Project design

 


 

PROJECT DESIGN
Within a multi-disciplinary (sedimentology, stratigraphy, geochemistry of sediment, paleomagnetic investigations) high-resolution (centimeter to decimeter scale) research project on Late-Quaternary sediments of the Ross Sea, TRACERS (PNRA16_00055 - A3) proposes to use tephrochronology (word composed by three different greek words
τέφρα = ash, χρόνος = time, and λογία = study, speech) as a key tool to date and synchronize natural archives, using the volcanic deposits (tephra) as isochronous marker at regional-continental scale.

The main aims of the project are: 1) to recover Late Quaternary sediments sequences deposited on the continental shelf of the Ross Sea and containing primary tephra (yellow areas in Figure 1), to 2) characterize these tephra in detail for their texture, mineralogy and geochemistry. The complete characterization of the tefra allow to attribute them a 3) unique “fingerprint” making them easily identifiable as a stratigraphic marker in other natural archives. These results allow to 4) synchronize and correlate natural archives extrapolating information obtained from each archive into a regional to continental framework. An additional very important result is a strong advance in 5) knowledge of the eruptive history of the Antarctic volcanoes (age, frequency, intensity of eruptions, volume of the material erupted) and in the 6) possible interactions between volcanic activity and cryosphere dynamic.
Sediment sequences were sampled through new coring designed specifically for tephrochronological purposes and to allow the recovery of the greatest number of tephra beds. In fact, sediment sequences where tephra have been previously identified were sampled for other purposes (e.g. reconstruction of the past extension of the ice shelf, etc.), often in areas not completely suitable for the good preservation of tephra or outside the main axis of dispersion.
The data base for the sampling site positioning were constituted of previous data of multibeam surveys collected during PNRA and NSF/USA geophysical cruises and single and multi-channel national and foreign seismic data available through the Seismic Data Library System. The sampling will be focused on coastal areas located downwind the active volcanoes along the North Victoria Land. Sediment cores from the Ross Sea, collected in previous cruises and held in Italian or foreign repositories will be studied (if necessary) to complete the recovered dataset.

Between December 2016 and February 2017 four members of the TRACERS project attended the XXXII PNRA - Antarctic campaign in the Ross Sea. During the campaign we recovered samples in 5 strategically positioned areas as a function of the possible dispersion of volcanic products. The sampling strategy included the recovery in each site of a piston cores and the box core  for the characterization of surface sediment presumably disturbed during drilling operations resulting in about 40 m of sediment sequences.