ABSTRACT GALLEN, SEAN FRANCIS. The Development of Topography in Ancient and Active Orogens: Case Studies of Landscape Evolution in the Southern Appalachians, USA and Crete, Greece. (Under the direction of Karl Wegmann). Understanding the development of topography is fundamental to the geosciences. Topography represents the sum of all tectonic and geodynamic processes that force the earth’s surface upward paired with those that act to bring it down. Spatial and temporal changes in topographic relief can modulate the various feedbacks between atmospheric, earth surface and rock exhumation processes, sediment flux, and the magnitude and style of gravity driven natural hazards. Plate tectonics provides the first-order framework necessary to understand how topography is built through the interaction of lithospheric plates. However, density contrasts in the mantle can also influence the elevation of the earth’s surface through dynamic topography, while poorly understood nuances of mountain building at convergent margins complicate drawing direct connections between tectonics and topography. Such linkages are further confounded by non-linearity between rock uplift and erosion, variations in rates of deformation, changes in climate and the properties of bedrock. Great advances in our understanding of the evolution of topography have been achieved, yet numerous questions remain regarding the evolution of topography in ancient and active orogens. This research addresses knowledge gaps in the development of topography through case- studies of landscape evolution in the southern Appalachians Mountains, USA and the forearc overlying the Hellenic subduction zone. Chapter 1 explores the origins of modern topographic relief in the southern Appalachians, where tectonic activity ceased prior to 200 Ma. Conventional theories invoked to explain modern relief in the region are challenged. Quantitative analyses of digital elevation models and numerical modeling are coupled to provide the magnitudes and timing of changes in topographic relief. The results suggest that the southern Appalachians experienced a phase of topographic rejuvenation during the Miocene that increased the distance between the valley bottoms and mountain peaks > 160%. The most parsimonious driving mechanism to explain all evidence presented is uplift by dynamic topography. Chapter 2 confronts a long-standing debate over the style of orogenesis above the Hellenic subduction zone where two competing hypotheses are used to explain the rise of topography. Distinguishing between these hypotheses hinges on the kinematics of large faults associated with a series to topographic escarpments, known as the Hellenic troughs. Late Pleistocene marine terraces, optically stimulated luminescence geochronology, and structural mapping in South-central Crete and the Late Quaternary eustatic curve provide the dataset to test the kinematics of the Ptolemy fault, one of the Hellenic trough faults. Long term (104 – 105 yr) rock uplift rates are synthesized and active faults identified. Fault-scaling properties demonstrate that active onshore extensional faulting is geometrically inconsistent with contractional shortening along the Ptolemy fault. This finding indicates that the Ptolemy, and probably all of the Hellenic trough faults, accommodates extension-to-transtension. The regional uplift of South-central Crete is interpreted as the result of underplating along the plate interface, as demonstrated by uplift of both the foot-and-hanging walls of active extensional faults with respect to sea level. The Hellenic troughs are grabens rising over an inflating subduction wedge. Chapter 3 exploits fortuitous geologic circumstances in South-central Crete to document the landscape response to changes in the rate of rock uplift and the impact that lithology has on geomorphic sensitivity to tectonic signals. Suites of topographic and drainage basin metrics responsive to rock uplift are used to evaluate how changing conditions are manifested in the landscape. Findings indicate that the landscape is insensitive to changes in rock uplift rate that initiated > 400 Ka, suggesting geomorphic response times here are long. Carbonates reduce ability of the landscape to record tectonic signals, likely due to the development of karst hydrology. These findings demonstrate that landscapes may not represent the active tectonic displacement field. © Copyright 2012 by Sean Francis Gallen All Rights Reserved The Development of Topography in Ancient and Active Orogens: Case Studies of Landscape Evolution in the Southern Appalachians, USA and Crete, Greece by Sean Francis Gallen A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Marine, Earth and Atmospheric Sciences Raleigh, North Carolina 2013 APPROVED BY: _______________________________ _______________________________ Dr. Karl W. Wegmann Dr. DelWayne R. Bohnenstiehl Committee Chair _______________________________ _______________________________ Dr. James P. Hibbard Dr. Elana L. Leithold _______________________________ Dr. Frank J. Pazzaglia DEDICATION This is dedicated to my grandparents, Frank and Patricia Sullivan. Their love and dedication to one another and their family has served as an important and positive example throughout my entire life. ii BIOGRAPHY I was born in a small town just east of Philadelphia, PA in November of 1981. I grew up in Manlius, NY and graduated from Fayetteville-Manlius high school in 2000. My love for the mountains encouraged me to enroll at the University of Vermont, where I discovered my passion for the geosciences. I graduated in 2004 and took some time off from academics, trading in the Green Mountains of Vermont for the Rockies of Wyoming and Utah. While out west I suffered a serious snowboarding injury that forced me to refocus and motivated me to pursue a Master of Science in geology at Western Washington University. My experiences at Western furthered my zeal for the geosciences, specifically tectonics, where my thesis research focused on tectonics and rock magnetism. During my Master’s I became intrigued by active tectonics and interactions between earth surface and tectonic processes. After graduating in 2008, I once again decided to take some time off from academics. This hiatus lasted only about a month before I knew I wanted to go back to school to pursue a Ph.D. focused on active tectonics. I was fortunate enough to have recently read a paper about some interesting work in the Yellowstone area and look up the lead author, Karl Wegmann. I learned that he studied active tectonics, was an Assistant Professor at North Carolina State University and was looking for students. I enrolled at North Carolina State University in 2009 where Karl has allowed me to work on numerous wonderful projects. Much of the research that I have carried out over the four years of my Ph.D. is presented in this dissertation. iii Curriculum Vita - Sean F. Gallen Dept. of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695 1. Professional Preparation: University of Vermont Geology & Political Science B.A. 2004 Western Washington University Geology M.Sc. 2008 North Carolina State University Earth Sciences Ph.D. 2013 2. Appointments: 2009 – 2013 Research Assistant/Teaching Assistant, North Carolina State University, Dept. of Marine, Earth and Atm. Sciences, Raleigh, NC 2008 Research Assistant, Western Washington University, Department of Geology, Pacific Northwest Paleomagnetism Laboratory, Bellingham, WA 2006 – 2007 Teaching Assistant, Western Washington University, Department of Geology, Bellingham, WA 3. Publications: In preparation: Gallen, S.F., Wegmann, K.W., Bohnenstiehl, D., Pazzaglia, F.J., Brandon, M.T., Fassoulas, C., in prep. Coastal Uplift, Activity and the Kinematics of the Hellenic Trough Faults: Tectonic Geomorphology of an Extending Forearc above a Retreating Subduction Zone, Crete, Greece: For submission to Geophysical Journal International. Gallen, S.F., Wegmann, K.W., in prep. Evaluating Landscape Response Times and Sensitivity to Temporal Gradients in Rock Uplift and Lithology in the Hellenic forearc, Crete, Greece: For submission to Geomorphology. Gallen, S.F., Wegmann, K.W., in prep. Rise of the Messara Graben: uplift rates and sediment flux from an actively extending forearc basin, Crete, Greece: For submission to Basin Research. Published: Gallen, S.F., Wegmann, K., Bohnenstiehl, D., 2013, Miocene rejuvenation of topographic relief in the southern Appalachians: GSA Today, v. 23, no. 2 p. 4-10. Gallen, S.F., Wegmann, K., Frankel, K., Hughes, S., Lewis, R., Lyons, N., Paris, P., Ross, K., Bauer, J., Witt, A., 2011. Hillslope response to knickpoint migration in the southern Appalachians: iv Implications for the evolution of post-orogenic landscapes: Earth Surface Processes and Landforms, v. 36, no. 9, p. 1254-1267. 4. Synergistic Activities: 1. Mentored two undergraduate students during NSF sponsored summer research exchange program between NCSU and Wake Technical Community College 2. Reviewer manuscripts submitted to Asian Journal of Earth Science 3. Invited research seminar at the geology department of Appalachian State University 5. Awards and Honors Sigma Xi Gants-in-Aid of Research ($500) - Did the Minoans do it? Testing Natural verses Anthropogenic Controls on Holocene Valley-Bottom Aggradation in the Messara Plain, Crete, Greece, 2012. People’s Choice Award, Best Talk – North