Terrigenous Signals in Sediments of the Low-Latitude Atlantic - Indications to Environmental Variations during the Late Quaternary: Part II: Lithogenic Matter

The inorganic terrigenous fraction of marine sediments offers a great number of different and well established proxy parameters to investigate the development of Earth's climate. Our present knowledge on climate variability through time is based, to a large part, on these proxies. This study presents a synthesis of multidisciplinary investigations which have been applied to late Quaternary sediments recovered from the low-latitude Atlantic during the Bremen Special Reseach Project 291. In the equatorial Atlantic terrigenous matter is supplied by eolian and fluvial pathways. In addition to the dust input from African deserts, the catchment areas of the three major rivers Amazon, Niger and Zaire (Congo) are the dominant sources. Small river systems are of local importance. Terrigenous records from near-continental and open pelagic depositional settings are discussed. The main questions we focused on are a) the control of climate change and b) the identification and timing of rapidly occurring events. Results from the lowlatitude Atlantic support the suggestion that both high-latitude and low-latitude forcing influence tropical climate and marine sedimentation. Apparently, the frequency of climate variability in the tropics during the late Quaternary is controlled by the precessional insolation cycle, whereas amplitudes and timing of climate change are mainly determined by the high latitudes in the Northern Hemisphere. Within the phase relationships, however, regional differences arise. Furthermore, there is evidence for climate instability during glacials and interglacials which probably occurred on decadal to centennial time scales.