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Distal-basin-floor-fan Deposits of the Middle Eocene Tyee Formation, Oregon,USA

By
M. L Sweet
M. L Sweet
1
ExxonMobil Upstream Research Co.
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R. T Beaubouef
R. T Beaubouef
2
ExxonMobil Exploration Co., Houston, Texas, USA
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John Beuhler
John Beuhler
2
ExxonMobil Exploration Co., Houston, Texas, USA
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Matt Grove
Matt Grove
2
ExxonMobil Exploration Co., Houston, Texas, USA
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Margie Kloska
Margie Kloska
2
ExxonMobil Exploration Co., Houston, Texas, USA
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Steve Mitchell
Steve Mitchell
2
ExxonMobil Exploration Co., Houston, Texas, USA
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Published:
January 01, 2008

Abstract

The middle Eocene Tyee Formation was deposited in the Oregon Coast Range fore-arc basin (Figure 1). Heller and Ryberg (1983) and Ryu and Niem (1999) describe the Tyee Formation as part of a 6-km (3.7-mi)-thick package of sedimentary rocks that rests unconformably on the Paleocene Siletz River Volcanics (Figure 2). The Umpqua Arch (Figure 1) appears to have influenced deposition of the Tyee and divided the basin into two sub basins. Field mapping by chan and Dott (1983) and Heller and Dickinson (1985) suggests that the Tyee depositonal system includes fluvial and deltaic deposits to the south and that this system prograded to the north through time.

Outcrops of the middle Eocene Tyee Formation along Highway 20, west of Corvallis, Oregon, display facies that are characteristic of the distal end of a sand-rich basin-floor fan. This area is more than 100 km (60 mi) basinward of slope and deltaic deposits of the Tyee Formation (Figures 1 and 3). A series of road cuts along Highway 20 exposes up to 460 m (1500 ft) of strike section that shows no evidence of channelization (Figure 4). The primary sedimentary facies here are relatively thick (1-3 m [3-10 ft]) beds of massive sandstones (Ta). These beds are, in many cases, capped by thin (0.2-0.6-m [0.7-2.0-ft]-thick) beds of organic-rich, muddy, fine-grained sandstones that contain rip-up clasts (Figures 5-7). We interpreted these muddy beds as slurry deposits (sensu Lowe and Guy, 2000), that is, deposits that record a flow transitional between turbidity currents and debris flows.

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Contents

AAPG Studies in Geology

Atlas of Deep-Water Outcrops

Tor H. Nilsen
Tor H. Nilsen
Desceased
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Roger D. Shew
Roger D. Shew
University of North Carolina
Wilmington, North Carolina
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Gary S. Steffens
Gary S. Steffens
Shell International E&P
Houston, Texas
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Joseph R. J. Studlick
Joseph R. J. Studlick
Maersk Oil America Inc.
Houston, Texas
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American Association of Petroleum Geologists
Volume
56
ISBN electronic:
9781629810331
Publication date:
January 01, 2008

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