Heinrich Events in North Atlantic Sediments: CT Scanning and Other Analyses.

• Main Author: Danino, Steffan
• Format: Thesis
• Language: English
• Published: Apollo - University of Cambridge Repository 2015
• Subjects: North Atlantic
• Online Access: https://dx.doi.org/10.17863/cam.8753; https://www.repository.cam.ac.uk/handle/1810/263411

The first objective of this thesis is to present a new method for counting ice rafted debris (IRD) in ocean cores, using computerised tomography (CT) scanning and the powerful image processing software package FIJI and its associated plugin BoneJ (Doube et al., 2010). This is the first time such a method has been demonstrated. CT scans have been carried out on North Atlantic sediment cores from Integrated Ocean Drilling Program (IODP) site U1308 (49°52'39.9"N, 24°14'17.2"W; the site used by Hodell et al., 2008), containing Heinrich events H1, H4 and H16. Additionally, a detailed manual IRD count has been carried out on samples of a core showing H4 to compare the efficacy of this computerised method, and to show the viability of CT scanning as a method of counting IRD. Secondly, this thesis seeks to establish how H16 compares to the well studied H4, using high resolution X-ray fluorescence (XRF) scanning and CT scanning of both events. The magnitude of the two events is identified as well as the nature of the two IRD peaks seen over the course of H16. Thirdly, the findings of the thesis will be placed within a wider glaciological and geological context, and current theories regarding Heinrich events reviewed in light of them. In Chapter 2 of the thesis, the mechanisms involved in ice-rafting events are explained, followed by a review of current theories regarding Heinrich event forcing in Chapter 3. In Chapter 4 a detailed account of the methods used in the analysis of the cores from site U1308 is presented, in particular the development of ice rafted debris detection using CT scanning, the results from which are presented in Chapter 5. This is contrasted in Chapter 6 with previous methods of debris counting by sampling, to evaluate the use of CT scanning as a means of counting ice rafted debris. In Chapter 6, the CT scan data is also compared to the XRF scan data collected, and XRF data is discussed and compared to the literature in order to evaluate current theories concerning Heinrich events.