Geology topics

Research about The Bahamas

Source-linked reports with geographic coverage including The Bahamas.

5 recordsLinked to original sources

USGS2022

Atlantic spotted and bottlenose dolphin sympatric distribution in nearshore waters off Bimini, The Bahamas, 2003–2018

Within nearshore waters off Bimini, The Bahamas, Atlantic spotted ( Stenella frontalis ) and common bottlenose ( Tursiops truncatus ) dolphins are sympatric but separated spatially in different geographic areas and water depth ranges. Afternoon surveys during summer months across a 16-year period showed S. frontalis used the northern part of the nearshore area more, while T. truncatus used the southern area more. Generally, examination of geographic zones and water depth distributions of both species before and after construction of a pier in the study area suggested these dolphins were not impacted, long-term, by this anthropogenic activity. Still some differences in use of the nearshore area were identified. For water depth, S. frontalis varied use between 5–<12 m and 12–<20 m, depending on location along the coast. In contrast, T. truncatus consistently used the 5–<12 m depths. This difference may be related to how each species used the nearshore area, with T. truncatus feeding more and S. frontalis travelling and doing other activities. A small change in the distribution of S. frontalis by water depth off the northern coast of Bimini was found, specifically an increased use of deeper (12–20 m) water post 2014, which is unlikely an effect of pier construction as S. frontalis continued to use the 5–12 m depths as they had before pier construction. How this change might be related to an unprecedented 2013 S. frontalis immigration event, which might have disrupted the social structure, habitat/resource use, and distribution of both species, is discussed.

Bimini↗

USGS2021

Novel microbiome dominated by Arcobacter during anoxic excurrent flow from an ocean blue hole in Andros Island, The Bahamas

Andros Island, The Bahamas, composed of porous carbonate rock, has about 175 inland blue holes and over 50 known submerged ocean caves along its eastern barrier reef. These ocean blue holes can have both vertical and horizontal zones that penetrate under the island. Tidal forces drive water flow in and out of these caves. King Kong Cavern has a vertical collapse zone and a deep penetration under Andros Island that emits sulfidic, anoxic water and masses of thin, mucoid filaments ranging to meters in length and off-white turbid water during ebb flow. Our objective was to determine the microbial composition of this mucoid material and the unconsolidated water column turbidity based on the concept that they represent unique lithoautotrophic microbial material swept from the cave into the surrounding ocean. Bacterial DNA extracted from these filaments and surrounding turbid water was characterized using PCR that targeted a portion of the 16S rRNA gene. The genus Arcobacter dominated both the filaments and the water column above the cave entrance. Arcobacter nitrofigilis and Arcobacter sp. UDC415 in the mucoid filaments accounted for as much as 80% of mapped DNA reads. In the water column Arcobacter comprised from 65% to over 85% of the reads in the depth region from about 18 m to 34 m. Bacterial species diversity was much higher in surface water and in water deeper than 36 m than in the intermediate zone. Community composition indicates that ebb flow from the cavern influences the entire water column at least to within 6 m of the surface and perhaps the near surface as well.

Andros Island, King Kong Cavern↗

USGS2019

Intense hurricane activity over the past 1500 years at South Andros Island, The Bahamas

Hurricanes cause substantial loss of life and resources in coastal areas. Unfortunately, historical hurricane records are too short and incomplete to capture hurricane-climate interactions on multi-decadal and longer timescales. Coarse-grained, hurricane-induced deposits preserved in blue holes in the Caribbean can provide records of past hurricane activity extending back thousands of years. Here we present a high resolution record of intense hurricane events over the past 1500 years from a blue hole on South Andros Island on the Great Bahama Bank. This record is corroborated by shorter reconstructions from cores collected at two nearby blue holes. The record contains coarse-grained event deposits attributable to known historical hurricane strikes within age uncertainties. Over the past 1500 years, South Andros shows evidence of four active periods of hurricane activity. None of these active intervals occurred in the past 163 years. We suggest that Intertropical Convergence Zone position modulates hurricane activity on the island based on a correlation with Cariaco Basin titanium concentrations. An anomalous gap in activity on South Andros Island in the early 13th century corresponds to a period of increased volcanism. The patterns of hurricane activity reconstructed from South Andros Island closely match those from the northeastern Gulf of Mexico but are anti-phased with records from New England. We suggest that either changes in local environmental conditions (e.g., SSTs) or a northeastward shift in storm tracks can account for the increased activity in the western North Atlantic when the Gulf of Mexico and southeastern Caribbean are less active.

South Andros Island↗

USGS2011

Observations and relocation of a West Indian Manatee ( Trichechus manatus ) off Bimini, The Bahamas

West Indian manatees ( Trichechus manatus ) are listed as vulnerable (IUCN Red List, 7 March 2009; Deutsch et al., 2008), with the subspecies Trichechus manatus latirostris and T. m. manatus (Florida and Antillean, respectively) considered endangered (IUCN Red List, 21 January 2011; Deutsch, 2008; Self-Sullivan & Mignucci-Giannoni, 2008). Manatees are not native to The Bahamas; however, sightings have been recorded periodically since 1904, with an increase in sightings documented in the 1990s (Lefebvre et al., 2001). In the area of Bimini, The Bahamas, the first recorded manatee sighting was in 1904 of a single individual that was apparently killed (Allen, 1942). The second was not until 1996, which was poorly documented. The small adult remained for approximately 6 wks before disappearing (Lefebvre et al., 2001). In 1998, a third sighting was reported off Bimini of a single individual. Although the animal was seen for several weeks and was relatively habituated to human presence (Al Sweeting, Jr., pers. comm., 28 November 2008), no data were collected on this individual nor any photographs suitable for identification purposes.

Bimini↗

USGS1985

Seismic structure and stratigraphy of northern edge of Bahaman-Cuban collision zone

Common-depth-point (CDP) seismic reflection data in the southwestern Bahamas reveal the northern edge of the tectonized zone that resulted from the late Mesozoic-early Cenozoic collision of Cuba and the Bahamas. Two seismic facies are present: a basin facies and a shallow-water carbonate-platform facies. In Santaren Channel, between Cay Sal and the Great Bahama Bank, a 5-sec thick group of coherent flat-lying reflections is inferred to represent an accumulation of deep-water basinal carbonate deposits approximately 10 km thick. At the southern end of Santaren Channel and in Nicholas Channel toward the west, the basinal carbonate section thins abruptly and overlies zones that lack coherent reflections. These structureless zones, which are attended by positive gravity anoma ies, are inferred to represent shallow-water carbonate-platform materials. Neither seismic facies has associated short wavelength magnetic anomalies. A 10-km broad anticline occurs at the south end of Santaren Channel. Platform carbonates in the core of this structure overlie Early Cretaceous and older basinal carbonate deposits and are onlapped by Late Cretaceous and Cenozoic basinal facies. The structure is inferred to be a hanging-wall anticline at the northern limit of the Cuban fold-thrust belt formed in the Late Cretaceous. In eastern Nicholas Channel, a 40-km broad, tilted block of platform carbonate material appears to have been uplifted prior to the latest Cretaceous. This feature is onlapped by Upper Cretaceous and Cenozoic deposits. A depositional-erosional carbonate-platform edge of Early Cretaceous age occurs in western Nicholas Channel at its juncture with the Straits of Florida. An Early Cretaceous platform margin at this location indicates that a deeper water embayment extended northward into the Straits of Florida, around northern Cay Sal Bank, and back into Santaren Channel during the Early Cretaceous.

American Association of Petroleum Geologists Bulle↗