External Controls on Deep-Water Depositional Systems
The principal objective of the meeting from which this set of papers arose was to gain an overview of the current state of knowledge of the roles and interplays of external controls on deposition in deep marine environments. By external controls we mean allocyclic or allogenic factors, i.e., those that are unrelated to the self-organization of the depositional system (autocyclic or autogenic); principal among these are climate, sea level, sediment supply, and tectonics. One of the big questions that the meeting sought to address concerned the comparability of the recent high-frequency, high-resolution record with the older, generally lower-frequency stratigraphic record of “deep time”; to what extent are the apparent differences a function of resolution, or of comparisons between a glacial and a nonglacial Earth? In fact, as the papers in this volume illustrate, the variability between individual systems, even in Late Glacial time, and the paucity of constraints on older systems makes these questions difficult to answer, but some useful conclusions can be drawn. The papers presented at the meeting were organized into themes that included: overviews of glacial sea-level change, and of climate modeling; external controls on large river-fed submarine fans, including the effects of climate and sea level on the fluvial system itself; influences of climate, sea level, and tectonics on a range of smaller modern systems; deep marine processes; the outcrop record of the pre-Pleistocene Earth; the subsurface record of the pre-Pleistocene Earth; and syntheses. The organization of the volume largely reflects this structure.
Paleomagnetic Secular Variation Time Constraints on Late Neogene Geological Events in Slope Sediment from the Eastern Tyrrhenian Sea
Published:January 01, 2009
Marina Iorio, Joseph C. Liddicoat, Francesca Budillon, Pasquale Tiano, Alberto Incoronato, Robert S. Coe, Ennio Marsella, 2009. "Paleomagnetic Secular Variation Time Constraints on Late Neogene Geological Events in Slope Sediment from the Eastern Tyrrhenian Sea", External Controls on Deep-Water Depositional Systems, Ben Kneller, Ole J. Martinsen, Bill McCaffrey
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Cored slope sediment from the Salerno Gulf in the eastern Tyrrhenian Sea ca. 20 km from the Italian coast preserves small-scale changes of Earth’s magnetic field behavior (paleomagnetic secular variation; PSV) between 25,000 years B.P. to the present. The age of the cored sediment is calculated from tephrochronology, 14C dates, and correlation to European PSV curves (Turner and Thompson, 1981, 1982; Thouveny et al., 1990) and relative intensity in sediment cored from the Mediterranean Sea (Tric et al., 1992). The analyzed sediments span for the first time the full Holocene and late Pleistocene PSV record in the eastern Tyrrhenian Sea, and results compare well with PSV records for Lac du Bouchet, France (Thouveny et al., 1990).
Sedimentation rates, established by PSV dating, are in good overall agreement with sedimentation rates calculated in a second core recovered about 300 m away that was dated by 14C and used for paleoclimate research (Buccheri et al., 2002). However, there are variations in the precision of the dating that depend on the chronologic method used. Moreover, it was found that in the late Pleistocene and to the Pleistocene–Holocene boundary, the sedimentation rate on the continental slope was controlled by global rapid sea-level pulses and cold climatic phases that induced reduction and/or rapid increments in the sediment deposition rate. However, in the middle Holocene during phases of continuous relative sea-level increase, the sedimentation rate on the slope was less sensitive to climatic control than on the continental shelf, whereas from the late Holocene to the present it seems that on both the continental shelf and slope local factors such as volcanic supply and human deforestation could have caused an increase in the sedimentation rate.