The Ammonite GenusGaudrycerasfrom the Santonian—Campanian of Antarctica: Systematics and Biostratigraphy

Mid Campanian‐Lower Maastrichtian magnetostratigraphy of the James Ross Basin, Antarctica: Chronostratigraphical implications

“…Several faunal groups that reach the Maastrichtian in the rest of the world disappeared in Antarctica by the beginning of the middle Campanian: inoceramids, most dimitobelid belemnites and trigoniids and ammonite families such as Scaphitidae, Baculitidae and Nostoceratidae, as well as the lytoceratid genus Gaudryceras , which disappear by the early‐late Campanian (Raffi & Olivero, ). These early extinctions were accompanied by both an increment in the abundance and diversification of endemic species of the ammonite family Kossmaticeratidae .…”

“…It constitutes a complete record of marine life since Early Cretaceous time providing evidence of nonglacial climates at polar latitudes. It also includes the Cretaceous – Palaeogene transition in the upper Marambio Group at Seymour (Marambio) Island (Figure ), which makes the basin infill important for palaeobiogeographic reconstructions of the Southern Hemisphere and global extinction patterns (Barreda, Palamarczuk, & Medina, ; Crame et al, ; do Monte Guerra et al, ; Iglesias, ; Raffi & Olivero, ; Reguero, Goin, Hospitaleche, Marenssi, & Dutra, ; Tobin et al, ). Most outcrops in the James Ross Basin are isolated, challenging lithological correlation, and it were decades of work by previous authors what achieved the stratigraphic column for the whole basin, based mainly on biostratigraphic correlations.…”

“…The reference stratigraphic framework adopted in this work was defined by Olivero (), who was able to establish a stratigraphic scheme for the Marambio Group based on ammonite assemblages (Figure ). Although the intra‐basin correlation of units has been successfully accomplished, problems of endemism and early extinction of several invertebrate groups (including ammonites) in Antarctica hamper global correlations (Crame et al, ; Francis et al, ; McArthur, Crame, & Thirlwall, ; Olivero, ; Olivero & Medina, ; Raffi & Olivero, ). This uncertainty makes obtaining an independent absolute age framework a necessary requisite to validate biogeographic and palaeoclimatological data for the Antarctic Peninsula in Cretaceous and Early Cenozoic times.…”

Coniacian-Campanian magnetostratigraphy of the Marambio Group: The Santonian-Campanian boundary in the Antarctic Peninsula and the complete Upper Cretaceous – Lowermost Paleogene chronostratigraphical framework for the James Ross Basin

“…Island and a possible boundary on Vega Island (Roberts et al, 2014), and is a key element in paleobiogeographic reconstructions of the Southern Hemisphere and global extinction patterns (Barreda et al, 1999;Crame et al, 1996;Iglesias 2016, Petersen et al, 2016Raffi and Olivero, 2016;Reguero et al, 2013;Tobin, 2017;Witts et al, 2016).…”

“…The stratigraphy of the basin is based mainly on the correlation of isolated sections using sequence stratigraphic principles in combination with biostratigraphy from palynomorphs, ammonites, and nannoplankton, as well as sparse 87 Sr/ 86 Sr isotopic data (Crame et al, 1999;do Monte Guerra et al, 2015;McArthur et al, 2000;Olivero, 2012a;Olivero et al, 1986). Although the intrabasin correlation of units has been well established, problems of endemism and early extinction of several biostratigraphically important invertebrate groups (notably heteromorph ammonites and inoceramid clams) in Antarctica hamper global correlations (Crame et al, 1996;Francis et al, 2006;McArthur et al, J o u r n a l P r e -p r o o f Journal Pre-proof Olivero, 2012a;Olivero and Medina, 2000;Raffi and Olivero, 2016). To overcome this obstacle, it is necessary to obtain an independent and precise age framework for the Cretaceous JRB infill.…”