Physicochemical conditions of sedimentation of the Fish Clay from Stevns Klint, Denmark, and its detrital nature: Vanadium and other supportive evidence

Title Physicochemical conditions of sedimentation of the Fish Clay from Stevns Klint, Denmark, and its detrital nature: Vanadium and other supportive evidence
Author: Premovi\'{c}, Pavle I; Pavlovi\'{c}, Neboj\v{s}a Z; Pavlovi\'{c}, Mirjana S & Nikoli\'{c}, Nikola D
Geochimica et Cosmochimica Acta, 1993
1993
http://www.sciencedirect.com/science/article/pii/001670379390004G
More details: Cretaceous-Tertiary (K/T) boundary samples of the Fish Clay in Denmark from three sites (Stevns Klint, Nye Kl\o v and Dania) have been analyzed mineralogically and chemically. All samples contain major amounts of biogenic calcite and smectite. In some samples, minor amounts of authigenic pyrite and siderite (Stevns Klint), and lepidocrocite (Dania) are also present. To obtain an indication of the chemical nature of the V present in the Danish boundaries, the samples were analysed for V and vanadyl (VO2+) at various stages of selective leaching. The results obtained indicate that the bulk of V is associated with the smectite fractions (?��47\% of total V); all VO2+ resides in the smectite portions. From the chemistry of VO2+, pyrite and carbonates, it is deduced that the oxidation potential and pH of the interstitial seawater of the Stevns Klint boundary was approximately 0.0 to ?��0.2 V and 6 to 7, respectively, during the accumulation of the lower black basal part, but rose during the accumulation of the upper grey part. The geochemical data do support the hypothesis that the Danish boundary smectite represents weathered clay (along with some asteroid and local material) that was redeposited to the Danish boundary sites after the K/T event. Substantial proportions of the VO2+ contents of the Nye Kl\o v and Dania smectite were probably already contained in the detrital clay arriving at the site of boundary sedimentation, but at the Stevns Klint site they have been significantly augmented by uptake from the interfacial and interstitial seawaters through the humic substances involvement. Abundances and major mineralogical residences have been determined for trace metals: Cr, Ni, Co and Ga; and minor Fe. Much of these elements is located in the boundary smectite structure as the corresponding ionic forms (CrOH2+, Ni2+, Co2+, Ga3+ and Fe3+) and is strictly detrital in character, i.e., having been transported to the Danish boundary sites already contained in smectite. All these metals in the Danish boundary smectite are well above normal abundances in clays.