Thesis advisor: J C. Hepburn / Thesis advisor: Yvette D. Kuiper / Metasedimentary rocks of the Merrimack terrane (MT) originated as a thick cover sequence on Ganderia consisting of sandstones, calcareous sandstones, pelitic rocks and turbidites. In order to investigate the age, provenance and stratigraphic order of these rocks and correlations with adjoining terranes, detrital zircon suites from 7 formations across the MT along a NNE-trending transect from east-central Massachusetts to SE New Hampshire were analyzed by U-Pb LA-ICP-MS methods on 90-140 grains per sample. The youngest detrital zircons in the western units, the Worcester, Oakdale and Paxton Formations, are ca. 438 Ma while those in the Kittery, Eliot and Berwick Formations in the northeast are ca. 426 Ma. The Tower Hill Formation previously interpreted to form the easternmost unit of the MT in MA, has a distinctly different zircon distribution with its youngest zircon population in the Cambrian. All samples except for the Tower Hill Formation have detrital zircon age distributions with significant peaks in the mid-to late Ordovician, similar abundances of early Paleozoic and late Neoproterozoic zircons, significant input from ~1.0 to ~1.8 Ga sources and limited Archean grains. The similarities in zircon provenance suggest that all units across the terrane, except for the Tower Hill Formation, belong to a single sequence of rocks, with similar sources and with the units in the NE possibly being somewhat younger than those in east-central Massachusetts. The continuous zircon age distributions observed throughout the Mesoproterozoic and late Paleoproterozoic are consistent with an Amazonian source. All samples, except the Tower Hill Formation, show sedimentary input from both Ganderian and Laurentian sources and suggest that Laurentian input increases as the maximum depositional age decreases. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

The Wrangellia composite terrane is one of the largest fragments of juvenile crust added to the North American continent since Mesozoic time, and refining its accretionary history has important implications for understanding how continents grow. New U-Pb geochronology and Hf isotopes of detrital zircons from Late Jurassic-Late Cretaceous strata from the forearc of the Wrangellia composite terrane allows more insight on the tectonic and paleogeographic history of the terrane. Our stratigraphically oldest samples from the Late Jurassic Naknek Formation have a detrital zircon U-Pb signature dominated by Early and Late Jurassic grains (195-190 Ma; 153-147 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Disconformably above the Naknek Formation are two poorly understood units Ks and Kc. The Ks unit is dominated by Early to Late Jurassic grains (159-154 Ma) with a few Paleozoic grains (347-340 Ma). Hf isotopic compositions of Carboniferous-Jurassic grains are juvenile to intermediate (εHf(t)=6.0-18.8). The overlying Kc unit has Late to Early Jurassic zircons (198-161 Ma), and an increase in Paleozoic ages (374-323 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Samples from the Matanuska Formation have major Late Cretaceous grains (90-71 Ma), and minor Early Cretaceous (137-106 Ma), Late to Early Jurassic (200-153 Ma), Paleozoic (367-277 Ma), and Precambrian grains (2597-1037 Ma). Hf compositions have a wider range from both the Late Cretaceous grains (εHf(t)=-1.5-14.9) and Paleozoic-Precambrian grains (εHf(t)=-23.7-16.3). Our results suggest an evolving provenance from Late Jurassic to Late Cretaceous time for the Wrangellia composite terrane forearc basin. The Late Jurassic Naknek Formation samples were dominantly derived from a juvenile to intermediate Jurassic igneous sediment source. During Early Cretaceous time, there is a slight increase in the number of Paleozoic grains in the Ks and Kc unit samples. The Early Cretaceous sediments have a mostly positive Hf isotopic compositions suggesting exhumation of Jurassic and Paleozoic juvenile igneous sediment sources. By Late Cretaceous time, our data illustrates another increase in Paleozoic grain abundances, in addition to the introduction of Precambrian grains, all with widely variable Hf isotopic compositions. We interpret this to reflect a larger sediment flux from the interior of Alaska where more evolved igneous rocks of that age are found.

This thesis evaluates the nature, provenance, geometry and morphology of incised valley fills to test assumptions made by valley models using ancient examples from well exposed outcrops, in the late Turonian Ferron Sandstone Member of the Mancos Shale Formation in southeastern Utah. The relevance of this work will have particular significance to long wavelength cycles of fluvial landscapes and valley morphology, non-marine reservoir characterization and significant implications for non-marine response to high frequency allogenic cycles such as climate change and changes in relative sea-level. This study illustrates the stratigraphic complexity of valley fill deposits at three levels of spatial resolution. At channel scale within the lower backwater, facies architecture and paleohydraulic analysis are used to predict the degree of shale drape coverage of point bars in a tidally-influenced incised channel. At channel belt scale the study documents a tidally incised, mudstone prone trunk-tributary valley fill and overlying highstand fluvial succession within a stratigraphic framework of fluvial aggragation cycles. 3D photogrammetry models and a high resolution GPS survey are used to restore the morphology of a trunk-tributary valley floor, revealing a surface of tidal ravinement and tidal drainage morphology. At a regional scale, this study radically revises the paleogeographic mapping of the Ferron trunk system, spanning over 1,600 km2. Provenance analysis reveals Ferron Notom trunk valleys were filled at times by sediment from the Mogollon Highlands of Arizona to the southwest, and alternately by sediment from the Sevier Thrust Front to the northwest. Evidence shows the Ferron trunk rivers, previously hypothesized to be an avulsive axial drainage, to be more analogous to Quaternary examples. / Thesis / Doctor of Philosophy (PhD)

Thesis (M.S.)--Indiana University, 2008. / Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Kathy J. Licht, Andrew P. Barth, R. Jeffery Swope, Gabriel M. Filippelli. Includes vitae. Includes bibliographical references (leaves 182-191).

Stratigraphic successions of sedimentary rocks represent an important repository for signals pertaining to the history and evolution of Earth. Whereas the specific processes reflected by the stratigraphic record differ with respect to a given depositional environment, deposits in deep-marine settings, particularly passive margins, provide a unique, long-term record of paleoclimate, paleoceanography, and tectonics affecting the basin in question. Whereas deep-marine strata may be used to answer myriad of questions regarding the evolution and development of Earth systems, this dissertation narrowly targets two distinct aspects of sedimentation in deep-sea settings. The first two chapters focus on the utility of sortable silt in reconstructing bottom-current intensity linked to major shifts in climate. First, the relationship of sortable silt to flow velocity was tested under controlled conditions in a flow-through flume. This chapter investigates the correlation of sortable silt metrics across several experimental parameters, which is found here to dispute longstanding assumptions that multiple metrics must correlate to infer sediment sorting by deep currents. Additionally, the results are compared to calibrations from natural settings, where the correlation between the two datasets is remarkably similar, validating the relationship of sortable silt with current velocity in the deep ocean. Chapter two leverages sortable silt to investigate the long-term evolution of the Deep Western Boundary Current in the North Atlantic, targeting contourite drifts offshore Newfoundland to investigate the Eocene-Oligocene Transition (EOT), the most recent global greenhouse-to-icehouse transition. Results suggest that the Deep Western Boundary Current intensified gradually from 35-26 Ma, not abruptly at the EOT, and change consistent with deepening of the Greenland-Scotland Ridge and enhanced overflow of deep water into the North Atlantic. Chapter three utilizes detrital zircon U-Pb dating to characterize source-to-sink pathways and linkages during the rift-to-drift transition, in the Early Cretaceous, along the U.S. mid-Atlantic passive margin. This work shows that onshore and offshore system segments were initially disconnected, and progressively integrated over the course of ~45 Myr. Taken together, this work demonstrates a focused yet powerful example of how deep-marine sedimentary systems can be leveraged to robustly model major changes throughout Earth history. / Doctor of Philosophy / Sediments and sedimentary rocks deposited in the deep ocean house long-term signals pertaining to important Earth processes and properties. The nature of a given deposit, for example, can be the direct result of climatic conditions or tectonic development in adjacent mountainous and coastal environments. While the range of questions that can be answered using the sedimentary record is vast, this dissertation narrowly focuses on 1) how deep-ocean currents change over long periods of time, and 2) how onshore and offshore depositional environments correlate during the early phases of supercontinent break-up. To address the reconstruction of deep-ocean currents, laboratory experiments were performed to test how the sortable silt proxy – the 10-63 um fraction of a deposit – correlates with current velocity, the first controlled test of the proxy since its inception by paleoceanographers nearly three decades ago. Sortable silt is then applied to sediments of Eocene-Oligocene age, recovered from contourites offshore Newfoundland, Canada, to assess the long-term behavior of the Deep Western Boundary Current in the North Atlantic across the Eocene-Oligocene Transition (EOT). While the EOT, a major global cooling that occurred ~33.7 Ma, is well-studied with respect to Antarctica and its surrounding ocean basins, little is known about the paleoceanographic response of the North Atlantic. Grain-size records show a gradual increase in sortable silt before, during, and after the EOT, through entirety of the 9 Myr record. This trend is interpreted to reflect a long-term invigoration of the Deep Western Boundary Current in North Atlantic, likely due to progressive deepening of the Greenland-Scotland Ridge. The final chapter leverages detrital zircon U-Pb geochronology to compare sediment provenance of Early Cretaceous fluvial sandstones with coeval, distal turbidite sands. Results suggest that coastal rivers were fed by a single source terrane during the earliest Cretaceous, disconnected from the regional catchment feeding the submarine fan. By the Aptian-Albian, coastal rivers share a detrital zircon signature with turbidite strata, suggesting that rivers were progressively integrated into the sediment-routing system feeding the offshore margin.

Indiana University-Purdue University Indianapolis (IUPUI) / Petrography of the sand fraction, particle size analysis, and detrital zircon U/Pb isotope data, and pebble count data were collected from Byrd Glacier moraines and central/western Ross Sea till in order to study the glacially-driven sedimentological dynamics of the Byrd Glacier and to trace material transported from the Byrd Glacier into the Ross embayment. Most of the petrographic data show evidence of local derivation with the exception of the sites from the Lonewolf Nunataks as indicated by exotic rock types within the sand and pebble fractions. This, in conjunction with particle-size data of the samples from the Lonewolf Nunataks indicate that material from underneath the East Antarctic Ice Sheet (EAIS) is being transported to the surface and deposited in this area. The U/Pb ages of zircons from the Byrd Glacier show dominant populations of Ross to Pan-African ages (~533 - 610 Ma) with varying populations of older (Grenville to Archean) zircons. Late Precambrian (~588 – 610 Ma) aged detrital zircons in samples from the head of the Byrd Glacier are older than other dated grains found in the vicinity and may be evidence of early development of the Ross belt or represent evidence of sub-glacial extension of the Mozambique structure found in Dronning Maud Land. The west central Ross Sea till samples have a variety of mineral and lithic fragments that include a dominant population of polymict at certain depth intervals. Detrital zircon data suggests the potential provenance of two of these intervals may be derived from Marie Byrd Land and possibly the Byrd Glacier. Using sand petrography and U/Pb detrital zircon age dating, positive correlation was found between specific samples from the head of the Byrd Glacier and the western Ross Sea. The ice-sheet flow models of Stuiver et al. (1981), Licht and Fastook (1998), and Licht et al. (2005) each show potential support from aspects of this study. It is possible that dynamic ice-flow regime changes of the West and East Antarctic Ice Sheets into the Ross Sea may have occurred some time during the LGM as suggested by geochemical and petrographical evidence found within intervals of central and western Ross Sea cores.

Indiana University-Purdue University Indianapolis (IUPUI) / U/Pb and (U-Th)/He (ZHe) dating of detrital zircons from glacial till samples in the Ross Embayment, Antarctica records cooling after the Ross/Pan-African orogeny (450-625 Ma) followed by a mid-Jurassic to mid-Cretaceous heating event in the Beacon basin. Zircons were extracted from till samples from heads of major outlet glaciers in East Antarctica, one sample at the mouth of Scott Glacier, and from beneath three West Antarctic ice streams. The Ross/Pan-African U/Pb population is ubiquitous in these Antarctic tills and many Beacon Supergroup sandstones, thus 83 grains were analyzed for ZHe to subdivide this population. Two ZHe age populations are evident in East Antarctic tills, with 64% of grains 115-200 Ma and 35% between 200-650 Ma. The older population is interpreted to be associated with the Ross/Pan-African orogeny including cooling of the Granite Harbour Intrusives and/or exhumation of the older basement rocks to form the Kukri Peneplain. The lag time between zircon U/Pb, ZHe and 40Ar/39Ar ages from K-bearing minerals show cooling over 200 My. Grains in East Antarctic tills with a ZHe age of 115-200 Ma likely reflects regional heating following the breakup of Gondwana from the Ferrar dolerite intrusions, subsidence within the rift basin, and a higher geothermal gradient. Subsequent cooling and/or exhumation of the Transantarctic Mountains brought grains below the closure temperature over a span of 80 My. This population may also provide a Beacon Supergroup signature as most of the tills with this age are adjacent to nunataks mapped as Beacon Supergroup and contain an abundance of vi Beacon pebbles within the moraine. Nine zircons grains from three Beacon Supergroup sandstones collected from moraines across the Transantarctic Mountains yield ages from 125-180 Ma. West Antarctic tills contain a range of ZHe ages from 75-450 Ma reflecting the diverse provenance of basin fill from East Antarctica and Marie Byrd Land. ZHe and U/Pb ages <105 Ma appear to be distinctive of West Antarctic tills. The combination of U/Pb, ZHe and 40Ar/39Ar analyses demonstrates that these techniques can be used to better constrain the tectonic evolution and cooling of the inaccessible subglacial source terrains beneath the Antarctic Ice Sheet.