Carboniferous strata of the Wandel Sea Basin unconformably overlie the Laurentian Precambrian crystalline rocks of the Caledonian hinterland at its northernmost exposures in Holm Land (~80°N). Complex zircon from an intermediate gneiss gives an upper-intercept age of 1878 ± 71 Ma, a protolith age which fits with the regional 1.8-2.0 Ga calc-alkaline arc. A strongly deformed pegmatite was intruded at 435 ± 17 Ma, and it is a rare example of Caledonian magmatism in the northern sector of the orogen. Omphacite confirms the presence of eclogite (sensu stricto) lenses in the basement complex, thus documenting the northern extent of the NorthEast Greenland eclogite province formed during the Caledonian collision with Baltica. Holm Land lies in the eastern block of the eclogite province, where an ultrahigh-pressure (UHP) meta morphic event took place at 365-350 Ma. Zircon from a Holm Land eclogite lacks a Eu anomaly, has a flat heavy rare earth element pattern, and gives a sensitive high-resolution ion microprobe U-Pb age of 423 ± 7 Ma, and it is thus interpreted as the time of high-pressure (HP) metamorphism. This age overlaps with the established age of widespread HP metamorphism for the eclogite province (i.e., 415-395 Ma), rather than the younger UHP metamorphism. Westward thrusting of the NorthEast Greenland eclogite province onto the Laurentian margin after 395 Ma and subsequent exhumation of this uppermost thrust sheet provided a substrate for Carboniferous deposition. Detrital zircon age spectra from arkosic sandstones of the late Viséan (ca. 330-340 Ma) Sortebakker and early Moscovian (ca. 310-315 Ma) Kap Jungersen Formations record the progressive unroofing of the NorthEast Greenland Caledonides. All seven samples have a major peak at 1.8-2.0 Ga, and five also have a 1.75 Ga peak, matching the Paleoproterozoic arc and later anorogenic granitoids that comprise the crystalline basement. Paleozoic grains are sparse in the Sortebakker sandstones, but they constitute a pronounced 400 Ma peak in the younger Kap Jungersen Formation. The composition of the detritusincluding garnet clasts, the high amount of discordant zircon (40%), and the large numbers of grains with metamorphic rims that cluster around 410 Ma-reflects a local provenance sourced in the NorthEast Greenland eclogite province, with some input from the overlying thrust sheets. Other Devonian and Carboniferous basins within and peripheral to the Caledonides also show distinct signatures, demonstrating that there is not a simple, representative detrital zircon signature for the Caledonian orogen.

Gilotti, for accepting me as her student, for being such a nice mentor and for the countless hours of revisions and advice on my thesis. Her constant encouragement and able guidance enabled me to develop better writing skills. I am indebted to my co-advisor Dr. William C. McClelland for his relevant and insightful advice, which helped me grasp a better understanding of the project. I would also like to thank Dr. Philip H. Heckel for his time and support towards the completion of this project. I would like to thank my dearest husband Vijay Govindarajan, for his unending love, emotional support and constant encouragement. His inspiring and motivating words helped me to work hard and succeed in this project. I would like to thank my beloved parents R. S. Ramarao and N. Saraswathi and my dear brother R. Prabhanjan for their unwavering love and support. I would also like to thank my in-laws R. Govindarajan and P. Prema Thulasi, for treating me as their own child and providing me with lot of love and encouragement. I am grateful the Department of Geoscience, University of Iowa, for providing such an ideal environment to work and also the financial support. I would like to thank all the faculty members and staff, especially Chris Harms, of our department for providing timely advice and helping me complete the project. In addition, a thank you to my friends Meredith Petrie, Shawn Malone and Neo McAdams for proof reading the manuscript. I thank the Central Microscopy Research Facilities, University of Iowa for helping me learn and use the SEM at Trowbridge Hall. I also thank the "GSA Student Research Grants 2010" for providing funds to my project. Funding for sample collection in Holm iv Land and analytical expenses was provided by Shell Oil Company through collaboration with Dr. Steve Bergman. My sincere thanks to Dr. Raymond Anderson, who selected me for the "Midwest Federation of Mineralogical and Lapidary Societies Scholarship" and also introduced me as a student employee to the Iowa Geological and Water Survey. I also thank Mr. Chris Kahle and Mr. Pete Kollasch, my supervisors at the survey, for hiring me as a student employee. Above all, I would like to thank the Almighty God, for blessing me and giving me this wonderful opportunity in my academic endeavor. v ABSTRACT Carboniferous sedimentary units unconformably overlie eclogite-facies Paleoproterozoic basement gneisses in Holm Land, NorthEast Greenland and record change in provenance as a function of tectonic disturbances that happened during mid-Carboniferous time. The Visean Sortebakker Formation contains arkosic sandstone with abundant gneissic lithic grains and a heavy mineral suite dominated by titanite, apatite and rutile but lacking garnet. ICPMS U-Pb ages on detrital zircons define dominant age groups at 1.75 and 1.98 Ga, broad peaks at 1.1-1.5, 2.2-3.0 Ga, and a few Caledonian metamorphic ages between 350 and 400 Ma. In contrast, Moscovian arkosic sandstone of the unconformably overlying Kap Jungersen Formation contains a heavy mineral suite of titanite, ...

No abstract