Mineralogy and origin of sediments from drill holes on the continental margin off Florida

Abstract

Drilling on the continental margin off Jacksonville, Fla., in 1965 was the first project undertaken by the Joint Oceanographic Institutions' Deep Earth Sampling (JOIDES) Program, sponsored by the National Science Foundation. The U.S. Geological Survey cooperated with the Oceanographic Institutions in this undertaking and is publishing the results of these investigations in a series of professional papers.

Regional Aspects of Deep Sea Drilling in the Western North Atlantic

“…Other studies have shown that abundant chlorite, mica and amphibole have definite northern affinities along the East coast (Hathaway et al, 1970). Thus it is apparent that the Tertiary sediment recovered from as far south as Cat Gap has been transported at least 1000 kilometers from sources to the north.…”

Mineralogy and Origin of Clay Minerals, Silica and Authigenic Silicates in Leg 14 Sediments

“…Apparently the cristobalite is of low-temperature (<80°C) diagenetic origin, originating from dissolved skeletal opal or devitrified volcanic glass, and re-precipitated in the pore space of pelagic clays, marls and terrigenous silts (cf. Flörke, 1955;Ernst and Calvert, 1969;Hathaway et al, 1970;Heath and Moberly, 1971). The high degree of unidimensional stacking disorder is caused by a very low temperature origin and the lack of foreign ions favoring further nucleation (Flörke, 1955).…”

“…The direct precipitation from sea water appears to be the exceptional case under extreme (for example, lagoonal) conditions. Diagenetically, these Mg-silicates can be formed in the pore spaces of montmorillonitic clays by the interaction with magnesium-rich pore solutions, especially in sediments of Miocene and older age (Füchtbauer and Muller, 1970, p. 193;Hathaway et al 1970). The deposits of palygorskite and sepiolite which are documented in the literature may be assigned to four major genetic types of facies associations (see also Hathaway and Sachs, 1965): 1) Evaporitic sequences in highly saline or alkaline fresh-water environments (desiccating lakes) and in highly saline lagoons, where sepiolite and palygorskite are directly precipitated from magnesium-rich brines in arid zones (Millot, 1960(Millot, , 1964Rateev et al, 1963).…”

“…The youngest clinoptilolite is Middle Miocene, but most zeolitic samples range from Latest Cretaceous to Paleogene in age. In the continental margin sediments off Florida clinoptilolite is mostly of Oligocene age and older; no post-Miocene zeolites have been discovered (Hathaway et al, 1970). It is therefore likely that clinoptilolite is diagenetically precipitated within the pore spaces of bentonitic clays.…”

“…This association can be explained by the decrease of solubility of silica in the presence of decaying organic matter. Carbonates are dissolved at those low-pH conditions and silica is precipitated from migrating pore solutions producing carbonaceous cherts (for example 135-8-1) and, if less silica is available, clinoptilolite or palygorskite (see also Hathaway et al, 1970).…”