Mid- and late-Holocene environmental change in western Ireland: New evidence from coastal peats and fossil timbers with particular reference to relative sea-level change

Abstract

The results of radiocarbon dating and dendrochronological investigations of timbers (mainly pine and oak) preserved in coastal peats on the Atlantic coast of mid-western Ireland are reported. These are complemented by the results of pollen analytical investigations, including a detailed pollen profile from Lough Atalia, a brackish lake located within present-day Galway city and immediately to the east of the medieval town. The results from the fossil timber investigations show that pine stumps exposed on coastal intertidal peats in mid-western Ireland date mainly to ca. 3000 BC, that is, they are coeval with the so-called ‘pine flushes’ on blanket bog in western Ireland. Many of the oak timbers are considerably older while an oak on peat in Turlin Bay, near Silverstrand, persisted until ca. 2100 BC. This fossil timber record, taken in conjunction with the pollen records, suggests conditions very different to those pertaining at present, including absence of direct marine influence because of relative sea levels (RSLs) that were probably at least 2 m, and possibly up to 4 m, lower than at present. Mid-Holocene conditions were less stormy, and lower precipitation and/or higher evapotranspiration facilitated tree colonisation of peat surfaces. Intertidal peat layers at Salthill show that present-day RSL began to be approached at ca. AD 500. This agrees with the evidence from An Loch Mór, Inis Oírr, which indicates that salinity in this brackish lake began to increase noticeably at/immediately prior to ca. AD 1000. A notable feature of the pollen record from L. Atalia is a yew ( Taxus)-dominated woodland phase of ca. 600 years duration centred on 2550 BC. A major and widespread expansion of yew at about this time is a distinctive feature of mid-Holocene woodlands in western Ireland.

Younger Dryas and Holocene environmental change at the Atlantic fringe of Europe derived from lake‐sediment stable‐isotope records from western Ireland

“…Over the last 1000 years, the widely varying δ 18 O ost values probably resulted from a combination of factors including changes in saline water input as a result of rising sea level in Galway Bay (O'Connell & Molloy ), variation in δ 18 O P (and hence δ 18 O L ) and evaporative enrichment. The steady increase in δ 13 C ost values over the same period may reflect enhanced aquatic productivity coupled with an increasing input of DIC from seawater.…”

“…During this time, lake level was considerably lower than at present . Sea levels were also low (Edwards & Craven 2017;O'Connell & Molloy 2017;Shennan et al 2018), but ostracod and other evidence point to slightly brackish lake conditions ). In the Early Holocene, woodland perturbations, ascribed to regional climatic deteriorations at 9200 and 8200 cal.…”

“…). Sea levels were also low (Edwards & Craven ; O'Connell & Molloy ; Shennan et al . ), but ostracod and other evidence point to slightly brackish lake conditions (Holmes et al .…”

Ireland: Submerged Prehistoric Sites and Landscapes

“…It is only within the last decade that a concerted effort has been made to investigate Irish submerged landscapes (Bell et al 2006;Westley et al 2011aWestley et al , b, 2014Westley 2015). Even this though has focused almost exclusively on the north coast, and the rest of Ireland has never been fully investigated beyond palaeoenvironmental investigations of a handful of intertidal peats (e.g., Whitehouse et al 2008;Simpson 2008;Williams and Doyle 2014;O'Connell and Molloy 2017).…”

A combined-method approach to trace submarine groundwater discharge from a coastal karst aquifer in Ireland

“…Eustatic sea level variations down to −120 m below modern sea level result in a range of lower base levels in coastal aquifers globally. Off the Republic of Ireland, sea levels are estimated to have dropped by 60-100 m below the present level at the Irish coast and Galway Bay between 15 and 26 ka ago (Edwards and Craven 2017;O'Connell and Molloy 2017). As a result, karst morphology extends beyond the shore into the sea, as is the case for the Burren Plateau (Kozich and Sautter 2018).…”