Cretaceous-Paleogene boundary Fish Clay at Højerup (Stevns Klint, Denmark): Zn, Pb and REE in kerogen

Geochemical analyses of Zn, Pb and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in the kerogen of the black marl at the Cretaceous - Paleogene boundary Fish Clay at H?jerup were performed. Substantial proportions of the Zn, Pb and rare earths were probably contained in terrestrial humic substances (the kerogen precursor) arriving at the marine sedimentary site. This is in accord with a previous hypothesis that kerogen is mainly derived from humic acids of an oxic soil in of the adjacent coastal areas of eastern Denmark. It is also suggested that humics enriched in Zn, Pb and rare earth elements were transported mainly through fluvial transport into the deposition site of the Fish Clay. Local weathering/leaching of the impact-eject fallout on the land surface and local terrestrial rocks by impact-induced? acid surface waters perhaps played an important role in providing Zn, Pb and rare earths to these humic substances. Apparently, chondritic and non-chondritic Zn originated from the impact fallout; Pb and rare earth elements were most likely sourced by exposed rocks in the coastal areas of eastern Denmark.

Cretaceous – Paleogene boundary Fish Clay at Højerup (Stevns Klint, Denmark): trace metals in kerogen

Geochemical analyses of trace metals (Ir, Ni, Co, Cr, Zn, Au and Pb) and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in kerogen of the black marl at the Cretaceous–Paleogene boundary Fish Clay at Højerup have been undertaken. Substantial proportions of the trace metals and rare earths were probably contained in terrestrial humic substances (the kerogen precursor) arriving at the marine sedimentary site. This is in accord with a previous hypothesis that kerogen is mainly derived from humic acids of an oxic soil in of the adjacent coastal areas of eastern Denmark. It is also suggested that humics were transported mainly through fluvial transport into the site of the deposition of the Fish Clay. The local weathering/leaching of the impact-ejecta fallout on the land surface or local terrestrial rocks by impact-induced? acid surface waters perhaps played an important role in providing trace metals and rare earths for these humic substances. Apparently, chondritic Ir, Au, Ni, Co, Cr and chondritic and non-chondritic Zn originated from the impact fallout; Pb and rare earth elements were most likely sourced by the rocks exposed in the coastal areas of eastern Denmark.

Geochemistry of the cretaceous-tertiary boundary (Fish Clay) at Stevns Klint (Denmark): Ir, Ni and Zn in kerogen

Geochemical analyses of trace metals (Ir, Ni and Zn) in the kerogen of the black marl of the Cretaceous-Tertiary boundary succession (Fish Clay) at Stevns Klint (H?jerup Church) were undertaken. The data for this kerogen were in accordance with a previous hypothesis that this (insoluble) geoorganic polymer was derived from humic substances (mainly humic acids) of a nearshore soil. Substantial proportions of Ir, Ni and Zn within the kerogen structure were probably contained in these substances arriving at the sedimentary site. It is proposed that these humics were probably transported by acid surface waters (induced by the KT asteroid impact) into the shallow marine basin of Stevns Klint. It is also suggested that local leaching/weathering of the asteroidal impact fallout on the land near these waters played an important role in providing Ir, Ni and Zn for these substances. Apparently, Ir, Ni and Zn of the kerogen were created by the chondritic component of the impact ejecta fallout.

Geochemistry of Ni in the Cretaceous-Tertiary succession Fiskeler (Fish Clay) at Stevns Klint (Denmark): cheto-smectite of the black marl

The Cretaceus-Tertiary (KT) boundary at Stevns Klint (the H?jerup succession), Fiskeler, consists of a thin red clay layer overlain by a thick one of black marl. These two layers are made up mainly from cheto-smectite and biogenic calcite. The black marl shows an enhanced concentration of Ni (655 ppm) within its smectite fraction. Additionally, its carbonate fraction also shows an enhanced concentration of Ni (245 ppm). It is reasoned that these enrichments represent a sudden and rapid input of high amounts of Ni into the late Cretaceus seawater at Stevns Klint. The ultimate source of Ni in both the carbonate and smectite fractions of the black marl was probably impact fallout, produced by the KT asteroidal impact, deposited on the nearby soil and leached by the (acid) surface waters. The geochemistry of the Ni supports the hypothesis that the smectite of this marl most likely has a local (marine or terrestrial) provenance and was probably redeposited, after its formation, from the original site to its present location at the KT boundary.

Planktonic foraminifers, biostratigraphy and the diachronous nature of the lowermost Danian Cerithium Limestone at Stevns Klint, Denmark

New material comprising more than four thousand specimens of planktonic foraminifers from the lowermost Danian Cerithium Limestone at Stevns Klint, Denmark, reveal significant lateral biostratigraphic differences along the 14 km long cliff. The Cerithium Limestone at Rødvig (Korsnæb) in the southern part of Stevns Klint is dominated by foraminiferal assemblages indicative of the Parvularugoglobigerina eugubina Zone (Pα). This pattern changes laterally towards the north, where the P. eugubina Zone becomes gradually thinner. At the northernmost locality investigated, Holtug quarry, the Cerithium Limestone unit is characterised solely by assemblages of the succeeding Parasubbotina pseudobulloides Subzone (P1a). This indicates that the Cerithium Limestone is diachronous and becomes gradually younger from the southern part of Stevns Klint towards the northern part. The data indicate that a hiatus including all of the P. eugubina Zone is present at the Fish Clay – Cerithium Limestone transition in the northern part of the cliff, whereas such a hiatus cannot be demonstrated in the southern part.