Sea and Shelf Ice Drilling

Extracting a direct geological record of climate and ice-sheet extent from offshore drilling in McMurdo Sound has continued on the back of the Cape Roberts Project. The successor project, ANDRILL, was designed to sample an expanded Neogene section with a pair of sites, one for the latest Neogene and the other for the middle Miocene transition. There was to be an added twist - the first site would be in the centre of the Victoria Land Basin and located on the ice shelf just south of Ross Island to obtain a history of the Ross Ice Shelf/expanded West Antarctic Ice Sheet cycle through late Neogene times. This required further technological development for maintaining an access hole through an ice shelf in deeper water and with deeper coring sought (Fig. 3.6).

Both holes have now been successfully completed with excellent recovery (Naish et al., 2008a; Harwood et al., in press; Table 3.2). They also overlap with each other and CRP-1 (Fig. 3.8), and provide record of numerous cyclic ice-sheet fluctuations under varying climatic regimes over the last ~ 18 million years. Perhaps the most interesting and unexpected result has been recovery of the 90 m of Pliocene diatomite in AND-1B, indicating open water in the Ross Embayment (and most likely throughout West Antarctica) for several hundred thousand years when global temperatures were only 2-3°C

Table 3.2: Antarctic coastal and continental shelf rock-drilling sites, 1973 to 2007.

Project

Year

Site

Latitude

Longitude

Elevation/ depth ( + ) (m)

Depth cored (m)

Recovery (%) '

Oldest core

References

Ross Sea

DSDP 28

1973

270

77°26'S

178°30'W

-634

423

62

Gneiss - early Paleozoic

Hayes, Frakes

et al. (1975)

271

77°26'S

178°30'W

-562

233

7

Diamict clasts - early Pliocene

272

77°26'S

178°30'W

-629

439

37

Diamict - early Miocene

273

77°26'S

178°30'W

-491

333

25

Diamict - early Miocene

McMurdo Sound area -

onshore

DVDP

1973

1

77°50'S

166°40'E

67

201

98

Basalt - Late Quaternary

Kyle (1981)

1973

2

77°51'S

166°40'E

47

179

96

Basalt - Late Quaternary

Kyle (1981)

1973

3

77°51'S

166°40'E

48

381

90

Basalt - Late Quaternary

Kyle (1981)

1974

10

77°35'S

163°31'E

3

182

83

Diamict - late Miocene

Powell (1981)

1974

11

77°35'S

163°25'E

80.2

328

94

Diamict - late Miocene

Powell (1981)

1974

12

77°38'S

162°51'E

75.1

185

98

Migmatite - early Paleozoic

Powell (1981)

McMurdo Sound area -

offshore

DVDP 15

1975

15

77°26'S

164°23'E

-122

62

52

Black sand - early Pleistocene

Barrett and

Treves (1981)

MSSTS

1979

1

77°34'S

163°23'E

-195

230

62

Mudstone - late Oligocene

Barrett (1986)

CIROS

1986

1

77°05'S

164°30'E

-197

702

98

Boulder conglomerate - late

Barrett (1989)

Eocene

CIROS

1984

2

77°41'S

163°32'E

-211

168

67

Gneiss - early Paleozoic

Barrett and

Hambrey

(1992)

CRP

1997

1

77°00'S

163°45'E

-154

148

86

Diamict - early Miocene

CRST (1998)

1998

2

77°00'S

163°43'E

-178

624

95

Mudstone - Oligocene

CRST (1999)

1999

3

77°00'S

163°43'E

-295

939

97

Sandstone - Devonian

CRST (2000)

ANDRILL 2006 1 77°55'S 167°01'E -840

ANDRILL

2007

2

77°46'S

165°17'E

-380

Prydz Bay ODP 119

1988

739

67°17'S

75°05'E

-412

741

68°41'S 68°23'S

76°43'E 76°23'E

-808 -551

742

67°33S

75°24'E

-416

ODP 188

2000

743 1166

66°55'S 67°42'S

74°42'E 74°47'E

-989 -475

Antarctic Peninsula ODP 178 1998

1097

66°24'S

70°45'W

-563

SHALDRIL

1099

1100 1102 1103

1

64°52'S 64°57'S 66°53'S 66°48'S 64°00'S 62°17'S

64°12'W 64°19'W 65°42'W 65°51'W 65°28'W 58°45'W

-1010 -1400 -459 -431 -494 -488

SHALDRIL

2006

3

63°51'S

54°39'W

-340

6

63°15'S 63°20'S

52°22'W 52°22'W

-506 -532

Note: ?-indicates age given is uncertain.

1285

98

Basalt - early Miocene

Naish et al.

(2008a)

1139

98

Diamict - late Oligocene

Harwood et al.

(in press)

487

34

Diamict - late Eocene-early

Barron, Larsen

Oligocene

et al. (1989)

226

32

Red beds - ?Eriassic

128

26

Sandstone, siltstone - ?early

Cretaceous

316

53

Mudstone, diamict - ?Eocene-

Oligocene

97

22

Diamict - Pleistocene

381

19

Claystone - late Cretaceous

O'Brien, Cooper

et al. (2001)

437

14

Diamict - early Pliocene

Barker,

Camerlenghi

et al. (1999)

47

99

Mud - Holocene

108

102

Mud - Holocene

111

5

Diamict - Pleistocene

15

6

Diamict - Pleistocene?

363

12

Diamict - late Miocene

108

87

Mud - Late Pleistocene

http://shaldril.

rice.edu/

20

32

Mudstone - late Eocene/early

Anderson

Oligocene

et al. (2007)

23

40

Muddy sand - mid-Miocene

21

6

Muddy sand - early Pliocene

4

64

Mudstone - Oligocene

Deep-sea sediment cores

Antarctic margin sed cores odph9,188

Ross Sea \

Antarctic ice cores A ^ \

Deep-sea sediment cores

Antarctic margin sed cores odph9,188

Ross Sea \

Antarctic ice cores A ^ \

Change in global temperature from present (°C)

Figure 3.8: Cenozoic time-temperature graph showing the time intervals now covered in moderate detail by McMurdo Sound Drilling. ODP Legs 119 and 188 covered the same interval but with significant time gaps and lower core recovery. Intervals covered by much higher resolution deep ice cores and the continuous record from multiple sites in deep-sea sediment cores are shown for comparison. The temperature curve from Crowley and Kim (1995), which is based on the isotope summary of Miller et al. (1987), is modified to show the effect of the methane discharge at 55 Ma (Zachos et al.,

Change in global temperature from present (°C)

Figure 3.8: Cenozoic time-temperature graph showing the time intervals now covered in moderate detail by McMurdo Sound Drilling. ODP Legs 119 and 188 covered the same interval but with significant time gaps and lower core recovery. Intervals covered by much higher resolution deep ice cores and the continuous record from multiple sites in deep-sea sediment cores are shown for comparison. The temperature curve from Crowley and Kim (1995), which is based on the isotope summary of Miller et al. (1987), is modified to show the effect of the methane discharge at 55 Ma (Zachos et al.,

higher and CO2 levels little more than those of today (Van Der Burgh et al., 1993; Ravelo et al., 2004).

The middle Miocene climatic optimimum has also been cored at the Antarctic margin for the first time (AND-2, Harwood et al., in press). Much remains to be done for a detailed analysis of sedimentary features, fossil assemblages, physical, chemical and magnetic properties and geochronology for comparing this record and that of AND-1B with those of deep-sea and coastal records in lower latitudes. There is also the prospect for the first time of correlating the last million years of the AND-1B core with the temperature and atmospheric CO2 record of the last eight glacial cycles in the ice core from Dome C (EPICA, 2004).

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