Holocene paleoenvironmental reconstruction in Galway Bay, a shallow coastal embayment along

240 Pages·2017·8.04 MB·English

Holocene paleoenvironmental reconstruction in Galway Bay, a shallow
coastal embayment along Ireland’s North-East Atlantic margin

Joyce D. Novak, BA, MSc
2017

Thesis submitted for the degree of Doctor of Philosophy

Department of Geography
Mary Immaculate College
University of Limerick

Supervisor: Dr. Catherine Dalton
Co-supervisor: Dr. Caroline Cusack

Submitted to the University of Limerick December, 2016
For Dylan and Nathan
"For whatever we lose (like a you or a me), it's always ourselves we find in the sea."
E. E. Cummings

For Dave
For everything…and more. A chuisle mo chroí.
“These shores, so different in their nature and in the inhabitants they support
are made one by the unifying touch of the sea. For the differences I sense in
this particular instant of time that is mine are but the differences of a
moment, determined by our place in the stream of time and in the long
rhythms of the sea.”
Rachel Carson, 1951
Title of Thesis: Holocene paleoenvironmental reconstruction in Galway Bay, a
shallow coastal embayment along Ireland’s North-East Atlantic margin
Author: Joyce Novak
Coastal environments are highly dynamic and complicated systems that vary spatially and
temporally over a range of timescales. This study explores the paleoenvironmental changes
recorded in sediment cores taken from Galway Bay, located on the coast of western Ireland.
Galway Bay is a large shallow bay, which is protected from ocean swells of the North Atlantic by
the Aran Islands. The inner bay receives freshwater mainly from the Corrib River Catchment.
Four c. 6 m sediment cores were extracted along an inner bay transect and are explored here in a
multi proxy paleoecological study to track environmental change during the Holocene period.
Physical proxies obtained using a Multi Sensor Core Logger (MSCL), geochemical signatures
acquired with X-ray fluorescence (XRF) scanning and microfossils (diatom and foraminifera)
were examined. A Holocene timeframe was established with 23 AMS 14C dates across the four
cores spanning c. 10000 cal years BP. A west-east progression is noted in the sediment
stratigraphy. The western most sediment core contained no sediment post c. 8500 cal years BP
while the eastern most sediment core, closest to the Corrib River outflow, contained the most
complete sediment profile with sediments from the early, mid and late Holocene. A sedimentary
hiatus spanning 5-7 ka is confirmed in two sediment cores. Change points in the sediment
profiles are identified, reflecting known climatic events, including marine transgression, a
possible 8.2 ka cooling event, freshwater phases and rising sea levels. The early Holocene
encompassed the highest rate of sediment accumulation and marine transgression is captured in
the proxy evidence. Coastal environmental change is postulated with water level rise and paleo
tidal ranges varying from Highest Astronomical Tide to Mean High Water with high to middle
marsh and mudflat development. The mid Holocene has a major break in sediment continuity
with no complete mid Holocene sediment profile preserved. The innermost bay core retained
sediment until c. 6000 cal years BP. The major hiatus is associated with a visible shell layer
possibly reflecting a possible storm event and a sediment washout. The shell layer is overlain
with late Holocene sediments (c. 500 years) in both inner bay cores reflecting either a return of
conditions facilitating sediment deposition, or sediments that have not yet been washed out. The
complex chronology and sedimentary profiles display a west to east progression along the inner
Galway Bay transect reflecting a spatial trajectory of chronological, physical, chemical and
biological change and thus environmental change as the rising sea made its way east into the
Galway Bay.
Declaration

I hereby declare that this thesis represents my work and has not been submitted in
whole or in part, by me or another person, for the purpose of obtaining any other
qualification.
Signed: __________________________
Date: __________________________
Acknowledgements
I would like to thank Mary Immaculate College for awarding me the MIC Studentship
which made this work possible. As well, for further research seed funding which was
used for radiocarbon dating of material in this project. The Marine Institute, for granting
me their Networking and Travel Award in 2012 and 2013.
My academic supervisor at MIC, Dr Catherine Dalton, for guiding me through the PhD
process. For her exceptional skills as an editor and imparting her knowledge of the paleo
world and academia to me. I am eternally grateful.
My supervisor at the Marine Institute, Dr Caroline Cusack, for sharing her enormous
intelligence with me and opening the MI to me. Your advice regarding ocean sciences
was invaluable and I could not have completed this without you. Your camaraderie as a
working mother and regarding sick children made me feel human.
To my fellow geography postgrads Margaret Browne and Darren Barry who have battled
in the trenches with me from Ireland to Italy (via Moneygall), provided countless hours
of informed discussion, sci-fi and superhero discussion, Japanese food, map making,
foram processing, stats confusion and who have cheered me on from the sidelines; I am
not quite sure I would’ve crossed the finish line without them. The Geography
Department at Mary Immaculate College: Dr Des McCaffrety, Dr Brendan O’Keefe, Dr
Helene Bradley-Davis, Dr Angela Cloke-Hayes, Dr Shane O’Sullivan, Grainne Dwyer
and Niall Walsh for continual support.
To the Marine Institute’s INFOMAR programme through which the sediment cores for
this project were obtained. Morris Clarke, Helen McCormick and Macdarra O’Cuaig in
the Fishery Ecosystem Advisory Service at the MI; Kieran Lyons, Trevor Alcorn and
Deirdre O’Driscoll in Data Services and Adam Leadbetter at the MI. Dr Mike Williams
(NUIG), Bill Wood, Dr Rosaleen Mylotte (UL), Dr. Paula Reimer (Queens), Dr Jonathan
Turner (UCD), Dr Steve McCarron (Maynooth), Dr Gil Scott, Dr Garrett Duffy (NUI
Galway), Cathal Clarke (NUI Galway), Dr Jonathan Lewis (Loughboro UK).
Tobi and Otis Rapp & Séan O’Connor at the MI Fishery Science Unit in Castletownbere
& Gavin Power, fisherman extraordinaire, for sharing your space with me for the past
five years, for all the seafood, putting up with my messiness and especially for all the
banter about life in this tiny little paradise at the edge of the world in West Cork.
Gretta Purcell for always minding the boys (and me).
The strong women on whose shoulders I stand: Catherine Martinez, Anita H. Martinez,
Catherine Novak-Doyle, Dr. Carolyn Tricomi, Dr. Anita DeStefano, Josephine
DeStefano – long stemmed American beauties all.
Colleen- for loving me more than her luggage.
Catherine Schnabel Martinez – for happily entertaining my endless stream of questions &
nurturing my inquisitive nature – how I wish you were here to share this moment.
And most of all, my parents (Mom & Bill, Daddy & Kathy) who are my champions, my
biggest fans and when need be, my financial backers. Your pride overwhelms me & your
love is boundless. Your relentless pursuit of this achievement was as great as my own.
Go raibh maith agat.
TABLE OF CONTENTS
CHAPTER 1: INTRODUCTION ....................................................................... 6
1.1 Research rationale .................................................................................. 6
1.2 Aims and objectives ................................................................................ 8
1.3 Structure of thesis ................................................................................... 9
CHAPTER 2: COASTAL ENVIRONMENTS ................................................ 11
2.1 Coastal processes .................................................................................. 11
2.1.1 Oceanic processes ................................................................................ 13
2.1.2 Coastal sedimentation......................................................................... 16
2.1.3 Estuarine processes ............................................................................. 17
2.1.3.1 Estuarine water circulation .................................................................. 18
2.1.3.2 Estuarine sedimentation ....................................................................... 18
2.1.4 Terrestrial processes in the coastal zone ........................................... 19
2.1.4.1 Terrigenous sedimentation and its effect on the coastal zone .............. 20
CHAPTER 3: HOLOCENE ENVIRONMENTAL CHANGE ...................... 23
3.1 The Holocene ......................................................................................... 23
3.2 Glacial activity as a precursor to Holocene environmental conditions
................................................................................................................ 24
3.3 Drivers of climate change in the Holocene ......................................... 27
3.3.1 External forces .................................................................................... 28
3.3.2 Internal modes of climate variability ................................................ 28
3.4 Climatic conditions in the Holocene .................................................... 30
3.4.1 Holocene climatic cyclicity ................................................................. 32
3.5 Relative Sea Level (RSL) during the Holocene .................................. 33
3.6 Paleoenvironmental applications ......................................................... 36
3.6.1 Radiocarbon dating ............................................................................ 37
3.6.2 Sediment stratigraphy ........................................................................ 38
3.6.3 Geochemical proxy analysis ............................................................... 40
3.6.3.1 Applications of geochemical markers in sediment cores ...................... 41
3.6.4 Microfossil analysis in paleoecological reconstruction .................... 42
3.6.4.1 Diatoms ................................................................................................. 43
3.6.4.2 Foraminifera ......................................................................................... 47
3.6.4.3 Transfer functions ................................................................................. 49
CHAPTER 4: METHODOLOGY .................................................................... 51
4.1 Study Area ............................................................................................. 51
4.1.1 Modern hydrological conditions in Galway Bay .............................. 55
4.1.2 The Corrib catchment ........................................................................ 57
4.2 Sediment coring .................................................................................... 57
4.3 Laboratory analysis .............................................................................. 60
4.4 Sedimentology ....................................................................................... 62
4.4.1 Core logging ........................................................................................ 62
4.5 Radiocarbon dating .............................................................................. 63
4.5.1 Calibration ........................................................................................... 64
4.6 Geochemistry – X-Ray Fluorescence (XRF) ....................................... 65
4.7 Diatoms .................................................................................................. 67
4.7.1 Diatom identification and enumeration ............................................ 68
4.7.2 Diatom dissolution and breakage ...................................................... 72
4.8 Foraminifera ......................................................................................... 72
4.9 Data Analysis ......................................................................................... 73
CHAPTER 5: RESULTS .................................................................................... 76
5.1 Sediment core extraction .................................................................... 76
5.2 Core Lithology .................................................................................... 78
5.3 Chronology ............................................................................................ 83
5.4 Sediment core VC001 ......................................................................... 88
5.4.1 Physical properties .............................................................................. 88
5.4.2 Geochemical properties ...................................................................... 91
5.4.3 Diatoms ................................................................................................ 95
5.4.4 Foraminifera ..................................................................................... 104
5.4.5 Synthesis of data for sediment core VC001 .................................... 109
5.5.1 Physical data ...................................................................................... 110
5.5.2 Geochemical (XRF) analysis ............................................................ 113
5.5.3 Diatoms VC003 and VC004 ............................................................. 116
5.5.4 Foraminifera VC003 ......................................................................... 120
5.5.5 Summary of results for sediment cores VC002, VC003 and VC004
122
CHAPTER 6: DISCUSSION ........................................................................... 123
6.1 Synthesis of Data ................................................................................. 123
6.2 Sediment chronology .......................................................................... 126
6.2.1 Hiatus ................................................................................................. 130
6.2 The Early Holocene (10235-8200 cal years BP) ............................... 137
6.2.1 Marine transgression ........................................................................ 137
6.2.2 Early Holocene paleoenvironmental coastline changes ................. 143
6.3 The Mid Holocene (8200-6063 cal years BP) .................................... 149
6.3.1 Mid Holocene paleoenvironmental coastline changes ................... 150
6.4 The Late Holocene (4200 to date) ...................................................... 154
6.4.1 Modern sediment deposits ................................................................ 155
CHAPTER 7: CONCLUSION ......................................................................... 159
CHAPTER 8: REFERENCES ......................................................................... 165
APPENDIX A: GRAIN SIZE ANALYSIS ................................................................. 211
APPENDIX B: AGE DEPTH PROFILES VC003 AND VC004 .............................. 213
APPENDIX C: XRF ELEMENTAL PROFILES VC001, VC002, VC003 AND
VC004 ............................................................................................................................. 215
APPENDIX D: DIATOMS .......................................................................................... 219
APPENDIX E: DCA FOR DIATOMS IN VC001 ..................................................... 224
APPENDIX F: DI SALINITY DATA ......................................................................... 225
APPENDIX G: FORAMINIFERA ............................................................................. 227
APPENDIX H: PCA FOR GEOCHEMICAL RATIOS ........................................... 230