Chronology and extent of Late Cenozoic ice sheets in North America: A magnetostratigraphic assessment

Publisher Summary This chapter discusses the classic four-fold subdivision of the Pleistocene in both North America and Europe dominated terrestrial Quaternary palaeoclimate, which have been studied for many decades. With the exception of the last major continental glaciation, the understanding of the extent and timing of ice-sheet development in North America has remained uncertain. With the more widespread use of magnetostratigraphy and detailed mapping of superficial deposits, it has become possible to identify the approximate: spatial extent of ice sheets, as well as the timing of their appearance and disappearance. It reviews that with appropriate sampling and analytical techniques, geomagnetic polarity data can be obtained from tills, as well as from altered sediments such as palaeosols, to provide a direct assessment of the palaeomagnetism of glacial and interglacial environments. The chapter discusses the advances which have been made in dating and modeling of past terrestrial climatic events. It has been in particular, the contribution of magnetostratigraphy which has provided timelines for glacial and interglacial events of the last 3.0 million years, and assigned sediments to the Chrons and Subchrons of this period. In the absence of absolute dating tools, magnetostratigraphy affords a valuable means of assigning terrestrial ice age deposits to the geological timescale, and most importantly, allows a correlation to the more complete marine record. The distribution of past ice sheets and their chronologies will be better defined with future magneto-stratigraphical work.