A deep-sea core collected on the continental slope off northern California contains a pollen stratigraphy for the past 20,000 yr that can be correlated to the pollen stratigraphy from the upper section of Clear Lake core CL-73-4. The occurrence in one sequence of pollen, reflecting the local continental paleoclimates, and marine microfossils reflecting the local paleoceanography, allows a comparison of concurrent responses of the local ocean and adjacent continental area to global climate changes. The interpretation of the two data sets gives a complex progression of changes that are probably interrelated, such as upwelling that produced coastal fogs. The changes in climatic and oceanographic environmental conditions that occurred in response to the switch from global glacial to interglacial conditions was not a smooth progression of increasingly moderate regimes; rather, the changes appear to be a complicated series of states that suggests a disequilibrium mode lasting from about 15,000 to 5,000 yr ago.

Abstract An important result of Deep Sea Drilling Project (DSDP) Leg 12 was the discovery of ice-rafted mineral grains in Pliocene sediments of the Labrador Sea and the Hatton-Rockall Basin. The oldest (first) occurrence of ice-rafted mineral grains in these sediments is associated with the evolutionary first appearance of the planktic foraminifer Globorotalia inflata (d’Orbigny) and the extinction of the coccolith Reticulofenestra pseudoumbilica (Gartner), or the first occurrence of the coccolith Emiliania ovata Bukry, or both. This association yields a paleontologic age estimate of 3.0 m.y.BP for the start of low-elevation Northern Hemisphere glaciation extensive enough to produce icebergs in the North Atlantic. Results from subsequent drilling in the North Atlantic (DSDP Legs 37, 48, and 49) confirm that the first ice-rafting is at about 3.0 m.y.BP, and further show that during the Late Pliocene, icebergs penetrated as far south as 45° N. lat in the central North Atlantic (DSDP Hole 410) but not as far south as 37° N. lat (DSDP Holes 333 and 335). The estimated age of 3.0 m.y.BP for the onset of Northern Hemisphere low-elevation glaciation derived from the North Atlantic is supported by a 3.2 m.y.BP estimate based on paleomagnetically controlled oxygen isotope data from the Equatorial Pacific. North Atlantic planktic foraminiferai assemblages show that warm sea-surface temperatures in the northwestern Atlantic preceded the initiation of Northern Hemisphere glaciation.