IODP Survey of the "Shackleton sites" on the Southwest Iberian Margin

Lead Research Organisation: University of Cambridge
Department Name: Earth Sciences


Advances in our understanding of the Earth's climate system will rely on our ability to link high-resolution sedimentary archives from the oceans, ice-cores and terrestrial sequences, and to interpret these records in the context of novel Earth system modeling approaches. Few places exist in the world where sufficiently detailed and unambiguous marine-ice-terrestrial linkages are possible. One challenge for IODP, and the broader drilling community in general, is to identify and recover marine, ice and terrestrial sequences from appropriate locations and with adequate temporal resolution to study processes of the integrated climate system.

One such region is the southwest Iberian Margin where it has been demonstrated that the surface oxygen isotopic record could be correlated precisely to temperature variations (i.e., d18O) in Greenland ice cores. By comparison, the benthic d18O signal in the same core resembled the temperature record from Antarctica. Moreover, the narrow continental shelf and proximity of the Tagus River results in the rapid delivery of terrestrial material to the deep-sea environment off Portugal, thereby providing a record of atmospheric changes and permitting correlation of marine and ice core records to European terrestrial sequences. This is the only place in the ocean where such marine-ice-terrestrial correlations have been demonstrated unambiguously. It is therefore highly desirable to extend the Iberian Margin record to encompass the full range of Plio-Pleistocene glacial-interglacial cycles by drilling with the JOIDES Resolution (JR).

Towards this end, Proposal 771-Full was submitted to IODP by an international group of 16 proponents led by the UK. The proposal was well received and reviewed by the Science Steering and Evaluation Panel (SSEP), but the IODP Site Survey Panel (SSP) identified major inadequacies in the quality of the seismic data:

"The panel raised several concerns on the suitability of the submitted data with regard to its appropriateness, both to image the target properly and with regard to the site location. The panel also discussed the need for 2 high-resolution lines and considered that places where Mass Transport Deposits (MTDs) or closely spaced faults were present deserved these 2 high-resolution lines."

This proposal requests 25 days of ship time to collect the necessary seismic and sediment data needed to meet the SSP requirements and recommendations. Several "stand-alone" scientific objectives are also proposed related to the modern hydrography and sedimentary processes on the southwest Iberian Margin, and calibration of palaeoceanographic proxies used for reconstructing past changes in deep-water circulation. This value-added science will make effective use of ship time and contribute key information needed to interpret the downcore records to be obtained by IODP.

Planned Impact

The primarily beneficiary will be members of the academic community who are engaged in IODP research, specifically millennial-scale climate variability in records from the Iberian Margin. The success of IODP is contingent upon grassroots efforts by the scientific community to propose the best science and identify the best places to drill on the ocean floor. As such, site survey is one of the most important activities for IODP and directly impacts the ultimate success of the program. The research proposed herein is directly relevant to the primary scientific objectives of the IODP Initial Science Plan. As such, the UK will benefit both through enhanced participation in the IODP and the results of the site survey will be important for the future success of the program.

More importantly for knowledge exchange will be links to the community through the Sedgwick Museum at the University of Cambridge, which attracts in excess of 84,000 visitors per year, including over 100 school group visits. We will establish a general display on how ocean drilling contributes to the study of past climate change. We will take advantage of the media and education resources available through IODP, including web content, media kits, an audiovisual library, fun and games activities for children, core replicas, press releases, brochures and other public relations materials. We will also engage school children with hands-on learning activities.

We will disseminate the results of our research to the wide range of beneficiaries through public and academic talks, a museum exhibit, workshops and symposia, and conference papers. Key scientific results deemed important enough to be of widespread media interest will be disseminated via the University of Cambridge's Office of External Affairs and Communications.


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Description Cruise JC089 of the RSS James Cook set sail from Vigo, Spain, on 04 August 2013. The objectives were to collect geophysical data, water column samples, and sediment cores to support a proposal under consideration by the Integrated Ocean Drilling
Program (IODP 771-Full) to drill a series of sites on the SW Iberian Margin. The primary survey area was the Promonotorio dos Prinicipes de Avis (PPA), a topographic feature elevated above the Tagus Abyssal Plain.
A total of 755 line kilometres of seismic reflection profiles were acquired using a 3-km streamer and a small airgun source consisting of a generator-injector (GI) gun. Data quality was generally good with penetration of 3-4 seconds two-way travel time with excellent resolution. The resulting set of crossing lines provides the survey data needed to support the IODP proposal 771-Full. An important by-product of this survey is seismic imaging of the water column (i.e., seismic oceanography), which
was calibrated by a combination of disposable hydrographic probes and CTD casts. Multibeam bathymetry and 3.5 kHz echosounder data were collected continuously during the seismic survey.
In total, 13 CTD casts were made using a trace metal free system to characterize the physical and chemical properties of water masses on the Iberian Margin. The data are useful for interpreting the water-column seismic profiles and for groundtruthing palaeoceanographic proxies preserved in surface sediment. Water was collected at 13 stations using 10 liter Niskin bottles, totaling 246 bottles from which subsamples
were taken for isotopic and elemental analysis. Large volume in-situ filtration was carried out at 6 stations using Challenger Oceanic Stand Alone Pumps (SAPs) to capture both suspended and sinking particles in the water column. Radiocarbon and
geochemical analysis of the filtered samples will be used to determine the age, source, and transport of particles on the Iberian Margin.
Sediment cores were acquired along a bathymetric transect to meet IODP site survey requirements and to study sedimentary processes (e.g., sediment provenance and focussing), bioturbation, and calibrate geochemical and sedimentological proxies on the Iberian Margin. We recovered 10 piston cores, 12 box cores, 10 kasten cores, 4 gravity cores, 13 megacores, and 1 grab sample. The long cores span the last deglaciation and range in water depths from 600 to 4670 m, constituting as yet one of the most complete vertical transects of sediment cores from a continental margin. We will use the cores to reconstruct bathymetric transects of geochemical properties (e.g.,
oxygen isotopes, Mg/Ca, benthic d13C, radiocarbon) and infer past changes in water mass distributions from the last glacial period through the Holocene. All cores have been split and analyzed for elemental variations using a core scanning XRF. Radiocarbon chronologies for the cores are under development.
Oxygen, pH, and redox gradients in sediment pore waters were determined using micro-electrodes inserted into Megacore tubes. Interstitial waters were sampled directly from the Megacores at 1-cm intervals using Rhizon soil moisture samplers. A total of 900 pore water samples were collected and alkalinity measurements were made onboard for each sample.
Exploitation Route The data collected has been used to support a proposal to the International Ocean Discovery Program (IODP) to drill the Iberian Margin. This proposal has received favourable reviews and sits with the IODP Operational Task Force for scheduling once the ship (JOIDES Resolution) returns to the North Atlantic (anticipated in 2020).
Sectors Environment

Description The data collected on Research Cruise JC089 has been used to support an IODP drilling proposal (771-Full2). The revised proposal was submitted to IODP on October 1, 2014 and the site survey data was deposited in the site survey data bank on November 1, 2014. The proposal was favourably reviewed and now sits with the IODP Operational Task Force awaiting scheduling when the ship (JOIDES Resolution) returns to the North Atlantic (anticipated in 2020).
First Year Of Impact 2014
Sector Environment
Description Educational Video -- Cruise JC089 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A movie and article was presented demonstrating research life aboard Cruise JC089 aboard the NERC vessel James Cooke.
The reaserch was a feature of the University of Cambridge's magazine, Research Horizons, volume 24, p. 34-35.
Year(s) Of Engagement Activity 2014