Interannual to Multidecadal variability in Denitrification and Biogenic Silica in the Gulf of California during the late Pleistocene

Title: Interannual to Multidecadal variability in Denitrification and Biogenic Silica in the Gulf of California during the late Pleistocene.Authors* Pichevin, Laetitia, Email: [e-mail], Web: University of Edinburgh* Massimo, Bollasina, Email: [e-mail], Web: University of Edinburgh* Alexandra, Nederbragt, Email: [e-mail], Web: Cardiff University* Ganeshram, Raja, Email: [e-mail], Web: University of EdinburghAbstract: Nitrogen Isotopic signal (permil) and biogenic silica concentration (weight %) in individually sampled, yearly laminations from Marion Dufresne Calyspo Piston Core MD02-2515 and CASQ core MD02-2517 (Holocene) retrieved from the Guaymas basin, Gulf of Califronia (27°29.01N; 112°04.46W; 881m water depth) in 2002.The data covers 10 annually resolved sections spanning around 200 years each, across the last Glacial-Interglacial cycle (MIS3 to Holocene). The sediment cores were retrieved as part of the IMAGES program during the MONA (North American Margins) cruise on board the Marion Dufresne in 2002.The aim of the data collection was to document interannual to multidecadal variability in denitrification and productivity to understand the natural variability in North-Eastern Pacific deoxygenation and its climatic causes over the late Pleistocene.Methods:The isotopic composition of sedimentary nitrogen (d15N, ‰) was measured by Continuous Flow-Isotope Ratio Mass Spectrometry (CF-IRMS) using a CE instrument NA2500 elemental analyser directly coupled to a VG Isotech Prism mass spectrometer at the University of Edinburgh, School of Geosciences. The determination of the opal content (%) by the molybdate-blue spectrophotometry was adapted from Mortlock and Froelich (1989).ReferencesMortlock, R.A. and P.N. Froelich, A Simple Method for the Rapid-Determination of Biogenic Opal in Pelagic Marine-Sediments. Deep-Sea Research Part a-Oceanographic Research Papers, 1989. 36(9): p. 1415-1426.

Pichevin, L.E., Bollasina, M., Nederbragt, A.J. et al. North Atlantic temperature control on deoxygenation in the northern tropical Pacific. Nat Commun 15, 7919 (2024). https://doi.org/10.1038/s41467-024-52197-6File descriptions: Excel table containing yearly Nitrogen Isotopes (permil) and Biogenic Sillica (weight %) data from 10 annually resolved sections from Calyspo Piston Core MD02-2515 and CASQ core MD02-2517 (Holocene) retrieved from the Guaymas basin, Gulf of Califronia (27°29.01N; 112°04.46W; 881m water depth.Sections III and 2 are of Holocene age (years listed from younger to older), sections 9 and 10 are during the Bolling/Allerod, sections 17 and 26 are from the last glacial period, section 45, 46, 47 and 50 are from Marine Isotopic Stage (MIS) 3.