Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: The rough boundaries of the shelf marine santuaries.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Detected by NOAA’s RV Okeanos Explorer during cruises in 2011 and 2012, this class represents plumes of gas found in the water column, originating from seafloor seeps, as detected by EK60 single beam sonar. Due to the relatively similar acoustic properties of oil and water, this sonar are unable to discern if oil seepage is associated with any of these gas plume sites. The EK60 swath width of detection is around 20-60 feet depending on water depth. Many of these plumes helped confirm BOEM seep-related anomaly polygons.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Natural gas plumes in the water column as detected by the RV Okeanos Explorer's EM302 multibeam sonar in 2011, 2012, and 2014. 400 foot diameter circles to indicate the uncertainty of the exact seep location on the seafloor, which varies with water depth. You will note many of the circles are clumped nearby each other. Due to the nature of overlapping swath data acquisition, some of those clumps may actually represent a single seep from the same spot on the seafloor; some are near the center of the swath (most accurate) and some well away from the center of the swath (less accurate). This is why there is a 400 foot diameter of uncertainty.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Erosional, deep sea channels associated with turbidite fans (basin floor fans and basin fill fans), as well as major and minor shelf-slope-break bypass downcutting from recent lowstands. Easily distinguished by their long, narrow, often sinuous character on amplitude and bathymetry displays.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Directly following the northern Florida Escarpment are long, linear high-positive amplitude anomalies extend along the face of the escarpment and, from several dives with manned submersibles and ROVs, have been found to be outcrops of Cretaceous-aged, well-indurated carbonate stratum. Each dive has proven these locations act as prime substrate for coral communities. Seismic data and paleontological data from well control on the Florida Platform establish the Cretaceous age of these rocks. The polygons in the anomaly_Cretaceous shapefiles are those mapped on 3-D seismic data; though there are 2-D data sets to the south along the escarpment, they are not amplitude balanced and were not used to add polygons to this shapefile data set.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Areas along the lower Florida Escarpment with high-positive amplitude response concentrated in valleys between discrete ridges which appear to be slump deposits of carbonates, likely of Cretaceous age. Since the Cretaceous carbonates along the steep slopes of the Escarpment have been shown to be good substrates for coral communities, it is likely that these talus deposits would support coral communities as well. Though chemosynthetic organisms have been seen at the base of the Escarpment by ROV and submersible dives, none of the talus deposits have been visited to our knowledge and the Okeanos Explorer’s multibeam did not detect any active water column gas plumes in the mapped area.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Small circular positive anomalies in 100 to 350 feet of water that are common in the region of the lower shelf near or next to the coral bio-banks of the northern Gulf of Mexico (East and West Flower Garden Banks, Rankin and Bright Banks, Stetson Bank, etc.). These are new anomaly types recognized through detailed analysis of shelf edge mapping done to extend BOEM’s bathymetry map onto to the shelf where data quality allows. They appear similar to mud volcanoes in size and shape, but are acoustically hard and do not show any indication of subsurface migration to the features.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Small circular positive anomalies in 100 to 350 feet of water that are common in the region of the lower shelf near or next to the coral bio-banks of the northern Gulf of Mexico (East and West Flower Garden Banks, Rankin and Bright Banks, Stetson Bank, etc.). The "confirmed patch reefs" have been visited by USGS ROVs and found to be hard substrate populated by mesophotic organisms. The "patch reefs" have the same acoustic properties, water depths, and relative size as the "confirmed" anomalies, but have not been visited.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Sand-rich turbidite fans which have intermittently dominated sedimentation in portions of the deep water Gulf of Mexico for millions of years and are the source of many of the subsurface sand reservoirs throughout the basin. There are a few large, discrete recent channel/fan complexes on the seafloor (especially in Alaminos Canyon) that have high-positive acoustic response on seismic data and are easily recognized on amplitude maps. These recent examples are good analogues of reservoir geometries for subsurface exploration/development activities.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Areas in the Gulf of Mexico where salt outcrops on the seafloor. It has a very similar high-positive amplitude response as hardground seep anomalies, but from vertical seismic profiles it’s clear that salt is outcropping and these are not seep related anomalies. These have been outlined with a unique class of polygon to distinguish them from authigenic seep carbonates. Two of these have been visited by the Alvin manned submersible and confirmed to be salt outcrops.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Located at the base of over-steepened slopes caused by shallow vertical and horizontal salt movement; surface sediments become unstable and flow downslope to rest on low-slope seafloor in front of the steep slopes.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive amplitude anomalies interpreted to be flows of sediment out of high flux vent sites on steep slopes. They either 1) contained hydrocarbons and were subsequently partially lithified, 2) attracted chemosynthetic clams which consumed what hydrocarbon was available (and since they were not located at the active seep site, subsequently died), or 3) are made up of acoustically faster sediment (i.e., sand). The flows that have been visited by submersibles are often a combination of two or more of the above.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Oval depressions interpreted to be created by the removal of sediment through rapid, and possibly, explosive gas expulsion. Few pockmarks have visible active migration pathways on vertical seismic profiles, but most appear to be dormant and without discernible active migration. Rapid expulsion is interpreted to be exclusively gas and appear to be purely destructive due to the removal of sediment. No sediment, brine, or oil expulsion has been observed during direct observations. Due to a lack of hard substrate and absence of continuing seepage at most pockmarks, chemosynthetic organisms and corals are unlikely to be associated with them. The pockmarks on the Florida Shelf are actually sinkholes created by underlying karsted formations.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive amplitude anomalies which have not yet been confirmed as seep-site hardgrounds – they are purely seismic interpretations. Due to the coarse vertical resolution of 3-D seismic (~30 feet), some of the high-positive anomalies visited by ROVs or submersibles have not had exposed authigenic carbonates at the seafloor due to soft sediment cover. There may be 28 feet of authigenic carbonate buried by 2 feet of hemipelagic mud, but the 3-D seismic amplitude will still show a strong high-positive anomaly.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive anomalies located directly below sea surface oil slicks, or within one water depth’s distance. Though not directly observed to be seeping oil, we are calling these possible oil seeps due to their proximity to the slicks. They are likely to have chemosynthetic and coral communities living on the carbonate hardgrounds.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive anomalies which have had direct observations of oil seepage from the seafloor, and all have had chemosynthetic and coral communities living on the carbonate hardgrounds.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive anomalies which have had direct observations of gas bubbling from the seafloor, and all have had chemosynthetic and coral communities living on the carbonate hardgrounds.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: An anomalously low-positive amplitude response on seismic compared to the typical hemipelagic muds. The most active and dynamic of this type exhibit a negative amplitude response, or acoustic trough, at the seafloor, resulting from a total phase reversal of the seafloor’s typical positive acoustic impedance. These areas have been observed to have rapid hydrocarbon flux, often with sediment and brine being expulsed with the hydrocarbons.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Low-positive/negative anomalies that are either directly below sea-surface oil slicks or are within 1 water depth’s distance, and therefore could be the source of the slick, but not yet confirmed to be.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Low-positive/negative anomalies that have been visually confirmed, through submersible or ROV, to be seeping oil.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Seeps observed to be expelling gas bubbles.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Cones of sediment typically on low slopes that are built at high flux sites that do not exhibit high positive amplitude response. The rate of flux at the expulsion sites is too rapid for bacterial consumption of the hydrocarbons to convert them to authigenic carbonate hardgrounds, thus sessile chemosynthetic organisms and corals are usually not found on these features. These are unconfirmed by direct observation.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Cones of sediment typically on low slopes that are built at high flux sites that do not exhibit high positive amplitude response. The rate of flux at the expulsion sites is too rapid for bacterial consumption of the hydrocarbons to convert them to authigenic carbonate hardgrounds, thus sessile chemosynthetic organisms and corals are usually not found on these features. These are confirmed by direct observation.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Mud volcanoes which have been observed seeping oil.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Mud volcanoes which have been observed seeping gas bubbles.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive amplitude anomalies that have been confirmed to be authigenic carbonates predominantly colonized by hard and/or soft corals, but have had chemosynthetic communities to a minor extent. These polygons also cover the rough boundaries of the shelf marine sanctuaries "Biobanks".
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive amplitude anomalies that have been confirmed to be hardgrounds with predominantly chemosynthetic communities, though most have corals to a minor extent. Confirmed via manned submersibles, ROVs, AUVs, camera sleds, trawls, and piston cores either by academia, government, or industry sponsored cruises.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: High-positive amplitude anomalies that have been confirmed to have significant seafloor natural gas hydrate exposures, but have always had active chemosynthetic communities near or adjacent to the hydrates.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Former seep_anomaly_positives polygons. High-positive amplitude anomalies which have been surveyed with side-scan sonar and/or hi-res multibeam, and exhibit significant acoustic backscatter response at the seafloor, indicating clean carbonate hardgrounds with the potential to be suitable substrates for benthic communities. However, no direct visual observation of active communities has yet been performed.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Former seep_anomaly_positives polygons that the 3-D seismic vertical profiles show clear subsurface migration pathways to the seafloor, but subsequent visual investigations by manned submersible, ROV, or AUV (by government, academia, and/or industry) indicate that there are no exposed carbonates at the site, and/or remote sensing by multibeam or sidescan show no elevated acoustic backscatter, suggesting the presence of buried authigenic carbonates. Though clear seafloor indications of seepage such as bacterial mats (e.g., Beggiatoa) and/or brine seeps may be present, no suitable substrates for megafauna such as corals or chemosynthetic organisms (e.g., tubeworms, mussels, etc) such as hardgrounds are present. If shown to be buried by any of these methods above, the anomalies in question will be removed from the list of potential hard substrates suitable for benthic organisms and the 2000’ buffer to protect any communities are removed.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Circular depressions on the seafloor of the Florida Platform, similar to pockmarks, but with deep surface roots (600 to 800ms), or possible vertical collapse or migration pathways leading up to them.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.
Description: Extensive fields of bottom current-scoured trenches on the floor of the ultradeep Gulf of Mexico at and in front of the Sigsbee Escarpment. BOEM has mapped the furrows as polygons around discrete packages of the linear depressions using 3-D seismic. Further resolution of the features is restricted by the vertical and horizontal limits of the 3-D seismic used. Furrows were found to be as deep as 10 meters and as wide as 30 meters, with currents from 20 to 60 m/sec scouring the seafloor.
Copyright Text: William Shedd (william.shedd@boem.gov), Jon Burrell (jon.burrell@boem.gov), Pierre Abadie (pierre.abadie@boem.gov) & Kody Kramer, Bureau of Ocean Energy Management, Office of Resource Evaluation, New Orleans, LA. & NOAA.