Some Trace Elements in the Carbonate Samples Recovered from Holes 390, 390A, 391C, and 392A of DSDP Leg 44

Abstract

We determined concentrations of trace elements in the carbonate fraction by atomic absorption analysis following the procedure described by Renard and Blanc (1971, 1972). The age of the samples studied range from Barremian to middle Eocene (Holes 390, 390A), Tithonian to Aptian (Hole 391C), and late Campanian to Barremian (Hole 392A). Mineralogically, they all contain low magnesian calcite. The results of the analysis are given in Tables 1 to 4. HOLE 391C Relationship With Insoluble Residues In some samples, we obtained sufficient insoluble residues, following treatment with acetic acid, to relate certain element concentrations to percentage of insoluble residue (Figure 1). We noted a distinct, positive correlation between concentrations of potassium, sodium, and magnesium and the percentage of insoluble residue. (Some of these elements may have been flushed into the insoluble fraction in spite of the precautions taken.) We found a positive, but less pronounced, relationship between zinc and strontium concentrations and insoluble residue, whereas we detected no correlation between manganese concentrations and insoluble residue. Because of this relationship we consider the results obtained for potassium, sodium, and magnesium, and those obtained for strontium, and zinc, when the samples contain more than 10 per cent insoluble, to be unreliable. Strontium The concentration curve of strontium contents is very characteristic for samples containing more than 90 per cent carbonates (Figure 2). The amount of strontium decreases continuously from the Aptian to the Tithonian sediments; a rapid decrease occurs in the lower Valanginian-upper Barremian sediments. We attribute this to increased diagenesis with greater depth which reflects the degree of diagenesis as a function of age. This is consistent with earlier claims of Sheeiman and Shirmohammadi (1969), Kinsman (1969), and Renard (1972) that strontium is a reliable measure of carbonate diagenesis. The similarity of the strontium concentrations and the sediment accumulation curves illustrates that the highest rate of sedimentation (2.8 cm/10 3 years) corresponds to the greatest loss of strontium. A rough correlation between the gradient of the strontium concentration curve and the sedimentation rate is given in Figure 3.

Strontium, Manganese, and Iron Contents, and Oxygen Isotopes in the Carbonate Fractions Recovered from Hole 398C, Leg 47B

“…The levels of strontium tend to increase during the Maestrichtian, a phenomenum shown quite clearly at Holes 390 and 390A of Leg 44 (Renard et al, 1978). One possible cause is the weakness of the diagenetic process during this time.…”

“…This decline continues gradually to the Hauterivian and is due to increasing diagenesis with depth (Renard et al, 1978). It appears that the strontium lost from the carbonates must be trapped readily by the argillaceous rocks since a positive correlation between the level of strontium and the percentage of insoluble matter is found only in Eocene and older rocks.…”

“…Figure 8 shows that those samples with a high concentration of iron have a correspondingly low concentration of manganese and vice versa. It becomes possible, therefore, to outline the basic characteristics of particular groups of samples, as we already have done for Leg 44 (Renard et al, 1978).…”

Trace Element Contents of Carbonates from Holes 549 and 550B (Leg 80): Comparison with Some Tethyan and Atlantic Sites

“…Previous studies of sediments from Holes 390, 391, 392, 398C, 400A, 516F, and 116 (Renard et al, 1978 have shown the potential use of Sr as a time marker for pelagic carbonate diagenesis (because of Sr loss with time). Also, the manganese-iron couple appears to be an indicator of submarine volcano-hydrothermal activity.…”

Variations in Trace Element Contents and Isotopic Compositions of Lower Cretaceous Carbonates from the Galicia Margin (ODP Leg 103): Reconstruction of the Paleochemistry of the Early Cretaceous Ocean

“…Previous studies of pelagic sediments from various Deep Sea Drilling Project (DSDP) sites and continental outcrops (summarized in Renard, 1985Renard, , 1986b have shown several things. First, these studies have documented that the influence of late burial diagenesis on the geochemistry of these sediments is considerably less than was originally thought (Veizer, 1977;Renard, 1979;Renard et al, 1978;Baker et al, 1982). Second, numerous chemical fluctuations, such as changes in Sr/Ca, Mg/Ca, and 13 C/ 12 C ratios, have occurred in the ocean during the last 140 m.y.…”