Paleosols and Soil Surface Analog Systems”, September 21-25, 2010, Petrified Forest National Park, Arizona” ______

Home , Paleosol, Soil biodiversity, Soil gas, Soil water (retention)

Program Volume for SEPM-NSF Workshop “Paleosols and Soil Surface Analog Systems”, September 21-25, 2010, Petrified Forest National Park, Arizona” ______

Tuesday, September 21, 2010 –Flight arrivals at Albuquerque, NM airport (afternoon and evening)

Evening, dual-occupancy accommodations for registrants pre-booked at Fairfield Inn, 2400 Centre SE, Albuquerque, NM 87106; 505-232-5800 – complimentary shuttle from airport to hotel (no planned workshop activities) Problems: e-mail [email protected] or [email protected] ______

Wednesday, September 22, 2010 –Depart Albuquerque, NM hotel (morning) and arrive in Holbrook for afternoon sightseeing at Petrified Forest National Park (PEFO)

8:00 AM Depart Fairfield Inn, driving northwest 3.5 hours to Holbrook, AZ

12:00 noon Arrive in Holbrook, AZ; check in to dual-occupancy accommodations for registrants pre-booked at Holiday Inn Express Hotel, 1303 Navajo Boulevard, Holbrook, AZ 86025; 928-524-1466; eat lunch (not provided as part of workshop fee) in Holbrook; option to rest during the afternoon, or …………………….

2:00 PM Depart Holbrook for Petrified Forest National Park (PEFO); tour of Aislyn Trendell and PEFO Visitor Center and Gift Shop (north entrance), petrified log Baylor Geology Grad localites, Interpretive Center (south entrance) students

6:00 PM Return to Holbrook hotel; dinner in Holbrook (not provided)

8:00 PM PEFO Park history and general geologic overview (in hotel) Dr. Bill Parker, NPS ______

Thursday, September 23, 2010 – Keynote and Invited Oral Presentations (morning)

7:30 AM Depart Holbrook for PEFO

8:00-8:15 AM Welcoming remarks from organizers and Superintendent Steven G. Driese and PEFO Superintendent

8:15-8:45 AM A short history and long future of paleopedology Gregory J. Retallack

8:45-9:15 AM Advances in paleosol applications in paleoclimatology Ronald Amundson

9:15-9:45 AM Pedosystem science approach to describing and interpreting Lee C. Nordt the fossil record of soils

9:45-10:15 AM Quantitative paleoenvironmental and paleoclimatic Nathan D. Sheldon reconstruction using paleosols and Neil J. Tabor

10:15-10:30 AM Coffee break

10:30-10:45 AM A paleoseasonality proxy for paleosols derived from modern Erick L. Gulbranson soil geochemistry

10:45-11:00 AM The formation of pedogenic carbonate in modern soils: Daniel O. Breecker Evidence from Texas and Tibet

11:00-11:15 AM Abundance of paleo-Vertisols in the Phanerozoic rock record: Steven G. Driese Product of preservation, recognition, or paleoclimate?

11:15-11:30 AM A method for finding probable locations of paleosols sensitive H. Curtis Monger and insensitive to climate change

11:30-11:45 AM The current status of the sphaerosiderite paleoclimate proxy Greg Ludvigson

11:45 AM-12:00 The Critical Zone: A deep time perspective Gail M. Ashley

12:00-1:00 PM Lunch provided on-site

Thursday, September 23, 2010 – Poster Presentations and Group Discussions (afternoon)

1:00-3:00 PM Posters on display, authors present: Bitting and Spencer, Deocampo and Ashley, Dworkin et al., Kraft et al., and Stinchcomb et al.

3:00-4:00 PM Q & A for authors of talks and posters, General discussions defining important issues: and possible break-out groups and leaders

4:00-5:30 PM Break-out group discussions

6:00-8:00 PM Barbecue and mixer at PEFO (Dr. Bill Parker, hot dogs and burgers, assisted by students) 2

8:30 PM Return to Holbrook ______

Friday, September 24, 2010 – Field Trip Stops One to Eight (morning and afternoon)

7:00 AM Depart Holbrook for PEFO

7:30 AM Depart from PEFO North-End Visitors Center

7:30 – 8:10 AM Drive to The Tepees (see Road Log) Bill Parker and Jeff Martz

8:10 – 8:30 AM Alluvial Sequence Stratigraphy Stacy C. Atchley

8:30 – 8:40 AM Depositional and Pedogenic History of Aislyn M. Trendell Stops One to Four

8:40 – 9:00 AM Stop One: Upper Triassic Flora in the Sidney Ash Newspaper Rock Bed

9:00 – 9:25 AM 1Hike to Stop Two

9:25 – 10:20 AM Stop Two: A Well-Drained/Gleyed Lee C. Nordt, Aislyn M. Trendell Paleo-Vertisol Sequence

10:20 – 10:40 AM 1Hike to Stop Three

10:40 – 10:55 AM Stop Three: Lacustrine Deposits Aislyn M. Trendell, William G. Parker, of the Blue Mesa Jeffrey W. Martz

10:55 – 11:10 AM 2Hike to overlook of Stop Four

11:10 – 11:30 AM Stop Four: The Lower Sonsela Member Aislyn M. Trendell

11:30 – 12:10 PM 1Hike Back to Vans

12:10 – 12:50 PM Rest Stop at Agate Bridge and Drive to Blue Mesa Overlook

12: 50 – 1:35 PM Lunch

1:35 – 2:25 PM Drive to Mountain Lion Mesa (see Road Log) William G. Parker and Jeff Martz

2:25 – 2:35 PM Sequence Stratigraphic Context of Mountain Lion Mesa Section Stacy C. Atchley

2:35 – 2:45 PM Stop Five: Discussion of Faunal Turnover William G. Parker, Jeffrey W. Martz

2:45 – 3:15 PM Stop Five: The Silcrete Steven G. Driese 3

3:15 – 3:30 1Hike to Stops 6 to 8

3:30 – 4:45 Stop Six and Seven: Pale-Vertisols, Rhizohalos, Lee C. Nordt and Carbonate Rhizocretions

4:45 – 5:05 Stop Eight: Plant Debris Beds Sidney Ash

5:05 – 5:25 Exit Park via Southern Entrance

6:30 – 7:00 PM Return to Holbrook, have dinner (not provided as part of workshop fee)

1 This hike is on soft substrate, relatively flat and no more than 1 mile distance. 2 More strenuous hiking - moderate grades for distances of up to 2 miles and minor amounts of climbing. ______

Notes:

Saturday, September 25, 2010 – Keynote and Invited Oral Presentations (morning)

7:30 AM Depart Holbrook for PEFO

8:00-8:15 AM Meeting updates (inside) and group photograph (outside) Steven G. Driese

8:15-8:45 AM Reconstructing marine-terrestrial paleoclimate linkages: Isabel P. Montañez A Carboniferous perspective

8:45-9:15 AM Pedologic approaches to alluvial sequence stratigraphy Paul J. McCarthy and Stacy C. Atchley

9:15-9:30 AM A geochronologic framework for the Late Triassic Chinle Jahandar Ramezani fluvial system at the Petrified Forest National Park: Sediment and David E. accumulation rates and paleoenvironmental implications Fastovsky

9:30-9:45 AM The distributary fluvial system (DFS) paradigm: Gary S. Weissmann Observations of fluvial form in modern continental sedimentary basins

9:45-10:00 AM Soil development on distributive fluvial systems (DFS): Adrian J. Hartley Modern day observations with implications for interpretation of the continental rock record

10:00-10:15 AM Coffee break

10:15-10:30 AM Buried alluvial paleosols dating to the Pleistocene-Holocene Rolfe D. Mandel transition in the Central Great Plains, U.S.A.

10:30-10:45 AM Untangling regional records of Eocene-Oligocene climate Dennis O. Terry change across Wyoming, Nebraska, and South Dakota

10:45-11:00 AM Towards a better understanding of the terrestrial ecosystem: Daniel J. Peppe integrating paleobotany, paleopedology, sedimentology, and geochemistry

11:00-11:15 AM Organisms as a major soil-forming factor, ecosystem Stephen T. Hasiotis engineers, and their significance to the Critical Zone: A deep-time perspective

11:15-11:30 AM Pedological reflections on naming of paleosols in the rock Larry P. Wilding record

11:30-11:45 AM NSF Sedimentary Geology and Paleobiology Program H. Richard Lane Director comments

12:00-1:00 PM Lunch provided on-site

Saturday, September 25, 2010 – Poster Presentations and Group Discussions (afternoon)

1:00-3:00 PM Posters on display, authors present: Demko and Cleveland, Flaig et al., Gerlowski- Kordesch and Stiles, Gulbranson et al., Mintz et al., Rosario-Diaz et al., and Rosenau et al.

3:00-4:00 PM Q & A for authors of talks and poster; Break-out working groups meet and prepare draft documents

4:00-6:00 PM Presentations of draft documents and round-table discussions leading to draft white paper

6:00-6:30 PM Return to Holbrook (+ some early departures from PEFO for Albuquerque airport)

6:30-8:30 PM End-Conference Dinner at Mesa Italian Restaurant ______

Sunday, September 26, 2010 – Depart for Albuquerque, NM airport

8:00 AM Depart for airport (early Sunday AM departures must be scheduled in advance)

11:30 AM Arrive at Albuquerque, NM airport to drop off registrants ______

Notes:

Abstract Volume for SEPM-NSF Workshop “Paleosols and Soil Surface Analog Systems”, September 21-2, 2010, Petrified Forest National Park, Arizona” ______

(1) Advances in paleosol applications in paleoclimatology (oral)

Amundson, Ronald1, Warren Sharp2, and John Valley3: 1Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720 USA ([email protected]); 2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709 USA; 3Department of Geoscience, University of Wisconsin, Madison, WI 53706 USA.

Paleosols are now well known reservoirs of paleoclimate information. Two the greatest difficulties impeding the extraction of more quantitative environmental information from these soils are (1) difficulties in developing precise chronological age constraints and (2) extracting non-integrated climatic signals from the soil’s chemistry. On-going advances in laboratory instruments and the development of new techniques have opened emerging avenues for paleosol dating and paleoclimate research. Cosmogenic surface exposure dating is becoming a mature field. However, more recently, the use of cosmogenic nuclides to estimate burial ages has been conducted, with the recent combined use of 26Al, 10Be, and 21Ne pushing the window of application further back in time: well into the Miocene (Balco and Shuster, 2009). This application has been further enhanced by much more rapid methods of 21Ne measurements by some laboratories. Soil carbonate laminations on gravels have been recognized to retain potentially 105 y records of stable C and O isotopes. Work just a decade ago focused on manual drilling and sample collection to exploit these records (Sharp et al, 2003). The development and expansion of facilities with laser ablation ICP-MS capabilities now makes it possible to conduct ~ μm scale sampling and U series age dating across these laminations, providing unprecedented understanding of growth rates. This rich age perspective is now matched by comparably scaled O isotope analyses made with Secondary Ion Mass Spectrometry (SIMS). The presentation will include some as yet unpublished fine resolution dating and O isotope measurements from Wyoming, and include in-progress research results from the Atacama Desert in Chile. The goal will be to suggest that carbonate bearing paleosols can yield unprecedented climatic and chronological information, enhancing our understanding of continental paleoclimate.

Balco, G. and D.L. Shuster. 2009. 26Al-10Be-21Ne burial dating. Earth and Planetary Science Letters. 286:570- 575.

Sharp, W.D., K.L. Ludwig, O.A. Chadwick, R. Amundson, and L. Glaser. 2003. High resolution dating by TIMS 230Th/U of paleosols in fluvial terraces of the Wind River Basin, Wyoming, USA. Quaternary Research 59: 139-150. ______

(2) The Critical Zone: A deep time perspective (oral)

Ashley, Gail M.: Dept. of Earth & Planetary Sciences, Rutgers University, Piscataway, NJ 008854-8066 USA ([email protected]).

The Critical Zone (CZ) is defined as the “ heterogenous, near surface environment in which complex interactions involving rock, soil, water, air and living organisms regulate the natural habitat and determine availability of life sustaining resources” in a report by the Committee on Basic Research Opportunities in the Earth Sciences (NRC, 2001). The concept immediately resonated with the biogeochemical community (formerly loosely organized under Weathering System Science) and a modestly-funded NSF Program entitled Critical Zone Observatories (NSF-CZO) was announced in 2006. The observatories operate on a watershed scale and involve both field and theoretical approaches.

The Critical Zone is an appealing unifying concept that accommodates research on: • Hydrologic cycle; Carbon cycle; Biogeochemical cycles • Gas exchange (major and trace) • Life processes (macro & microbial; plant & animal) • Weathering (chemical & physical & biological) • Erosion & deposition (physical processes) • Cycling of contaminants (e.g. organics, metals) • Soils

Although the 2001 NRC Report emphasized the application of the CZ concept to current global change issues, sustainability, and land-ocean interaction, there was also plea for the using the CZ to understand the formation of a geological record that encodes a four-billion year history of Critical-Zone processes, including changes in the composition of atmosphere and ocean, glacier development, fluvial processes and environmental variations caused by volcanic episodes, meteor impacts and other extreme events. However, any emphasis on time, particularly deep time has essentially disappeared from the NSF-CZO program. The current CZ research is focused on the modern weathering machine and assumes a static system. However on geological time scales, the real world is constantly changing: Long term- evolution of a planet and its spheres Intermediate term – plate tectonics and astronomic forcing Short-term – ocean and atmospheric coupling; the Anthropocene

There are many challenges, though, when applying a conceptually simple idea of a “Critical Zone” to the realities of the geological record, such as determining boundaries of a specific Critical Zone, dating Critical Zones, teasing out the effects of diagenesis and overprinting, etc..

Has the train left the station? Is it too late to apply the CZ concept to deep time questions?

We should be thinking in terms of Paleo Critical Zone and its own NSF program. The Earth’s surface is a continually changing boundary layer with a changing atmosphere (temperature, pressure, and composition), evolving plant and animal communities, hydrosphere, bedrock composition, and topography.

At the moment research focused on integrative records of a changing Earth Surface, is falling through the funding cracks. ______

(3) Ground-penetrating radar recognition and optically-stimulated luminescence dating of a Holocene alluvial unconformity and paleosol in the upper Delaware River Valley, USA (poster)

Bitting, Kelsey1, Joel Spencer2 and Regina DeWitt3: 1Dept. of Earth & Planetary Sciences, Rutgers University, Piscataway, NJ 008854-8066 USA ([email protected]); 2Dept. of Geology, Kansas State University, Manhattan, KS 66506-3201 USA ([email protected]); 3Department of Physics, Oklahoma State University, Stillwater, OK 74074, USA ([email protected]).

Ground-penetrating radar (GPR) survey reveals a widespread unconformity in a latest-Pleistocene to Holocene alluvial terrace along the northern Delaware River, New Jersey. The unconformity is characterized by onlap and downlap of radar reflectors above, and minimal erosional truncation of reflectors below paleo-topographic highs. The high-amplitude reflector associated with the unconformity indicates a strong electromagnetic contrast with the surrounding sediments, associated with increased water retention. Examination of cores shows that sediments immediately beneath the unconformity have finer grain size and increased organic carbon content, consistent with the presence of a relatively well-developed paleosol at this surface. Based on GPR data, targeted sediment coring was conducted for the purpose of optically-stimulated luminescence (OSL) dating. Four sediment samples were collected from a 7 m deep core under low-intensity red safelighting; two samples were taken at estimated depths above and below the unconformity, while two deeper samples were taken to constrain the timing of the initiation of overbank deposition at the site. Later examination of the core in daylight conditions revealed that sample S2, immediately below the unconformity, was located within the top 20-30 cm (upper Bt horizon) of the paleosol. Dose rate calculations for OSL are commonly calculated using the assumption that radioactive daughter products remain in equilibrium. However, leaching during pedogenesis may remove soluble daughter products. Alternately, a subsurface paleosol horizon may create an impediment to groundwater infiltration, causing a buildup of soluble radioactive daughter elements at this contact. Chemical weathering ratios based on major and minor element analyses of the OSL samples confirm likely leaching and chemical weathering of the sample within the paleosol, as well as a lesser degree of alteration of the sample above the major paleosol. Measurements are in progress to determine whether samples are affected by radioactive disequilibria, but the results are expected to alter the ages by no more than 10%. Samples S3 and S4 at the base of the core indicate that deposition of sand on the alluvial terrace first occurred around 15.13 +/- 0.82 ka. Low overdispersion of the single aliquots for OSL dating of this unit suggest the possibility of eolian deposition at this early time period. Sample S2, within the upper Bt horizon of the paleosol, dates to approximately 8.66 +/- 0.62 ka. As a result of likely high rates of bioturbation in the upper portions of the paleosol, the OSL age of the sample immediately below the unconformity is interpreted as a hybrid age most closely approximating the time of burial of the unconformity, rather than the time of sediment deposition (as is typical in OSL dating). Finally, sample S1 above the unconformity dates to approximately 9.91 +/- 0.65 ka, within error of the age of the S2 sample below. Within the error of the OSL dating technique, timing of the unconformity and development of the paleosol prior to about 9 ka coincide with a period of warming and drying weather in the upper Delaware. Reinitiation of deposition atop the unconformity around 9 ka coincides with the early Holocene hypsithermal period, which may have resulted in greater warming and drying that destabilized vegetation, causing significant reworking of sediment during rare high-magnitude flood events. ______

(4) The formation of pedogenic carbonate in modern soils: Evidence from Texas and Tibet (oral)

Breecker, Daniel O.1, Steven G. Driese2, Lee C. Nordt2 , Lauren A. Michel2, Jason S. Mintz2, Jay Quade3, Mathieu Daëron4, and John M. Eiler5: 1Department of Geological Sciences, The University of Texas at Austin, University Station C1100, Austin, TX 78712-0254 USA ([email protected]); 2Department of Geology, Baylor University, One Bear Place 397354, Waco, TX 76798-7354 USA ([email protected]; [email protected]; [email protected]; [email protected]); 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721 USA ([email protected]); 4Laboratoire des Sciences du Climat et de l'Environnement, CNRS – CEA – UVSQ, F91198 Gif-sur-Yvette, France ([email protected]); 5Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, California 91125 USA ([email protected]).

Paleosol carbonate is perhaps the most widely applied paleosol – based paleoenvironmental proxy. Numerous researchers have used paleosol carbonate to reconstruct a wide variety of paleoenvironmental variables including mean annual precipitation, soil temperature, paleoelevation, atmospheric CO2 concentration and paleovegetation. It is important to understand the environmental conditions and mechanisms of modern pedogenic carbonate formation in order to accurately use paleosol carbonate to reconstruct ancient environments. A consistent picture of carbonate formation in soils has been provided by recent geochemical work. Multiple lines of evidence indicate pedogenic carbonate forms when soils are hot and dry and when soil CO2 concentrations are near their annual minimum values. Measurements made in modern soils from the southern Tibetan Plateau indicate that soil carbonate forms at temperatures approximately 15°C higher than local mean annual air temperature. Carbonate formation temperatures calculated from measured Δ47 values of modern pedogenic carbonate are approximately 15°C higher than local mean annual air temperature. The oxygen isotope fractionation factor calculated from measured δ18O values of pedogenic carbonates and meteoric (spring, stream and soil) waters independently suggests that the carbonate formation temperatures are approximately 15°C higher than mean annual air temperature. These calculated carbonate formation temperatures are in good agreement with measured soil temperatures in southern Tibet at ~50 cm soil depth during late June. Together these results indicate that pedogenic carbonate forms in oxygen isotope equilibrium with local meteoric water and that the bond ordering in the carbonates records the carbonate formation temperature. Low δ18O values of meteoric water occur on 18 high plateaus and in rain shadows on the leeward side of mountain belts. The measurement of both Δ47 and δ O values in pedogenic carbonates may allow us to distinguish soils formed on an ancient high plateau from soils formed in an ancient rain shadow. Monitoring of soil CO2 concentrations in a modern Vertisol at the USDA-ARS Riesel watershed in Riesel, TX provides mechanistic evidence for carbonate formation when the soil is hot and dry. CO2 concentrations at the depth of carbonate accumulation (~1 m) during the winter were 2.0-4.4% by volume. Soil CO2 concentrations increased during the spring and early summer up to 9.4% in one location. CO2 concentrations decreased to 1.7-2.0% during June and/or July, perhaps driven by drying and cracking of the clay-rich soil. Soil temperature increased from 10-11°C in February to 26-27°C in July. The solubility of calcite in the soil solution, calculated assuming the system H2O-CO2-CaCO3 using measured values of soil 2+ pCO2 and soil temperature, is dominantly controlled by pCO2 and decreased from 3.5 mmol Ca /L in the beginning of June to 1.8 mmol Ca2+/L in August. These results suggest that calcium carbonate becomes most insoluble when soil CO2 decreases during the hot, dry portion of the summer. ______

(5) Paleosols as tools for defining accommodation-fill-based units in a sequence stratigraphic framework (poster)

Demko, Timothy M., and David M. Cleveland: ExxonMobil Upstream Research Co., Houston, TX 77252 USA ([email protected]; [email protected]).

Although paleosols have been demonstrated to be useful tools in defining depositional packages in continental strata, and marginal marine strata that have experienced at least some periods of subaerial exposure, most applications of paleopedology address the implications for stratal architecture only at the local scale of the depositional environment. Herein, we will outline the concepts and methodological framework for using paleosols as criteria for helping define stratal packaging at the scale of depositional systems and sedimentary basins, i.e. within a sequence stratigraphic framework. At its most basic level, the goal of sequence stratigraphy is to define packages in sedimentary strata that reflect changes in accommodation (space available for deposition) and its relative rate of fill by sediment flux. Parasequences, systems tracts, and sequences, as originally conceived in marine and marginal-marine strata, are recognized by identifying surfaces that bound successions of genetically related strata with characteristic lithofacies assemblages and/or stacking patterns. These bounding surfaces are chosen to mark significant changes in accommodation: flooding surfaces, over which there are significant increases in accommodation, and sequence boundaries, which mark a relative lack of accommodation, even to the point of erosion ("negative accommodation"). Characteristic stacking patterns (progradation, aggradation, retrogradation) of these accommodation-based units are determined by the relative balance between the rate of accommodation generation and the rate of sediment flux. Because of the important implications of changes in this balance to interpretation and prediction of stratal architecture, surfaces over which stacking patterns change are assigned special significance (e.g. transgressive surface, maximum flooding surface, sequence boundary). Accommodation in continental and marginal marine settings can be created by several mechanisms: 1) a relative rise in base level due to subsidence (tectonic, compaction, etc.); 2) eustatic sea level rise; 3) and/or changes in the equilibrium of fluvial systems (controlled by discharge, sediment flux, and sediment grade). In marginal marine settings, an increase in accommodation may result in a marine transgression. Subsequent progradation of sediment may eventually result in fill to subaerial exposure (terrestrialization) and pedogenesis. In these cases, paleosols mark the ultimate fill of accommodation, and subsequent base level rise would create a marine flooding surface/parasequence boundary above. Significant base level falls in marginal marine settings causes incision of fluvial systems and the cutting of incised valleys. Interfluve areas between drainage basins become stranded from deposition and are subject to longer periods of well-drained conditions and develop paleosols relatively more mature than those that may be present in the subsequent valley fill strata. These interfluve paleosols mark a sequence boundary or flooding surface sequence boundary (FSSB). In continental settings (outside the influence of eustatic base level), soils can form at any landscape surface. Interfluve areas (floodplain, overbank, etc.) make up the majority of any alluvial plain, with the trunk drainage channels of major channels covering a relatively small component of the overall landscape. Because paleosols that form under a distinctive climatic signature represent an amount of time that is roughly equivalent to, or less than Milanković-scale cycles, they, in effect, allow for chronostratigraphic control in alluvial strata. When fluvial systems are in equilibrium, paleosols in adjacent areas are not provided with any significant new sediment supply. During this time, climate is the dominant influence across the landscape and the result is the development of a mature, complexly overprinted, or amalgamated paleosol with features reflecting the physiochemical processes of formation. More mature paleosols record longer durations over which the fluvial regime remained in equilibrium providing for increased depth of pedogenic alteration. When fluvial systems are in disequilibrium, one of two general scenarios will ensue. Landscape degradation will result in the loss of alluvial plain strata due to increased downcutting and floodplain scavenging. Conversely, landscape aggradation will result in the rapid buildup of interfluves with a concomitant rise in water table. These conditions promote the 11

development of immature and wetland paleosols. The basic observable units in alluvial strata are meter-scale fining-upward successions (fluvial aggradational cycles; FAC) that represent accommodation fill by floodplain aggradation. Larger-scale stacking patterns of these units (FAC sets) record longer-term trends in accommodation and sediment flux, and as in marginal marine succession, changes in stacking pattern are related to allogenic and allocyclic controls. Surfaces that define these changes are important, correletable, chronostratigraphic boundaries. ______

(6) Wetland sediments and paleosols: It’s all about water table (poster)

Deocampo, Daniel M.1, and Gail M. Ashley2a: 1Dept. of Geosciences, Georgia State University, Atlanta, GA 30302 USA ([email protected]); 2Dept. of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854 ([email protected])

Wetlands are depositional environments and ecosystems that range between ephemerally wet to fully aquatic continental habitats. They are commonly associated with localized groundwater discharge, e.g. springs and seeps. The sediment and paleosol records of wetlands are products of a unique setting that can be both subaerial and water-saturated at the same time. Wetlands tend to occupy low-gradient portions of the landscape in places where the phreatic zone is at least ephemerally exposed at the surface, and hydrophytic vegetation has an opportunity to colonize. Such conditions have been documented on hillslopes, fluvial floodplains, and exposed lake flats following lacustrine regression. Paleosols from these settings record a paleocatena controlled by climate, depositional setting, and hydrogeologic context. The persistence of wetlands requires a regular water source (e.g. groundwater discharge locations determined by topography or faults) coupled with an impermeable or poorly drained substrate. Sedimentation in wetlands is characterized by low sedimentation rates, extensive bioturbation (by micro-, macro-, and mega-fauna and flora), high organic carbon productivity, and geochemical reactions consistent with the chemistry of inflowing water. Aqueous CO2 levels are often elevated in wetlands due to high rates of microbial respiration; this suppresses pH and impacts the thermodynamic stabilities of carbonate, silicate, and sulfide mineral systems. Histosols (peats) and other hydric soils typified by anaerobic conditions (indicated by gley color and minerals like pyrite and siderite) are common in sites with permanently high water table. In some situations, aquatic vegetation will maintain equilibrium with hydrostatic head, building large "blister wetlands” under conditions of artesian discharge. Even wetlands fed primarily by surface water have low clastic sedimentation rates; phreatophytes and aquatic marsh vegetation limit transport of detrital material into wetlands. Inorganic components of wetland sediment are therefore largely limited to reworked material originally deposited prior to colonization of the wetland by vegetation, with the possible admixture of aeolian sediment or volcaniclastic airfall. The signature of wetland diagenesis or pedogenesis includes production of redoximorphic features; enhanced hydrolytic alteration or dissolution of soluble phases; and preservation of biotic indicators of wetland habitats. Wetlands developed on carbonate-rich sediment can be recognized by characteristic facies such as brecciation, pseudomicrokarst, laminar calcretes, and others (Alonso-Zarza and Wright, 2010). The depth of development of wetland indicators into underlying sediment depends primarily on biotic factors such as root growth, infauna, and the actions of large vertebrates. There are many challenges to recognizing and interpreting paleosols formed in ephemerally or permanently wet environments. Important future research questions include 1) What are the physical and biogeochemical impacts of microbes, diatoms, testate amoebae, ostracodes, chrysophytes, and others in an environment with potentially dramatic hydrological changes? 2) How are regional climate and climate change recorded in these localized wet spots over human and geological timescales? 3) To what degree do external factors (i.e. water, wind, and biota) influence the bulk composition of fine-grained soil matrix (plasma)? 4) In a setting where everything is fundamentally a secondary deposit, how can episodes of (bio)mineralization and 12

diagenesis be distinguished, providing insight into complex biogeochemical reactions? Whatever interpretations emerge from the study of wetland paleosols, it is crucial that they be looked at not as isolated systems, but rather as part of the larger hydrogeologic and depositional systems in which they occur.

apresenter ______

(7) Abundance of paleo-Vertisols in the Phanerozoic rock record: Product of preservation, recognition, or paleoclimate? (oral)

Driese, Steven G., and Lee C. Nordt: Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]).

Paleosols satisfying diagnostic criteria for classification as Vertisols in USDA Soil Taxonomy (hereafter "paleo- Vertisols") are clay-rich paleosols that show abundant evidence for shrink-swell processes. They have provided important information on paleoenvironments, including Phanerozoic estimates of atmospheric pCO2 and changes in soil morphology accompanying the evolution and diversification of terrestrial land plants. Modern Vertisols are characterized by macro- and micromophological characteristics formed in response to shrink-swell phenomena associated with seasonal precipitation or soil-moisture deficits. Many of these features preserve well in the ancient rock record, and can be easily recognized in the field and in thin section. Stable carbon and oxygen isotope analysis of pedogenic carbonate in Vertisols help to elucidate the soil ecosystem (dominance of C3 vs. C4 flora) and changes in soil water compositions that may indicate climate change. Similar information may be preserved in the isotopic compositions of paleosols, as well as constraints on paleoatmospheric pCO2 using the soil carbonate paleobarometer. Most importantly, paleo-Vertisols are common in the geological record, ranging in age from the Precambrian to the Cenozoic, and have formed over a wide range of paleolatitudes, ranging from equatorial-low latitude to as high as 78o. The wide spatial and temporal distribution of paleo-Vertisols reflects the potential for their formation under wide ranges of moisture regimes (from semiarid to sub-humid). Their widespread distribution also reflects the predominantly physical controls on Vertisol formation, thus these soils are not limited to specific environments or ecosystems. Terrestrial facies comprising stratigraphic intervals within Paleozoic redbed deposits in eastern North America contain primarily paleo-Vertisols, paleo-Entisols and paleo-Inceptisols. Vertisol-like paleosols appear over-represented in the rock record as compared with their present global distribution of 2-3% of modern soils. Possible hypotheses that might explain this include: (1) Strong preservational bias: Vertisols characteristically have a high fine-clay content, are cohesive, and the consolidated clay is erosionally resistant to both fluvial channel migration and to marine transgression. Vertisols characteristically form in low-elevation, low-relief areas (floodplains and coastal mud margins are favored sites), and thus may have a higher preservation potential in the geological record. Also, less time is necessary for subaerial exposure and pedogenesis in order to form a paleosol because Vertisols are known to form very rapidly (within 10s to 100s of years). (2) Strong recognitional bias: Macroscale features of Vertisols, including pedogenic slickensides, gilgai, pseudo- anticlines, and angular blocky peds are diagnostic and are easy for geologists to identify in paleosols. The sepic- plasmic microfabrics of Vertisols are usually well-preserved in paleosols and visible in thin sections. The dominance of physical (shrink-swell) processes involved in the genesis of Vertisols implies that neither the presence of root traces, textural differentiation, carbonate redistribution nor color horizonation are necessary for their identification as paleosols. (3) Paleogeographic, paleoclimatic and parent materials: Vertisols can form over wide ranges of latitudes and under varying moisture regimes from parent materials that are base-rich to base-poor; the only strict climatic requirement is that a period of seasonal soil moisture deficit occurs that promotes drying and cracking. These hypotheses are being currently evaluated by actualistic studies of Vertisols in the Texas Coast and Blackland Prairies, with the expressed purpose of identifying specific morphological and 13

chemical features that have preservation potential in the geological record and which are climatically and chronologically sensitive indicators. ______

(8) Isotopic reliability of dispersed organic matter in paleosols (poster)

Dworkin, Stephen I. (Steve), Lee C. Nordt, and Stacy C. Atchley: Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]; [email protected]).

Dispersed (bulk) organic matter in paleosols has the potential to provide two of the input parameters into Cerling’s atmospheric pCO2 paleobarometer equation. These variables are the carbon isotopic composition of CO2 diffusing into the soil from the atmosphere and the carbon isotopic composition of CO2 resulting from below ground plant respiration and decomposition (collectively called soil respiration). Commonly, the carbon isotopic composition of time equivalent marine carbonates has been used as a proxy for the composition of the atmosphere however; the tenuous correlation between marine and terrestrial rocks limits the resolution of the resulting atmospheric pCO2 reconstruction. Therefore, this study investigates the use of dispersed organic 13 matter in paleosols as a record of atmospheric δ CO2 and concludes that with careful evaluation, this material can provide a reliable isotopic record of atmospheric composition. We then proceed to use dispersed organic 13 matter in paleosols from west Texas paleosols to reconstruct an eight million year record of atmospheric δ CO2 that spans the late Cretaceous and early Tertiary. Although it has been clearly demonstrated that the carbon isotopic composition of the atmosphere can be reconstructed from the isotopic composition of plant tissue, it is still unclear if dispersed organic matter in paleosols can be used for the same purpose. The concern arises because as plant litter is incorporated into soil and is subsequently decomposed, only a tiny fraction of the original organic matter is preserved. It has been suggested that as the decomposition process proceeds, carbon isotopes making up the the soil organic matter are kinetically fractionated thus rendering the remaining organic matter useless for reconstruction of atmospheric 13 δ CO2. A second concern is that environmental stress during plant formation may cause restricted stomatal 13 conductance of CO2 resulting in carbon isotope ratios that cannot be interpreted in terms of atmospheric δ CO2. In order to investigate the isotopic reliability of dispersed organic matter in paleosols we compared the isotopic composition of bulk organic matter from a west Texas paleosol that formed just prior to the K/T boundary to the carbon isotopic composition of organic matter from five different terrestrial locations of similar age. We hypothesize that if ancient organic matter that formed in different locations at the same time preserve 13 the same isotopic composition, it supports the idea that these fossil plants reflect atmospheric δ CO2. Of the six locations, five (including the west Texas paleosol) have organic matter with very similar carbon isotopic compositions (average δ13C = -26.5 +/- 0.5 ‰) while plants at the sixth location apparently formed under environmental stress. This suggests that dispersed organic matter preserved in west Texas paleosols record 13 atmospheric δ CO2 as faithfully as bulk organic matter from coals or carbonaceous mudrocks. Therefore, we have measured the abundance and character of dispersed organic matter in B-horizons from a succession of 39 paleosols that span the K/T boundary in west Texas. Organic carbon concentrations vary between 0.07 and 0.28 wt % and average 0.14 wt %. The δ13C of this organic matter varies between -28.1 13 and -25.1 ‰. This corresponds to atmospheric δ CO2 values between -8.6 and – 5.8 ‰. In general, the 13 atmospheric δ CO2 exhibits a gradual increase from about -8 ‰ at71 Ma to about -7 ‰ at 63.5 Ma. ______

(9) Anatomy, evolution and paleoenvironmental interpretation of an ancient Arctic coastal plain: Integrated paleopedology and palynology from the Late Cretaceous (Maastrichtian) Prince Creek Formation, North Slope, Alaska, USA (poster)

Flaig, Peter P.1, Paul J. McCarthy2 and Anthony R. Fiorillo3: 1 Dept. of Geology and Geophysics, and Geophysical Institute, University of Alaska Fairbanks, P.O. Box 755780, Fairbanks, AK, 99775 USA (Current address: University of Texas at Austin, Bureau of Economic Geology, Austin, TX, 78758 USA, [email protected]); 2 Dept. of Geology and Geophysics, and Geophysical Institute, University of Alaska Fairbanks, P.O. Box 755780, Fairbanks, AK, 99775 USA ([email protected]); 3 Museum of Nature and Science, P.O. Box 151469, Dallas, TX, 75315 USA ( [email protected])

The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation exposed along the Colville River in northern Alaska records high-latitude, alluvial sedimentation and soil formation on a low-lying, low gradient, muddy coastal plain during a greenhouse phase in Earth history. This study combines outcrop observations, micromorphology, geochemistry, and palynological analyses of paleosols in order to reconstruct local paleoenvironments of weakly developed, high-latitude coastal plain soils. Sediments of the Prince Creek Fm. include quartz- and chert-rich sandstone channels and floodplains containing organic-rich siltstone and mudstone, carbonaceous shale, coal and ashfall deposits. Vertically stacked horizons of blocky-to-platy, drab- colored mudstone and siltstone with carbonaceous root-traces and mottled aggregates separated by sandy intervals indicate that the development of compound and cumulative, weakly-developed soils on floodplains alternated with overbank alluviation and deposition in distributary channels on crevasse splay complexes on floodplains . Soil formation occurred on levees, point bars, crevasse splays and along the margins of floodplain lakes, ponds, and swamps. Soil-forming processes were repeatedly interrupted by alluviation, with sediment added on top of soil profiles by flooding of nearby distributary channels. Alluviation is evidenced by thin (<0.5 m) sand and silt horizons within soil profiles, along with common pedorelicts, papules, and fluctuations with depth in a variety of molecular ratios (e.g. Ti/Zr, Ba/Sr, Fe/Al, Al/Si, and Al/(Na+K+Ca+Mg)). Abundant carbonaceous organic matter and root-traces, Fe-oxide depletion coatings, and zoned peds (soil aggregates with an outermost Fe-depleted zone, darker-colored, Fe-rich matrix, and lighter-colored Fe-poor center) suggest periodic waterlogging, anoxia and gleying. In contrast, Fe-oxide mottles, ferruginous and manganiferous segregations, insect and worm burrows, and rare illuvial clay coatings suggest recurring oxidation and periodic drying out of some soils. Trampling of sediments by dinosaurs is common. Jarosite mottles and halos surrounding rhizoliths, and rare pyrite and gypsum found in some distal paleosols implies a marine influence on pedogenesis at the distal margins of the coastal plain. Biota including Peridinioid dinocysts, brackish and freshwater algae, fungal hyphae, fern and moss spores, projectates, age-diagnostic Wodehouseia edmontonicola, hinterland bisaccate pollen and pollen from lowland trees, shrubs, and herbs indicate an Early Maastrichtian age for all sediments in the study area. The assemblage also demonstrates that although all sediments are Early Maastrichtian, strata become progressively younger from south north. The integration of biota with paleopedological data provides additional clues to regional biomass, paleo-relief, clastic input from channels, and the location of paleosol profiles relative to the paleo-coastline. Paleosols of the Prince Creek Fm. are similar to modern aquic subgroups of Entisols and Inceptisols and, in more distal locations, potential acid sulfate soils. A reconstruction of pedogenic processes suggests that these ancient high latitude soils were influenced by seasonally (?) fluctuating water table levels and, in distal areas, a marine influence. These results offer a unique glimpse into greenhouse sub-environments on a paleo-Arctic Cretaceous coastal plain governed by a near polar light, temperature, and precipitation regime upon which dinosaurs thrived. ______

(10) Interpreting sedimentation patterns and paleoclimate from the Vertisol successions of the Triassic- Jurassic Hartford Basin (Newark Supergroup), Connecticut, US (poster)

Gierlowski-Kordesch, Elizabeth H.1 and Cynthia A Stiles2: 1Department of Geological Sciences, 316 Clippinger Labs, Ohio University, Athens, OH 45701-2979 USA ([email protected]); 2National Soil Survey Center, Lincoln, NE 65808 USA ([email protected]).

The Hartford Basin in Connecticut, U.S.A. contains sedimentary rocks that accumulated as sediments within a Triassic-Jurassic rift valley. The sedimentary fill reflects the source area materials from the surrounding highlands and contains paleosol sequences that contain imprints of the climate and hydrology of the region. Detailed description of the paleosol horizons from three of the formations within this rift basin highlights the depositional paleoenvironments as well as the climatic and hydrologic influences on sedimentation and soil formation. The continental fill of the Hartford Basin contains four sedimentary formations interbedded with three basalt flows (all dated as approximately 200-202 Myr). These sedimentary formations, the New Haven Arkose (NHA), the Shuttle Meadow Formation (SMF), the East Berlin Formation (EBF), and the Portland Formation (in order from oldest to youngest) are intercalated with the Talcott, Holyoke, and Hamden Basalts, respectively. The three lowermost formations are composed of breccias, conglomerates, sandstones, siltstones, mudrocks, and limestones. The paleosols are found within the massive mudrock facies. Analyses of sedimentation patterns and lithologies in the basin indicate that New Haven Arkose depositional sequences occurred under more humid seasonal conditions than those of the Shuttle Meadow and East Berlin Formations. Aridity increased from Shuttle Meadow to East Berlin time. The morphology and geochemistry of paleosols found within these formations confirm this interpretation. ______

(11) A paleoseasonality proxy for paleosols derived from modern soil geochemistry (oral) 1 1 2 Gulbranson, Erik L. , Isabel P. Montañez , and Neil J. Tabor : 1Department of Geology, University of California-Davis, One Shields Ave, Davis CA 95616 USA ([email protected]; [email protected]); 2Department of Earth Sciences, Southern Methodist University, Dedman College, Dallas TX, USA ([email protected]).

The morphology and geochemistry of paleosols has the potential to record long-term climatic parameters such as atmospheric CO2, seasonal temperatures and mean annual precipitation, as well as internal characteristics of the soil important for supporting soil biological activity and surface ecosystems. Here, we explore the possibility of inversely estimating the temporal trends in rainfall versus evapotranspiration from physico- chemical properties of soil that are likely to be preserved during lithification and burial diagenesis. Climatic seasonality, in turn, is a first order control on plant ecosystems and knowledge of the climate state and plant ecosystem is crucial to understanding terrestrial biogeochemical cycling. We used a pedogenic energy model to link influxes of energy to the soil from sources that are intimately tied to climate (precipitation and net primary production). In turn these variables are evaluated against chemical weathering and evapotranspiration, which reflect the export of energy from the soil to the environment. At equilibrium this model predicts the relative proportions of rainfall and evapotranspiration from knowledge of the state of the soil (chemical weathering and morphology). Transfer functions were developed to estimate net primary production and evapotranspiration. Precipitation and the degree of chemical weathering are constrained by existing and accepted geochemical climofunctions and chemical proxies. The required input parameters to this model are 1) knowledge of the soil morphology, 2) accurate and complete major element concentration data for the active soil and parent material and 3) the latitude or mean annual temperature (±5ºC) that the soil formed under. Estimates of net primary production and actual evapotranspiration are in turn are used to constrain the humidity province that the soil formed under. We applied this proxy to modern soils along three latitudinal 16

transects of the coterminous United States for which soil morphology, major element data and climate data are known. The correlation coefficient between the modeled climate regime using only the latitude, morphologic and major element data of soils, and the measured climate is r=0.95. We conclude that this proxy provides an accurate and precise determination of climatic seasonality, which used in conjunction with paleoecologic data and isotopic analyses of C, H, N, and O can provide greater fidelity of terrestrial biogeochemical cycling of ancient environments. ______

(12) The response of late Paleozoic mid-latitude terrestrial ecosystems to deglaciation and floral reorganization (poster)

Gulbranson, Erik L., and Isabel P. Montañez: Department of Geology, University of California-Davis, One Shields Ave, Davis CA 95616 USA ([email protected]; [email protected]).

Paleosols of the late Paleozoic Paganzo Group preserve a record of late Pennsylvanian climate amelioration following the demise of the well-documented mid-Carboniferous glacial event. A stratigraphic interval of predominantly plinthic paleosols intermixed with argillic horizon-bearing paleosols occurs in the late Pennsylvanian Patquia Fm. over a broad region of the Paganzo Basin. Fluvial channel incision associated with plinthites within the stratigraphic interval suggests a peneplain or piedmont-like geomorphology and allows for regional determinations of paleoclimate to be assessed and independently verified. Major element geochemistry and paleosol morphology of late Pennsylvanian paleosols indicate a monotonous record of mean annual precipitation (MAP) punctuated by significant decreases in MAP preceding maximum marine flooding surfaces. An analysis of climatic seasonality, however, indicates relative stability in the temporal patterns of precipitation and evapotranspiration potential implying consistent atmospheric circulation trends for the high-latitude region of southwestern Gondwana during the late Pennsylvanian. Despite the relatively stable seasonality, the variability in MAP may indicate latitudinal shifts in the high-pressure polar fronts. Quantitative estimates of net primary production for the studied paleosols are consistent with a mesic soil temperature regime, which is general agreement with quantitative estimates of summer temperatures from pedogenic goethite isotope geochemistry. Carbon isotope geochemistry of goethite collected from plinthites in the studied stratigraphic interval imply seasonal flooding of the paleosols, which is consistent with the proposed geomorphic template and estimated climatic seasonality. Moreover, the carbon isotope values and mole fraction of goethite-

associated carbonate suggest a maximum partial pressure of atmospheric CO2 of 783ppmv under a mesic

temperature regime. However, due to hysteresis effects on soil CO2 during flooding our estimates of atmospheric CO2 point to lower values approaching pre-industrial levels. Taken together, the qualitative paleopedology and sedimentology and the quantitative geochemistry of late Pennsylvanian paleosols in the Paganzo Basin indicate a substantial departure from climates suitable for the maintenance of tidewater glaciers documented in the mid- Carboniferous and reveal a quasi-stable climate similar to mid-latitude continental regions under interglacial or perhaps greenhouse climate conditions. ______

(13) Soil development on distributive fluvial systems (DFS): Modern day observations with implications for interpretation of the continental rock record (oral)

Hartley, Adrian J.1, Gary S. Weissmann2, Gary J. Nichols3, L.A. Scuderi2, and S.K. Davidson1: 1Department of Geology & Petroleum Geology, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UE, UK ([email protected]); 2University of New Mexico, Department of Earth and Planetary Sciences, MSC03 2040; 1 University of New Mexico, Albuquerque, NM 87131-0001, USA ([email protected]); 3Department of Geology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK (Gary.Nichols-Dean-of- [email protected]).

Recent work has shown that rivers in active sedimentary basins form either (1) distributive fluvial systems (DFS), or (2) axial stream systems that parallel the basin trend, with the vast majority of sedimentation in the basin occurring on the DFS. These observations have implications for the interpretation of ancient fluvial deposits and the soils that form on these deposits. We use remotely sensed data and preliminary field observations from our database of over 700 continental basins and 400 large DFS (>30 km radius) to document variations in observed and inferred soil types on DFS. Examples are drawn from different tectonic and climatic settings. Important points are:

1) A spring line is present on the distal portion of on a number of DFS, and on others a downstream transition from a relatively well-drained to a relatively poorly-drained surface is observed. The groundwater source is most-likely from recharge along the proximal DFS reaches. This downstream change results in a transition from well-drained to poorly-drained soils. The nature of this change can vary significantly depending on the prevailing climate within the depositional basin. These observations provide an autocyclic mechanism for explaining changes in soil type within an individual sedimentary system. Taken out of context these differences in soil character could be interpreted to represent changes in climate and result in erroneous interpretation of the rock record. 2) Cycles of aggradation and incision driven by changes in the sediment supply to discharge ratio in DFS catchments can result in significant variations in soil maturity in immediately adjacent DFS. For example, during the Plio-Pleistocene, glaciated catchments experienced rapid aggradation during glacial outwash periods and incision during interglacials, with mature paleosols and exposure surfaces marking periods of incision and sediments with relatively immature paleosols marking periods of rapid aggradation. In contrast, adjacent DFS with non-glaciated catchments experienced much more subtle but similar cycles. This means that it may be possible to correlate between adjacent DFS using soil stratigraphy, but also that soil maturity will vary significantly between adjacent DFS. This observation also raises questions about the applicability of soil maturity models to the rock record, in particular is it true that all soils display an increase in maturity with distance from an active channel belt? Are models available that consider soil maturity when fluvial channel systems become detached from their surrounding floodplain?

As it is likely that DFS make up the majority of fluvial deposits in the sedimentary record, an understanding of the controls on soil distribution within the context of DFS is clearly important for interpreting the rock record. Our preliminary observations indicate that soil type can vary significantly with position on DFS and that soil maturity can vary significantly in both proximal and distal locations in response to cycles of incision and aggradation. We hope that by integrating observations of present day soils within the context of distributive fluvial systems can lead to an improved understanding of paleosol development in the rock record. ______

(14) Organisms as a major soil-forming factor, ecosystem engineers, and their significance to the Critical Zone: A deep-time perspective (oral)

Stephen T. Hasiotis1 and Mary J. Kraus2: 1University of Kansas, Department of Geology, 1475 Jayhawk Blvd., room 120, Lawrence, KS 66045 USA ([email protected]); 2University of Colorado, Department of Geological Science, Campus Box 399, Boulder, CO 80309 USA ([email protected]).

Organisms have been one of the most important of all the soil-forming factors since the Devonian (~416 million years ago). Research on modern and ancient soils, biota, and trace fossils shows that animals are mostly responsible for sediment mixing, acting to help build and destroy pedogenic structures and voids, and playing a major role in nutrient cycling via the work of detrivores and saprovores. The work of extant organisms in soils can be measured in the field and laboratory. In paleosols, trace fossils—tracks, trails, burrows, nests, rooting patterns, borings, and biolaminates—are proxies for soil biodiversity, behavior, and the work of organisms. Excellent examples abound in paleosol successions preserved in the Paleogene Willwood Formation, Upper Jurassic Morrison Formation, and Upper Triassic Chinle Formation in the Rocky Mountain region of the USA. The role of bioturbation is significant to understanding pedoturbation in modern and ancient soils in that the work of animals produces the macrochannels and macropores in which abiotic pedoturbation can take place. Bioturbation also allows for greater exchange between the soil atmosphere and Earth’s atmosphere, greater infiltration of precipitation and overland flow, and greater incorporation of organic matter into the subsurface, all of is part of the Critical Zone (CZ) as defined by the NRC. The rate and depth of work by animals is much greater than that of plants via root penetration and tree throw. Although plants contribute the majority of organic matter and acids that assist in the breakdown of lithic constituents, their roots displace very little material in comparison to the material displaced upward and downward by animals. Burrows and nests of animals can penetrate to ~100 m below the surface, and modify over 1 km3 to as much as ~10 km3 for an individual nest of some social insects. Animals displace sediments by diffusive (mm-scale particle movement) and advective (cm- to m-scale particle movement) methods via a combination of carrying, pulling, pushing, raking, cutting, and forcing. Penetration and mixing depth depend on the amount of soil moisture in the vadose zone, position of the phreatic zone, and the frequency and magnitude of depositional events. Many modern and ancient soil organisms can be classified as ecosystem engineers as they create, modify, and maintain habitats by directly or indirectly modulating the availability of resources to other species by bioturbating and redistributing soil material, creating and destroying pedogenic structures and macrochannels-pores, and ventilating and irrigating soils. Autogenic engineers change the habitat via their own physical structures, whereas allogenic engineers change the environment by shifting living or nonliving material from one physical situation to another. Trace fossils and their intimate association with the paleosols preserve how biotic activity shaped landscapes and above- and belowground ecosystems through time. Well-documented trace fossil records of termites, ants, crayfish, burrowing mammals and reptiles, and earthworms in paleosols as far back as the Triassic and Jurassic suggest these organisms are geoengineers, helping to shape the CZ for nearly 245 Ma. ______

(15) Isotopic record of Holocene paleoclimate from paleosols in Nochixtlán Valley, Oaxaca, Mexico (poster)

Kraft, Rebecca A.1, Naomi E. Levin1, Raymond. G. Mueller2, Benjamin H. Passey1, and Arthur A. Joyce3: 1Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 USA ([email protected]; [email protected]; [email protected]). 2Department of Soil Science and Geoarcheology, Richard Stockton College of New Jersey, PO Box 195, Pomona, NJ 08240 USA ([email protected]). 3Department of Anthropology, University of Colorado at Boulder, 1350 Pleasant St., Boulder, CO 80309 USA ([email protected]).

Six episodes of erosion identified between 4,220 BC and the present are the physical expression of Holocene environmental change in the Nochixtlán Valley, Oaxaca, Mexico. Within the Rio Verde drainage, highland erosion produced lowland deposition, causing geomorphic and ecological changes on the Pacific Coast (1). The two earliest periods of erosion are likely the result of climatic changes, four subsequent episodes correspond to demographic and land use changes identified in the archeological record (2). Correlation of erosional episodes to changes in demography and land use suggests an anthropogenic origin. Abundant well-preserved paleosols exposed in cutbanks of the Rio Verde have the potential to clarify the roles of two important sources of geomorphic change: 1) climate and 2) the anthropogenic impact of the intensification of agriculture. Our preliminary contribution to this problem is the application of carbonate clumped isotope thermometry. As a paleoenvironmental proxy carbonate clumped isotope thermometry represents an opportunity to obtain terrestrial soil paleotemperature, refine the calculation of the δ18O meteoric water from δ18O of pedogenic carbonate, and determine local environmental conditions for pedogenic carbonate. Here we present isotopic data from 100+ paleosols in cutbank exposures of the Rio Verde’s tributaries within the Nochixtlán Valley. More than 40 14C ages from soil organic matter date the sequence of paleosols between10,500 BC to the present and constrain individual periods of soil formation to short (102 years) and potentially longer (103 years) timescales. Preliminary temperatures calculated from carbonate clumped isotope thermometry range from 19˚C to 28˚C. δ18O soil water data range from -9.4‰ to -3.9‰ (SMOW), calculated using soil temperatures from mass-47 enrichments of CO2 (Δ47), which fall within values of meteoric waters in the region today (3). Soil temperatures calculated from Δ47 values of modern pedogenic carbonates are within the range of local maximum annual temperatures for the Nochixtlán Valley and correspond to temperatures 18 during months with low precipitation and peak potential evapotranspiration (4). δ O and Δ47 data from actively forming soils suggest pedogenic carbonates from buried soils record conditions in the Nochixtlán Valley during the warmest, driest part of the year. Initial results for δ13C of pedogenic carbonates range from -0.8‰ to -8.5‰, indicating soils were dominated by C4 plants or contained a mix of C3 and C4 vegetation. These results represent the first step toward a more detailed record of Holocene paleoenvironment in the Nochixtlán Valley. Beyond regional record of paleoclimate, these paleosols represent a natural laboratory outfitted with well-dated paleosols, different length scales of soil duration, and a high rate of agricultural disturbance that should make anthropogenic change detectable with micromorphological and geochemical studies. The Nochixtlán paleosols represent the opportunity to investigate the context of pedogenic carbonate formation, evaluate the soil organic matter dynamics, and develop a multi-proxy record of regional environmental change. 1. A. M. Goman, A. A. Joyce, R. G. Mueller, Quaternary Res 63, 250 (2005). 2. A. A. Joyce, R. G. Mueller, World Archaeol 29, 75 (Jun, 1997). 3. L. I. Wassenaar, S. L. Van Wilgenburg, K. Larson, K. A. Hobson, J Geochem Explor 102, 123 (Sep, 2009). 4. A. Mendoza, M. Ordonez, M. Briones-Salas, Biodiversidad de Oaxaca. (WWF, Mexico, 2004). ______

(16) The current status of the sphaerosiderite paleoclimate proxy (oral)

Ludvigson, Greg A.1, Luis A. González2, Jennifer A. Roberts2, David A. Fowle2, and Steven G. Driese3: 1Kansas Geological Survey, 1930 Constant Ave., Univ. of Kansas, Lawrence, KS 66047 USA ([email protected]); 2Dept. of Geology, University of Kansas, Lawrence, KS 66045 USA ([email protected]; [email protected]; [email protected]), 3Department of Geology, Baylor University, Waco TX 76798 USA ([email protected]).

By the mid-1990s, the wide availability of automated online carbonate reaction devices coupled to stable isotope ratio mass spectrometers permitted carbon and oxygen isotope analyses of carbonate microsamples (≤ 1 mg) to investigate the paleohydrology of authigenic siderite (FeCO3). Siderite is a common pedogenic mineral in the reducing groundwaters of poorly-drained soils in siliciclastic depositional systems. Genetic interpretations of siderite-bearing paleosols typically involve late stages of ferric oxide reduction associated with hydromorphism during base level rise. Siderite is ubiquitous in coal-bearing strata, and has been used to characterize the time-averaged δ18O of paleoprecipitation in terrestrial settings with positive precipitation- evaporation balances. These include the equatorial humid belt (0° to 10° latitude), and the temperate to polar humid belts (30° to 90° latitude). Equator-to-pole transects of soil groundwater δ18O values using soil carbonates as a preferred substrate necessarily include major belts of siderite-bearing soil systems. Sphaerosiderite refers to a common morphology of mm-scale spherulitic siderite aggregates, although other morphologies including massive microcrystalline and single lath-shaped crystals are also commonly observed. The seminal paper describing the carbon-oxygen isotopic diagenetic trend of meteoric sphaerosiderite lines and their applications to paleoclimatology appeared in Ludvigson et al., 1998 (Geology 26:1039-1042). The major application of the sphaerosiderite paleoclimate proxy has involved the oxygen isotope mass balance of the mid-Cretaceous hydrologic cycle in the northern hemisphere. A Cretaceous transect through the Americas currently extends from Colombian stations near the paleoequator to North Slope Alaskan stations near the North Pole. The most recent additions to this large published dataset were reported by M.B. Suarez et al., 2010 (JSR 80:480-491) and Robinson et al. 2010 (J. Geol. Soc. London 167:303-311). The seminal paper outlining the oxygen isotope mass balance model of the Cretaceous hydrologic cycle appeared in Ufnar et al., 2002 (Palaeo-3 188:51-71), although a revised mass balance model incorporating new tropical datasets, lead- authored by M.B. Suarez, is currently in review to Palaeo-3. The characterization of Cretaceous Arctic paleoprecipitation with very light δ18O values (Ufnar et al., 2002; Ufnar et al., 2004, GSA Bull. 116:463-473) led to the interpretation of an intensified Cretaceous hydrologic cycle, with increased rainout of 18O from atmospheric moisture during poleward transport from the tropics. This result is controversial, as recent GENESIS GCM simulations with a water isotope module do not simulate the light δ18O values reported from siderites in the Albian Nanushuk Formation of the Colville Basin. There is disagreement about whether the light δ18O values are actually representative of zonal Arctic climate, or evidence for local orographic effects of the ancestral Brooks Range, or even possible evidence for a dilute fresh water cap on the Arctic Ocean. Additional isotope sampling from a wider sampling network is underway to address these uncertainties. This effort includes multiproxy coordination with dinosaurian tooth enamel phosphate in the Maastrichtian Prince Creek Formation, and more sampling over a wider area from the Nanushuk Formation. One source of uncertainty during the original formulation of the sphaerosiderite paleoclimate proxy concerns low-temperature siderite-water 18O fractionations. The equilibrium isotope relationship of Carothers et al. (1988; GCA 52:2445-2450) was extrapolated from laboratory experiments at 33° C down to lower sedimentary temperatures. Until now, there have been no actualistic field studies to test the applicability of that equation. We are carrying out field studies at a site of historic siderite formation in coal tar-contaminated anthropogenic fills in Chattanooga, TN (described by Driese et al. in press to JSR). Seasonal soil temperatures, and groundwater δ18O and δD values, DIC δ13C values, groundwater alkalinity and ionic chemistry, and 21

microbial populations were sampled in early March and late August 2010. Data collection is still underway, but preliminary results suggest that a less temperature-sensitive siderite-water 18O fractionation proposed by Zhang et al. (2001; GCA 65:2257-2271) might better explain the data. ______

(17) Buried alluvial paleosols dating to the Pleistocene-Holocene transition in the Central Great Plains, U.S.A. (oral)

Mandel, Rolfe D.: Kansas Geological Survey, 1930 Constant Ave., Lawrence, KS 66047 USA ([email protected]).

A systematic study of the effects of late Quaternary landscape evolution in stream valleys of the Central Great Plains documented widespread, deeply buried paleosols that formed in terrace fills of large streams (> 5th order), in alluvial fans, and in draws in areas of the west-central Plains with a thick loess mantle. Alluvial stratigraphic sections were investigated along a steep bio-climatic gradient that extends from the moist- subhumid forest-prairie border of the east-central Plains to the dry-subhumid and semi-arid shortgrass prairie of the west-central Plains. Radiocarbon ages indicate that most large streams were characterized by slow aggradation accompanied by cumulic soil development from ca. 11,500 to 10,000 14C yr B.P. In the valleys of some large streams, these processes continued into the early Holocene. The soil-stratigraphic record in the draws of western Kansas indicates slow aggradation punctuated by episodes of landscape stability and pedogenesis beginning as early as ca. 13,300 14C yr B.P. and spanning the Pleistocene-Holocene boundary. The development record of alluvial fans in western Kansas is similar to the record in the draws; slow aggradation was punctuated by multiple episodes of soil development between ca. 13,000 and 9,000 14C yr B.P. In eastern Kansas and Nebraska, development of alluvial fans was common during the early and middle Holocene, but evidence shows fan development as early as ca. 11,300 14C yr B.P. Buried paleosols dating between ca. 12,600 and 9000 14C yr B.P. were documented in fans throughout the region. Based on the paleosol record and a suite of nearly 90 14C ages, alluvial settings of the Central Plains were relatively stable during the Pleistocene-Holocene transition. No evidence exists for high-magnitude floods that would have rapidly deposited large volumes of fine-grained sediment on floodplains during this period. Instead, small quantities of alluvium were gradually deposited, allowing soil development to keep pace with alluviation. The result was “upbuilding” or cumulization of soils, a process that also occurred on alluvial fans during this period. In the valleys of a few streams, cumulization during the Pleistocene-Holocene transition resulted in the development of a thick, organic-rich soil. In most steam valleys, however, pedocomplexes consisting of two or more soils with overthickened horizons formed between ca. 11,500 and 9,000 14C yr B.P. These pedocomplexes are products of fluctuating rates of alluviation. Cumulization periodically slowed or completely ceased, resulting in the formation of discernable stable surfaces within the pedocomplexes. Although landscape stability and concomitant soil development were underway as early as ca. 13,400 14C yr B.P. in some alluvial settings, 11,000-10,000 14C yr B.P. appears to encompass a major episode of quasi- stability characterized by cumulative soil development in stream valleys throughout the Central Plains. This episode coincides with the Younger Dryas (YD), a period of cooler climate compared to the preceding Allerod interstadial. A reduction in moisture, which seems to have characterized the YD in the mid-continent, cannot by itself account for the thick, organic-rich alluvial soils that formed during this period. The ubiquitous YD paleosols typically have overthickened A horizons and organic-rich B horizons that are products of either in situ organic-matter accumulation during periods of slow alluviation, gradual deposition of organic-rich alluvium, or a combination of both processes. Regardless of the dominant process of soil melanization, alluviation did not cease during the YD. Instead, the rate of alluviation slowed and allowed thick, organic-rich soil horizons to form. 22

Perhaps strong zonal airflow at the surface restricted the northward penetration of moist Gulf air masses into the Central Plains during the Pleistocene-Holocene transition. This would have created atmospheric conditions unfavorable for the development of powerful, flood-generating mid-latitude cyclones. Weak Pacific storms depleted of Gulf moisture may have generated enough rainfall and associated runoff to promote alluviation in streams, but at a slow rate, thereby allowing cumulative soils to develop. In stream valleys across the Central Plains, rapid alluviation after ca. 9000 14C yr B.P. was driven by strong mid-latitude cyclones, resulting in deep burial of soils dating to the Pleistocene-Holocene transition. ______

(18) Strong seasonality during early forestation on tectonically influenced landscapes in the Middle Devonian, Appalachian Basin, New York (poster)

Mintz, Jason S.1a, Steven G. Driese1, R. Hunter Harlow1a,2 and T. Colby Wright1,3: 1Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]); 2Kansas Geological Survey, 1930 Constant Ave., Lawrence, KS 66047 USA ([email protected]); 3Department of Geology and Geophysics, University of Alaska, Fairbanks, AK USA ([email protected]; [email protected]).

Middle Devonian terrestrial strata deposited in the Appalachian Basin record very dynamic landscapes characterized by extreme rainfall seasonality and tectonically driven changes in sedimentation, contemporaneous with development of forest ecosystems on these landscapes. The Middle Devonian clastic wedge, derived from the Acadian orogen, was deposited during a series of tectophases as Avalon accreted onto the Laurentian continent. These tectophases have been recognized as a series of subsidence and sedimentation pulses in the Appalachian Basin that we have been able to identify and correlate in the fluvial sections using fluvial cycle thickness and paleosol maturity. Several fluvial sequences are defined by increases in accommodation that coincide with a change in fluvial style from suspended-load-dominated sedimentation to a bed-load-dominated system. As accommodation in a sequence subsequently decreased, fluvial style returned to a suspended-load system with increased paleosol occurrence, maturity and drainage. Several soil orders are represented in these paleosols ranging from weakly-developed paleo-Entisols, moderately-developed paleo- Inceptisols and strongly-developed paleo-Vertisols and vary from poorly- to well-drained. Using the newly defined paleo-precipitation proxy CALMAG (a geochemical ratio from bulk soil material in fine-grained paleosols), mean annual precipitation (MAP) for the majority of these paleosols is estimated at ~1600 mm/year. Six paleosols, however, have lower estimates (ranging from ~850—1350 mm/year), as a result of elevated weight % CaO, which occurs at sequence boundaries in response to base-level fall or in extremely aquic paleosols. Carbonate-bearing vertic paleosols forming in a tropical climate suggest strong precipitation seasonality. Under seasonal climate conditions geochemical ratios from bulk matrix material in hydromorphic paleosols can be influenced by the average timing and duration of subaerial exposure that can result from changes in base-level or geomorphic position on the landscape. Using paleo-MAP proxies from geochemical ratios in vertic paleosols without contextual pedogenic and stratigraphic information may misrepresent changes in pedogenesis from geomorphic or hydrologic variability as changes in climate.

aco-presenters ______

(19) Pedologic approaches to alluvial sequence stratigraphy (oral)

McCarthy, Paul J.1a, and Stacy C. Atchley2a: 1Department of Geology and Geophysics, University of Alaska- Fairbanks, Fairbanks, AK 99775-5780 USA ([email protected]); 2Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]).

Alluvial stacking pattern analysis has emerged as a methodology for sequence stratigraphic interpretation of discontinuously exposed, relatively conformable successions of paleosol-bearing alluvial strata. The alluvial stacking pattern approach evolved from a similar methodology developed by marine carbonate sequence stratigraphers. Both methodologies presume that cyclic deposition is the product of composite accommodation change and varying sediment supply. Within alluvial successions, autogenic processes of channel avulsion and related channel drift back and forth across an alluvial valley are thought to account for meter-scale fluvial aggradational cycles (FACs) and decameter-scale fluvial aggradational cycle sets (FAC-sets). Variations in long-period rates of subsidence and/or eustatic sea level change influence the nature of FAC stacking. Within a single subsidence or eustatic cycle, initial high rates of accommodation gain rapidly aggrade the alluvial depositional profile. Associated FACs are thicker than average, evolve from relatively coarser- to finer-grained deposits, and include poorly-developed and poorly-drained paleosols. As the rate of accommodation gain decelerates, FACs thin and become increasingly fine-grained, and associated paleosols are better developed yet also poorly-drained. Immediately preceding long-term base-level fall during the apogee of base-level rise, channel drift across the alluvial valley may deposit a laterally-extensive alluvial sandstone complex. Paleosols are less likely preserved at this time due to channel migration and reworking of overbank fines. During accommodation loss, i.e., long-period base level fall, channel incisement progresses such that interfluve areas are increasingly better drained and less frequently inundated by floodwater sediment. Consequently, the interfluve portions of sequence bounding unconformities are characterized by the best developed, best drained, and oftentimes compound paleosols. Under circumstances where basin-scale studies allow reconstruction of fluvial environments in three dimensions, pedostratigraphic methods enable reconstruction of the lateral variability of sequence-bounding paleosols. Paleosols across sequence-bounding unconformities vary depending upon their paleo-landscape position. The sequence boundary can be partitioned into three zones along an up-dip transect based upon both paleosol development and architecture. Weakly developed, hydromorphic paleosols within Zone 1 form as the coastal plain progrades in response to relative sea-level fall. Further updip (Zone 2) fluvial incision results in better drained interfluves that receive no new sediment, resulting in well-developed, welded paleosols. Slowly aggrading alluvial environments in the most proximal foredeep constitute Zone 3 where cumulative, compound and complex paleosol successions develop. Because accommodation, sediment supply and hydrological conditions vary both updip and along-strike, these paleosol successions represent lateral facies equivalents. The sequence-bounding, soil-forming interval is a geosol composed of welded paleosols in Zone 2 that splay both up-dip and down-dip into less well-developed paleosol complexes. Updip variability along the sequence boundary is controlled primarily by changes in the accommodation/sediment supply ratio, by hydrological variation associated with floodplain incision during valley formation, and by tectonic subsidence rate that varies in time and space. Consequently, it is unlikely that any single paleosol “type” represents a laterally extensive sequence boundary in three dimensions.

aco-presenters ______

(20) A method for finding probable locations of paleosols sensitive and insensitive to climate change (oral)

Monger, H. Curtis and David Rachal, Professor and Graduate Student: Department of Plant and Environmental Sciences, New Mexico State University, Las Cruces, NM 88003 USA ([email protected]).

Paleosols vary in their sensitivity to climate change, which is the major driving force that causes biomes to expand, contract, and migrate laterally. Soil profiles adapt intrinsically and extrinsically to migrating bioclimatic zones. Intrinsic adaptations take place within soil profiles in response of bioclimatic conditions. Intrinsic adaptations include the dissolution of primary minerals, precipitation of authigenic minerals, accumulation of organic matter, the downward transfer of clay particles in suspension, colloids and ions in solution, and the upward bioaccumulation of calcium, magnesium, potassium, and phosphorus. Given sufficient time, intrinsic adaptations produce soil profiles in equilibrium with their external environment, such as Mollisols (thick dark A horizon) in grasslands, Alfisols (O-A-E-Bt horizons) in temperate deciduous forests, and Oxisols (O-A-Bo horizons) in tropical rainforests. Extrinsic adaptations take place outside the soil profile in response to landscape stability or instability. Key variables are erodible sediments (particle size, depth), moving water or wind, depositional environments, and ground cover. Ground cover is the key variable that controls landscape stability or instability. The rates at which a landscape shifts from stability to instability determines whether paleosols form in an episodic or gradual sedimentary environment. Four combinations of intrinsic and extrinsic sensitivities are possible. On one extreme, a paleosol may be both intrinsically and extrinsically sensitive, such as a paleosol on a south-facing piedmont slope derived from feldspar loess on a semiarid mountain range. On the other extreme, a paleosol may be doubly insensitive, such as a paleosol on a low-relief outcrop of quartzite bedrock in a cold dry climate. A methodical assessment of intrinsic and extrinsic sensitivities provides a tool for prospecting the global landscape for climate change records in paleosols. ______

(21) Reconstructing marine-terrestrial paleoclimate linkages: A Carboniferous perspective (oral)

Montañez, Isabel P. 1, Jason Antognini1, James W Bishop2, Michael J.Eros3, Erik L Gulbranson1, and Neil J. Tabor4: 1Dept. of Geology, University of California, Davis, CA 95616 USA ([email protected]); 2Chevron Energy Technology Company, Houston, TX USA; 3Exxon-Mobil Corporation, Nigeria OBO Exploration Projects, Houston, TX 77060 USA; 4Huffington Dept. of Earth Sciences, Southern Methodist University, Dallas, TX 75275-0395 USA ([email protected]).

Evaluating climate forcing-feedbacks in the deep-time requires reconstructing marine-terrestrial mechanistic linkages between atmospheric composition, regional hydroclimate expression of mean climate change, ice sheets, and sea-level. Here we present a cross-equatorial Euramerican reconstruction of Pennsylvanian paleoclimate based on correlated proxy records from cyclothemic successions of the Donets Basin, eastern Ukraine, and the Appalachian and Illinois basins, U.S. and compare these records to a higher-latitude Gondwanan terrestrial record (northwestern Argentina). The hierarchy of cyclicity recorded in the U-Pb calibrated, mixed carbonate-siliciclastic succession of the Donets Basin was used to define a 30 myr (Visean through early Ghzelian) relative sea-level history that can be correlated at high-precision to the paralic U.S. mid-continent and Illinois basin cyclothemic successions and the terrestrial-dominated Appalachian Basin record. The Donets relative sea-level history defines several periods of maximum sea-level lowstand that correspond within <± 0.3 myr to the U-Pb constrained ages of two glaciations in southwestern Gondwana (Gulbranson et al., 2010) and four discrete glaciations in eastern Australia (Fielding et al., 2008). The mid-to- 25

late Pennsylvanian is characterized by a ~9 myr period of long-term sea-level rise that is punctuated by at least four episodes of sea-level fall and inferred short-lived glaciation (<0.5 to 1.5 myr). Each glaciation become increasingly shorter-lived and less extensive through the Pennsylvanian and can be correlated to sea level lowstands inferred from the cyclothemic record of the mid-continent (Heckel, 2008) and Appalachian and Illinois Basins. Overall, correlated lowstands in the paleotropical successions consist of stacks of cyclothems containing thick and laterally widespread Histosols, Spodosols, Ultisols, and heavily gleyed Vertisols, meteoric cements with anomalously negative δ18O values, and high CIA values of paleosol B-horizons (Appalachian Basin) all indicating humid to perhumid conditions. In contrast, highstand intervals in all three Euramerican basins are characterized by sedimentologic and paleosol indicators of substantially lower effective moisture and high seasonality (calcic Vertisols, Calcisols, evaporates, change in fluvial depositional style, diminished coals) and low CIA values of paleosol B-horizons (Appalachian Basin). The marked and geologically rapid shift to overall drier climate proximal to the mid-to-late Pennsylvanian transition is also recorded in higher-latitude southwestern Gondwana by a coincident large shift in CIA inferred precipitation and increased seasonality following the last evidence of glaciation in western Gondwana. The δ13C values of pedogenic carbonates, coal macerals, discrete plant matter, and a subset of organic matter occluded in pedogenic rhizoliths and nodules in the Illinois and Appalachian basins define changes in modeled pCO2 for the ~15 million year period of the mid- 4 6 to-late Pennsylvanian that covary with 10 to 10 year sea-level highstands (700 to 1200 ppmv ±500 ppmv) and lowstands (200 to 500 ppmv ±500 ppmv) defined by the Donets and mid-continent cyclothemic record. This trend, which does not correlate with meteoric cement and pedogenic calcite δ18O values or soil order, could record changes in soil moisture and soil productivity or greenhouse gas-forcing of Carboniferous glacial-deglacial history. Fully coupled ocean-atmosphere-ice sheet climate simulations for the Carboniferous support a similar range of CO2 variation between glacial minima and maxima inferred from the reconstructed geographic extent of well-constrained glacigenic deposits in Southern Gondwana. ______

(22) Pedosystem science approach to describing and interpreting the fossil record of soils (oral)

Nordt. Lee C., and Steven G. Driese: Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]).

Paleosols are the most pervasive fossil features of ancient terrestrial ecosystems, preserving properties reflecting differing intensities of climate and biota operating on parent material as modified by topography through time. For paleosologists to remain leaders in the discovery and dissemination of information regarding earth’s history and its application to future global changes issues, enhanced quantitative biogeochemical interpretation of fossil soils is imperative. Because the pedosphere is the product of multiple interacting earth systems as part of the Critical Zone, pedosystem science is an organizational framework for studying interdependent entities of an integrated whole. This approach is predicated on the description, analysis, and interpretation of the physical, chemical, morphological, and biological pedo-subsystems with consistency and through a common language. Transferring the pedosystem science approach to the fossil record of soils promotes hypothesis testing, model building, and ultimately the discovery of new and unexpected information as we are better able to decode the archive of terrestrial biogeochemical data at multiple temporal and spatial scales. Traditionally, however, the study of fossil soils has operated through field and micromorphological description, and whole-rock geochemistry. Because the latter is the weakest link of this tripartite methodological approach, we know little about the ancient colloidal world that governs most physical and chemical reactions as understood through the concepts of modern soil science. Here, the physical pedo- subsystem consists of whole-soil properties characterized by particle-size distribution (including fine clay), bulk 26

density (for porosity and water holding capacity), COLE (for shrink-swell), calcium carbonate and other salts, and pedogenic iron oxides (Fed, Feo). The chemical pedo-subsystem is characterized principally by pH and EC as solution properties, and by CEC (cation exchange capacity), base saturation, and ESP (exchangeable sodium percentage) as surface properties. The biological pedo-subsystem encompasses the organic matter fraction and associated elemental constituents, and evidence of faunal and floral activity. Preliminary investigations on a group of Cretaceous Vertisols from the Big Bend area and an Alfisol from southern Alberta, Canada indicate that with a combination of field morphological descriptions, whole-rock molecular oxides, pedotransfer functions, direct analytical analysis after sample dispersion, mass balance calculations, and micromorphological point counts, many components of ancient pedo-systems can, in fact, be quantified. Once the ped-subsystems are merged, powerful interpretations regarding nutrient cycling, climate reconstruction, and taxonomic classification can be performed on fossil soils. For example, plant nutrient availability is largely dependent on pH-Eh relations interpreted from pedotransfer functions and the distribution of iron redox features. Evidence is emerging that a family of rainfall curves is needed based on recognition of taxonomically-defined soil orders and affiliated properties. Further, reliable taxonomic classification of paleosols is advanced because of the acquisition of quantitatively-relevant data used as pedotransfer functions. Rather than a discipline fast approaching steady state in terms of what it has to offer to the earth science community, pedosystem science indicates that we are just penetrating the surface of information still residing in paleosols. To not fully understand the ancient pedosystem as the foundational framework from which all other interpretations follow, we will have little more to offer in future decades as a discipline, and what we do offer will be from a collapsing base of inference. ______

(23) Towards a better understanding of the terrestrial ecosystem: integrating paleobotany, paleopedology, sedimentology, and geochemistry (oral)

Peppe, Daniel J.: Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]).

The colonization of the land by vascular plants in the late Ordovician (~450 Ma), followed by their diversification beginning in the early Devonian (~408 Ma), is one of the most significant events in the history of the planet. As soon as plants were capable of living on land, they began to fundamentally alter the terrestrial world, the earth’s atmosphere, and in turn, the earth’s climate. For example, rooting systems in plants allowed for landscape stabilization and promoted weathering of substrate, translocation of soil materials, and clay illuviation. This enhanced chemical and physical weathering, coupled with the production of lignin, a bacterially-resistant organic compound, may have been the major driver of the significant decrease in atmospheric CO2 levels and the global cooling trend that occurred from the late Devonian into the Carboniferous. Other important events, such as the evolution of forests and the evolution and diversification of angiosperms have likely contributed to changes in global rates of chemical and physical weathering, further modifying the landscape and the earth’s climate. The colonization of the land by vascular plants, the evolution of trees and forest ecosystems, the transition from gymnosperm to angiosperm dominated communities, and the paleoclimatic significance of these events has been clearly demonstrated using paleobotany, sedimentology, paleopedology, and geochemistry. Surprisingly, although each of these fields often tests similar, related hypotheses, and each can inform on interesting and unique aspects of paleoclimate and paleoenvironmental reconstruction, the methods are infrequently integrated in a single study. For example, paleobotanists often study the terrestrial ecosystem’s response to patterns of climate change by focusing on the megafossil record and neglecting the detailed paleoenvironmental record available in the paleosols and the strata in which the fossils are preserved. At the same time, paleopedologists, sedimentologists, and geochemists examine the terrestrial ecosystem’s response to 27

changes in climate by concentrating on the morphology of paleosols and major element geochemistry, without examining the plant fossil record in detail. Any study that combined all of these methodologies would be able to more accurately infer the terrestrial ecosystem’s full response to patterns of climatic change. Thus, future research on the paleoclimate and paleoenvironment of terrestrial ecosystems should be focused on developing interdisciplinary and collaborative projects that integrate paleopedology, geochemistry, sedimentology, and paleobotany which will allow for a better understanding of the terrestrial ecosystem, as well as, its responses to patterns of climatic change through earth’s history. ______

(24) A geochronologic framework for the Late Triassic Chinle fluvial system at the Petrified Forest National Park: Sediment accumulation rates and paleoenvironmental implications (oral)

Ramezani, Jahandar 1a, David E. Fastovsky2a, Samuel A. Bowring1, Stephen I. Dworkin3, Stacy C. Atchley3, and Lee C. Nordt3: 1Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 USA ([email protected]; [email protected]); 2Geosciences, University of Rhode Island, Kingston, RI 02881 USA ([email protected]); 3Department of Geology, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]; [email protected]).

High-precision geochronology within a refined stratigraphic context has the potential to revolutionize the reconstruction of ancient sedimentary systems. The Chinle Formation of the southwest United States is a spectacular terrestrial record, with faunas that are key elements of land vertebrate biostratigraphy, and sedimentary rocks – including thick paleosol sequences – that are important indicators of Late Triassic paleoclimates. We used high-precision U-Pb geochronology (CA-TIMS technique) on isolated volcanic zircon from interbedded tuffaceous sandstones and siltstones throughout PEFO to construct a reliable temporal framework for the Chinle. The maximum depositional ages of 9 tuffaceous samples indicate that the three members of the Chinle exposed at PEFO – the Blue Mesa, the Sonsela and the Petrified Forest Members combined – were deposited over a period in excess of 17 m.y. during the Norian stage of the Late Triassic. Our results affirm that sedimentary records of ancient fluvial sequences, particularly those bearing paleosols, preserve a very small fraction of the total time represented by the succession. Whereas the duration for deposition of any single fluvial architectural element of the Chinle might be unconstrained in any part of the sequence, the average sediment accumulation rate for a given stratigraphic thickness can be estimated based on the bracketing dated tuffs. The results demonstrate remarkably higher rates for the central, sandstone- and conglomerate-rich Sonsela Member as compared to the mudstone-dominated, lower Blue Mesa and upper Petrified Forest Members. Both the Blue Mesa and Petrified Forest Members contain thick successions of paleosols. In the case of the former, these are gleyed but not otherwise easily interpretable within a modern soil-science context, whereas in the case of the latter, well-developed vertic features preserve the general structure of the paleosol. Thick mudstone sequences either imply unusually deep profiles or stacked sequences of active profiles, potentially involving compound pedogenesis in an aggrading floodplain. In both the Blue Mesa and Petrified Forest Members, units are clearly stacked affirming not the length of time for deposition and/or pedogenesis, but rather the length of time of the hiatuses. The Sonsela Member is likewise riddled with hiatuses; however, these are most likely disconformities associated with missing (eroded) deposits rather than hiatuses in sediment accumulation associated with pedogenesis.

aco-presenters ______

(25) A short history and long future of paleopedology (oral)

Retallack, Gregory J.: Department of Geological Sciences, University of Oregon, Eugene, OR 97403-1272 USA ([email protected]).

The concept of paleosols dates back to eighteenth century discovery of geological unconformities and fossil forests, but the term paleopedology was first coined by Polynov in 1927. During the mid-twentieth century in United States, paleopedology became mired in debates about stratigraphic correlation of Quaternary paleosols, and in controversy over the red-bed problem. By the 1980's, a new generation of researchers envisaged red beds as sequences of paleosols and as important archives of paleoenvironmental change. At about the same time, Precambrian geochemists began sophisticated analysis of paleosols at major unconformities as a guide to the long history of atmospheric oxidation. It is now widely acknowledged that evidence from paleosols can inform studies of stratigraphy, sedimentology, paleoclimate, paleoecology, global change and astrobiology. For the future, one promising avenue of research are paleopedological power laws based on greenhouse crises of the geological past as guides to the causes and consequences of ongoing global warming. Past greenhouse crises have been of varied magnitude, and paleosols reveal both levels of atmospheric CO2 and degree of concomitant paleoclimatic change. Empirical power laws are already available predicting climate change consequent on different levels of atmospheric CO2. There is also the prospect of astropedology, completing a history of soils in sedimentary settings within Precambrian rocks, on other planetary bodies such as the Moon and Mars, and within meteorites formed on planetismals during the origin of the solar system. Changes in soil-forming processes and life on land through geological time have been vital in the paleoclimatic history of planetary bodies. On Earth, for example, paleosols now reveal that Proterozoic, late Paleozoic and Neogene ice advances curtailed newly evolved biological productivity responsible for cooling. ______

(26) Paleosol stratigraphic significance in a distributary fluvial system record and their modern soil analogs in northwestern Argentina (poster)

Rosario-Díaz1, Jose J., Theresa E. Jordan1, C.N. Garzione2, and P. Higgins2: 1Cornell University, Ithaca, NY USA ([email protected]); 2University of Rochester, Rochester, NY USA.

The focus of this paper is on paleosols that developed within a distributary fluvial system during the Miocene and Pliocene, an analogous to modern soils and environment in Northwestern Argentina today. The area of study spans a deformed foreland basin and its modern counterpart, with the Eastern Cordillera located at the west border and the Chaco basin to the east. This area experienced about 30% shortening between late Miocene and present time, with an expected displacement of the fluvial sedimentary environments of the same magnitude. The nonmarine basin fill was measured, described, and sampled at the Iruya, Peña Colorada, and La Porcelana river sections. The time framework was constrained by volcanic ash dates, U-Pb detrital zircon ages, and magnetostratigraphy. Paleosols were identified and described in the field (texture, color, profile development) and chemical analyses were performed in the laboratory. Laboratory studies included XRD, thin section, and stable isotope geochemical analyses. The spatial distribution of the paleosols was compared to modern Northwestern Argentinean soils by Geographical Information analyses. The time framework encompasses about 13 Ma to 5 Ma. Each of the three stratigraphic columns displays a progressive upward coarsening sequence, with the most pronounced fluvial sedimentary environmental gradient at the Iruya River section. The Iruya section, exposed near the Eastern Cordillera, represents the most proximal section in the foreland basin.

Paleosols are developed in between sandstone layers; the paleosol parent material was mud and fine sand deposits. The fine deposits are interpreted as floodplain strata. The degree of paleosols maturity varies from poor to well develop. Poorly developed paleosols are identified with paleosol horizons no thicker than 40 cm and no sedimentary structures observed. The more developed paleosols are over 40 cm thick, show redox features in many cases, contain calcium carbonate including carbonate nodules, and display clay illuviation with kaolinite and illite mineralogy. Clay illuviation is observed in thin sections as coatings for calcium carbonate nodules and lining pore spaces within the paleosol matrix. Isochronisms can be observed between clay and calcium carbonate coating in the calcium carbonate nodules. Oxide nodules occur less frequently. The most complete record of stable isotopic properties, for δ18O and δ13C, of the paleosols comes from the Iruya River section. Isotope values of δ13C range from -12 to -9 ‰ PDB, and for δ18O from -10 to -4 ‰. The mineralogy of the paleosols supported by the thin section analyses suggests variability between dry and wet soil conditions during the Mio-Pliocene. The isotopic data suggest that the climate since 6 Ma was characterized by stronger seasonality (wet-cold / dry-warm) than at earlier times. The modern soils in the Chaco basin are analogous to these paleosols in Northwestern Argentina. The Mio-Pliocene sedimentary facies show that the paleosols developed over a distributary system similar to modern Chaco conditions. Most of the paleosols are categorized as Entisols and Alfisols. Today those soil classes are distributed in the Chaco within the river bank and nearby floodplain areas, areas that experience sediment input often. The more developed soils of the Chaco are found on terraces where they experience very little detrital input, and are represented by Mollisols. The coarsening upward sequence, which is interpreted as the eastward progressive movement of the orographic front, does not control the paleosol development, but it does affect the frequency with which paleosols are preserved in the stratigraphic record. ______

(27) Pennsylvanian –Early Permian paleosols of the Illinois and Midcontinent basins: Implications for paratropical climate during the Late Paleozoic Ice Age (poster)

Rosenau, Nicholas, and Neil J. Tabor: Department of Earth Sciences, Southern Methodist University, Dedman College, Dallas TX, USA ([email protected]; [email protected]).

A comparison of the morphology, mineralogy and geochemistry of paleosols from Pennsylvanian (Moscovian; Atokan) - Lower Permian (Artinskian; Wolfcampian) strata in the Illinois and Midcontinent basins is presented here in order to provide a better understanding of the dominant pedogenic processes that operated in two paratropical North American basins during the Late Paleozoic Ice Age (LPIA) and provide information on low latitude paleoenvironmental conditions that prevailed during this time. High-resolution conodont biostratigraphic correlation between these two basins permits comparison of paleoclimate between basins with reasonable age constraints. Pennsylvanian (Desmoinesian-Missourian) paleosols in the Illinois and Midcontinent basin display stratigraphic trends in the distribution of paleosol color, clay mineralogy, and structure that reflect conditions driven by both local, to regional or global climate. The majority of Pennsylvanian paleosols contain well- developed pedogenic slickensides, angular blocky structure, and accumulations of pedogenic carbonate and preserve low chroma (gley) colors, identifiable fossil plant organic matter, sphaereosiderite and pyrite. Early Permian (Wolfcampian) paleosols in the Midcontinent exhibit basin well-developed pedogenic slickensides, angular blocky structure, and accumulations of pedogenic carbonate and preserve high chroma, reddish-brown colors. The <2μm size fraction of paleosol matrix in Desmoinesian-Missourian paleosols in the Illinois and Midcontinent basins are dominated by vermiculite, HIM, illite and kaolinite, and subordinated amounts of 2:1 phyllosilicates, whereas Lower Permian (Wolfcampian) paleosols in the Midcontinent basin are dominated by illite, HIM, and subordinate amounts of kaolinite. 30

Measured δ13C and δ18O values of Desmoinesian-Missourian paleopedogenic sphaerosiderites in conjunction with measured δD and δ18O values of an upper Desmoinesian flint clay (kaolinite) deposit provide an estimate of soil paleotemperature of 27 ± 3ºC and δ18O value of soil water of ~ -3‰ during this time. This soil water δ18O value is consistent with modeled paleoprecipiation δ18O values during the late Pennsylvanian. The δ13C values of co-occurring fossilized plant matter and pedogenic calcium carbonate across the Desmoinesian-Missourian boundary in the Midcontinent basin (Kansas) have been obtained and may provide information on tropospheric pCO2. This study of combined field, mineralogic and geochemical data document stratigraphic variations in pedogenesis across the Pennsylvanian landscape in two paratroical basins and that are interpreted to be the result of three likely interrelated local to global factors: 1) groundwater fluctuation, (2) climate change, and (3) glacioeustasy. ______

(28) Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols (oral)

Sheldon, Nathan D.1a, and Neil J. Tabor2a: 1Department of Geological Sciences, University of Michigan, 2534 CC Little, 1100 N. University of Ave., Ann Arbor, MI 48109, USA ([email protected]); 2Department of Earth Sciences, Southern Methodist University, P.O. Box 75395, Dallas, TX 75275, USA ([email protected]).

Paleosols (fossil soils) are preserved throughout the geologic record in environments ranging from alluvial depositional systems to residual interbasaltic volcanic systems. Until recently, paleosols were studied using primarily qualitative methods. However, in recent years, paleopedology has shifted from a largely qualitative field, based on comparisons with modern analogues, to an increasingly quantitative endeavor. Some of this transition arose from application of existing techniques to new materials, but much of the recent innovation in paleopedology research results from new techniques applied to new materials. Among the most important recent innovations are thermodynamic modeling of soil formation, isotope geochemistry, and applications of empirical relationships derived from modern soils. A variety of semi-quantitative and quantitative tools has been developed to examine past weathering and pedogenesis, and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time of pedogenesis. The great advantage of paleosol-based paleoclimatic proxies in comparison to marine paleoclimatic proxies is that soils form at the Earth's surface, in direct contact with the atmospheric and climatic conditions at the time of their formation. Paleoclimatic properties that may be reconstructed using these new proxies include mean annual precipitation (MAP) and temperature (MAT) during pedogenesis, the atmospheric composition of important gases including CO2 and O2, the moisture balance during pedogenesis, the soil gas composition, reconstructed vegetative covering, and paleo-elevation. Examples to be discussed include reconstruction of MAP and MAT using whole rock geochemistry, reconstruction of paleotemperatures using pedogenic carbonate “clumped” isotopes, reconstruction of atmospheric paleo-CO2 levels using pedogenic carbonates and goethites, and paleo-vegetation reconstruction using pedogenic carbonate and paleosol organic matter. Promising new techniques for understanding paleo-moisture regimes and paleotemperature based on soil organic matter will also be introduced, along with an examination of remaining challenges for existing proxies and possibilities for future developments in quantitative paleoclimatology.

aco-presenters ______

(29) Post-glacial climate change and solar irradiance cycles responsible for coherent changes in Great 13 Plains and Mid-Atlantic δ Csoc values (poster)

Stinchcomb, Gary E., Steven G. Driese, and Lee C. Nordt: Department of Geology, One Bear Place #97354, Baylor University, Waco, TX 76798-7354 USA ([email protected]; [email protected]; [email protected]).

A continuous record (10.5 ka – modern, ka = weighted mean Cal. yr BP) of Holocene buried soils and alluvium 13 in the Mid-Atlantic region, USA, shows distinct secular changes in the relative δ Csoc values that are coherent with previously published records from the Great Plains. Because of the broad correlation between both the Great Plains and Mid-Atlantic isotope time-series, we invoke post-glacial climate change and solar irradiance cycles as primary forcing mechanisms influencing C3:C4 biomass. Early mid-Holocene (8ka – 6ka) data from 13 both records display relatively lower δ Csoc values compared to their respective modern means. These data 13 correlate with an interval of continental-wide cooling following the “8.2ka event”. Subsequent δ Csoc values during the late mid-Holocene (6ka – 3ka) are notably heavier and occur during the warm Hypsithermal period. 13 Both studies document heavy δ Csoc excursions at the onset of the Neoglaciation (3ka – 2ka) and during the Medieval Climate Anomaly (1.2ka – 1.0ka). These excursions correlate with previously documented increases in mean July temperature and drying episodes. However, previous research in the Mid-Atlantic region has 13 shown that increases in δ Csoc during the past 2,000 years may reflect intensification of maize (C4)-based 13 farming. An exception to the isotope coherency described above is a distinct heavy δ Csoc excursion recorded in the Mid-Atlantic region, dated to 9.3ka (Beta-282837). This corresponds to an episode of early Holocene warming and drying that culminates with the “9.2ka event”. Because these records are coherent and the % C4 reflects mean July temperature in the Great Plains, we can only conclude that a similar process is occurring in the Mid-Atlantic region but with less % C4 biomass. As with the Great Plains, the isotopic composition of soil organic carbon holds great promise as a paleoclimate proxy for regions east of the Mississipi River. The valley bottoms are replete with buried soils and steps should be taken to construct a more spatially extensive Holocene 13 δ Csoc record for the entire Eastern USA. ______

(30) Untangling regional records of Eocene-Oligocene climate change across Wyoming, Nebraska, and South Dakota (oral)

Terry, Dennis O., Jr.: Department of Earth and Environmental Science, Temple University, Philadelphia, PA 19122 USA ([email protected]).

The White River Group of the northern Great Plains preserves the transition from Hothouse to Icehouse conditions across the Eocene-Oligocene Boundary. This transition is interpreted as a change toward progressively cooler and drier climatic conditions in this region from the Eocene into the Oligocene, although the magnitude and timing of this change is still subject to debate. Preservation of this record is variable across the region, which may be partially responsible for differing interpretations as sections through any one area only capture local climatic and environmental change. In an effort to resolve the dynamics of this climate transition across the study region, paleosols along and within defined isochronous zones, delineated by volcanic ashes and magnetostratigraphy, are currently being compared from central Wyoming to southwest South Dakota. To date, over 100 paleosol profiles have been logged throughout the White River Group of Wyoming, Nebraska, and South Dakota. Although gaps in the data still exist, preliminary interpretations can be made. In general, localities farther to the northeast experienced slower sedimentation rates, sometimes coupled with periods of downcutting and erosion, which promoted pedogenesis over deposition. Areas to the southwest experienced greater rates of deposition, resulting in weaker, more frequent periods of pedogenesis occurring within thicker

sections. Depositional environments are dominated by fluvial and eolian processes, but vary in influence depending on proximity to Laramide uplifts and volcanic centers. Comparisons of late Eocene paleosols from central Wyoming to northwest Nebraska show a greater influence of volcaniclastic input in Wyoming, but the same up same up-section changes in pedogenic style are present in both areas. Paleosols lower in the section formed under humid climates with progressively younger paleosols suggesting increasingly drier conditions, but when isochronous intervals of pedogenesis are compared, paleosols to the west formed under drier conditions. Within the early Oligocene of northwest Nebraska and southwest South Dakota, paleosols show up-section changes related to progressively eolian dominated, drier conditions in both regions, but with varying degrees of fluvial influence. Periods of fluvial dominance are present within the early Oligocene in both Nebraska and South Dakota, but through time, eolian influence becomes greater in Nebraska, whereas a mixed eolian/fluvial influence is found in isochronous deposits in South Dakota. As with paleosols of the late Eocene, early Oligocene paleosols within isochronous intervals suggest drier conditions to the west (and south). Although paleosols suggest an east-west aridity gradient throughout the Eocene-Oligocene, it is possible that this gradient is simply the byproduct of increased sedimentation to the southwest which in turn reduced the degree of pedogenic modification. Traditional paleopedology alone may be insufficient to resolve this issue. When compared with the geochemical archive of fossil vertebrates within these deposits, similar paleoclimatic patterns appear. Carbon and oxygen stable isotopes from the carbonate component of fossil bone suggest that water stress was greater in Wyoming than Nebraska during the late Eocene, and rare earth elements suggest that aridity increased through the Oligocene of northwest Nebraska. When taken as a whole, the White River Group preserves both local climate trends and regional climate gradients during the Eocene and Oligocene, but only when spatio-temporal variables of soil formation are taken into consideration. The addition of geochemical data from fossil bones enhances paleoclimatic interpretations and highlights the importance of utilizing multiple paleoclimate proxies. ______

(31) The distributary fluvial system (DFS) paradigm: Observations of fluvial form in modern continental sedimentary basins (oral)

Weissmann, Gary S.1, Adrian J. Hartley2, Gary J. Nichols3, L.A. Scuderi1, and S.K. Davidson2: 1University of New Mexico, Department of Earth and Planetary Sciences, MSC03 2040, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA ([email protected]); 2Department of Geology & Petroleum Geology, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UE, UK ([email protected]); 3Department of Geology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK ([email protected]).

When we think of fluvial systems and associated soils and their preservation in the rock record, we typically draw upon our experiences with tributary rivers which are the most common in the world. Indeed, most facies models that we use to interpret the rock record have been developed on tributary rivers that exist outside active sedimentary basins or, if the river system studied lies within a sedimentary basin, the models developed typically do not place the studied reach into the context of the basin. A review of over 700 modern continental sedimentary basins around the world showed that rivers in active sedimentary basins are not tributary in nature; rather they form either (1) distributive fluvial systems (DFS), variously called megafans, fluvial fans, and even alluvial fans in the literature, or (2) axial stream systems that parallel the basin trend, with the vast majority of sedimentation in the basin occurring on the DFS. In these continental sedimentary basins, we have identified over 400 fluvial megafans (>30km in length), with countless smaller DFS filling the basins. These observations have implications for the interpretation of ancient fluvial deposits and the soils that form on these deposits. Rivers on DFS differ from tributary rivers in many, potentially significant ways, including the following: 33

• A radial pattern of channels away from an apex (or intersection point) exists on DFS, though many of the DFS rivers do curve to become subparallel to the basin strike distally. In contrast, tributary systems tend to form dendritic patterns. • Channel systems commonly decrease in width and discharge and thus cross-sectional area distally, while tributary systems tend to increase in size downstream. • Rivers on DFS do not lie within valleys unless the system is in an incised phase. • Meanderbelts tend to be more laterally mobile on the open DFS, forming “simple” meanderbelts rather than “amalgamated” meanderbelts during aggradational phases on the DFS, where avulsion processes in “amalgamated” meanderbelts are dominated by chute and neck cutoffs and “simple” meanderbelts switch nodal avulsion before developing to the point of having many chute or neck cutoffs (though some exceptions exist). Tributary systems, or those confined in valleys, tend to be dominated by chute and neck cutoffs. • Floodplain deposits on DFS are often dominated by avulsion deposits, especially in distal portions of the DFS. • Greater preservation of floodplain deposits appears to occur on DFS dominated by braided streams than found in braided streams of tributary systems. • Axial streams in a basin, if confined laterally, and rivers that are incised into the DFS appear to be similar in character to tributary systems.

We expect soil morphology to vary with position on DFS, with different soil types found in proximal, medial, and distal locations as well as laterally away from the active channel belt. Additionally, cycles of incision and aggradation should develop characteristic soil distributions. We hope this alternative view to fluvial facies distributions can lead to discussions about facies prediction based on paleosol character on DFS. ______

(32) Pedological reflections on naming of paleosols in the rock record (oral)

Wilding, Larry P.: Professor Emeritus, Department of Soil and Crop Sciences, Texas A & M University, College Station, TX, 77845 USA ([email protected]).

Generally soils are developed along polygenetic pathways, on dynamically evolving landforms, in nonuniform parent materials, under the influence of paleoclimates. Properties of older soils commonly reflect welding of contemporaneous and paleoenvironments. Our ability to use modern soils as proxies of the biological and physiochemical evolution of Earth is most meritorious but tempered by such uncertainties. With the advent of modern biogeochemical tools, including stable isotope analyses, radioisotopic dating, micromorphology, and mass balance reconstructions, extension of paleosol inferences is augmented. Soil Taxonomy (ST) has been used extensively by paleopedologists to name paleosols in the bedrock (deep-time) record with modern soil equivalents. Paleoenvironmental inferences have been made from such correlations. Unfortunately, ST currently does not accommodate such systematic cataloging of paleosols. Buried paleosols are recognized and classified in ST only when recent sediments cover the paleosols by < 50 cm. When overburden sediments are thicker, the paleosols are not considered in the ST placements. Soils on older geomorphic surfaces with extreme development of a diagnostic property, for example an argillic horizon, are placed in Pale great groups (Paleudalfs, Paleustolls, Paleargids, etc,) but these classes do not imply paleosols per se. Another limitation with ST is that this system only classifies the upper 2 m of soil cover. Many paleosols lie below that depth. Finally, ST requires multiple morphological and laboratory criteria to place soils even at the order level within the system; many of these criteria are not directly attainable from paleosols in bedrock. Differentiae in ST have three main requirements: magnitude of pedogenic expression, loci of this expression, and specific thickness requirements over which the expression occurs. For example, it is not sufficient to document the evidence for translocated clay by textural differences with soil depth or by 34

micromorphology in thin sections; rather an argillic horizon requires that translocated clay reach some minimum limit of expression within some specific depth limit. Diagnostic properties for placing soils into orders include argillic, kandic, natric, andic, cambic, spodic, mollic, oxic, calcic, petrocalcic, gypsic, petrogypsic, salic, duripan, organic/inorganic materials, gelic materials, soil moisture and soil temperature regimes. Necessary properties to verify these differentiae that are not directly obtainable from rock paleosols include: cation exchange capacity, exchangeable cations, base saturation, phosphate content, phosphate fixation, organic carbon content, active amorphous chemical compounds (OM/metal complexes), moisture and temperature regimes, soil texture, soil structure, soil consistency, bulk density, water retention, soil thickness, color, and specific horizonation. Compaction, temperature increases, and loses of labile reactive amorphous constituents during lithification and diagentic processes pose concerns. Hence, placement of paleosols in the rock record with ST equivalents should be done with caution. Paleoclimatic inferences from such placements should be made with equal constraints because orders in ST occur over broad biogeographic regions. Vertisols, Inceptisols, and Entisols represent the best prospects for using ST equivalents of modern soils as bedrock paleosol proxies. This is in part because it requires a minimum data set to place these soils in ST. Further, these soils commonly occupy extensive young geomorphic surfaces (i.e. fluvial/deltaic deposits) that are extensively preserved in the rock record. Perhaps geoscientists should initiate a joint interdisciplinary “thinktank” to develop criteria for cataloguing paleosols that are correlative with ST but use paleosol properties that can be more easily recognized and verified in the rock record. Principles of ST could be used as a starting point, but paleosol criteria could be selected that are more appropriate for rock materials. This would likely enhance interests in revising ST to better accommodate recognition and cataloguing of paleosols as important morphogenetic markers of paleoenvironments. Herein lies an important opportunity for critical zone research to synergistically advance the understanding of pedological, geological, hydrological, environmental, and archaeological sciences.

Notes: