Geology topics

A. Leventer

Publications and source records attributed to A. Leventer.

3 recordsLinked to original sources

USGS2007

Solar forcing and El Niño-Southern Oscillation (ENSO) influences on productivity cycles interpreted from a late-Holocene high-resolution marine sediment record, Adélie Drift, East Antarctic Margin

Core JPC17B was collected from the Adélie-Drift, a nearly 300-m thick drift deposit at 140ºE along the Indian Ocean sector of the Antarctic continental shelf. Sediments consist of nearly continuously laminated diatom mud and diatom ooze, with accumulation rates on the order of 20-21 m kyr -1 based on 10 AMS radiocarbon dates. Spectral analysis was performed on time series of opal content, d 13 C org , Ti content, and Ba content. Strong decadal to century- scale variability is present in all proxies. Opal and Ti-time series show strong variance at periods of 11, 22 and 110- years, which are suggestive of solar forcing. Ba-time series exhibits strong variance at a period of 3-3.6-yr, consistent with possible El Niño-Southern-Oscillation (ENSO) forcing.

Open-File Report↗

USGS2004

Synthetic seismograms linking ODP sites to seismic profiles, continental rise and shelf of Prydz Bay, Antarctica

Synthetic seismograms provide a crucial link between lithologic variations within a drill hole and reflectors on seismic profiles crossing the site. In essence, they provide a ground-truth for the interpretation of seismic data. Using a combination of core and logging data, we created synthetic seismograms for Ocean Drilling Program Sites 1165 and 1166, drilled during Leg 188, and Site 742, drilled during Leg 119, all in Prydz Bay, Antarctica. Results from Site 1165 suggest that coring penetrated a target reflector initially thought to represent the onset of drift sedimentation, but the lithologic change across the boundary does not show a change from predrift to drift sediments. The origin of a shallow reflector packet in the seismic line across Site 1166 and a line connecting Sites 1166 and 742 was resolved into its constituent sources, as this reflector occurs in a region of large-scale, narrowly spaced impedance changes. Furthermore, Site 1166 was situated in a fluvio-deltaic system with widely variable geology, and bed thickness changes were estimated between the site and both seismic lines.

Proceedings of the Ocean Drilling Program: Scienti↗

USGS1996

Productivity cycles of 200-300 years in the Antarctic Peninsula region: Understanding linkages among the sun, atmosphere, oceans, sea ice, and biota

Compared to the rest of the world's oceans, high-resolution late Holocene paleoclimatic data from the Southern Ocean are still rare. We present a multiproxy record from a sediment core retrieved from a deep basin on the western side of the Antarctic Peninsula that reveals a dramatic perspective on paleoclimatic changes over the past 3700 yr. Analyses completed include measurement of magnetic susceptibility and granulometry, bed thickness, particle size, percent organic carbon, bulk density, and microscopic evaluation of diatom and benthic foraminiferal assemblages and abundances. Downcore variability of these parameters demonstrates the significance of both short-term cycles, which recur approximately every 200 yr, and longer term events (≈2500 yr cycles) that are most likely related to global climatic fluctuations.

Geological Society of America Bulletin↗