An Authigenic Gypsum, Pyrite, and Glauconite Association in a Miocene Deep Sea Biogenic Ooze from the Falkland Plateau, Southwest Atlantic Ocean

Abstract

Authigenic gypsum, pyrite, and glauconite are disseminated throughout an unusually long (346 m) Miocene section of mixed biogenic carbonate and diatomaceous ooze drilled on the Falkland Plateau at DSDP Site 329 (water depth, 1519 m). The present organic carbon content of the sediment is low, ranging between 0.1 and 0.1%. Gypsum occurs as euhedral single or twinned crystals of selenite up to 5 mm in diameter, sometimes in the form of gypsum rosettes. These crystals are intact and unabraded, comprising up to 4<Vo of the washed sample. The authigenic nature of the gypsum is demonstrated by the presence of diatoms and radiolarians embedded within the gypsum crystals.The gypsum co-occurs with pyrite and glauconite in these samples. The pyrite occurs as framboids, foraminiferal infillings, rods, and granular sheetlike masses composed of pyrite octahedra. The glauconite occurs as foraminiferal infillings and as free grains. The gypsum and pyrite were identified by energy-dispersive X-ray analysis and scanning electron micrographs. Some of the gypsum has grown on pyrite, indicating that it precipitated after the pyrite, perhaps in response to a change in pH conditions. The formation of the mineral suite can be explained by current models of in situ sulfide and sulfate precipitation coincident with diagenesis and oxidation of much of the original organic carbon.

Gypsum in modern Kamchatka volcanic hot springs and the Lower Cambrian black shale: Applied to the microbial-mediated precipitation of sulfates on Mars

“…Gp = gypsum. grown with pyrite rods in deep sea sediments (Muza and Wise 1983). Although pseudo-hexagonal, fibrous, prismatic, and lenticular gypsum crystals may indicate dynamic soil environments in soils of southwestern Iran (Owliaie et al 2006) or in the Las Vegas basin and southern New Mexico in the U.S.A. (Buck and Van Hoesen 2002;Buck et al 2006), the variations of these crystal habits are still not comparable to those found in the hot springs of Kamchatka.…”

Influence of diagenesis on the stable isotopic composition of biogenic carbonates from the Gulf of Tehuantepec oxygen minimum zone

“…[41] The formation of gypsum crystals in marine sediments has been reported and described in only a few studies [Siesser and Rogers, 1976;Briskin and Schreiber, 1978;Muza and Sherwood, 1983;Hoareau et al, 2011]. In order to characterize the sedimentary context where gypsum might precipitate, Hoareau et al [2011] calculated the gypsum saturation index for numerous ODP/IODP cores using the available pore water data.…”

“…Calculations of gypsum saturation in several sediment cores drilled in the frame of the Ocean Drilling Program and the Integrated Ocean Drilling Program (ODP/IODP) revealed that gypsum formation in marine sediments is related either to the presence of evaporitic brines or volcanogenic material [Hoareau et al, 2011]. However, gypsum crystals have also been observed in sediments barren of evaporitic or volcanogenic material [Siesser and Rogers, 1976;Briskin and Schreiber, 1978;Muza and Sherwood, 1983]. In the study of Siesser and Rogers [1976], gypsum crystals were thought to have grown in organic-rich suboxic sediments, where low pore water pH induced by high rates of iron sulfide precipitation led to dissolution of the foraminifera.…”

Pyritized Diatoms in the Sediments at the Distal End of the Bengal Fan

“…In pyrite grains from marine sediments Siesser (1978) found K, Si, Al, Ti, and Mg in quantities less than 0.05% by weight. Muza and Wise (1983) detected slightly higher quantities of these and Ca and Zr in sheet-like and framboidal pyrite.…”