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Re: Late Cretaceous Arctic Climates - RESEND


There is indeed gathering evidence for glacial episodes in the Southern Hemisphere during the Early Cretaceous;

Alley, N. F., and L. A. Frakes. 2003. First known Cretaceous glaciation: Livingston Tillite Member of Cadna-owie Formation, South Australia. Australian Journal of Earth Sciences 50(2):139-144.

A 2 m-thick diamictite occurs near the base of the Cretaceous Eromanga Basin succession at Trinity Well, at the northern extremity of the Flinders Ranges in South Australia. The diamictite consists of a matrix of silt- and clay-size particles and a framework of sand and coarser materials up to small boulder size. Scanning electron microscope study reveals the presence of numerous quartz grains displaying extreme angularity and surface textures attributed to glacial crushing. Sandy sediments considered as fluvioglacial in origin and a locally developed facies displaying flow structures attributed to solifluction processes constitute the basal 3–5 m of the sequence. In places these directly underlie the diamictite and rest with angularity on Neoproterozoic Adelaidean strata. Conformably above the diamictite at the type locality ‘Recorder Hill’ is a sequence approximately 15 m thick of fine sand and silt units containing lonestones up to ~70 cm diameter and hummocky cross-stratification. These sediments have been assigned to the Cadna-owie Formation and are dated on palynology as Berriasian to Valanginian. The occurrence of diamictite containing glacially affected quartz grains contributes to our interpretation that the southern margin of the Eromanga Basin, and at least the adjacent part of the northern Flinders Ranges, were affected by glaciation in the Early Cretaceous. The associated dropstone and solifluction facies and nearby glendonite pseudomorphs after ikaite are further evidence of at least intermittent cold climates at this time.

Which could at least go some way to helping explain the repeated trangression/regression cycles in the Great Artesian Basin, as has been suggested for other Cretaceous contexts;

Miller, K. G., P. J. Sugarman, J. V. Browning, M. A. Kominz, J. C. Hernández, R. K. Olsson, J. D. Wright, M. D. Feigenson, and W. Van Sickel. 2003. Late Cretaceous chronology of large, rapid sea-level changes: Glacioeustasy during the greenhouse world. Geology 31(7):585-588.

We provide a record of global sea-level (eustatic) variations of the Late Cretaceous (99–65 Ma) greenhouse world. Ocean Drilling Program Leg 174AX provided a record of 11–14 Upper Cretaceous sequences in the New Jersey Coastal Plain that were dated by integrating Sr isotopic stratigraphy and biostratigraphy. Backstripping yielded a Late Cretaceous eustatic estimate for these sequences, taking into account sediment loading, compaction, paleowater depth, and basin subsidence. We show that Late Cretaceous sea-level changes were large (.25 m) and rapid (K1 m.y.), suggesting a glacioeustatic control. Three large d18O increases are linked to sequence boundaries (others lack sufficient d18O data), consistent with a glacioeustatic cause and with the development of small (,106 km3) ephemeral ice sheets in Antarctica. Our sequence boundaries correlate with sea-level falls recorded by Exxon Production Research and sections from northwest Europe and Russia, indicating a global cause, although the Exxon record differs from backstripped estimates in amplitude and shape.

Stoll, H. M., and D. P. Schrag. 1996. Evidence for Glacial Control of Rapid Sea Level Changes in the Early Cretaceous. Science 272:1771-1774.

Lower Cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves. Strontium data from an interval spanning 7 million years in the Berriasian-Valanginian imply that global sea level fluctuated about 50 meters over time scales of 200,000 to 500,000 years, which is in agreement with the Exxon sea level curve. Oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes. If glaciation caused all the rapid sea level changes in the Cretaceous that are indicated by the Exxon curve, then an Antarctic ice sheet may have existed despite overall climatic warmth.


mariusromanus@aol.com wrote:
I've been talking about the extremely good possibility for at least seasonal ice at the poles during the K for years. So, I for one am glad to see yet another article that says this was probably the case. And Guy, there's really every reason to believe that the South Pole was the same... especially since, if memory serves, there were already a good deal of elevated mountain ranges at the time, and land completely cut off from the ocean. Isolate elevated land masses where the sun doesn't shine for part of the year and ocean currents that are obstructed due to those very same land masses, and you will get ice. I don't think there is really any way to avoid it. Similar situation goes for the North Pole as well (not so much the mountains, though there were some such as the Brooks Range in AK for example, but definitely the ocean current situation).


-----Original Message-----
From: GUY LEAHY <xrciseguy@q.com>
To: Dinosaur Mailing List <dinosaur@usc.edu>
Sent: Sun, Jul 19, 2009 11:16 pm
Subject: Late Cretaceous Arctic Climates



Interesting... wonder if the southern Polar oceans were similar?

Guy Leahy

Colin McHenry Ph.D.
Computational Biomechanics Research Group http://www.compbiomech.com/
School of Engineering (Mech Eng)
University of Newcastle
NSW 2308

t: +61 2 4921 8879
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