectonic history of the Great South Basin. In Ballance, P.F. (ed), South Pacific sedimentary Field, B.D. and Browne, G.H., 1989. Cretaceous and Cenozoic sedimentary basins and geological evolution of the Canterbury basins. Sedimentary basins of the world 2, 365-373. Amsterdam, Elsevier Science. region, South Island, New Zealand. New Zealand Geological Survey Basin Studies, 2. Wellington, 94p.

Cook, R.A., Sutherland, R., Zhu, H. and others, 1999. Cretaceous-Cenozoic geology and petroleum systems of the Great South Lee, D., Lindqvist, J., Douglas, B., Bannister, J., Cieraad, E. 2003. Paleobotany and sedimentology of Late Cretaceous-Miocene Basin, New Zealand. Institute of Geological & Nuclear Sciences Monograph, 20. Lower Hutt, New Zealand, 188p, 2 nonmarine sequences in Otago and Southland. Geological Society of NZ Misc. Public 116B, FT9-1 to 48.enclosures.

9. References

Figure 1: Location map showing seismic data and wells used in this study. Polygons indicate areas where seismic data were sufficiently dense for attribute analysis to be carried out.

Figure 3: Seismic section showing major sequence boundaries and stratal terminations in the Cretaceous-Neogene of the Great South Basin.

Figure 8: Paleogeographic map for sequence (Raukumara Series).S2 Figure 7: Paleogeographic map for sequence (Clarence Series).S1

Figure 9: Paleogeographic map for sequence (early Mata Series).S3 Figure 10: Paleogeographic map for sequence (late Mata Series).S4

The stratigraphy and basin evolution of the Great South Basin have been described in a number of previous studies (Field and Browne et al., 1989; Beggs, 1993; Cook et al., 1999).

This study aims to develop an improved seismic stratigraphic framework for the mid Cretaceous–Neogene section of the Great South Basin, utilising an increased number of second order seismic stratigraphic sequences, in order to better understand its tectono-sedimentary evolution.

These sequences have been calibrated with well log data, to produce a series of updated paleogeographic maps that will aid in the prediction of reservoir and source rock distribution. The results from four sequences within the mid to Late Cretaceous are presented in this poster.

1. Introduction

3. Seismic stratigraphyndFour 2 -order

sequences have been identified within the Cretaceous (S1–S4) between five mapped horizons. There are a further six sequences in the Paleocene-Eocene (S5–S10) and two in the Oligocene-Recent (S11–S12).

These sequences can be placed in the following tectonic regimes:syn-rift (S1–S2), post-rift passive thermal subsidence (S3–S10) and compressional (S11–S12).

NR = normal regressionFR = forced regressionTR = transgression

7. Revised Cretaceous paleogeographies for the Great South Basin

1

2

5

3

4

6

TW

T (

s)

50 km

top Paleocenetop Paleocene

S9

S5

S8S7

S6

S10

S11S12

BasementBasement

NW

FR

TR

NR

FR

TR

NR

TR

NR

NR

FR NR

OMV-08-075

top Miocenetop Miocene

top Eocenetop Eocene

SEProgradingclinoforms

Syn-rift basin fill

Oligocene - Recent

Paleocene - Eocene

Cretaceous

Jurassic and older

Channels

Onlaps

Downlaps

Truncations

Submarine fans

Major canyons

Non-marine sandy

Legend

Non deposition/erosion

Non-marine to marginal-marine coaly/lacustrine

Shoreface/shallow-marine

Shelfal

Volcanics/intrusions

Exploration wells

+ Gas shows

0 Gas & Condensate shows

ª Dry hole

µ Oil shows

= Unknown

Seismic lines

Faults

Uppermost bathyal

5. Examples of seismic facies

Figure 2: Flowchart showing methodology used in this study. Data used include ~50,000 line km of publicly available 2-D seismic data, eight offshore wells and published outcrop data (Cook et al. 1999; Lee et al., 2003).

Figure 4: Gross lithology and seismic facies character at well Toroa-1.

(A) RMS amplitude between T00 and K80–T00 slice 2 (B) RMS amplitude between and K80K80–T00 slice 2

Figure 6: (A-B) RMS amplitude maps of the OMV and HUNT G seismic lines for part of sequence S4. High amplitudes indicate likely coaly facies. (C) Seismic section showing isoproportion slices. RMS amplitude maps relate to intervals between the slices.

(C)

2. Data and methods

—The S1 sequence represents the initial syn-rift fill, deposited mainly in alluvial, fluvial, ?lacustrine and deltaic settings. Source rocks are mostly fluvio-deltaic/lacustrine.

—The S2 sequence represents the later syn-rift phase, with sediments deposited in fluvial, ?lacustrine, deltaic, shoreface and shelf environments. Widespread marginal-marine coaly source facies development.

—The S3 and S4 sequences represents a phase of post rift thermal subsidence. There is widespread marginal- marine and shelf facies development.

—The Paleocene–Eocene was a time of thick marine clastic deposition during passive subsidence and westward marine transgression.

—The Oligocene–Early Miocene was a time of maximum transgression, with widespread condensed limestone deposition.

—Most of the Neogene section is characterised by incised channels, submarine fans, contourites and regressive deposits.

4. Well to seismic facies calibration

6. Seismic amplitude mapping

Figure 5: Seismic sections showing examples of seismic facies types, which include: non-marine (alluvial fans, fluvial, lacustrine), marginal-marine (deltaic, estuarine), shoreface/shallow-marine, shelfal and submarine fans.

8. Conclusions

HighLow

100 km

5 km

Paleogeographicmaps

Published (onshore and offshore studies,

wellsheets)

literature

Seismic datainterpretation and identification

of sequence boundaries

Isochronmaps

Attributeanalysis

Depositional boundariesseismic polygons

Gross lithology anddepositional environment

in wells

Seismic faciescharacterisation

Well toseismic tie

SENW

A OMV-08-075

OMV-08-109

SW NE

B

?lacustrine muds

fluvio-deltaic

4500

4000

SENW

C

K40K40

Hunt-f-423

3500

2000

2500

3000

4000

prograding delta (bright amplitudeindicates coaly facies)

fluvial (flood plain) shelfal

shoreface/shallow-marine

K40K40

K60K60

K80K80

T00T00

25 km

Top Murihiku

Top Murihiku

?lacustrine/alluvial fans

K40K40alluvial

fans

5 km

fluvio-deltaic

?lacustrine facies

T00T00

K80K80

san

dst

on

e 7

0%

+ s

iltst

on

e 2

0%

+ c

arb

on

ate

2%

+

coal

8%

(gr

oss

lith

olo

gy o

f S3

; cu

ttin

gs)

Toroa-1

Ma

rgin

al m

arin

e

Ma

rgin

al m

arin

e

Sh

elf

al

RHOB(g/cc)

NPHI(v/v)

1.95 2.95

0.45 -0.15

SP(mv)

DT(us/ft)

-60 200

240 40

MSFL(ohmm)0.02 200

GR(GAPI)

CALI(in)

0 200

5 35DEPTH (m)

3900

4000

4100

4200

4300

4400

4500

2500

3000

3500

ms

K80K80

K60K604 km

shelfal:sandstone/siltstone >97% + carbonates 3%

shelfal:sandstone/siltstone >97% + carbonates 3%

mariginal-marine(1-5 m thick

individualcoal seams)

mariginal-marine(1-5 m thick

individualcoal seams)

Seismic lineFigure 3

Seismic lineFigure 3

5 km

slice1slice1

slice2slice2

slice3slice3K80K80

T00T00

top Murihikutop Murihiku

top Cretaceous (T00)top Cretaceous (T00)

K60K60

K40K40

K80K80

AcknowledgementsThis project was carried out as part of ongoing research into the evolution of New Zealand's petroleum basins, as part of the EEZ and Petroleum Basin Research (PBR) programmes at GNS Science, funded by direct core funding provided to GNS Science by the New Zealand Government.

GNS Science

GNS Science1 Fairway DriveAvalonLower Hutt 5010PO Box 30368Lower Hutt

Seismic sequence stratigraphic framework and paleogeography of the mid Cretaceous–Neogene section in the Great South Basin

Top Murihiku

Top Murihiku

S1

S2

S3

S4

submarinefan?

1Tusar R. Sahoo , Kyle J. Bland and Dominic P. Strogen 1t.sahoo@gns.cri.nz