Quaternary climate variability of North America from marine archives

Abstract

Subtropical arid to semi-arid regions across the globe are predicted to expand and to experience more frequent and intense periods of aridity and drought in response to rising atmospheric carbon dioxide and increased global temperatures by 2100. This transition is suggested to be already underway in the North American South West (NASW). The geological record provides a way to evaluate this prediction because of the occurrence, millions of years ago, of past episodes of atmospheric carbon dioxide loading equivalent to those projected for AD 2100. However, terrestrial North American climate records stretching back to the Pliocene are rare and fragmentary due to the episodic nature of lacustrine deposits and terrestrial erosion associated with the advance and retreat of the Pleistocene Laurentide Ice Sheet. Records of dust in marine sediment cores provide away to circumvent the issues with terrestrial climate records, but sound knowledge of the origin of the terrigenous fraction is required to properly interpret these palaeoclimate proxy records. This thesis presents i) new Pb, Nd and Sr radiogenic isotope data from sources of dust from the North American continent ii) radiogenic isotope maps of the North American bedrock compiled from the literature, iii) an evaluation of dust deposition in both the subtropical Eastern Pacific Ocean and mid-latitude North Atlantic Ocean and iv) new down-core records of organic biomarkers offshore of northern Baja California. These data improve the spatial and geochemical characterisation of North American dust sources, enable the discrimination between sources of fluvial and aeolian material originating from the arid NASW in the subtropical Eastern Pacific Ocean and clarify the origin of the terrigenous material deposited in the mid-latitudes of the North Atlantic during the intensification of Northern Hemisphere Glaciation (iNHG).

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Identifiers

ORCID for Gabriella Erin Jardine: orcid.org/0000-0001-5778-6487

ORCID for Paul Wilson: orcid.org/0000-0001-6425-8906

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