The Interplay of Collisional Tectonics and Late Cenozoic Glacial Climate in Alaska and the northeastern Pacific Ocean

A Continental Dynamics/NSF and JOI/USSSP Sponsored Workshop 

4-5 May, 2003 University of Texas at Austin

Gulf of Alaska Tectonics and Climate Interactions Workshop Report-Science Plan Outline

1. Global Questions:

1. What are the three-dimensional kinematic and dynamic processes of oblique micro-plate accretion, and what are the implications for continental growth?
2. What have been the critical Neogene climatic shifts in the high-latitude Pacific and what were the consequences for northern hemisphere climate, glaciation, and environmental change?
3. At what temporal and spatial scales does orogenesis drive global climate and how do major glacial fluctuations influence orogenesis?
4. How can we use this natural laboratory with its active tectonics, abundant geologic hazards, aggressive glacial processes, and dramatic landscape for geoscience education and outreach?

2. Why Gulf of Alaska margin?

A. Overview/Intro

B. Key Points

n Mini-orogeny that allows for the study of tectonic and climatic processes and their interactions at a tractable scale

n Ongoing rapid uplift characterized by extreme topographic relief in a high-latitude environment with high erosion rates, aggressive glaciation, and massive denudation and sedimentation

n A unique 4600-m-thick sedimentary record of glacimarine deposition recording at least 6 My of tectonic and climatic interaction.

n Highest global glacial erosion rates provide the world’s greatest sediment accumulation rates that allow for very high resolution proxy records

n Ability to constrain the marginal marine environment and to assess the feasibility of human coastal migration routes

n Encompasses a subduction to strike-slip transition that is observable onshore and offshore

n Landscape sculpted primarily by glacial erosion

n Due to the relatively confined and closed source-to-sink depositional system, there is little lag in sediment production and deposition

n Expanded marine record of Neogene climate within the north Pacific that can enhance other high-latitude climate records

n The prime site for assessing the history of the North Pacific decadal-scale climate change (PNA, PDO) due to its immediate location and ultra-high precipitation

n Modern analog for processes that have constructed much of the continental crust

n Observable deformation patterns in oblique convergent settings reflect climatic influences

n Earliest record of northern hemisphere glaciation and may provide insight into the initiation of the Cordilleran ice sheet

n Illuminate the currently poorly constrained history of the Cordilleran ice sheet relative to its significance on global climate proxies

n Allow imaging of crust-mantle interaction at a subduction to strike-slip transition

n Plate boundary has generated the second largest historical earthquake and tsunami

n Also generated the largest area of coseismic uplift (1964) and the greatest documented coseismic uplift (14.2 m in 1899)

n Type location for temperate glacimarine systems and their models

n Tectonic setting, Neogene stratigraphy and sedimentary processes, glacial mass-balance, structural and metamorphic history are reasonably well-characterized which allow development of integrated experiments in tectonic and climatic interaction

II. Background

1. Outstanding Problems: Atmospheric/Oceanic, Lithospheric

2. State of Knowledge:

Tectonics, Paleoceanography, Sediment modeling, Holocene glacial history, Deposition history, Outreach, Previous Drilling, Previous Seismic Imaging

III. Detailed Questions

1. Tectonic

n What are the far-field effects that are coupled with the tectonic driving forces generating the Yakutat collision?

n What is the areal distribution of strain?

n What is driving the orogen?

n Are there differential rates of exhumation and denudation within the orogen?

n What are the timing of the deformation phases?

n What are the dynamics of the mantle and how do they interact with the tectonics?

n What were the major tectonic events, kinematics and thermal history?

n What are the structures that accommodate the relative motions in 3-D?

n What are the tectonic processes, 3-D effects, and driving forces behind a subduction to strike-slip transition?

n How much and what incoming material is transferred to the upper plate? How does the transfer occur?

n What is the magmatic input from the mantle?

n What are the driving mechanisms and have they evolved?

n Where, when, and at what rate does strain accumulate (on 10⁰ to 10⁷ yr scales)?

n To what extent does mass redistribution affect strain localization?

n Deformation history and strain rates?

n Transition Fault?

2. Climate

n How have the atmospheric, marine, and surficial processes co-evolved with the formation of the Chugach-St. Elias mountains?

n What temporal and spatial variations in climate is required to get a coupled tectonic and climatic system?

n What are the feedbacks within this coupled tectonic and climatic system?

n What are the highest resolution of observations and over what time scale?

n What were the oceanic circulation patterns and what have been the significant changes?

n What factors are the ice fields sensitive to?

n What is the Neogene climate history of the high-latitude Pacific and what are the consequences for northern hemisphere climate and glaciation?

n Stationary of PDO/ENSO scale climate variability?

n Holocene climate and glacier oscillations?

n Sedimentary budgets of individual basins?

n Sed. processes associated with glacial-marine interactions?

n Sediment budgets over glacial-interglacial timescales?

n Regional climate responses to glaciation?

3. Interplay

n What factors are the ice fields sensitive to?

n What is spatial and temporal history of glaciation and glacial erosion (in the context of active orogenesis)?

n When is the onset of glaciation and what is the glacial history (10³ to 10⁶ yr timescale)?

n Where and when is glacial erosion occurring and what is the interaction between uplift and erosion?

n What is the evolution of topography?

n What is the tectonic budget (influx, efflux, crustal thickening)?

n What is the timing, distribution, and rate of exhumation?

n What and where is being eroded, where is it going, what is the volume/rate, and redistribution of mass?

n What are solute fluxes and what are their effect on CO₂ and C cycling /sequestration

n How deep do effects extend relative to the spatial/temporal distribution of glaciers?

n Do strain localizations determine glacier locations or do glacier locations determine strain localizations?

n What are the tectonic-climatic linkages and how do they influence the evolution of orogenesis, sediment flux, and northern hemisphere climate?

n At what temporal and spatial scales does orogenesis drive global climate and how do major climate fluctuations influence orogenesis?

n when is the onset of glaciation, and what is the northern hemisphere climatic effect of tectonic uplift in the Gulf of Alaska?

n What are the tectonic processes, 3-D effects, and driving forces behind a subduction to strike-slip transition?

n How are tectonic and erosional fluxes grossly balanced through the interrelationships among glacial processes, landscape evolution, crustal deformation, and geodynamics?

n What are the temporal and spatial scales of cooperation among climatic and tectonic processes and at what scale can they be resolved?

n Relative timing of tectonic and climatic events?

n Long term sediment budget balance?

n How did it all start?

IV. Key Measurements and Techniques

A. Tectonics-

• Modern Near-Surface Velocity Field (GPS, Earthquake Seismology, Paleoseismology, Offshore Deformation, Modeling) –
• Paleo-velocity Field (Field geology, Paleomag., Onshore/Offshore Stratigraphy, Offshore Seismic)
• Chronology/Long term Exhumation Rates (Low and Hi T methods, Paleomag. modeling, PTt studies)
• Crustal Architecture (Active and Passive Seismic Imaging and Modeling, Field Geology, MT, Aerogeophysics, seafloor mapping, downhole seismometers, petrological observations, fluid regime characterization)
• Rheology (Velocity from seismics, thermal structure from thermochronometry, viscosity from rebound studies and post-seismic deformation, modeling, downhole in situ stress measurements)
• Mantle Architecture and Kinematics (slab characterization, anisotropy, melt production, heat transfer, and volcanism from earthquake seismology and possibly MT

B. Climate

· Modern Climate (rates and patterns of precipitation, local and regional instrumentation, mass balance of glaciers, ice cores, tree rings, oceanographic measurements, lacustrine and marine proxies, coring, recent stratigraphy, ultra-high resolution seismics (Chirp), pollen)

· Little Ice Age (tree rings, ice cores, lacustrine and marine proxies, stratigraphy, ultra-high resolution seismics, coring, pollen, glacial modeling, sedimentary modeling)

· Holocene (tree rings, ice cores, lacustrine and marine proxies, glacial proxies, marine and terrestrial paleoecology, high-res stratigraphy, seismic, and coring)

· Late Pleistocene-Holocene (Glacial history, ice cores, lacustrine and marine proxies, glacial modeling, sedimentary modeling, seafloor imaging, high-res to MCS seismic, drilling, paleoecology)

· Plio-Pleistocene (Glacial history, marine proxies, onshore and offshore stratigraphy, biostratigraphy, paleoecology/paleoclimatology/Paleoceanography, glacial modeling, sedimentary modeling, GCMs, MCS, and drilling)

· Neogene (Glacial onset, ice sheet onset, paleozoology, paleoclimatology/

· Paleoceanography, marine proxies, on-land stratigraphy, new long cores for site-survey requirements, MCS and drilling in outer shelf and fan, paleotopography, GCMs, glacial modeling, sedimentary modeling)

C. Interplay

• Modern Fluxes (Glacial dynamics, erosion rates, sediment transport and dispersal rates, accumulation rates and volumes, spatial correlation of active structures and erosion, storativity, earthquake cycle, provenance and thermal structure)
• Temporal Variation of Fluxes (Tectonic effects, Climate effects, Glacial/Interglacial cycles, Earthquake cycle, provenance, sediment volumes and sed-glacial modeling, high-density strain measurements, high density thermochronometry)
• Landscape and Seafloor Evolution (Remote sensing, seafloor mapping, structural deformation, glacial buzz saw)
• Glacial Isostacy and Tectonics (Local sea level history, glacial history, modern and paleoseismology, glacial sequence stratigraphy (marine and lacustrine), surface distortion (e.g. terraces), LIDAR, regional warping)

V. Implementation/Recommendations –

• Outreach
• GPS array to be installed early
• Marine – MCS early
• Continuation and Expansion of glacial and fluvial monitoring studies
• Vital to gain access to or copies of existing industry and USGS data
• Modeling to aid sampling strategies should occur early in program
• Establish a GIS database for integration, establish housing and long-term storage of data (includes interacting with community databases)

VI. Education and Outreach

Numerous ideas suggested at workshop, will then them notes of these

VII. Links to other programs

Earthscope

· PBO- 3 sites in GOA: Yakatat, Cape Yakataga, and Kayak Island, so PBO should be augmented some continuous multi-year sites as well as campaign

· USARRAY- Long time off, maybe recommend using flex array in GOA earlier and within GOA study area

-GLOBEC

-MESH/ESH

-Ice Core Studies

-MARGINS (CSM, S2S if wise to mention at all)

Appendices- Workshop Abstracts + posters