Barker, Peter F (1983): (Table 1) Lithology of DSDP Hole 72-516F sediments [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.813390, Supplement to: Barker, PF (1983): Tectonic evolution and subsidence history of the Rio Grande Rise. In: Barker, PF; Carlson, RL; Johnson, DA; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 72, 953-976, https://doi.org/10.2973/dsdp.proc.72.151.1983
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Abstract:
Drilling at Site 516 on the northern shoulder of the main Rio Grande Rise has improved our understanding of the tectonic evolution and subsidence history of the Rise and of the entire Rio Grande-Walvis seamount and aseismic ridge system. Evidence from this site indicates that basalts at the bottom of Hole 516F were produced at the ridge crest and that the ridge crest was subaerial. I attribute the anomalous elevation of the Rise to an eastward ridge crest jump to the western end of the Rise, 91 Ma, and, recognizing a southward progression of such eastward jumps, I suggest a model for the Rio Grande-Walvis system involving a slow westward component of drift of the ridge crest off a hot-spot swell. This drift caused off-axis volcanism that in the Cretaceous succeeded but in the Cenozoic failed to capture the ridge crest. The probable mechanism of capture involved counteraction of the ridge push force within the lithosphere by a swell push force. This would make capture more likely in lithosphere produced by fast spreading, perhaps explaining the change of mode at the end of the Cretaceous.
Within the pelagic carbonate sedimentary succession at Site 516, the partly volcaniclastic, turbiditic middle Eocene Unit 4 contains volcanic ash beds (yielding a 47.4 ± 0.7 Ma K-Ar age from fresh alkalic biotite) and a 15-m-thick basal slide. Reflection profiles show it was produced by sliding from and by subaerial erosion of a large tilted and uplifted guyot upslope from the site. Data from the site suggest that a single short off-axis event affected the entire crestal region of the Rise. Perhaps the same midplate hot spot that produced an 80-50 Ma volcanic episode in the Serra Geral of Brazil was responsible, but that was not the present Tristan hot spot.
The data from Site 516 have been incorporated into a detailed model for the subsidence history of the main body of the Rise. The model uses an "oceanic" thermal isostatic model, but accounts for the effect of subaerial subsidence and incorporates the changes of the middle Eocene event. A detailed sediment compaction model is developed, and a smooth eustatic sea level correction is applied. The effects of "basement compaction" and use of local rather than regional isostatic compensation are assessed each at about 50 m. The computed paleodepth at Site 516 ranges from sea level 84.0 Ma through a Paleocene 1250 m maximum and middle Eocene 600 m minimum to 1313 m today. The "tectonic" depth curves for both Sites 516 and 357 are compared with paleoecologic depth estimates. In general, these paleoecologic estimates lie deeper, probably because of the difficulties of applying accurate subsidence and compaction corrections to the comparison sites.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Latitude: -30.276500 * Longitude: -35.285000
Date/Time Start: 1980-03-11T00:00:00 * Date/Time End: 1980-03-11T00:00:00
Minimum DEPTH, sediment/rock: 96.5 m * Maximum DEPTH, sediment/rock: 1261.0 m
Event(s):
72-516F * Latitude: -30.276500 * Longitude: -35.285000 * Date/Time: 1980-03-11T00:00:00 * Elevation: -1313.0 m * Penetration: 1270.6 m * Recovery: 690.1 m * Location: South Atlantic/CONT RISE * Campaign: Leg72 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 127 cores; 1092.5 m cored; 9 m drilled; 63.2 % recovery
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Lithologic unit/sequence | Unit | Barker, Peter F | |||
| 2 | Depth, top/min | Depth top | m | Barker, Peter F | ||
| 3 | Depth, bottom/max | Depth bot | m | Barker, Peter F | ||
| 4 | DEPTH, sediment/rock | Depth sed | m | Geocode – mbsf | ||
| 5 | Description | Description | Barker, Peter F | |||
| 6 | Description 2 (continued) | Description 2 | Barker, Peter F | #2 | ||
| 7 | Description 2 (continued) | Description 2 | Barker, Peter F | #3 | ||
| 8 | Description 2 (continued) | Description 2 | Barker, Peter F | #4 |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
55 data points
Data
| 1 Unit | 2 Depth top [m] | 3 Depth bot [m] | 4 Depth sed [m] (mbsf) | 5 Description | 6 Description 2 (#2) | 7 Description 2 (#3) | 8 Description 2 (#4) |
|---|---|---|---|---|---|---|---|
| 1 | 0 | 193 | 96.5 | Foraminiferal and nannofossil ooze, pale brown to white; foraminiferal sand layers occur near 65 m. | |||
| 2 | 193 | 332 | 262.5 | Light gray nannofossil ooze and chalk with chert nodules and biogenic silica; unit boundaries defined by shallowest and deepest occurrences of chert. | |||
| 3 | 332 | 634 | 483.0 | Light gray to greenish gray chalk and limestone; parallel laminations common below 470 m; extensive burrowing throughout. | |||
| 4 | 634 | 874 | 754.0 | Interbedded pelagic limestone, volcanic ash layers, and allochthonous turbidites and breccias; limestones are generally similar to Unit 3, although CaC_3 decreases down section toward marly limestone (<60% CaCO3). | Ash layers are commonly altered to bentonite. Displaced units are variable in composition and structure, including carbonate and volcanogenic components, graded sequences and upgraded breccias, and some with mud clasts. | Unit boundaries are (1) uppermost turbidite layer and (2) the base of Maestrichtian limestone slumped block. Amorphous silica cement is present below 800 m. | Physical properties show a transition to high density and velocity down section within the limestone units of Unit 4 and a sharp decrease in both at the base. |
| 5 | 874 | 1000 | 937.0 | Nannofossil limestones, grading from light gray at the top of the unit to reddish brown below 930 m. Anastomosing laminations (microstyolites) are common throughout. This unit contains the Cretaceous/Tertiary boundary in Core 89, | within which lithologic variability is striking (clay, marl, and limestone units interbedded). The uppermost 40 m of Unit 5 contains amorphous silica, apparently remobilized from the volcanics of Unit 4. | ||
| 5a | 874 | 930 | 902.0 | Nannofossil limestones, grading from light gray at the top of the unit to reddish brown below 930 m. Anastomosing laminations (microstyolites) are common throughout. This unit contains the Cretaceous/Tertiary boundary in Core 89, | within which lithologic variability is striking (clay, marl, and limestone units interbedded). The uppermost 40 m of Unit 5 contains amorphous silica, apparently remobilized from the volcanics of Unit 4. | ||
| 5b | 930 | 1000 | 965.0 | Nannofossil limestones, grading from light gray at the top of the unit to reddish brown below 930 m. Anastomosing laminations (microstyolites) are common throughout. This unit contains the Cretaceous/Tertiary boundary in Core 89, within which | lithologic variability is striking (clay, marl, and limestone units interbedded). The uppermost 40 m of Unit 5 contains amorphous silica, apparently remobilized from the volcanics of Unit 4. Kaolinite and illite are present in Subunit 5b, but not above | ||
| 6 | 1000 | 1240 | 1120.0 | Bioturbation within both reddish and greenish intervals argues against anoxic conditions of deposition of Unit 6. Inoceramus fragments are abundant below 1150 m, with scattered occurrence as shallow as 1080 m. | |||
| 6a | 1000 | 1130 | 1065.0 | Greenish gray and reddish brown limestones and interbedded marly limestones | |||
| 6b | 1130 | 1240 | 1185.0 | Greenish gray to dark gray recrystallized dolomitic limestones | |||
| 7 | 1240 | 1251 | 1245.5 | Varicolored volcanic and calcareous turbidites and breccias. The uppermost sediment recovered in Core 124 consists of four cobbles of ferruginous chert, | underlain by a 20-cm-thick reddish limestone (probably pelagic) containing Inoceramus fragments. The remaining sediments of Cores 124 and 125 are displaced from shallower sites | ||
| 8 | 1251 | 1271 | 1261.0 | Olivine-plagioclase phyric tholeiitic basalt; calcitic vein filling contains fragments of coralline algae and bryozoa. |