Publication Date

Spring 2016

Degree Type


Degree Name

Master of Science (MS)


Moss Landing Marine Laboratories


Ivano Aiello


Bowers Ridge, Ice-rafted debris, North Hemisphere Glaciation, Siliciclastic

Subject Areas

Marine geology; Paleoclimate science


The analysis and interpretation of sediment cores constitutes an important data record that can be used to evaluate paleoclimatic conditions and changes over time. The causes for the cooling trend that began in the Eocene, and its intensification with the onset of North Hemisphere Glaciation (NHG), remain under debate. Using sediment core samples from Site U1341 in the Bering Sea, the principal goal of this thesis was to examine the record at 1.9-4.2 Ma, using sedimentologic tools to interpret the siliciclastic fraction and ascertain whether and which portion is due to ice-related input. Previous research estimates the onset to begin at 2.75 Ma by using IRD occurrence and a sharp decline in opal accumulation (Haug et al., 2005). A reevaluation of this critical period will be important for gaining a better understanding of the onset of NHG. In this study, over 200 samples from 1.9-4.2 Ma were used to study the onset of NHG. The > 250 μm siliciclastic mass accumulation rates (MAR) for the samples indicate an initial increase in abundance between 3.3 and 3.6 Ma before decreasing between 2.7 and 3.2 Ma. Another increase in abundance was observed between 2.7 Ma and the end of the record at 1.9 Ma. The provenance, composition, and surface texture features of quartz were also analyzed. It is uncertain whether the first occurrence of > 250 μm siliciclastics was the result of ice-related processes or from other mechanisms like local re-sedimentation from Bowers Ridge. The implications of both possibilities were evaluated.