Stable oxygen and carbon isotope compositions of Campanian grainstones and rudstones

Petrographic descriptions and stable oxygen and carbon isotope compositions of microsamples of Campanian-age sediment gravity-flow deposits from Northeast Providence Channel, Bahamas, indicate deep-marine cementation of shallow-marine skeletal grains that were transported to the channel during the Late Cretaceous. Shallow-marine components are represented by mollusks, especially rudists, and shallow-water benthic foraminifers as well as sparse echinoderm and algal grains. The sole evidence of diagenesis in shallow-marine environments consists of micrite envelopes around skeletal grains. Shallow-marine skeletal grains have mean stable isotope values of -3.1 per mil d18O and +2.6 per mil d13C. The d18O values are consistent with precipitation in equilibrium with warm (20°-30°C), shallow-marine water. Deep-marine components are represented by equant calcite spar cements and rip-up clasts of slope sediments. Spar cements, exhibiting hexagonal morphology with scalenohedral terminations, most commonly occur as thin isopachous linings in the abundant porosity. Deep-marine cements have mean stable isotope values of - 1.1 per mil d18O and +2.7 per mil d13C. Deep-marine cements are 18O-enriched relative to shallow-marine skeletal grains, consistent with precipitation in equilibrium with colder (10°-20°C), deep-marine waters. The cement .source during lithification appears to have been dissolution of aragonite and high-magnesium calcite skeletal grains, which made up part of the transported sediment. Interbedded periplatform ooze remains uncemented, or poorly cemented, probably because of lower permeability. Equant spar cements that occur in gravity-flow deposits recovered from Hole 634A have stable isotope compositions similar to spars in Lower and mid-Cretaceous shallow-water limestones exposed on the Bahama Escarpment, to Campanian-Paleocene deep-marine hardgrounds recovered during DSDP Leg 15 in the Caribbean, and to spars in Aptian-Albian talus deposits at the base of the Campeche Escarpment recovered during DSDP Leg 77.

(Table S1) Age determination of Emperor Seamounts basement

The Hawaiian-Emperor hotspot track has a prominent bend, which has served as the basis for the theory that the Hawaiian hotspot, fixed in the deep mantle, traced a change in plate motion. However, paleomagnetic and radiometric age data from samples recovered by ocean drilling define an age-progressive paleolatitude history, indicating that the Emperor Seamount trend was principally formed by the rapid motion (over 40 millimeters per year) of the Hawaiian hotspot plume during Late Cretaceous to early-Tertiary times (81 to 47 million years ago). Evidence for motion of the Hawaiian plume affects models of mantle convection and plate tectonics, changing our understanding of terrestrial dynamics.

Quartz content, accumulation and sedimentation rates at DSDP Hole 91-595A

The quartz contents of sediments from Hole 595A, determined by X-ray diffractometry, serve as an indicator of eolian transport of terrigenous material to the central southern Pacific. The quartz contents are very small and, within limits of analytical resolution, vary only slightly from the Cretaceous to the present. However, the accumulation rate of the eolian quartz does change significantly. The quartz accumulation reflects the changing position of the site with respect to the terrigenous source areas and the variations in wind systems through time.

Mineralogy of sediments from the Exmouth Plateau and Argo Basin

Correlation of mineral associations from sediment recovered on the northwestern Australian continental margin document the juvenile-to-mature evolution of a segment of the Indian Ocean. Lower Cretaceous sediments contain sandy-to-silty radiolarian claystone that consists of highly smectitic mixed-layered illite/smectite (I/S) in addition to minor amounts of diagenetic pyrite, barite, and rhodochrosite. These immature, poorly sorted sediments were derived from nearby continental margin sources. Discrete bentonite layers and abundant smectite are the alteration products of volcanic material deposited during early basin formation. Abundant quartz-replaced radiolarian tests suggest high surface-water productivity, and calcareous fossils indicate water depths were above the calcite compensation depth (CCD) in the juvenile Indian Ocean. The increase in pelagic carbonate from the mid- to Late Cretaceous signals the transition to mature, open-ocean conditions. Similar to other slowly deposited contemporaneous deep-sea sediments, mid- to Upper Cretaceous sediments of the northwestern margin of Australia contain palygorskite. This palygorskite is associated with calcareous sediment across the ooze-to-chalk transition, detrital mixed-layered I/S, and zeolite minerals in places. This palygorskite occurs above the transformation from opal-A to opal-CT. The underlying opal-CT sediment contains abundant smectite and zeolite minerals. Calcareous sediment dominates the Cenozoic, except at abyssal sites that were not inundated by calcareous turbidites. Paleocene and Eocene sediments contain abundant smectite and zeolite minerals derived from the alteration of volcanic material. Palygorskite was found to be associated with sepiolite and dolomite in Miocene sediments from Site 765 in the Argo Basin. Pliocene and Quaternary sediments contain detrital kaolinite and mixed-layered I/S, abundant opal-A radiolarian tests, and minor amounts of pyrite

Insoluble residues of the fine-grained sediments from DSDP Leg 67 Holes

Insoluble residues of Late Cretaceous to Quaternary deep-sea samples from slope, trench, and oceanic plate sites south of Guatemala were examined, specifically for the distribution of clay minerals in the <2-µm fraction and of silt grains in the 20-63-µm fraction. Widespread "oceanic" particles (biogenic opal, rhyolitic glass) and their diagenetic products (smectite, clinoptilolite, heulandite) were distinguished from terrigenous material - illite, kaolinite, chlorite, plagioclase, quartz, and heavy minerals. The main results of this investigation are: (1) At Site 494 on the slope immediately adjacent to the trench, terrigenous supplies testify to a slope position of the whole sequence back to the Late Cretaceous. (2) At Site 495 on the Pacific Cocos Plate, "oceanic" and terrigenous sedimentation are clearly separated. Whereas the pelagic sedimentation prevailed in the early Miocene, terrigenous minerals appeared in the middle Miocene in the clay fraction, and in the early Pliocene in the coarse silt fraction. These terrigenous supplies are interpreted as having been transported by suspension clouds crossing the slope and even the trench. The alternative, however, an eolian transport, cannot be excluded.

Planktonic foraminifers in DSDP Holes 30-289 and 33-315A

The work is based on samples from Deep-Sea Drilling in the Pacific Ocean and from natural sections in its continental setting. Species composition of planktonic foraminifera from Maastrichtian sediments of the Pacific and South Atlantic oceans, as well as from marginal seas of Australia and New Zealand and epicontinental basins of the northern hemisphere has been analysed. Two main issues: reconstruction of Maastrichtian climatic zonality, and reconstruction of Maastrichtian paleodepths. Four bipolar climatic zones have been distinguished. According to preservation of planktonic foraminifera and composition of their complexes three levels of dissolution have been identified.

Magnetic susceptibility, XRF and color reflectance data of DSDP Hole 72-516F, cores 113 and 114

Deep marine successions of early Campanian age from DSDP site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession and eccentricity related variations. Elemental abundance ratios point to a similar 5 climatic origin for these variations and exclude a quadripartite structure - as observed in the Mediterranean Neogene - of the precession related cycles as an explanation for the inferred semi-precession cyclicity in MS. However, the semi-precession cycle itself is likely an artifact, reflecting the first harmonic of the precession signal. The sub-Milankovitch variability is best approximated by a ~ 7 kyr cycle as shown by 10 spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession induced variations in insolation between the tropics.

Campanian-Maestrichtian planktonic foraminifera of the southern South Atlantic

Campanian-Maestrichtian planktonic foraminifers were examined from Sites 698 (2128 m water depth) and 700 (3611 m water depth) on the Northeast Georgia Rise (southern South Atlantic, 51°S). Site 698 penetrated 72.5 m of Campanian-Maestrichtian chalk and limestone with only 18.2% recovery, whereas Site 700 recovered 66.8% of a 152.7-m section of Coniacian-Maestrichtian limestone. Preservation of planktonic foraminifers from both sites is moderate in Maestrichtian samples, but worsens with increasing depth in the Campanian. The Northeast Georgia Rise planktonic foraminifers are typical of Late Cretaceous Austral Province faunas described from other southern high-latitude sites; species diversity is low and the assemblages are dominated by species of Heterohelix, Globigerinelloides, Hedbergella, and Archaeoglobigerina. Five species, including Globigerinelloides impensus Sliter, Archaeoglobigerina australis Huber, Archaeoglobigerina mateola Huber, Hedbergella sliteri Huber, and Rugotruncana circumnodifer (Finlay), are considered to be endemic to the Austral Province. Formation of a cool temperate water mass in the circum-Antarctic region, resulting from the final breakup of the Gondwana continents, may have led to increased provincialism of the Austral Province planktonic foraminifers during Campanian-Maestrichtian time. Magnetobiostratigraphic correlation of eight planktonic foraminifer datum events at Hole 700B with ages determined for datums at ODP Leg 113 Holes 689B and 690C (Maud Rise, 65°S) demonstrates regional synchroneity of first and last occurrences within the Austral Province. As was observed at the Maud Rise, several keeled and nonkeeled species previously thought to have been restricted to warmer low-latitude regions first occur later at the Northeast Georgia Rise than at the low-latitude sites. The causes for high-latitude diachroneity among these immigrant species are not clear; neither oxygen and carbon isotope data from the Maud Rise sites nor calcareous nannoplankton distributions for the southern South Atlantic region show conspicuous changes that correlate to the delayed first occurrences.

Paleomagnetic of igneous rocks of ODP Leg 114

A paleomagnetic study was made of 12 samples of trachytic basalt from the base of ODP Hole 698A on the Northeast Georgia Rise (southwest Atlantic) and four samples of andesitic basalt and nine samples of volcanic breccia from the base of ODP Hole 703A on the Meteor Rise (southeast Atlantic). The magnetic intensities of the Hole 703A samples are anomalously low, possibly reflecting alteration effects. The mean magnetic intensity of the Hole 698A samples is high, and compatible with the model of Bleil and Petersen (1983) for the variation of magnetic intensity with age in oceanic basalts, involving progressive low-temperature oxidation of titanomagnetite to titanomaghemite for some 20 m.y. followed by inversion to intergrowths of magnetite and other Fe-Ti oxides during the subsequent 100 m.y. These results support the interpretation of the Hole 698A basalts as true oceanic basement of Late Cretaceous age rather than a younger intrusion. Well-defined stable components of magnetization were identified from AF and thermal demagnetization of the Hole 698A basalts, and less well-defined components were identified for the Hole 703A samples. Studies of the magnetic homogeneity of the Hole 698A basalts, involving harmonic analysis of the spinner magnetometer output, indicate the presence of an unevenly distributed low-coercivity component superimposed on the more homogeneous high-coercivity characteristic magnetization. The former component is believed to reside in irregularly distributed multidomain magnetite grains formed along cracks within the basalt, whilst the latter resides in more uniformly distributed finer magnetic grains. The inclination values for the high-coercivity magnetization of five Hole 698A basalt samples form an internally consistent set with a mean value of 59° ± 5°. The corresponding Late Cretaceous paleolatitude of 40° ± 5° is shallower than expected for this site but is broadly compatible with models for the opening of the South Atlantic involving pivoting of South America away from Africa since the Early Cretaceous. The polarity of the stable characteristic magnetization of the Site 698 basalts is normal. This is consistent with their emplacement during the long Campanian to Maestrichtian normal polarity Chron C33N.