Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
  • Problem Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Please see Alcorn et al. (2026) for a more detailed methodology.

Core MAZ-1E-04 (MAZ-I E04G) was collected on the oceanographic cruise MAZ-I aboard the R/V "El Puma" on April 28, 2015 using a gravity corer.

Total organic carbon (TOC %) was analyzed using a Perkin-Elmer 2400 CHN elemental analyzer with a reproducibility of 2.5% relative standard deviation (RSD). TOC % was measured to support interpretation of C:N ratios. Before analysis, inorganic carbon was dissolved with 4.5 mL of 1M H₃PO₄ and samples were filtered onto precombusted (at 400°C for 5-8 h) glass filters. Samples were then dried at 40°C and wrapped in tin discs for measurement. Sedimentary δ¹⁵N and δ¹³C_org were measured on the GV-IRMS interfaced with a Euro Elemental Analyzer, and %N was measured on a Perkin Elmer 2400 Elemental Analyzer. Inorganic δ¹³C was removed from δ¹³C_org samples through acidification, and δ¹³C_org results are presented relative to VPDB. Sedimentary δ¹⁵N  was calculated using the following equation: δ¹⁵N = ((¹⁵N/¹⁴Nsample) / (¹⁵N/¹⁴N_ref) – 1) * 1000 where ¹⁵N/¹⁴N_ref  refers to atmospheric N₂. Standards and duplicates were run every 20 samples with 0.05‰ reproducibility. Measurements of δ¹⁵N and δ¹³C_org were taken at each 1 cm interval.

- Loaded sheet 1 from "Supplementary Table S7.xlsx" (Excel format) with missing values treated as empty string or "nd"; resource named using filename as "supplementary_table_s7-1"
- Renamed fields: "Depth (cm)" to "Depth_core", "Age (ybp)" to "Age", "δ15N (‰)" to "d15N", "δ13C (‰)" to "d13C", "%N" to "pct_N", "C:N" to "C_N_ratio"
- Exported file as "991502_v1_bulk_sediment_maz-1e-04.csv"

NSF abstract: 

Oxygen minimum zones (OMZs) are naturally occurring regions of low oxygen found across large swaths of the ocean at depths of 100 to 1000 meters below the surface. OMZs play an important role in biogeochemical cycling and ecosystem function and any change in the expanse of their low oxygen waters can have far reaching implications for marine life and valuable fisheries resources. Marine oxygenation is variable on multiple timescales in response to global climate change, with recent observations showing that OMZs have expanded over the past half century. This project will explore promising new geochemical and morphologic proxies applicable to low-oxygen environments in the planktic foraminifer Globorotaloides hexagonus, a unicellular calcifying organism whose fossil record in seafloor sediments is well suited to reconstructing past low-oxygen environments in the water column. The project will focus on the extensive OMZ of the eastern tropical Pacific. The first goal is to evaluate and calibrate the targeted measurements for modern G. hexagonus collected live in plankton tows. The second goal is to apply these proxies to fossil specimens in sediment cores to generate records of glacial-Holocene change. The outcomes will be useable proxies for generating records of the OMZ environment, and a better understanding of how a major regional OMZ changed during the most recent period of rapid climate change. Both outcomes represent important progress towards understanding natural oscillations in the OMZ as well as modeling and planning for a changing OMZ in the face of global climate perturbations. The project will provide opportunities for undergraduate researchers as well as support a female early career researcher. 

The marine sedimentary record is the most promising archive from which to reconstruct long term marine oxygenation. However, significant limitations exist in the available proxies for low oxygen marine environments. This project aims to address this need by evaluating and applying a range of promising geochemical (trace element and stable isotope) and morphologic (area-density and porosity) proxies relevant to low oxygen environments in the planktic foraminifer Globorotaloides hexagonus. The project will develop viable proxies based on the morphology and geochemistry of G. hexagonus shells previously collected in depth-distributed MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) tows from the eastern Pacific. The results from this proxy development in modern shells will then be ground-truthed and applied to two already well characterized sediment cores from the Mexican Margin and Panama Basin that span from the Last Glacial Maximum through the Holocene. The sediment records will be used to reconstruct past conditions in the eastern tropical Pacific OMZ, where significant questions about glacial-interglacial oxygenation persist. This research will lead to a more mechanistic understanding of how OMZs respond to climate more broadly.