For over 20 years, the Ocean Discovery Lecture Series (formerly the Distinguished Lecturer Series) has brought the remarkable scientific results and discoveries of the International Ocean Discovery Program and its predecessor programs to academic research institutions, museums, and aquaria. Since 1991, over 750 presentations to diverse audiences have been made through the Lecture Series.
We are thrilled to congratulate ESS Professor Cecilia McHugh on being named a Distinguished Lecturer for the 2017-2018 academic year! As part of her duties Dr. McHugh will give at least 6 lectures this year on her work on Pleistocene Seismicity in New Zealand.
To understand the influence of eustasy on continental margin sedimentation and test the concepts of sequence stratigraphy, Integrated Ocean Drilling Program Expedition 317 drilled four sites on the continental shelf and upper slope of the Canterbury Basin, eastern South Island, New Zealand. We present results from upper slope Site U1352 (320 m water depth). A high-resolution multiproxy approach involving geochemical elemental analyses, lithostratigraphy and biostratigraphy, calibrated to an oxygen isotope scale, was applied to understand sedimentation over the past ~1.8 million years. Multichannel seismic data (EW00-01 survey) provided a seismic sequence stratigraphic framework against which to interpret the data. Seismic sequence boundaries are represented by a unique geochemical signature and arrangement of overlying sedimentary facies. However, several such geochemical-lithologic units are commonly contained within each seismic sequence. These higher frequency, intrasequence geochemical units generally correlate with100 ky glacial-interglacial Milankovic variability in the late Pleistocene, revealing that it took several glacio-eustatic cycles to build each seismic sequence. These findings support prior results obtained from Pleistocene sediments recovered by Ocean Drilling Program Leg 174A that drilled on the New Jersey margin with similar objectives to those of Expedition 317. In both northern and southern hemisphere siliciclastic settings there is a strong correlation between seismic sequences and glacio-eustasy, but the correlation between isotopic cycles and sequence boundaries is not one-to-one: only a subset of the glacioeustatic cycles result in a preserved seismic sequence boundary. Furthermore, late Pleistocene sequence boundaries on the two margins are not synchronous. Local conditions cause different isotopic peaks to be preferentially preserved as sequence boundaries in each location and preserved seismic sequences contain different groupings of marine isotope stages. Therefore, high-frequency Pleistocene seismic sequences may not correlate globally even though they are driven by glacio-eustasy.