Colombian Basin Research Articles

Pliocene closing of the Isthmus of Panama, based on biostratigraphic evidence from nearby Pacific Ocean and Caribbean Sea cores

Pliocene and Pleistocene planktonic foraminiferal biogeography and paleoceanography have been examined in Deep Sea Drilling Project (DSDP) sites of the Panama Basin (Pacific Ocean) and Colombian and Venezuelan Basins (Atlantic Ocean) to determine the timing of the isolation of Atlantic and Pacific tropical planktonic faunas resulting from the development of the Central American isthmus. Previous studies have suggested a late Miocene to middle Pliocene occurrence of this event. The Panama Basin (DSDP site 157) and the Colombian Basin (DSDP site 154A) share two early Pliocene biogeographic events: (1) great abundance of sinistral coiling Neogloboquadrina pachyderma at 4.3 m.y. ago at site 157 and 0.7 m.y. later at site 154A, and (2) a sinistral-to-dextral change in the coiling-direction preference in Pulleniatina 3.5 m.y. ago at both locations. Identification of these events farther to the east in the Venezuelan Basin (DSDP site 148) is complicated by insufficient lower Pliocene core recovery, but abundant sinistral N. pachydcrma appear to have extended far to the east in the Caribbean 3.6 m.y. ago; perhaps the early Pliocene abundance of this form is not indicative of cool water. The coiling-direction history and stratigraphic ranges of Pulleniatina became different in the Atlantic and Pacific Oceans during the early Pliocene; this is inferred to result from geographic isolation of the assemblages. Saito (1976) used the temporary disappearance of this genus from Atlantic waters at 3.5 m.y. ago to mark the closure of the Isthmus of Panama, but I show that in the Colombian Basin (site 154A) its disappearance was closer to 3.1 m.y. ago. This suggests the possibility of surface-water communication between the Atlantic and Pacific until that time.

Upper Quaternary sediments of the Colombia Basin: Spatial and stratigraphic variation

The spatial and stratigraphic variations of upper Holocene and upper Quaternary sediments in the Colombia Basin reflect the terrigenous influx from South America and Panama. Calcium carbonate, composed of foraminifers and coccoliths, accumulates uniformly across the basin and is modified by terrigenous dilution and carbonate dissolution which reflect bathymetry. Glacial sediments of the Colombia Basin are lower in carbonate, have higher total accumulation rates, and thicken toward the continental margin in comparison to interglacial sediments. Carbonate accumulation is relatively constant between glacial and interglacial intervals, whereas clay accumulation greatly increases. The primary cause of carbonate variation in Colombia Basin sediments is the terrigenous influx due to rapid erosion of shelf and upper slope sediments during eustatic lowering of sea level. This relationship should be true for most marginal basins and much of the Atlantic Ocean. This mechanism for variation of sediment composition implies that the carbonate record reflects not only climatic and ice-margin fluctuations but also changing erosional and depositional environments.

A radial pattern of sea-floor deformation in the southwestern Caribbean Sea

Research Article| June 01, 1978 A radial pattern of sea-floor deformation in the southwestern Caribbean Sea Eric Christofferson; Eric Christofferson 1Department of Geological Sciences, Rutgers—The State University, New Brunswick, New Jersey 08903 Search for other works by this author on: GSW Google Scholar Martha M. Hamil Martha M. Hamil 1Department of Geological Sciences, Rutgers—The State University, New Brunswick, New Jersey 08903 Search for other works by this author on: GSW Google Scholar Author and Article Information Eric Christofferson 1Department of Geological Sciences, Rutgers—The State University, New Brunswick, New Jersey 08903 Martha M. Hamil 1Department of Geological Sciences, Rutgers—The State University, New Brunswick, New Jersey 08903 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1978) 6 (6): 341–344. https://doi.org/10.1130/0091-7613(1978)6<341:ARPOSD>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Eric Christofferson, Martha M. Hamil; A radial pattern of sea-floor deformation in the southwestern Caribbean Sea. Geology 1978;; 6 (6): 341–344. doi: https://doi.org/10.1130/0091-7613(1978)6<341:ARPOSD>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Discontinuous bathymetric lineaments and faults are disposed radially and concentrically about a cluster of seamounts in the southwestern Caribbean Sea. The lineament system extends at least 350 km from the least-squares center of strike intersections and includes more than 350,000 km2 of sea floor on the Nicaraguan Rise and in the Colombian Basin. This center, the probable deformation center, lies near San Andres Island at lat 12.6°N, long 81.6°W. The central position of the seamount cluster suggests that volcanism accompanied the deformation. The age and duration of the event are unknown. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Structure of Colombia Basin, Caribbean Sea, from profiler-sonobuoy measurements

Seismic velocities and layer depths were computed from 26 air gun/sonobuoy profiles made along a southwesterly traverse of the Colombia basin. Penetration to the deeper crustal layers and the upper mantle was achieved with a large air gun sound source. The crustal structure of the Colombia basin is a complex arrangement of basement ridges and interposed basins that is masked by an overburden of thick, flat-lying sediments. Earlier two-ship refraction stations were inadvertently located on the basement ridges, which had led to the mistaken conclusion that the basin contains unusually thick crust. Mantle refractions from two sonobuoy profiles in the undisturbed parts of the basin suggest a normal oceanic crust that has been depressed by the addition of about 3 km of sediment. The reflection records from the Colombia basin show that the basement rocks have considerable relief, unlike the smooth B″ (acoustic basement) surface in the Venezuela basin. Furthermore, there is no consistent reflector in the sediments that can be correlated with horizon A″ in the Venezuela basin. Sound velocity in the sediments increases at a normal rate south of about 14°N, but to the north where there is no intermediate (horizon A″ type) reflector, the rate of increase is unusually high, owing to a thinner overburden on a high-speed sediment layer. Accordingly, the horizon A″ and B″ usage is not followed in the present work in the Colombia basin.

Winnowing of Recent and Late Quaternary Deep-Sea Sediments: Colombia Basin, Caribbean Sea

ABSTRACT Sediments of the Colombia Basin, Caribbean Sea, contain evidence of current winnowing. Although bottom photographs reveal a relatively tranquil bottom over most of the basin, current smoothing of the seafloor is observed on and adjacent to the Hess and Beata Escarpments. Current scour is observed at one location on the Hess Escarpment. The proportion of foraminiferal, coccolith, and clay components in 52 surface sediment samples suggests that fine particles (including coccolith carbonate) are being sorted and removed. The foraminifera to total CaCO3 ratio (F/C) is highest on and adjacent to the major escarpments and reflects the increased foraminiferal content relative to total CaCO3 caused by partial removal of the fine fraction coccolith carbonate. The increased currents associated with the escarpments are caused by streamlining and acceleration of water masses as they pass around the obstructions. The lack of erosional bed forms as revealed by bottom photographs and absence of fractionation towards larger foraminifera shows that only fine particles are being sorted and removed. The erosion a sociated with current smoothing of the bottom is probably responsible for the observed winnowing. Sediment cores from winnowed areas (F/C > .60) have irregular carbonate curves, more small-scale CaCO3 variation, hiatuses, and mixed faunas when compared to cores from unwinnowed areas (F/C < .50). Thus, areas near escarpments which are being winnowed today have been winnowed throughout the past 150,000 years. Therefore, the geographic extent and intensity of winnowing must be known to interpret properly sediment cores in these areas.

Colombian Basin magnetism and Caribbean plate tectonics

A shipboard magnetic survey of the central Caribbean Sea has detected certain Late Cretaceous magnetic anomalies predicted in the northern Colombian Basin by a sea-floor spreading model of the region. The locations, trends, widths, lengths, shapes, polarities, and amplitudes of index anomalies 33 and 34 were specified by models derived earlier. All of these dimensions have been observed except one, the width of reversed anomaly 34, which may point to a change in spreading rate or to a possible error in the magnetic reversal scheme used. The extended sea-floor spreading model is generally consistent with drilling results from the Caribbean Sea, but it could be specifically confirmed — or rejected — by drilling to basement in the Colombian Basin.

Seismic profile tying Caribbean DSDP Sites 153, 151, and 152

In April and May 1971, the R/V Alaminos (cruise 71-A-4, leg 5) recorded a 710-km-long seismic profile in the central Caribbean Sea. This southeast-northwest profile began on the lower Colombian-Venezuelan continental margin, crossed the Aruba Gap, Beata Ridge, and Colombian Basin, and ended on the southern flank of the Nicaraguan Rise. Our principal purpose was to tie three significant Deep Sea Drilling Project (DSDP) sites on one continuous profile. Within the accuracy of our satellite navigation, we tied Sites 153, 151, and 152, respectively, on the north edge of the Aruba Gap, crest of the Beata Ridge, and lower southern flank of the Nicaraguan Rise. Two seismic reflectors, designated Horizons A″ and B″, have been identified and traced through much of the southern Caribbean Sea. The former is a lower Paleogene siliceous or cherty chalk or limestone; the latter is basalt or a coarser grained mafic equivalent, overlain directly by Upper Cretaceous sedimentary rocks. Overlying Horizon A″ is an upper Paleogene and Neogene unit of acoustically transparent and pelagic fossiliferous chalk, ooze, and marl. The pelagic section between the reflectors is similar but more indurated and siliceous than the unit above. Horizon A″ is somewhat more restricted in area than Horizon B″. Along this profile it is absent from the crest and steep flanks of the Beata Ridge and from local promontories on the lower flanks of the Beata Ridge and Nicaraguan Rise, and it is masked through the central Colombian Basin by a prominent set of reflectors. DSDP results at Site 152, where Horizon A″ is absent, indicate uplift of the ridge and erosion prior to deposition of the upper pelagic unit. Excellent correlation between this profile and the DSDP results permits reconstruction and interpretation of the complete stratigraphic history along this section. We believe that with the stratigraphic data available and with the gift of hindsight, scientists can now program seismic lines that will be extremely useful in illustrating stratigraphic patterns and solving problems. Tying a series of selected DSDP sites into a continuous profile or a network of lines will permit the study of regional and three-dimensional stratigraphic patterns, sedimentational processes, and tectonics. This is another method of further utilizing these drilling results.

Deep-sea dune-like features

Three different types of dune-like features in depths between 2,500 and 4,000 m were observed on what is supposed to be the outer Magdalena Fan, Colombian Basin. Each feature has its own characteristic height and length pattern as well as its location with regard to the local slope of the sea bottom. They have in common, however, that internal reflectors all dip in a westerly direction. Reflectivity changes on 3.5-kHz records may indicate the presence of textural variations. Since the area is generally considered to be void of any continuous, deep currents, it is suggested that these large bodies are fan lobes emplaced by high-viscosity turbidity currents or debris flows. Temporal, locally induced currents, moving at least partly in easterly direction, may have caused a winnowing effect resulting in textural variations.

Quartz Microtextures as Indicators of Subaqueous Density Flow: ABSTRACT

Quartz samples from density flow deposits from the Colombia basin (Caribbean Sea) were analyzed for surficial microtextural associations using the scanning electron microscope. Microtextural abrasion patterns were found to vary in the A division of turbidites, grain-flow deposits, debris-flow deposits, and in material resulting from washover on the Magdalena deep-sea fan. The observed microtextural patterns are useful criteria for the identification of the transport mechanisms of other deposits assumed to have resulted from density flows. Relative distances of travel of contemporaneous turbidites could be ascertained from impact densities on A division sand grains. The limiting conditions on such analyses are a minimum of postdepositional alteration of the mechanical textures of the grains and a lack of intense abrasion features received during episodes of predensity-flow transport. End_of_Article - Last_Page 2206------------

Linear Magnetic Anomalies in the Colombia Basin, Central Caribbean Sea

The inference of a volcanic sea-floor–spreading genesis for the lithospheric slab beneath the Caribbean Sea is supported by the discovery and mapping of large easterly trending lineations of crustal magnetism within the Colombia basin. Furthermore, critical examination of available descriptive data and theoretical calculations strongly imply that the Colombia basin linear magnetic anomalies are not associated with sediment-buried topography of the Colombia basin igneous crust. The direction of decreasing crustal ages within the Colombia basin can be utilized as a first-order test of plate-tectonic genetic syntheses of the Caribbean Sea floor. The easterly trending anomalies of crustal magnetism and the smooth floor of the basin imply that the parent spreading center lay either to the north or to the south of the present physiographic boundaries of the basin. The direction of decreasing crustal ages within the Colombia basin cannot be conclusively deduced from available data. The igneous crust beneath the basin floor has not yet been directly sampled. However, a correlation of the Colombia basin crustal magnetic anomalies with Late Cretaceous index anomalies 27 to 33 can be made if the assumption of a nearly constant rate of crustal genesis is valid. This crustal magnetism age correlation implies that the parent spreading center lay to the south of the basin. The correlation is inconsistent with a simple Pacific-emplacement theory and suggests that the Isthmus of Panama did not evolve upon the Colombia basin lithospheric slab. Direct crustal sampling in the Colombia basin by the next Deep Sea Drilling Project expedition to the Caribbean Sea (projected date, July 1975) is suggested as a meaningful test of the basin's sea-floor spreading genesis. If crustal ages can be established through drilling to the igneous basement, then the mapped distribution of linear magnetic anomalies could be sufficient to firmly establish the age gradient of the lithospheric slab beneath the central Caribbean Sea.

Sea Floor off Magdalena Delta and Santa Marta Area, Colombia

The slope bordering the Magdalena delta and the adjacent outlier of the Andes has a complex morphology. This includes typical delta-front slope valleys directly off the Magdalena River and off its old mouths, bordered to the west by anticlinal hills and synclinal valleys, and to the north by fault blocks with a northeasterly trend. To the east, the slope has a concentration of mud diapirs rising mostly from between 400 and 750 fm (730 and 1,370 m). Farther east, a partly filled synclinal valley extends seaward from the Golfo de Santa Marta. Off the mountainous coast east of Santa Marta, a large submarine canyon winds down the slope almost to Colombia Basin. This canyon cuts through a large fault scarp, which forms part of the southeast margin of the basin. The sea-floor relief has been formed by a combination of complex faulting and folding, prograding sediment from the Magdalena with attendant formation of slump valleys, partial filling of structural valleys with the sediment, diapiric intrusion of plastic mud from underlying formations, and marine erosion producing a large submarine canyon. The source of the sediment that has excavated the canyon is unknown but presumably is supplied by streams entering the sea from a north outlier of the Andes.

Heat flow in the Caribbean and Gulf of Mexico

Eighty-seven new heat-flow values have been obtained in the Caribbean Sea and the Gulf of Mexico. Values in the Caribbean are, in general, uniform; only 5 of the 59 existing values lie outside the range 1–2 μcal cm−2 sec−1. Above-average heat flow is found in the area of the Cayman trough and the Yucatan basin. The excess flux may represent energy released during shear at the boundary between the Caribbean and Atlantic crustal plates. Resolution of the heat-flow pattern in the area of the Antilles Island arc is inhibited by too few values, some of which are of low reliability; below-average heat flow is found east of the arc and above-average heat flow west of it. The average heat flow in the Venezuelan basin is nearly the same as the average of all ocean basins. In the Colombia basin, heat-flow values trend from below average in the east to above average in the west. Through most of the Gulf of Mexico, the heat flow is uniformly low. A decrease of temperature gradient with depth in the sediment is characteristic of most of the Gulf measurements, and is not completely accounted for by known processes. The area of knolls, which includes the Sigsbee knolls, has uniformly high heat flow, 2.1 μcal cm−2 sec−1, which supports the hypothesis that the area is underlain by salt structures.

Diapiric Intrusions in Foreset Slope Sediments Off Magdalena Delta, Colombia

The Magdalena River of Colombia is prograding its delta rapidly onto the slope that leads north into Colombian basin of the Caribbean. Results of this encroachment are intermittent slope failures that break the jetties at the river mouth and sever the cables on the sea floor outside. Another possible result of the delta encroachment was indicated from the work of a Scripps Institution expedition which led to the discovery of steep-sided domes rising as much as 200 m above the sea floor in water depths of 900-1,200 m. Subbottom profiling showed that these domes, about 1 km wide, have intrusive relations to the foreset beds and can be traced down to at least 700 m below the bottom. The profiles indicate that the domes generally are flanked with ring depressions, which are u derlain by downbent strata, in contrast to the usual upbending of strata flanking salt domes. One explanation for these diapirs is that they are giant mudlumps somewhat akin to those off the passes of the Mississippi. Alternatively, they may be mud volcanoes such as are found on the adjacent lands.

Radium and radiocarbon in Caribbean waters

The measurements of vertical and areal distribution of radiocarbon, radium-226, and oxygen indicate that the deep water (>1500 m) of the Colombian and Venezuelan basins are not presently renewed. The renewal time of deep water in these basins is estimated between 50 and 400 years. The radium content is found to be rather uniform in the Venezuelan basin, 5.8 × 10−14 g/l; it varied between 4–6 × 10−14 g/l in the Colombian basin. In the Puerto Rico Trench the radium content was found to increase with depth from 3.4 × 10−14 g/l at the surface to 8.0 × 10−14 g/l at 7400 m depth.

Geophysical measurements in the western Caribbean Sea and in the Gulf of Mexico

The data from 48 seismic refraction profiles in the western Caribbean Sea and in the Gulf of Mexico are presented in the form of structure sections crossing the Colombian basin, Nicaraguan rise, Cayman trough, Cayman ridge, Beata ridge, Yucatan basin, Campeche bank, and Sigsbee deep. The Cayman trough has a remarkably thin crust, which suggests that it is a tensional feature. Although parts of the basins have a relatively thin crust, similar to the oceanic type, the shallower areas are intermediate or almost continental in structure. In the Gulf of Mexico the main basin is similar to typical ocean basins in structure except that the high-velocity crust is overlain by very thick sediments. The depth to the mantle is appreciably greater in the Gulf than in an ocean basin. This may be partly the result of loading by the sediments, but large scale tectonic activity is a more likely cause. The Sigsbee escarpment, the northern boundary of the main basin, appears to be the surface expression of a fault or sharp flexure in the layers beneath the unconsolidated sediments.