Ton, Geoden und Minerale des Barrême von Hoheneggelsen

An organic origin for the carbonate concretions of the Ohio Shale

“…Furthermore, there appears to be a progressive radial decrease in authigenic constituents, particularly if the central zone samples are excluded. This result accords with the observations of Lippmann (1955), Raiswell (1971 ), and Oertel and Curtis (1972), who interpreted similar data in terms of concretion growth by cementation of pore space during progressive compaction of the host shale. The relatively low cement contents of the calcite centers might indicate late-stage dissolution of calcite.…”

“…Similarly large porosities are typical of modern marine sediments in the uppermost few meters of the sediment column. Such values have also been calculated for early diagenetic concretions from numerous other localities (Lippmann, 1955), but the indicated sediment densities are extremely low and pose a problem for hydrostatic support of the large, dense concretions. It must be concluded that either (1) such porosity calculations are unrealistic, perhaps because much of the original sediment contained carbonate or silica that dissolved, or perhaps because the crystals of the growing concretion have mechanically displaced much of the sediment; or (2) the concretions originated as some type of low-density material.…”

“…Weeks (1957) demonstrated that fishbearing carbonate concretions from Colombia formed shortly after deposition of the sediment and proposed that decay of proteinaceous material led to rapid precipitation of carbonate and hence to the remarkable preservation of the fossils. Lippmann (1955) proposed that the ratio of acid-soluble to acid-insoluble components in concretions may be used to estimate the sediment porosity at the time of concretion growth and argued that his results demonstrated extremely high porosities (t=:;;75 percent) in some instances. Oertel and Curtis (1972) provided novel structural data that generally substantiate Lippmann's (1955) deductions, but they also presented evidence that a stage of slow, protracted growth followed the initial stage of rapid growth of their concretions.…”

“…Lippmann (1955) proposed that the ratio of acid-soluble to acid-insoluble components in concretions may be used to estimate the sediment porosity at the time of concretion growth and argued that his results demonstrated extremely high porosities (t=:;;75 percent) in some instances. Oertel and Curtis (1972) provided novel structural data that generally substantiate Lippmann's (1955) deductions, but they also presented evidence that a stage of slow, protracted growth followed the initial stage of rapid growth of their concretions. Girin (1967) and Galimov and others (1968) suggested that concretions preserve a sequential record of the diagenetic processes to which the host rock was subjected.…”

Sedimentology and hydrocarbon potential of the Dinantian oil-shales of Northern Britain

“…This is taken to indicate that the nodules began to grow before appreciable compaction of the host muddy ooze, and hence in the upper few tens of metres of the sediment column. In addition, since the precipitation of carbonate during nodule growth probably fills pores without too much displacement or replacement of detritus (Lippmann 1958;Oertel and Curtis 1972), the carbonate content may be used as an estimate of porosity at cementation. The carbonate content of the nodules ranges between about 80 wt.…”