Minerals (Aug 2023)
Transgression Related Holocene Coastal Glendonites from Historic Sites
Abstract
This study examines the occurrence of glendonite along coastlines since 1825, which have been previously referred to under different names such as Pseudogaylussite, Fundylite, and Kool Hoot across eleven sites. By utilising element ratios and 14C radiometric dating techniques, we establish a more accurate chronology for these varied sites ranging from 10 to 1 thousand years before the present (Ky BP). Sites include tidal flats, coastal barrier islands, and Wadden Sea environments. While some sites still exist, others are only known through publications and museum collections. Our research expands upon previous findings by presenting petrographic evidence that correlates with glendonite formation. Through the examination of the Olenitsa site on the Kola Peninsula, we demonstrate that marine bioclasts enclosed within concretions surrounding glendonites provide temporal context, suggesting that these outcrops were formed during a single event under changing conditions. Notably, certain sediment structures at selected sites indicate the occurrence of cold-water ice-raft storm events and the presence of drop stones. Furthermore, our paper explores the association of historic coastal sites with the formation of ikaite, highlighting the limitations of relying solely on geochemistry and isotopic analysis for interpretation. Intriguingly, we observe that pseudomorphs are abundant in specific areas but absent in adjacent regions with similar environmental, physical, and chemical conditions. No apparent connection is found between volcanic dust cloud-induced cold spells and glendonite. The distribution of coastal glendonites is more likely related to periods of climatic cooling through other means. We show that radiometric dating with 14C provides an indication of age, but the results can be erroneous due to the inclusion of older carbon sources in the analysis. The oldest locations discussed in this study are Kool Hoot (Alaska) and the river Clyde (Scotland), and the youngest glendonites discussed are from the Bay of Fundy in Canada. Occurrences from the Wadden Sea are intermediate in age and sit between the other two groups. The age of the Olenitsa site on the Russian Kola Peninsula is uncertain and still debated. We show that measuring the ratio of Mg/Ca can indicate how much the recrystallised ikaite preserved as calcite is influenced by diagenetic pore waters.
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