Site 30

Abstract

The main goal for Site 29, that of obtaining a complete biostratigraphic sequence of pelagic foraminifera and calcareous nannofossils in the upper Carib beds (sediments above Horizon A"), was not realized due to the paucity of carbonate in the post-Eocene sediments in the deeper parts of the Venezuelan Basin. For this reason a nearby site at a higher level, which would certainly have remained above the carbonate compensation depth since the Cretaceous, was required to fulfill the biostratigraphic goals. This site lies on the Aves Ridge in an area which should correlate with the well-known stratigraphy of the nearby Barbados, Trinidad and Margarita sections. The Aves Ridge or Swell, with crestal depths about 500 fathoms, parallels the Lesser Antilles island arc and separates the Grenada Basin on the east from the Venezuelan Basin on the west. Reflection profiler records crossing the Ridge show the eastern and western flanks draped with sediments which are apparently continuous with those in the basins on both sides. On the Grenada Basin side, the sediments descending from the Ridge appear to be buried by turbidite sediments in some places. The sediments on the Ridge flanks resemble the Carib beds of the Venezuelan Basin, both in character and thickness. From geophysical measurements, the Aves llidge is believed to represent a deformation of the crust by warping under stress of sea-floor spreading, accompanied by intrusive or near-surface volcanic activity suggested by magnetics studies of the area (Edgar, 1968). Geophysical studies suggest that the Aves Ridge appears to show a common positive gravity axis with the Dutch West Indies and may have been elevated in early Tertiary time (Ewing, Talwani and Ewing, 1965). Dredging results from depths of 1000 to 2000 meters from the western slopes of the Aves Ridge (Fox et ah, 1970)

Genetic Relations Between the Aves Ridge and the Grenada Back‐Arc Basin, East Caribbean Sea

“…6 of 29 Correlation of GARANTI seismic data with offshore well data (Bader et al, 1970b;Edgar et al, 1973;Ysaccis, 1997) and onshore geological observations (Speed et al, 1993). Well-seismic ties are illustrated in more detail in supporting information ( Figures S1-S4).…”

“…IODP drillings (1,397-1,401) west of Martinique ( Figure 2) penetrated Plio-Quaternary sediments only (Le Friant et al, 2013). However, offshore drill hole data (Bader et al, 1970b;Edgar et al, 1973;Ysaccis, 1997) and onshore geological observations (Speed et al, 1993) in surrounding areas provide distant stratigraphic constraints on deeper units (Figure 3). We tied seismic horizons to known chronostratigraphic surfaces in drill holes, and then extended them line-to-line throughout the basin.…”

“…Correlations with wells give ages ranging from late Miocene to recent for U3 ( Figure 3). On the Aves Ridge, DSDP drilling results indicate a predominantly hemipelagic calcareous sedimentation with a slight volcaniclastic contribution (Bader et al, 1970b;Edgar et al, 1973). In the Grenada Basin, IODP drillings west of Martinique penetrated landslide deposits, composed of hemipelagic sediments interbedded with volcaniclastics from the Lesser Antilles Arc (Le Friant et al, 2013).…”

“…As none of our seismic lines covers these sites, we projected the drill holes to the nearest GARANTI lines (GA26 A and GA28 A in Figure 2). Located in a small basin between two ridges, DSDP 30 penetrated 430 m of Miocene to Recent calcareous oozes (Bader et al, 1970b). Located atop a ridge, DSDP 148 penetrated 250 m of Plio-Quaternary calcareous oozes lying unconformably upon volcanic sands and clays, which bear reworked fossils of Miocene, Paleocene, and Late Cretaceous ages (Edgar et al, 1973).…”