Paleoenvironmental conditions across the CretaceousePaleogene transition at the Apennines sections (Italy): An integrated geochemical and ichnological approach

Two distal CretaceousePaleogene (K/Pg) boundary sections in the Central Apennine region (Italy) have
been studied: Bottaccione Gorge and Contessa Highway. Geochemical and carbon isotope analyses on the
infilling of trace fossils and on the host sedimentary rocks were performed to determine paleoenvironmental
conditions during the CretaceousePaleogene transition. Major and trace element contents
were measured in a 63 cm-thick interval at Bottaccione Gorge (from 22 cm below to 41 cm above the K/
Pg boundary) and in a 72 cm-thick interval at Contessa Highway (from 43 cm below to 29 cm above the
K/Pg boundary). Even though the K/Pg ejecta layer is now depleted at these sections due to continuous
oversampling, the uppermost Maastrichtian and lowermost Danian deposits record the paleoenvironmental
conditions prior to and after the K/Pg event. We used redox-sensitive element ratios (V/Al, Cr/
Al, Co/Al, Ni/Al Cu/Al, Zn/Al, Mo/Al Pb/Al and U/Mo) and detrital element ratios (K/Al, Rb/Al, Zr/Al and
ƩREE/Al) as proxies of certain environmental parameters, used for paleoenvironmental reconstruction. In
general, similar values for elemental ratios are registered within Maastrichtian and Danian deposits,
which supports similar paleoenvironmental conditions prior to and after the K/Pg event as well as the
rapid reestablishment of the pre-impact conditions (i.e., oxygenation, nutrient availability, and/or sedimentary
input). An enrichment in certain redox-sensitive elements above the K/Pg at the Bottaccione
Gorge section suggests lower oxygenation, as also evidenced by the tracemaker community. Carbon
isotope composition data from the infilling material of trace fossils furthermore reveals values similar to
those of the host rocks at the corresponding depth, which supports an active infilling by nearly
contemporaneous bioturbation during sediment deposition.