Here you can see a close up view of one of the “tar lily” “pedals.” The first asphalt extrusion had a number of corals and anemones colonizing it. These organisms allowed our science team to give these features an approximate age on the order of tens to hundreds of years old. Image courtesy of NOAA Okeanos Explorer Program, Gulf of Mexico 2014 Expedition. Download larger version (jpg, 2.1 MB).
Okeanos Explorer EX1402L3
Dive 12: April 24, 2014: Tar Lilies. Video courtesy of NOAA Office of Ocean Exploration and Research. Download (mp4, 357.7 MB)
The primary objective of Dive 12 was to investigate an approximately 60 meter-long sidescan acoustic target, which was suspected to be a shipwreck. The dive was conducted in water depths of 1,925-1,930 meters. The site was approached from the southwest, across a flat, sedimented seafloor characterized by scattered black areas suggestive of bacterial mats and a number of unbranched bamboo corals and holothurians. Sea pens, shrimp, and polychaetes were also present in this area. A wooden log was found, heavily infested with squat lobsters. Within minutes of observing the first part of the suspected shipwreck, it became clear that the feature was not man-made, but a natural phenomenon that was nicknamed a “tar lily.” Discussion between the shore and the ship zeroed-in on the likeliest explanation – that this feature was a flower-like extrusion of asphalt at the seafloor – the first of its kind documented in this area of the Gulf of Mexico. Each “petal” of the tar extrusion or “flower” was curved and had internal layering, a result of de-volatilization of the asphalt rising from the sub-seafloor upon its contact with seawater. The first “tar lily” was colonized by fly trap anemones, unidentified sponges, goose neck barnacles, octocorals, sea pens, squat lobsters, and bamboo corals. There were also a few chemosynthetic fauna, including tube worms, bacterial mats, and Alvinocaris shrimp. At the second “tar lily,” there were more chemosynthetic worms, a spiral coral, a few octocorals, and several branching bamboo corals. On both structures, there was evidence for the presence of hydrate from seafloor staining near the base of asphalt extrusions. However, no bubbles of either gas or oil were observed escaping from either structure.