Programmatic context
The AMARYLLIS-AMAGAS cruise resulted from merging two complementary, international and multidisciplinary scientific research projects, namely AMARYLLIS (“From Amazon deep-sea sediments to natural climate variability and slope instability processes”) and AMAGAS (“Degassing of the Amazon deep-sea fan: depth distribution and activity of seafloor fluid vents”).
These two projects rely on the close collaboration of dozens of scientists working in universities and public research institutes in France (9 research institutes), Brazil (7 universities), Germany (2 universities) and Sweden (1 university).
The cruise took place in two legs on board the French Research Vessel (R/V) Marion Dufresne for a total duration of 49 days, 27 days for leg 1 and 22 days for leg 2. It started in Bridgetown (Barbados) on 16 May 2023, called at Paramaribo (Suriname) on June 11-12 2023 for the change of legs, and ended in Recife (Brazil) on 3 July 2023.
Legs 1 and 2 of the AMARYLLIS-AMAGAS cruise are also called AMARYLLISAMAGAS I and AMARYLLIS-AMAGAS II. Either term is used in this cruise report.

Scientific objectives
The AMARYLLIS-AMAGAS cruise aims to better establish the major but uncertain role played by the Amazon region in the Earth's global climate system. Its role as a terrestrial carbon sink depends on processes that are still poorly constrained: the intensity and distribution of continental precipitation, the fertilization of soils by Saharan dust and the potential instability of gas hydrates formed in the accumulation zone of sediments transported by the Amazon River (hereafter referred to as the "Amazon cone").
Given these uncertainties, the cruise has 4 main scientific objectives:
(1) to reconstruct the past climatic history of the Amazon and northeastern Brazil, in terms of regional variability and mechanisms controlling precipitation and vegetation, on various time scales of over the last million years (ranging from anthropogenic to millennial and orbital);
(2) to assess the contribution of Saharan dust deposited in this region in the presentday and over the last million years, in particular its role as a fertilizer for the Amazon rainforest;
(3) to examine the relationship between gas hydrates and large-scale submarine landslides in the upper Amazon cone, by assessing fluid circulation and the physical properties of the sediments;
(4) to assess the extent of gas outflows into the ocean at the scale of the Amazon cone as a whole.