Benetti, Sara

Edwards, Robin

McCullagh, Denise

Plets, Ruth

English

A multi-disciplinary investigation into the elements that have shaped Galway Bay since the last glaciation to present day. Sedimentological and geophysical data will be combined to produce geomorphological and stratigraphic maps; sediment cores will provide specific clues on how the sedimentary and oceanic processes have altered the bay over time

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                  Name of Lead Investigator  Sara Benetti Email s.benetti@ulster.ac.uk  Organisation name Ulster University Organisation type:            ☒HEI   ☐Public Sector (other)     ☒Private Sector Department/section School of Geography and Environmental Science  Project Title Past and Modern Environments of Galway Bay Contract No. 2015-sc-073                 Geoscience Research Geological Survey of Ireland Research Programme  - Short Call 2015, Final Report -  2	2. Project	information:Title	of	project	 Past	and	Modern	Environments	of	Galway	Bay.	Did	 you	 make	 any	 formal	amendment	 to	 the	project	workplan	/	budget?		☐	 yes ☒ no	If	yes,	please	specify:	Project	Report	(max	1500	words,	excluding	figures	and	headings):	(i) Objectives	and	scientific/engineering	targets	beyond	the	state	of	the	art	The	overarching	aim	of	 this	project	was	 to	extend	our	knowledge	of	the	sedimentary	environments	 in	Galway	Bay	from	post	last	glacial	maximum	until	the	present	day.		Specifically	the	project	objective	were:	(1) To	identify,	interpret	and	assess	the	timing	of	sedimentary	processes	that	have	occurred	in	Galway	Bay	since	the	end	of	the	last	glacial	period;	(2) To	 produce	 a	 high	 resolution	 geomorphological	 map	 of	 the	 bay	 using	 the	 INFOMAR	 multibeam	bathymetric	and	backscatter	data;	(3) To	reconstruct	a	detailed	seismic	sequence	stratigraphy	of	Galway	Bay	using	the	INFOMAR	pinger	(3.5	kHz	data).	3	Objective	one:	sedimentary	processes	of	Galway	Bay.	Twenty-two	sediment	cores	collected	in	Galway	Bay	in	2013	and	2014	by	Ulster	University	(Fig.	1)	were	split,	described	and	analysed	as	part	of	the	project:	- Microfossil	 samples	 were	 collected	 or	 picked	 for	 radiocarbon	 dating	 of	 the	 sediments	 (Table	 1).	 A	radiocarbon	database	for	Galway	Bay	is	still	being	compiled	as	the	final	3	samples	have	been	submitted	for	analysis	but	the	results	have	yet	to	be	received	(expected	delivery	date	is	Thu,	Dec.	29).	Samples	were	all	 submitted	 to	 Beta	 Analytic	 (http://www.radiocarbon.com)	 due	 to	 the	 relatively	 rapid	 turn-around	compared	to	other	analytical	laboratories.	- The	 longest	 cores	 were	 run	 for	 geochemical	 analysis	 under	 the	 ITRAX	 core	 scanner	 at	 BOSCORF	 in	Southampton	 (http://www.boscorf.org/instruments/itrax-high-resolution-xrf-analysis-sediment-cores)	(Cores:	01GC;	01VC	to	04VC;	06VC;	07VC;	09VC;	10VC;	12VC	to	15VC;	17VC;	18VC;	20VC;	22VC).	Fig.	1	–	Location	of	sediment	cores	used	in	the	study.	The	two	areas	identified	by	the	rectangles	include	the	cores	in	Fig.	2.	Table	1.	List	of	samples	submitted	for	radiocarbon	dating	(samples	with	asterisk	are	those	still	outstanding.	Final	results	are	available	on	request	upon	publication	in	peer-reviewed	paper.	Sample	 Depth	(cm)	 Material	 Lithofacies	CV13031_02VC	 279-280	 Shell	 Silty	sand	CV13031_03VC	 71	 Shell	 Turritella	layer	CV13031_03VC	 72	 Shell	 Turritella	layer	CV13031_06VC	 144.5-145.5	 Shell	 Silty	sand	CV13031_07VC	 120-121	 Shell	 Turritella	layer	CV13031_10VC	 126-127	 Shell	 Turritella	layer	CV13031_10VC	 200-201	 Shell	 Turritella	layer	CV13031_12VC	 148-152.5	 Shell	 Diamicton	CV13031_13VC	 100-101	 Shell	 Turritella	layer	CV13031_13VC	 177-179	 Shell	 Turritella	layer	CV13031_13VC*	 235-236	 Foraminifera	 Silty	sand	CV13031_20VC	 81-82	 Shell	 Turritella	layer	CV13031_20VC*	 117-118	 Foraminifera	 Diamicton	CV13031_22VC	 38-39	 Shell	 Turritella	layer	CV13031_22VC*	 269-270	 Foraminifera	 Sandy	Silt	CE14T_03GC	 53-54	 Shell	 Turritella	layer	Interpretation	of	lithofacies	resulted	in	the	identification	of	3	lithological	units,	which	can	be	correlated	throughout	 many	 of	 the	 cores	 in	 both	 the	 North	 and	 South	 sounds	 (Fig.	 2).	 	 With	 the	 use	 of	 AMS	radiocarbon	dates	all	of	the	sedimentary	units	have	been	constrained	within	the	Holocene.		4	The	presence	of	a	“Turritella	Layer”,	so	named	due	to	the	abundance	of	the	marine	gastropod	Turritella	gn.	 (Fig.	 3)	was	discovered	 in	many	of	 the	 cores	 and	has	been	dated	 to	4,500	 to	6,500	years	BP.	This	timeframe	correlates	well,	albeit	 it	 is	a	little	younger	in	Galway	Bay,	with	a	similar	layer	found	in	other	regions	in	Southern	Brittany	and	Northern	Scotland.		X-ray	fluorescence	(XRF)	analysis	shows	increased	ratios	of	Cl/Fe	in	younger	deposits,	showing	a	general	trend	of	progression	from	estuarine	to	open	marine	conditions.	Further	analysis	of	the	ITRAX	data	will	be	carried	out	by	comparing	relative	ratios	of	other	elements	in	order	to	identify	other	potentially	significant	trends	in	relative	ratios.	Fig.	2	-	Core	logs	for	the	longest	and	more	meaningful	cores	in	two	transects	corresponding	approximately	to	the	North	and	South	sounds	(Fig.	1).	The	top	lithofacies	(green)	is	a	sandy	silt	and	clay	facies,	which	is	often	followed	by	a	distinct	shell	hash	interlayer	(blue)	which	we	named	the	“Turritella	Layer”.	This	layer	is	then	underlaid	by	a	fine	silty	 sand	 facies	 (purple),	with	 a	 general	 lower	 abundance	of	microfossils	 and	 the	occurrence	of	 rare	 gravel	 and	pebble	grains.	Fig.	4	–	Photo	of	several	specimens	of	Turritella	(left).	The	shells	found	in	Galway	Bay	are	on	average	2-4	cm	in	length.	Examples	of	Turritella	layers	in	the	x-radiographs	(centre,	for	core	1GC)	and	in	the	core	face	(right	for	core	22VC).	5	Objective	two:	geomorphological	map.	A	high	resolution	geomorphology	map	(Fig.	6)	of	the	bay	was	created	through	the	interpretation	of	the	seafloor	 landforms	 from	 the	bathymetric	and	backscatter	data.	Multibeam	data	were	also	analysed	 in	ArcGIS	through	slope	analysis	and	hydrological	tools	(Fig.	5).	The	map	 shows	 the	 various	 several	 types	 of	 landforms	 in	 Galway	 Bay,	 including	 sediment	 dunes	 and	erosional	scouring,	and	suggests	that	tidal	and	oceanic	currents	may	have	played	and	possibly	still	play	a	role	 in	 the	 evolution	 of	 these	 features.	 Marine	 terraces	 are	 visible	 near	 the	 present	 day	 coastline,	suggesting	a	 submerged	palaeo-shoreline	at	a	much	 lower	sea	 level.	When	compared	 to	 the	model	of	Bradley	et	al.	(2011)	the	marine	terraces	match	the	position	of	the	coastline	around	9kaBP	(-23.5m	RSL)	and	11kaBP	(-33m	RSL).	Fig.	5	–	Multibeam	bathymetric	and	backscatter	data	for	Galway	Bay	(top)	and	examples	of	the	spatial	analysis	results	obtained	using	ArcGIS	tools	(bottom).	6	Fig.	6	–	Geomorphological	map	of	Galway	Bay.	Objective	three:	seismic	stratigraphy.	Analysis	of	high	resolution	seismic	reflection	(3.5	KHz)	data	in	Galway	Bay	have	revealed	the	presence	of	three	seismic	units	(Fig.	7).	Unit	1,	the	deepest	unit,	is	the	acoustic	basement,	the	folded	faulted	nature	shows	the	granite	of	the	north	and	the	limestone	to	the	south.	It	 is	separated	from	unit	2	by	an	upper	boundary	erosional	 surface	 consisting	of	high	 reflective	 strata.	Unit	 2	 represents	 the	oldest	preserved	sediments	and	is	interpreted	to	be	glacial	till,	produced	during	the	last	glaciation	of	Ireland.	Within	this	unit	 infilled	 channels	 are	 visible	 throughout	 the	 study	 site,	 but	particularly	 in	 the	 inner	bay	 area.	 This	represents	a	meandering	channel	system	extending	from	both	the	Burren	and	Connemara	that	widens	and	deepens	towards	the	outer	bay.	The	nature	of	the	channel	system	is	unclear	as	it	could	be	related	to	both	glacial	and	proglacial	or	fluvial	origin.	Unit	3	is	the	uppermost	unit	and	represents	deposition	and	reworking	 during	 deglaciation	 and	 under	 present	 conditions.	 Within	 this	 unit,	 palaeodeltas	 and	palaeoshorelines	 are	 evident,	 suggesting	 a	 sea	 level	 lowstand.	 Sediment	 cores	 are	 entirely	 contained	within	this	unit.	Isopach	maps	of	each	unit	have	also	been	produced	and	can	be	submitted	upon	publication	of	project	results	(example	in	Fig.	8).	7	Fig.	7	–	Examples	of	seismic	pinger	(3.5kHz)	data.	(A)	Infilled	palaeochannels	visible	across	the	outer	bay	area;	(B)	Prograding	palaeodelta	is	visible	extending	southwest	from	the	present	day	inner	bay	area.	Position	of	lines	is	shown	in	Fig.	1.	Fig.	8	–	Example	of	isopach	processing	(Unit	2)	in	the	software	Kingdom.	(ii) Implementation	(including	reference	to	timelines,	milestones,	management)	The	 objectives	were	 achieved	within	 the	 timeframe	 of	 the	 project	 and	 the	 specific	 results	 are	 shown	previously,	although	 the	work	on	 the	scientific	 results	will	 continue	 for	 few	more	months	 through	 the	preparation	of	3	manuscripts	to	be	submitted	to	peer-reviewed	journals.	Two	issues	were	experienced	during	the	project.	1. The	corruption	of	an	external	hard	drive	caused	loss	of	some	interpretation	of	the	seismic	data.This	meant	that	some	the	work	had	to	be	redone	half	way	through	the	project.	2. An	underestimation	of	the	time	needed	to	collect	the	required	sample	amount	of	foraminifera	forradiocarbon	dating	meant	some	delays	in	the	submission	of	samples	to	the	lab.	Additionally,	 splitting	 and	 initial	 work	 on	 the	 sediment	 core	 showed	 quite	 extensive	 reworking	 of	sediments.	Therefore	 it	was	decided	not	to	pick	microfossil	samples	 for	 isotopic	analysis	as	the	results	would	have	not	been	reliable.		8	(iii) Outputs	(please	use	bullet	points)	• Detailed	seismic	stratigraphy	of	Galway	Bay.• Geomorphological	map	of	Galway	Bay.• Geochronological	constraints	on	the	evolution	of	Galway	Bay	using	AMS	radiocarbon	dates.• Production	of	a	Story	Map	of	Galway	Bay	(this	will	be	delivered	once	all	radiocarbon	dates	arereceived	and	final	isopach	maps	are	produced).• Presentation	of	results	at	local	and	international	conferences	(see	App.	1)• Draft	of	3	separate	papers	for	submission	in	peer	reviewed	journals	(map	to	Journal	of	Maps;seismic	data	to	Geo-Marine	Letters;	sediment	cores	to	the	Holocene).	This	is	an	ongoing	workthat	will	continue	in	future	months.Impact/value	of	the	project	(Max	500	words):	The	research	conducted	has	potential	applications	for	departments	across	several	disciplines.	• The	detailed	geomorphology	map	will	allow	more	information	on	the	processes	currently	shapingthe	bay	and	the	potential	effects	of	such	processes	on	the	coastline.	This	kind	of	information	is	of	particular	 relevance	 to	 future	exploitation	of	 the	 region	 for	marine	 renewable	energy	and	 the	SMART	 BAY	 project.	 Sedimentological	 data	 from	 the	 seafloor	 and	 the	 subsurface	 can	 also	 be	valuable	when	assessing	the	feasibility	of	offshore	installations.	• A	detailed	high	resolution	seismic	stratigraphy	has	revealed	evidence	of	submerged	channels	andother	palaeo	features,	such	as	deltas,	and	provided	information	into	past	environments	across	the	bay.	The	AMS	radiocarbon	database	for	Galway	Bay	will	allow	correlations	between	the	results	from	this	project	and	the	paleoenvironmental	information	from	other	areas	off	the	west	coast	of	Ireland	allowing	for	a	much	better	geochronology	over	a	wider	area.	Together	these	results	will	inform	the	wider	scientific	community	about	changed	in	paleoenvironmental	conditions	on	the	western	coast	of	Ireland	and	can	be	used	for	sea	level	and	climate	reconstructions	and	modelling.	• The	story	map	of	Galway	Bay	can	be	used	as	an	outreach	tool	to	the	wider	community	througheasily	understood	and	accessible	 information	 that	will	be	 freely	distributed.	Once	 finalized	 (an	initial	 draft	 is	 available	 on	 request)	 it	 will	 be	 delivered	 to	 INFOMAR	 for	 publication	 on	 the	INFOMAR	web	site.	9	Appendix	1	–	Publications	&	Presentations:	[Conference	Presentation]	McCullagh,	D.,	Benetti,	S.,	Plets,	R.	and	Edwards,	R.	(2016)	The	changing	seascape	of	Galway	Bay.	2016	AGU	Fall	Meeting,	San	Francisco,	USA,	12-16-DEC-16	[Conference	Presentation]	McCullagh,	D.,	Benetti,	S.,	Plets,	R.	and	Edwards,	R.	(2016)	Past	and	modern	environments	of	Galway	Bay	Western	Ireland.	INFOMAR	Seminar	2016	Galway,	Ireland,	19-OCT-16	[Conference	Presentation]	McCullagh,	D.,	Benetti,	S.,	Plets,	R.	and	Edwards,	R.	(2016)	The	changing	environment	of	Galway	Bay	since	the	LGM.	Irish	Quaternary	Association	Annual	Spring	Meeting	2016	Coleraine,	Northern	Ireland,	09-APR-16	

Geological Survey of Ireland Research Programme - Short Call 2015, Final Report Past and Modern Environments of Galway Bay

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Geological Survey of Ireland Research Programme - Short Call 2015, Final Report Past and Modern Environments of Galway Bay

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