Calcareous nannofossils from the Upper Cretaceous of northern James Ross Island, Antarctica: a pilot study

Abstract

The Czech sci en tific ex pe di tion to north ern James Ross Is land, Antarctica has tested the use of cal car e ous nannofossils as a pos si ble tool for strati graphic cor re la tion of Cre ta ceous and Neo gene strata. Only a few sam ples with poor nannofossil con tent gave use ful in for mation for biostratigraphy. The Lower Campanian Chiastozygus garrisonii Zone and Gephyrobiscutum diabolum Subzone, re spec tively, was es tab lished in the lower part of the Santa Marta For ma tion, Lachman Crags Mem ber, from the com mon oc cur rence of Gephyrobiscutum diabolum as so ci ated with Broinsonia parca parca and Acuturris scotus. De pos its of the Late Mio cene Men del For mation yielded ex clu sively re worked nannofossils from the older Up per Cre ta ceous de pos its. Nannofossils in di cate at least two dis tinct strati graphic lev els: Mid dle Coniacian and Santonian-basal Campanian, and these must have been sourced from the im me di ate area. The ma jor ity of the ma rine de posit sam ples stud ied were bar ren of nannofossils, prob a bly due to late diagenetic sec ond ary decalcification. Lilian Švábenická and Radek

Nature and timing of biotic recovery in Antarctic benthic marine ecosystems following the Cretaceous–Palaeogene mass extinction

“…The first diagnostic Danian foraminiferal assemblage also occurs at the top of the LBF, 1 m below the contact with the SF (Huber ), although this record may be affected by secondary diagenetic decalcification which is a common issue with calcareous microfossil assemblages in the James Ross Basin (Švábenická et al . ).…”

Nannofossils, foraminifera and microforaminiferal linings in the Cenozoic diamictites of Cape Lamb, Vega Island, Antarctica

“…These species have been previously identified in situ in sediments of the Santa Marta Formation, Santonian to lower Campanian in age, at Lachman Crags (Guerra et al 2012;Švábenická et al 2012).…”

Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

“…The substrate for biofilms is composed of boulders and pebbles of the stony littoral zone, petrographically corresponding to compact and massive basaltoids (Smellie et al, 2008;Svojtka et al, 2009). Rounded or subrounded quartz grains that are incorporated ("trapped") within biofilms cannot originate from basaltic volcanic rocks forming the bottom of both lakes and substrate of the studied biofilms.…”

“…Shao (2008) and references therein). These grains and particles are usually derived from erosion of the rocks either in the very close vicinity of the locality (weathering of basaltic rocks), but mainly come from remote locations where especially Upper Cretaceous marine sedimentary sequences are outcropping (Smellie et al, 2008;Svojtka et al, 2009). The amount of mineral grains transported into the lake by wind does not stop the growth of cyanobacterial-microalgae biofilms, due to their ability of incorporating and "trapping" mineral grains within the living tissue (Riding, 2011).…”

“…Although calcite fossils may be partly or completely dissolved during diagenetical processes in the fossil record (e.g. Schneider et al, 2011;Švábenická et al, 2012), their preservation potential is relatively high. Therefore, we expect to find fossil and/or subfossil calcite spicules from the Quaternary lake sediments of the studied area.…”