3. North on the Dalton Highway
Photo Credit: Beth Hook, Perot Museum
Photo Credit: Beth Hook, Perot Museum
Evan Kevin
Joe
Ashley
Sarah
Lauren
Arctic Circle Campground
Study Location
Dalton Highway
Galbraith Lake
Campground
Slope
Mountain
Approximate
Location:
68.74° N 149.02°W
Slope Mtn.
A
B
4. Tectonic and Climatic Setting
• Brooks Range uplift and formation of a foreland basin
• Rapid deposition: detailed high-latitude paleoenvironmental record
• Greenhouse Arctic: MAT = 10 ºC (50 ºF); 4-5x CO2, near-max global sea levels
Study Area
Image: Ron Blakey (http://jan.ucc.nau.edu/~rcb7/105moll.jpg)
Albian-Cenomanian (113-94 Ma) Paleo-Arctic
5. Geologic Background: Foreland Basin Stratigraphy
Arctic Alaska
Microplate
Generalized Modern Cross Section of the North
Slope Foreland Basin (LePain et al., 2009)
Brookian Stratigraphy (Shimer et al., 2014)
Reconstruction of Nanushuk Formation
Depositional Systems(LePain et al., 2009)
Albian-Cenomanian Geology
• Torok and Nanushuk formations
• Initial “Brookian” megasequences
• 2000 m of sediment in 10-20 my
= thick paleoenvironmental record!
A
B C
10. SM1: Delta Front Deposits (Nanushuk Fm.)
Nanushuk Fm.
Torok Fm.
BIG QUESTION: how did the Cretaceous delta system evolve in
response to tectonic, climatic, and biologic changes over time?
14. Summary
• sedimentary facies: prodelta turbidites and lower shoreface sandstone
• horizontal burrows → detrital feeding, oxygenated, carbon-rich environment
• lack of shelled invertebrates: rapid sedimentation, turbid water
modified from a figure adopted from Allen (1970) by Prothero and Schwab (2014) Modified from LePain et al. (2009)
15. Mudstone Geochemistry Project
• SM1 and SM2 (Torok Formation)
• 62 mudstone samples: XRF, XRD
• Paleoredox conditions
• Correlation and possible fault
16. Analytical Methods
Methods
• XRD
• LOI
• XRF (Majors)
• XRF (Minors)
Calculating Factors of Enrichment:
EF =
(Xsample/Alsample)
(Xaverage/Alaverage)
17. y = 0.606x + 0.364
R² = 0.692
y = 0.948x + 0.204
R² = 0.750
y = 0.796x - 0.386
R² = 0.095
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
EnrichmentFactor(X)
Enrichment Factor (Ni)
Minor Element Cross-plots
Ni v Cu
Ni v V
Ni v U
Tribovillard, Nicolas, et al, 2006, Trace metals as paleoredox and
paleoproductivity proxies: An update: Chemical Geology, 232, p. 12-
32.
18. Possible Exception to Suboxic Conditions
0
0.5
1
1.5
2
2.5
3
3.5
4
-10
-5
0
5
10
15
20
LOIWeight%
∆EFUvsNi
∆EF U vs Ni LOI
∆ Enrichment and
LOI
Tribovillard, Nicolas, et al, 2006, Trace metals as
paleoredox and paleoproductivity proxies: An update:
Chemical Geology, 232, p. 12-32.
19. Correlations
more proximal more distal
Elevation(m)
• irregular U-enrichment, LOI
• possible correlative surface
• rapid prodelta aggradation or thrust faulting
27. Origin of Terrestrial Carbon
δ13Catm = (δ13Cplants + 18.67) / 1.10 Arens et al. (2000)
Cool mixed hardwood,
conifer, and fern
28. Age Location Source 13C ‰ (VPDB) Range Source
Middle
Maastrichtian
Lower Cantwell
Formation, AK
Wood -27.85 -22.42 (Salazar-Jaramillo et al.,
2016)
Bulk -27.10 -22.95
Cenomanian Dakota
Formation, NE
Bulk -24.00 -23.00 (Gröcke et al 2006)
Albian-
Cenomanian
North Slope,
Alaska
Bulk -26.09 -22.50 This study
Aptian Hokkaido,
northern Japan
Wood -25.40 -21.80 (Ando et al., 2002)
Aptian Isle of Wright,
England
Wood -29.00 -19.00 (Gröcke et al 1999).
Comparison to Previous Studies
29. Marginal Marine to Non-Marine
Nanushuk Formation Facies
Distributary
Mouth Bar
Upper
Shoreface
34. Acknowledgements: Bob Varga, Whitman College Geology Dept., UAF
Geosciences, Lisa Greer (W&L), Bosiljka Glumac (Smith), Carol deWet
and Stan Mertzman (F&M), Karla Hubbard (Oberlin), Paul Myrow, (CC),
WSU Stable Isotope Core Lab, Tom Gillispie (AK-OHA), Tony Fiorillo and
Beth Hook (Perot Museum), Yoshi Kobayashi (Hokkaido University)
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