Late Holocene Sea-Level Change Around Newfoundland Julia Daly
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The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library 8-2002 Late holocene sea-level change around Newfoundland Julia Daly Follow this and additional works at: http://digitalcommons.library.umaine.edu/etd Part of the Geology Commons, and the Glaciology Commons Recommended Citation Daly, Julia, "Late holocene sea-level change around Newfoundland" (2002). Electronic Theses and Dissertations. 600. http://digitalcommons.library.umaine.edu/etd/600 This Open-Access Dissertation is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. LATE HOLOCENE SEA-LEVEL CHANGE AROUND NEWFOUNDLAND C BY Julia F. Daly B.A. Carleton College, 1994 M.S. University of Delaware, 1997 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (in Geological Sciences) August, 2002 Advisory Committee: Daniel F. Belknap, Professor of Geological Sciences, Advisor Joseph T. Kelley, Professor of Geological Sciences Kirk A. Maasch, Associate Professor of Geological Sciences Detmar Schnitker, Professor of Marine Sciences Trevor Bell, Assistant Professor of Geography, Memorial University of Newfoundland LATE HOLOCENE SEA-LEVEL CHANGE AROUND NEWFOUNDLAND By Julia F. Daly Thesis Advisor: Dr. Daniel F. Belknap An Abstract of the Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (in Geological Sciences) August, 2002 Analysis of basal salt-marsh peats and tide-gauge data from several locations around Newfoundland yield high-resolution late Holocene sea-level reconstructions and constrain differential sea-level change. The transition between rising and falling local sea levels and the influence of glacioisostasy on relative sea-level change around Newfoundland through the late Holocene are not well known fiom previous research. The patterns of local relative sea-level change during this time have important implications for constraining numerical models of sea-level change, and therefore inferences about ice sheet thickness and the response of the lithosphere to deglaciation. I investigated the stratigraphy of salt marshes at four locations around Newfoundland: a) Hynes Brook (SW), b) St. Paul's Inlet (west), c) Deadman's Bay (NE), and d) Placentia (SE). At each location, surficial samples were used to determine the modern floral and foraminifera1 zonation. These zones were applied to basal peat samples to constrain the paleo-mean high water (MHW) level associated with the sample. Sea-level histories for each location are constructed by combining AMS 14cdates with paleo-MHW ranges for a series of basal samples. At three locations (Hynes Brook, Deadman's Bay, Placentia), sea level has risen during this time. At St. Paul's Inlet, sea-level change during the late Holocene appears to have a more complex history. Sea level has remained close to present over the past 2,000 years, but may have experienced a subtle transition fiom falling to rising between 2000 and 1000 years BP. This trend contrasts strongly with the transgression interpreted at Hynes Brook, approximately 160 km to the southwest, and supports the hypothesis of continuing glacioisostatic influence on the Northern Peninsula. Identification of the timing and position of this hinge and differential late Holocene sea- level trends provide important constraints on numerical models predicting isostatic responses to deglaciation. ACKNOWLEDGEMENTS I would like to thank Dan Belknap and Joe Kelley for their help in shaping this project, thoughthl criticism, and continuing encouragement and support. Kirk Maasch and Detrnar Schnitker provided valuable advice, and are thanked for participating on the committee. Trevor Bell provided substantial in-kind support for this research and facilitated fieldwork in Newfoundland. Alison ~randds,Alice Kelley, and Shane Greene provided able field assistance and good company. Roland Gehrels introduced me to foram analysis and I am grateful for his interest in the project and good counsel. Tim Patterson and Jean-Pierre Guilbault assisted with foram identification. Kelley Edwards assisted with SEM image acquisition. The Geological Society of America and the University of Maine Association of Graduate Students funded this research. Tim Jull at the University of Arizona AMS facility arranged for two-dozen radiocarbon dates at a reduced fee. Encouragement fiom Steve Norton, Meredith Kelly, and Martin and Lesa O'Connell is appreciated. Doug Reusch is gratefully acknowledged for support in the field, lab, and home. TABLE OF CONTENTS .. ACKNOWLEDGEMENTS............................................................................................... -11 ... LIST OF FIGURES ..........................................................................................................viii .. LIST OF TABLES .............................................................................................................xi1 CHAPTER 1 . INTRODUCTION ............................................................................................1 Introduction and Statement of Problem .......................................................1 Previous Research .......................................................................................-7 Studying late Holocene sea-level change........................................ 7 Salt-marshes and sea-level rise ............................................7 Salt-marsh records .............................................................12 Tide-gauge records .........................................................................14 Sea-level change around Newfoundland ....................................... 15 . Numerical predictions ........................................................16 Pleistocene-Holocene records ............................................16 CHAPTER 2 . METHODS ......................................................................................................20 Field Methods............................................................................................ 20 Laboratory Methods ...................................................................................23 . Foramlnlferal Analysis ...................................................................23 AMS 14 C Samples.......................................................................... 26 Tide-Gauge Analysis .....................................................................26 Definition and Description of Lithologic Units .........................................27 Freshwater Peat ..............................: ...............................................28 . Transition Peat ..............................................................................-28 Higher High Marsh Peat ................................................................ 29 High Marsh Peat ...........................................................................-29 Substrate......................................................................................... 30 CHAPTER 3 . TIDE-GAUGE RECORDS............................................................................. -31 Introduction and Previous Work ................................................................31 Results........................................................................................................ 35 Linear Regression Analysis........................................................... 36 Wavelet and Evolutionary Spectral Analysis................................ 38 Discussion................................................................................................. -41 CHAPTER 4 . MODERN FORAMINIFERAL SURFICIAL ZONATIONS......................... 44 Introduction and Previous Research ..........................................................44 Results ........................................................................................................47 Introduction................................................................................... -47 Population and Diversity................................................................ -47 Cluster Analysis .............................................................................49 Site Zonations ................................................................................59 Discussion.................................................................................................. 61 CHAPTER 5 . HYNES BROOK. PORT-AU-PORT PENINSULA .......................................63 Introduction and Geologic Setting............................................................. 63 Previous Work ...........................................................................................66 Results ........................................................................................................67 Salt-Marsh Stratigraphy ................................................................-67 Radiocarbon Dates ........................................................................-69 Sea-level Reconstruction.............................................................. -72 Discussion.................................................................................................. 75 CHAPTER 6 . ST . PAUL'S INLET ........................................................................................77 Introduction and Geologic Setting............................................................