(Table 1) Composition of ice-rafted debris and quartz grain concentration at DSDP Sites 71-513 and 71-514

The surficial few meters of sediment at Sites 511 and 512 on Maurice Ewing Bank consist of a lag deposit of icerafted sands and gravels ranging from lower Pliocene to Quaternary in age. The sediments contain up to 62% angular to subangular gravel of mixed lithology.
Significant volumes of sand- and gravel-sized ice-rafted detritus (IRD) first reached the Falkland (Malvinas) Plateau and southeasternmost Argentine Basin in the late Miocene (6.9 Ma) in response to the rapid buildup and grounding of the ice sheet in West Antarctica. IRD accumulation rates remained relatively low until 4.15 Ma, after which they increased markedly. Peaks of IRD accumulation at Sites 513 and 514 can, in most instances, be correlated directly with colder climates in Antarctica and southern Patagonia.