Sea-ice biomarkers, benthic and planktonic foraminiferal abundance, and total organic carbon in Holocene sediments from outer Petermann Fjord, Greenland

Composite sediment core OD1507-03TC-41GC-03PC was collected at an average water depth of 976 m in outer Petermann Fjord during The Petermann 2015 Expedition to Petermann Fjord and adjacent Hall Basin in Nares Strait, northern Greenland. Previous results showed that the splice covers large parts of the Holocene, from the present to 6,900 cal yrs BP (Reilly et al. 2019). The core was sampled approximately every 5 cm for sea-ice related biomarker and total organic carbon (TOC) analyses and approximately every 10 cm for foraminiferal abundance counts. Where enough material was available, the depth of foraminiferal samples match the depth of biomarker samples. Sea-ice related biomarkers (IP25, HBI II, Brassicasterol, Cholesterol, Dinosterol, Campesterol, and β-sitosterol) where extracted using saponification (5% potassium hydroxide (KOH) in methanol (MeOH):H2O (9:1, v/v); 70°C, 1 h) followed by extraction of the non-saponifiable lipids into hexane (3 x 2 mL). After sample purification the different biomarkers were analysed on an Agilent 7890B GC fitted with an HP-5ms Ultra Inert column (30 m x 250 μm x 0.25 μm) coupled to a 5977A series mass selective detector and equipped with a Gerstel multipurpose sampler (MPS) at Aarhus University. TOC measurements and analysis of the carbon isotopic composition of the TOC were performed on 10 mg of the same sample material as for biomarker analyses. The samples were treated with 35% HCl prior to analyses, to remove inorganic carbon. The stable isotope δ13Corg and % wt TOC were measured using a continuous-flow IsoPrime IRMS coupled to an Elementar PyroCube elemental analyser at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. Samples for foraminiferal abundance counts were wet sieved at 63 µm and counted wet, submerged in a 'storage' solution of 70 % distilled water and 30 % ethanol with baking soda to preserve fragile calcareous and agglutinated tests. A wet splitter was used when necessary to achieve a count of at least 200-300 benthic foraminifers.