Ice in Tropical Pangaea: An “Outrageous” Hypothesis that Inspired a Modern Sediment- Unaweep Canyon Weathering Study (Colorado) G.S. (Lynn) Soreghan (w/ Many Collaborators) University of Oklahoma

Distal Cutler (Loess) Utah

Proximal Cutler (Dropstone) Utah Main Points: • Alpine glaciation in tropical Pangaea, that extended to low elevation (<1600 m) • The Late Paleozoic was colder Unaweep Canyon than most think. (Colorado) • How? Understanding this helps us refine climate models. • This inspired trip to Peru (modern weathering study).

Distal Cutler (Loess) Utah

Proximal Cutler (Dropstone) Utah

Starting Point: Unaweep Canyon-- An Enigmatic Landscape

“To attribute this cañon to the streams now occupying it is manifestly absurd” (Henry Gannett, 1882) Why “Absurd”?

Colorado River

Gunnison River

Unaweep Canyon

10 km Uncompahgre Plateau

Dolores River Geology

Deep, wide canyon through Mesozoic, Precambrian, perpendicular to Plateau Two underft streams fow from subtle divide Longitudinal Profle

Unaweep Divide

West Creek East Creek Previous Ideas for Formation of Unaweep Canyon

• River Incision & Abandonment? • Incision by Gunnison and/or Colorado rivers, and subsequent abandonment, possibly by tectonic deformation of the Uncompahgre Plateau (e.g., Peale, 1877; Gannett, 1882; Lohman, 1961; Cater, 1966; Sinnock, 1981). • But. Problems… • Canyon shape is strange. • No evidence for neotectonic deformation. Previous Ideas for Formation of Unaweep Canyon

• River Incision & Abandonment? • Incision by Gunnison and/or Colorado rivers, and subsequent abandonment, possibly by tectonic “warping” of the Uncompahgre Plateau (e.g., Peale, 1877; Gannett, 1882; Lohman, 1961; Cater, 1966; Sinnock, 1981). • Pleistocene Glacial Origin? • Classic glacial landforms of Unaweep’s inner gorge (Cole and Young, 1983). Unaweep’s Classic Shape– Glacial?

Nearest Pleistocene glacial moraines above 2750 m Floor of Unaweep Canyon peaks (Unaweep Divide) at 2150 m No high-elevation source region; no deposits (moraines) A New Hypothesis: Is Unaweep Canyon part of a very ancient landscape? • Elements of this hypothesis: • Unaweep Canyon was created ~300 Million years ago (late Paleozoic), by ice… • was then buried, and… • was exhumed (not carved) by the Gunnison River only recently (since ~6 Ma). • was then abandoned (~1.4 Ma) and partly reflled. • Two parts to the problem: • The age of the canyon • The origin of the canyon • So, how does one “date” a canyon (or valley)? Geomorphic Attributes

Hanging valleys beheaded by Mesozoic strata. How else can a landscape be dated? Sediment Fill of Paleozoic Age?

Mixed Paleo/Mesozoic pollen & Precambrian/Mesozoic clasts (Cenozoic age)

Recent Landslide

|P-P pollen & Precambrian clasts (Paleozoic age?) Outcrop

Upr Paleozoic (?) seds in canyon; If so, then it’s a Paleozoic landform Summary: Canyon Age

• Geomorphic cross-cutting relationships • Mesozoic section cross-cuts features of inner gorge • Palynomorph (fossil pollen & spores) content • Basal fll contains late Paleozoic palynomorphs • Provenance (sediment source) • Basal fll has (exclusive) Precambrian provenance • Paleomagnetic signature • Basal fll (core) yields low (late Paleozoic?) inclination

Our Hypothesis: Unaweep inner gorge is a paleolandscape that dates from ~300 My • If so, then we need to understand the setting of Colorado (and the greater region) during the Late Paleozoic, ~300 million years ago. Brief Digression: Modern Earth

Icehouse climate, characterized by large continental ice sheets; Current interglacial; last glacial maximum (LGM) ~18,000 yrs ago

[Images from www.johnstonsarchive.net] “Ice House” Climates in Geologic History

Quaternary Neoproterozoic

Late Paleozoic Late Paleozoic Pangaea (~300 Ma)

(image from Dr. Ron Blakey, NAU) Global mountain-building (owing to assembly of Pangaea)

Icehouse climate (Gondwanan glaciation; low CO2, 3% less solar luminosity) Ancestral Rocky Mountains = western equatorial Pangaea The Ancestral Rocky Mountains

Uncompahgre Uplift

Paradox Basin

(image from Dr. Ron Blakey, NAU)

• So, setting was tropical (<7o), but in mountains. A New Hypothesis: Is Unaweep Canyon part of a very ancient landscape? • Elements of this hypothesis: • Unaweep Canyon was carved 300 Million years ago (late Paleozoic), by ice… • was then buried, and… • was exhumed (not carved) by the Gunnison River only recently (beginning ~5-6 Ma). • was then abandoned (~1.4 Ma) and partly reflled. • Two parts to the problem: • The age of the canyon • The origin of the canyon • So, how does one evaluate the genesis of a canyon (or valley)? How Did The Canyon/Valley Form?

• Geomorphology (shape) of inner gorge • Glacial attributes (valley shape, cirques, truncated spurs, hanging valleys, aretes, etc) • Longitudinal profle of basement surface. • Sedimentology of Paleozoic canyon fll • Diamictite texture, striated clasts, low Chemical Index of Alteration (<52) • Sedimentology of Cutler Formation • An arid fan or proglacial outwash?… Truncated Hanging Valley Spur

Hanging Valley?

http://margopare.blogspot.com Is Unaweep V-shaped or U-shaped? Canyon Shape-- Gravity Data

⇐ V-shaped model

U-shaped model ⇒

(Davogustto BS thesis, 2005) Canyon Fill

10 km Well

Outcrop

• Late Paleozoic (?) diamictite in outcrop & subsurface Diamictite in Core Glacial Deposits?

If Unaweep = glacial, then |P-P Cutler Formation at mouth = proglacial. But Cutler = “arid alluvial fan” since at least the 1950s. Is Cutler Formation Alluvial Fan, or Proglacial Outwash? • Sedimentary facies of both are similar. • Issue: Cutler interpreted as humid fan (by Campbell, 1979, 1980), and arid fan (Mack & Rasmussen, 1984) • Problems with the alluvial fan hypothesis… Proximal Cutler contains: - Subaqueous debris fows (graded) - Thick successions of graded gravels (turbidites) - Large-scale slumps, dropstones All signaling subaqueous deposition (Gilbert Delta)… Distal Cutler contains: - Thick crossbedded gravels (food deposits) - Deposits recording high-discharge events All indicating fuvial system with much water & power Proximal Cutler Formation

Unaweep Canyon ‘Proximal’ Cutler Foresets (<1 km) -- Graded Debris Flows ‘Proximal’ Cutler Foresets (<1-3 km) -- Graded Beds Proximal Cutler Lonestones Proximal Cutler— Dropstones onlap above

rupture below “Distal” Foresets

“Medial-Distal” Fluvial Medial/Distal Cutler -- Streamfood A Possible Analog?

Lake Paron, Huascarán National Park, Peru How High Was the Ice?

• LGM tropical glaciers reached (as low as) 2100 m, more generally ~3000 m. • Cutler = highland to shore in distance of 60-80 km • Maximum reasonable gradients from analog systems ≤0.02 • ⇒ Elevation at toe of ice was ≤1200-1600 m (!)

Paradox Basin Paleogeography Why is this a Problem?

• Tropical glaciers that persisted to within 1200-1600 m of sea level imply a global climate that was much colder than currently accepted. But climate models currently cannot replicate this. • Evidence should exist elsewhere. • How do we further test the hypothesis? Carb-Perm Dust: Thickest on Earth

⇐ Cutler Loess (>250 m, Utah)

Maroon Loess ⇒ (>700 m, Colorado) Study Modern Sediment?

• It is difficult to distinguish non-glacial from pro- glacial stream sediment using facies alone. Could sediment weathering attributes (physical & chemical) help? • Hypothesis: texture, chemistry, and mineralogy of granite-sourced alluvial sediments of non-glacial and proglacial systems exhibit differences. These differences lead to potential paleoclimate proxies for interpreting alluvial sediment in the rock record. Field Sites to Date

277K Average Annual Temperature 297K Norway Puerto Rico 4200mm 1769mm

Antarctica California Avg Annual Precipitaon Avg Annual Precipitaon

18mm 253K 295K 150mm Why Is This Important?

Two Big Reasons: 1— Develop quantitative metrics to enable distinction of paleoclimate from clastic sediments. 2— Chemical weathering consumes atmospheric CO2; if glacial sediments more reactive than non-glacial, implies enhanced weathering fuxes during “icehouse” intervals (w/ major impacts on carbon cycling). Conclusions— Pangaean Ice

• Hypothesis of ice at the equator, 300 My ago--recorded in W. US by glacially carved paleolandscape and pro/ periglacial sediments. The ice extended down to low- moderate elevation. • Implications? Late Paleozoic climate was —at times— remarkably cool. • How did this occur? (Need to use climate modeling…) • How to further test? Modern sediment-weathering study to develop paleoclimate proxies. Acknowledgements-- Pangaean Ice--

• R. Young, R. Johnson (UA), Y. Suarez, O. Davogustto, J. Haffener (Geophysics) • M. Soreghan (Sedimentology, Geochemistry) • M. Hamilton (U Toronto, Geochronology) • D. Sweet, D. Elmore (Paleomagnetics) • C. Eble (U. Kentucky, Palynology) • S. Kaplan, K. Marra, K. Moore (Geomorph, Sed, Structure) •T. Eccles, T. Foster, N. Suneson (Geologic Mapping) More Thanks... • Massey Ranch • Belle Chesnick (2V) Ranch) • Jerry & Virginia Lewis • Rex Beach • Ron Tipping • Dahl & Donna Aubert • Dave & Shelly Hawks • Paul Bristol (Bedford Ranch)

Many Kind Landowners Funding Acknowledgements

Funding– U.S. National Science Foundation (2002, 2007) U.S. Geological Survey EDMAP program (2010, 2011, 2012) Himes Drilling, Grand Junction, Colorado (2004) Sediment Weathering Study Antarctica Puerto Rico

Dr. Megan Elwood Madden, Dr. Young Ji Joo Graduate students: A. Stumpf, K. Marra, C. Smith; Undergraduates: R. Funderberg, F. Cartegena, A. Velez Funding: U.S. NSF, PRF Fund, Maxey Professorship University of Oklahoma J-1 Internship Program Upcoming Presentations for Students

Graduate Education in the United States— What, Why, When, Where, and How Dr. Lee Williams, Dean of the Graduate College, University of Oklahoma

The Application of Science and Engineering to Unconventional Reservoirs Mery Diaz, Peruvian OU Graduate, Petroleum Engineering

19 February 2016 19:00 at the Geological Society of Peru Visit Unaweep.