On-ice vibroseis: Sediment features below Ekström Ice

(1)

Emma C. SMITH¹

¹Alfred Wegener Institute, Bremerhaven, Germany

²Dept. Of Geosciences, University of Tübingen, Germany

³BGR, Hannover, Germany

4Geodesy and Glaciology, Bavarian Academy of Sciences and Humanities, Munich, Germany

5Department of Geosciences, University of Bremen, Germany POLAR18 – 22nd June 2018

Antarctic Peninsula

Ronne- Filchner Ice Shelf Ekström Ice Shelf

Reinhard DREWS², Todd EHLERS², Dieter FRANKE³, Christoph GAEDICKE³, Coen HOFSTEDE¹, Gerhard KUHN¹,

Astrid LAMBRECHT⁴, Christoph MAYER⁴, Ralf TIEDEMANN^1,5, Olaf EISEN^1,5

On-ice vibroseis: Sediment features below Ekström Ice

Shelf, East Antarctica

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On-ice vibroseis: Sediment features below Ekström Ice Shelf, East Antarctica

Emma C. SMITH¹

¹Alfred Wegener Institute, Bremerhaven, Germany

²Dept. Of Geosciences, University of Tübingen, Germany

³BGR, Hannover, Germany

4Geodesy and Glaciology, Bavarian Academy of Sciences and Humanities, Munich, Germany

5Department of Geosciences, University of Bremen, Germany POLAR18 – 22nd June 2018

Antarctic Peninsula

Reinhard DREWS², Todd EHLERS², Dieter FRANKE³, Christoph GAEDICKE³, Coen HOFSTEDE¹, Gerhard KUHN¹,

Astrid LAMBRECHT⁴, Christoph MAYER⁴, Ralf TIEDEMANN^1,5, Olaf EISEN^1,5

and other

^

(3)

Antarctic Peninsula

Under Ice Shelves – Why?

? ?

?

Credit: Borrowed with permission from Reinhard Drews

§  Sea floor topography à past ice dynamics

§  Sub-sea floor à geological history

§  Cavity à ocean circulation and ice melt

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Antarctic Peninsula

Under Ice Shelves – Why?

? ?

?

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Antarctic Peninsula

Under Ice Shelves – Why?

? ?

?

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Ekström Ice Shelf – Seismic Data

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Ekström Ice Shelf – Seismic Data

Eisen et al., Polar Sci., 2015

1500 m, 60 channels

Sweep: 10 – 220 Hz Time: 10 seconds SPs 75 – 750 m

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Ekström Ice Shelf – Seismic Data

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Ekström Ice Shelf – Sea-floor Bathymetry

Elevation (from SL)

> -250

-1100

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Ekström Ice Shelf – Sea-floor Bathymetry

> -250

-1100

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Palaeo-trough

a’

a

> -250

-1100

a a’

(12)

a

a’

a’’

a

a’’

> -250

-1100

a’

Palaeo-trough

(13)

a

a’

a’’

a

a’’

> -250

-1100

a’

Palaeo-trough

(14)

a

a’

a’’

a

a’’

> -250

-1100

a’

Palaeo-trough

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a a’ a’’

> -250

-1100

Two-way travel time (ms)

400

600

800

1000

~50 m

1500 m Seismic multiple

Base glacial debris Sea floor Explora wedge

GZW/Outcrop ~ 150 m GZW

~50 m height

Grounding Zone Wedge

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> -250

-1100

b b’ b’’ b

b’’ b’

Grounding Zone Wedge

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> -250

-1100

Two-way travel time (ms) ⁴⁰⁰

600

800

Seismic multiple

Glacial debris Truncated dipping sediment

~50 m

2500 m

Volcanic Explora wedge

Layered sediments

b b’ b’’

~ 50 m

Grounding Zone Wedge

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> -250

-1100

Grounding Zone Wedge - Extent

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> -250

-1100

Grounding Zone Wedge - Extent

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> -250

-1100

Possible GZW

a a’ a’’

Two-way travel time (ms)

400

600

800

1000

~50 m 2000 m

Seismic multiple

Glacial debris Truncated dipping sediment

Volcanic Explora wedge

c c’

c’

c

Grounding Zone Wedge – The Missing Part

x

•  Ice retreat features – layered grounding zone wedges found across the trough mouth allow us to begin to reconstruct retreat history of area

What this space!

•  A whole host of other features seen at and beneath sea-floor

•  Age of sediments can be retrieved through sub-shelf drilling and sediment sampling – 2018/19 season.

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Summary

•  Evidence of a palaeo- ice stream trough beneath the Ekström ice shelf

•  Rougher topography within the trough than in surrounding

“smoother” areas

•  Ice retreat features – layered grounding zone wedges found across the trough mouth allow us to begin to reconstruct retreat history of area

What this space!

•  A whole host of other features seen at and beneath sea-floor

•  Age of sediments can be retrieved through sub-shelf drilling and sediment sampling – 2018/19 season.

Thank you!

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Grounding Line Extension

> -250

-1100