Clay-Sized Minerals from Cores of the Southeast Pacific Ocean, Deep Sea Drilling Project, Leg 35

Abstract

Terrigenous illite, chlorite, kaolinite, and small amounts of vermiculite occur in sediments at the four sites drilled during DSDP Leg 35. Montmorillonite (mix-layered clay), which can result from alteration of volcanogenic material on land and under water, increased and the amount of chlorite plus kaolinite decreased in the older sediments from Sites 322, 323, and 325. The trend in illite content is not well defined.In the Pliocene-lower Miocene age sediments, the crystallization of montmorillonite was more or less constant and increased noticeably only in horizons above the basalts (Sites 322 and 323) as a result of hydrothermal activity. The montmorillonite content increases with depth without a change of its crystallization, perhaps due to the greater influx of montmorillonite into the older sediments, or as the result of postdepositional changes of the clay minerals. This same tendency exists in most oceanic sediments. Other diagenetic but nonclay minerals, clinoptilolite, cristobalite, and goethite, occur in the cores.

Geological record and reconstruction of the late Pliocene impact of the Eltanin asteroid in the Southern Ocean

“…4), are consistent with authigenic formation by submarine diagenesis (hydrothermal alteration) and are also known from other parts of the Bellingshausen Sea in sediments older than late Miocene 13 , including Core PS2664-1 recovered ϳ400 km north of the San Martin seamounts. Sediments younger than the late Miocene differ markedly, consisting of smectite that is only moderately crystallized, and significant amounts of terrigenous illite and chlorite 13 , as also recorded in the late Pliocene to Quaternary sequences of SU I.…”

Late Quaternary variability of ocean circulation in the southeastern South Atlantic inferred from the terrigenous sediment record of a drift deposit in the southern Cape Basin (ODP Site 1089)

“…This conclusion is based on the low concentrations of smectite in aeolian dusts and nearshore surface waters along the African coast (Chester et al, 1972;Behairy et al, 1975) and also in clay samples from sediment traps deployed in the ACC region at di¡erent depth levels (Petschick, unpublished data). Most smectite probably is introduced through Drake Passage via the ACC, originating from the erosion of hydrothermal and authigenic smectite-bearing sediments, widespread in the southeastern Paci¢c Ocean (Gorbunova, 1976;Honnorez, 1981;Cole and Shaw, 1983). Likewise, the scouring of exposed pre-Pleistocene sediments on the Falkland Plateau contributes to smectite £uxes in the ACC (Robert and Maillot, 1983;Walter et al, 2000).…”