Borehole 22/10a-4 (57°44’8.47”N; 1°50’26.59”E) provides a continuous core through the Forties Sandstone Member and into the Lista Formation (Fig. 2). The core consists of variably fissile claystone with interbedded fine to coarse grained sandstone layers interpreted as turbidites, with occasional mm-thick ash layers (Fig. 3). All samples in this study were taken from claystone horizons to avoid sampling substantial quantities of reworked material. The section of 22/10a-4 analysed in this study is from 2605 m to 2634 m (core depth), chosen because this part of the core is predominantly in claystone facies and provides a greatly expanded section over the onset of the CIE (Figs. 2 and 3). At 2609–2613 m the claystone becomes finely laminated with alternately pale and dark laminae couplets ranging from 1 to 25 per mm (Fig. S2). The pale laminae consist of clay and silt, and the dark laminae are rich in organic carbon and pyrite inclusions. Laminae were counted at 26 horizons throughout the core and approximately 13 pairs per mm.
Borehole 22/10a-4
57°44’8.47”N; 1°50’26.59”E
section of 22/10a-4
core depth
from 2605 m to 2634 m
m
the claystone
becomes finely laminated
2609–2613 m
m
alternately pale and dark laminae couplets
ranging from 1 to 25 per mm
mm
core
26 horizons
horizons
Laminae
approximately 13 pairs per mm
pairs per mm