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Exp. 389 Sampling and Measurement Plan

Core section enscribung during Exp. 310 'Tahiti Sea Level', credit: ECORD/IODP — Core section enscribing during Exp. 310 'Tahiti Sea Level', credit: ECORD/IODP

Offshore Sampling and Measurements Plan

Owing to the nature of MSP expeditions, there is commonly limited laboratory space offshore, and as such there is no splitting of the cores at sea. The scientific analyses undertaken onboard are consequently limited to a subset of the expedition dataset. Offshore scientific activities include those essential for core curation, securing head space sediment samples and samples for pore-water chemistry, sampling for shipboard biostratigraphy, measurement of ephemeral properties including physical properties, and downhole logging.

This sampling and measurements plan is subject to amendment according to the scientific needs/interests of the Science Party and/or operational constraints. Routine measurements and core flow will be undertaken in line with the IODP-Mission Specific Platform (MSP) standard measurements procedures.

The following measurements will be carried out offshore:

Curation The cores will be curated and labelled, and stored in a temperature-controlled reefer (~4°C). There will be no splitting of the cores at sea with the majority of scientific analyses being conducted during the Onshore Science Party (OSP) at the BCR/MARUM is scheduled for February 2024.
All data will be recorded in the offshore Drilling Information System (ExpeditionDIS) database.
Curation will be done in the designated area on board the drilling platform. Curatorial representatives onboard will have delegated responsibility in the absence of the ESO Curation and Laboratory Manager and IODP Curator for the Bremen Core Repository (BCR) and MSPs, Dr. Ursula Röhl.

Core catcher (CC) description and sampling, if available, for initial sedimentological, micropaleontological, petrophysical and/or structural characterization, including perhaps taking a CC image. If no core catcher sample is recovered, a sample from the lower end of each core will be taken for shipboard analysis. Thin section billets may be taken in representative sections for preparation in advance of the OSP, as advised by the offshore sedimentologists.

Geochemistry Headspace sediment samples will be taken from the fresh cut end of a core section on a routine basis (in suitable lithologies and dependent on core recovery) and stored in the reefer container for onshore analysis.

In suitable lithologies, pore-water samples (e.g. squeezers and/or rhizone moisture samplers) will be taken on a routine basis. Pore-water will be extracted immediately from cores and ephemeral properties (e.g. salinity, pH, alkalinity and ammonia) will be analyzed. Sample splits for onshore analysis (e.g. cations, sulfide, ¹³C) will be prepared and preserved whilst offshore and stored in the reefer container.

Core physical properties Temperature-equilibrated cores will be measured on the expedition platform in a containerized laboratory utilizing a multi-sensor core logger (MSCL). All cores (>10 cm) will be measured on the multi-sensor core logger (MSCL; gamma density, P-wave velocity, electrical resistivity, magnetic susceptibility and natural gamma radiation). Note: the choice of liner will affect which measurements can be conducted successfully. Only natural gamma ray and density data can be acquired of core in aluminum liners. In addition, the likely vuggy nature of the reef sediments may cause drainage of some pore water during core cutting or potential transfer from alumimum to plastic liners which may negatively affect the quality of electric resistivity and p-wave velocity measurements. Scientists should keep in mind that transfer of sediments from one liner type to another may change the core consistenty and, thus, its physical properties.

GPC operation onboard RV Kaimei — Core on deck during Exp. 325 'Great Barrier Reef Environmental Changes', credit: ECORD/IODP

Initial core receiving area during Exp. 310 'Tahiti Sea Level' — ECORD/IODP

Interstitial water sampling with Rhizons

Onshore Sampling and Measurements Plan

The OSP will be undertaken at IODP Bremen Core Repository, MARUM, University of Bremen, laboratories.
The following work flow according to IODP MSP standards will take place after the expedition and during the OSP:

CT scanning: after the offshore phase the whole-round cores will be scanned completely in a X-ray CT-scanner at BGS.
Core splitting: the cores will be split into a working and an archive half in line with IODP procedures.
Core description: IODP standard facilities for core description, including access to a CoreWall visualisation system will be provided. Core description will be undertaken on the archive half of the cores. For data entry, ESO will employ a version of the offshore Drilling Information System (DIS), called “ExpeditionDIS”, which is comparable with others being used in IODP.
Digital line-scan imaging: high resolution images of the archive half of the cores will be acquired utilising an XRF-core scanner mounted with a line-scan camera.
Thin section and smear slide preparation: as requested.
Inorganic geochemistry: whole-rock and pore fluid chemistry; inductively coupled plasma–optical emission spectrometry (ICP-OES); ion chromatography (IC); energy dispersive X-ray fluorescence (ED XRF); and total carbon (TC) / total organic carbon (TOC) content (LECO CS analyzer) / carbonate content.
Biostratigraphy: facilities to wash and sieve samples including controlled access to the HF lab at MARUM for palynology sample processing, microscopes including options for image capture.
X-ray diffraction analysis (XRD): bulk mineralogy.
Paleomagnetic measurements: natural remnant magnetism (NRM) with stepwise demagnetization (2G longcore cryogen magnetometer) or samples (robot system which feeds up to 100 adapted sample cubes).
Physical properties measurements:
- Thermal conductivity on whole cores will be acquired by ESO staff prior to the OSP at MARUM utilising a needle probe system. Additional standard IODP physical properties measurements may be undertaken on whole cores at this time in the event offshore datasets are incomplete. This may be owing to time (natural gamma radiation) or permitting issues (gamma density).
- Physical properties of discrete samples: P-wave velocity and moisture and density properties (MAD) including: wet bulk density; grain density; porosity; and void ratio. For MAD measurements, core samples will be oven-dried (60° ± 5°C), the dried sample volume will then be quantified using a Quantachrome penta-pycnometer with sample masses being measured using a high-precision balance.
- Undrained shear strength (S_u): measurements utilizing a torvane, pocket penetrometer, and/or fall cone (on request) can be undertaken on the working half of the core.
- Color reflectance: measurements acquired using a MSCL mounted with a Minolta spectrophotometer.

Core sampling: A detailed sampling plan will be devised following review of all revised sample requests by the Sample Allocation Committee (SAC), prior to the start of the OSP and after the scientists have submitted their revised sample requests.

Gruppenbild — Group picture taken during the Onshore Science Party (OSP) of Exp. 381 'Corinth Rift Paleoseismology'