Pacific Guyots Research Articles

Compositional Variations and Genesis of Sandy-Gravel Ferromanganese Deposits from the Yōmei Guyot (Holes 431, 431A DSDP), Emperor Ridge

This research presents results characterizing the mineral and chemical composition of ferromanganese (Fe-Mn) deposits from Yōmei Guyot (Holes 431 and 431A), recovered during the Deep-Sea Drilling Project (DSDP) Leg 55 R/V “Glomar Challenger”. The Fe-Mn deposits are represented by sandy-gravel clasts. The mineral composition and bulk concentration of major and minor elements, as well as the distribution of rare earth elements and yttrium patterns in mineral fractions of Fe-Mn samples, showed that the deposits are composed of fragments of Fe-Mn hydrogenetic crusts and diagenetic nodules. The morphology of Fe-Mn clasts from Holes 431 and 431A DSDP, as well as a comparison with growth conditions of Fe-Mn deposits from N-W Pacific Guyots, allowed us to establish a Late Pliocene age for the formation of this Fe-Mn placer from Yōmei Guyot. Accumulations of ferromanganese clasts in a sedimentary unit led us to classify this geological body as a new mineral resource of the World Ocean.

Erratum: Modern and ancient hiatuses in the pelagic caps of Pacific guyots and seamounts and internal tides

Erratum: Modern and ancient hiatuses in the pelagic caps of Pacific guyots and seamounts and internal tides

Modern and ancient hiatuses in the pelagic caps of Pacific guyots and seamounts and internal tides

Incidences of non-deposition or erosion at the modern seabed and hiatuses within the pelagic caps of guyots and seamounts are evaluated along with paleo-temperature and physiographic information to speculate on the character of Late Cenozoic internal tidal waves in the upper Pacific Ocean. Drill core and seismic reflection data are used to classify sediment at the drill sites as having been either accumulating or eroding/nondepositing in the recent geological past. When those classified sites are compared against predictions of a numerical model of the modern internal tidal wave field (Simmons, 2008), the sites accumulating particles over the past few million years are found to lie away from beams of the modeled internal tide, while those that have not been accumulating are in internal tide beams. Given the correspondence to the modern internal wave field, we examine whether internal tides can explain ancient hiatuses at the drill sites. For example, Late Cenozoic pelagic caps on guyots among the Marshall Islands contain two hiatuses of broadly similar age, but the dates of the first pelagic sediments deposited following each hiatus do not correlate between guyots, suggesting that they originate not from ocean chemical changes but from physical processes, such as erosion by internal tidal waves. We investigate how changing conditions such as ocean temperature and basin physiography may have affected internal tides through the Cenozoic. Allowing for subsequent rotation or uplift by plate tectonics, ancient submarine ridges among the Solomon, Bonin and Marianas Island chains may have been responsible for some sediment hiatuses at these distant guyot sites.

10.1007/s11491-008-1011-9

A detailed investigation of microstructures of the phosphorites from Christmas Island under a scanning electron microscope coupled with an analysis of their chemical composition revealed that both their structure and composition are quite similar to those of the granular and microgranular phosphorites on present-day continents, as well as those of the phosphorites on some of the Pacific guyots. Their composition, together with their geological position and interrelationships with the surrounding rocks, proves that the ornitogenic hypothesis based on the presumed guano accumulation followed by its transformation into phosphatic rock is not compatible with the field observations. Meanwhile, the problem of the source of the Fe and Mn impregnation in the phosphorites remains unresolved and needs further investigations.

On the origin of phosphorites from Christmas Island in the Indian Ocean

A detailed investigation of microstructures of the phosphorites from Christmas Island under a scanning electron microscope coupled with an analysis of their chemical composition revealed that both their structure and composition are quite similar to those of the granular and microgranular phosphorites on present-day continents, as well as those of the phosphorites on some of the Pacific guyots. Their composition, together with their geological position and interrelationships with the surrounding rocks, proves that the ornitogenic hypothesis based on the presumed guano accumulation followed by its transformation into phosphatic rock is not compatible with the field observations. Meanwhile, the problem of the source of the Fe and Mn impregnation in the phosphorites remains unresolved and needs further investigations.

Formation setting of early Mesozoic basalts of the Russian Far East: Accretion of the Pacific guyots or epicontinental rifting?

Formation setting of early Mesozoic basalts of the Russian Far East: Accretion of the Pacific guyots or epicontinental rifting?

The first finds of cretaceous belemnites from the Magellan Rise, Pacific Ocean

The occurrence of belemnites in Mesozoic sediments of the Pacific guyots is established for the first time (rostra Dimitobelidae gen. et sp. indet. from the late Campanian-Maastrichtian detrital limestone of the DVGI Guyot, Belemnitella? sp. from oolitic limestone of the Gelendzhik Guyot, which are presumably of the Santonian-Maastrichtian age, and Belemnitidae? gen. et sp. indet. from the Maastrichtian oolitic limestone of the Butakov Guyot, the Magellan Rise). In recent years, fossil cephalopods important in stratigraphic and paleobiogeographic aspects have been found at five guyots of that rise. New data on fossil invertebrates from the study region suggest breaks in the sedimentation here at the terminal Maastrichtian, Paleogene, and initial Neogene time. Possible limits of vertical migration in the tropical Pacific are estimated for the Late Cretaceous belemnites based on preliminary results of the oxygen isotope analysis.

Lower Cretaceous carbonate platform of the eastern Levant (Galilee and the Golan Heights): stratigraphy and second-order sea-level change

The marine succession of the late Early Cretaceous carbonate platform of the eastern Levant was located at the southern border of the Tethyan Ocean. The studied areas of Galilee and the Golan Heights represent a transect across the shallow inner platform. The investigations were focused on carbonate platform biostratigraphy and facies analysis. A precise stratigraphic interpretation of the Upper Barremian–Albian succession was compiled on the basis of the definition of larger benthic foraminifer biozones allowing subdivision of the succession into six well-dated intervals. Detailed analyses of facies and sedimentological parameters allow interpretation of platform development, in connection with platform geometry, as well as relative third-order and second-order sea-level changes. The observed facies patterns reflect a depositional geometry changing from a ramp to a flat-topped platform during Late Barremian–Middle Albian times. Three second-order depositional sequences were recorded in the studied mid-Cretaceous succession of the eastern Levant (MCEL-1 to MCEL-3). The facies analysis clearly indicates their origin in relative sea-level variations. The stratigraphic framework allows biochronostratigraphic calibration of these depositional sequences (MCEL-1: Upper Barremian–Lower Aptian, MCEL-2: uppermost Lower Aptian–middle Upper Aptian, MCEL-3: middle Upper Aptian–Middle Albian) and correlation with stratigraphic charts of local and regional sequences. The second-order sequence boundaries and maximum flooding surfaces correlate with basic sea-level variations recorded on the Arabian Plate, here interpreted as originally eustatically enhanced by subsidence. Tethyan signals are recorded around the Aptian/Albian boundary. A noticeable deepening in the upper Lower Aptian correlates with an extended platform drowning during the Selli Level (Oceanic Anoxic Event 1a: OAE 1a). Orbitolinid beds at this level suggest a deepening facies and a possible response to nutrient enhancement developing at the continental margin during OAE 1a. Eight third-order depositional sequences were observed in the Upper Barremian–Albian interval. They comprise successions of the inner ramp facies from open marine to restricted lagoons or tidal flats. The age and frequency of the Upper Barremian–Lower Aptian sequences correlate with those observed on the Pacific guyots or the Arabian Plate suggesting influence by regional sea-level cycles.

The ‘Darwin Point’ of Pacific Ocean atolls and guyots: a reappraisal

The ‘Darwin Point’, where atolls drown, has been redefined as a function of climate, sea-level history, paleolatitude, seawater temperature and light. During the last 34 Ma, in the Hawaiian-Emperor Chain, the Darwin Point has been shown to shift at least between 24 and 30°N latitude. Atoll drowning there is correlated with decreased seawater temperature and light and depends on sea-level history as well as the elevation of atoll summits at the time of sea-level transgressions. If the atoll top falls below 30 m with respect to sea level and the rate of sea-level rise is more than 15 mm/yr, the atoll will drown. Results of the Ocean Drilling Program legs 143 and 144, which investigated the histories of several NW Pacific guyots, indicate that the demise of the shallow-water carbonate platforms there was related to either a temporal (110–100 Ma) eustatic sea-level event, the paleolatitude location (0–10°S) of nutrient-rich water, and/or increased seawater temperature (greenhouse effect) unconducive to the production of calcium carbonate by shallow-water organisms. Hence, the Darwin Point phenomena of atolls and guyots cannot be viewed as a manifestation of any single factor, rather, it results from a combination of factors including: decreased water temperature and light related to higher latitude; the amplitude and rate of sea-level changes; presence of nutrient-rich waters; and/or elevated seawater temperatures. It is indeed dynamic, both in time, space, and cause.

Stratigraphy, paleoceanography, and evolution of Cretaceous Pacific guyots; relics from a greenhouse Earth

Many guyots in the north Pacific are built of drowned Cretaceous shallow-water carbonates that rest on edifice basalt. Dating of these limestones, using strontium- and carbon-isotope stratigraphy, illustrates a number of events in the evolution of these carbonate platforms: local deposition of marine black shales during the early Aptian oceanic anoxic event; synchronous development of oolitic deposits during the Aptian; and drowning at different times during the Cretaceous (and Tertiary). Dating the youngest levels of these platform carbonate shows that the shallow-water systems drowned sequentially in the order in which plate-tectonic movement transported them into low latitudes south of the Equator (paleolati- tude 0°-10° south). The chemistry of peri-equatorial waters, rich in upwelled nutrients and carbon dioxide, may have been a contributory factor to the suppression of carbonate precipitation on these platforms. However, oceanic anoxic events, thought to reflect high nutrient availability and increased produc- tivity of planktonic organic-walled and siliceous microfossils, did not occasion platform drowning. Neither is there any evidence that relative sealevel changes were the primary cause of platform drowning, which is consistent with the established resilience of shallow-water carbonate systems when influenced by such phenomena. Comparisons with paleotemperature data show that platform drowning took place closer to the Equator during cooler intervals, such as the early Albian and Maastrichtian, and farther south of the Equator during warmer periods such as Albian-Cenomanian boundary time and the mid-Eocene. Initiation of one carbon- ate platform relatively close to the Equator, at paleolatitudes more northerly than those where others drowned, took place during the cool early mid-Aptian. These correlations are in accord with an interpretation that excess warmth in shallow peri-equatorial waters proved inimical for many carbonate-secreting organisms living on the platforms, allowing subsidence or eustatic sealevel rise to outpace sedimentation and guyots to form. A parallel may be drawn with the recent phenomenon of coral and foraminiferal bleaching, whereby photosynthetic sym- bionts succumb to prolonged high temperatures (G30°C) and the host organism dies. The fact that most Cretaceous guyots reside in the north Pacific may not be solely related to the age-distribution pattern of ocean floor but to their having run the gauntlet of a difficult and dangerous passage across the Equator. North Pacific guyots are relics from the Cretaceous (and Eocene) ''greenhouse'' Earth.

Development of northwest Pacific guyots: General results from Ocean Drilling Program legs 143 and 144

Results of the Ocean Drilling Program legs 143 and 144, which investigated the nature and origin of seven guyots in the northwest Pacific Ocean, document a history of prolonged volcanism (128–84 Ma), followed by subsidence, accumulation of shallow‐water carbonates, emersion following a sea‐level fall, then continued subsidence, and drowning. Generally, the life span of a guyot is of the order of 5–20 million years. The stratigraphic sequence in each guyot consists of 3–10 m‐thick, shoaling‐upward cycles, which display a 100‐Ka periodicity perhaps related to sea‐level fluctuations. The drilling results indicate that the demise of the shallow‐water carbonate platforms is related to either a temporal (110–100 Ma) event or paleolatitude location (0–10°S) involving nutrient‐rich water not conducive to production of calcium carbonate by shallow‐water organisms. Following emergence and erosion, re‐submergence occurred during a rise of sea‐level. However, the rate of sediment accumulation was unable to keep pace with the rate of sea‐level rise and the guyots drowned. Subsidence continued as the lithospheric plate cooled. The majority of guyots are now at ~ 1500 m below sea‐level. Plate movements over the past 100 million years have carried the guyots from ~ 14°S to their current location in the northwest Pacific. Guyots are flat‐topped submerged volcanic islands capped by thick sequences of shallow‐water carbonates. The flat‐top morphology is constructional, not related to wave planation as originally thought and reported in most textbooks.

The paradox of drowned carbonate platforms and the origin of Cretaceous Pacific guyots

Geochemical, stratigraphic and palaeolatitudinal data from deep boreholes drilled through Pacific guyots—flat-topped seamounts—help to explain the drowning of these Cretaceous shallow-water carbonate platforms that once thrived through the accumulation of biogenic and inorganic calcium carbonate sediment in mid-oceanic regions. The platforms drowned sequentially over a 60-million-year interval while they were being transported northward by Pacific plate motion through a narrow equatorial zone (∼0–10° S). Such platforms were apparently resistant to the effects of Cretaceous oceanic anoxic events. Although the mechanism responsible for drowning remains unknown, the tropics have not always been the refuge for atolls that they are today.

Organic geochemistry of Lower Cretaceous sediments from northwestern Pacific guyots (ODP Leg 143)

Organic geochemistry of Lower Cretaceous sediments from northwestern Pacific guyots (ODP Leg 143)

Biological Signals in Carbonate Platforms in Sequence Stratigraphy: Examples from the Cretaceous of Pacific Guyots, Europe and Azerbaidjan : ABSTRACTS

Biological Signals in Carbonate Platforms in Sequence Stratigraphy: Examples from the Cretaceous of Pacific Guyots, Europe and Azerbaidjan : ABSTRACTS

Organic geochemistry of Lower Cretaceous sediments from Northwestern Pacific guyots (ODP leg 143)

Organic geochemical data of Lower Cretaceous shallow water sediments from two sites (865 and 866) drilled during ODP leg 143 are presented. The organic matter is mainly terrestrial at the bottom of the sedimentary column at site 865, whereas algal and/or bacterial organic matter is dominant at site 866. This is the first evidence of shallow water deposition of organic matter during the Early Cretaceous in the Northwestern Pacific. The lower Aptian organic carbon-rich layers from the shallow water sediments of site 866 are geochemically similar to coeval mid-water sediments of site 463.

Large-scale motion between Pacific and Atlantic hotspots

STUDIES of true polar wander (TPW), the rotation of the solid Earth with respect to the spin axis1, have suggested that there has been 10–15° of relative motion over the past 130 Myr (refs 2–4). In such studies, the orientation of the spin axis is recovered from continental palaeomagnetic poles (corrected for relative plate motions), and compared with a deep-mantle reference frame defined by hotspot locations. But deducing relative plate motions becomes increasingly difficult for older (Mesozoic) time periods, hindering tests of TPW on timescales comparable to those of large-scale mantle convection; moreover, the assumption of hotspot fixity is controversial5,6. We examine here a more direct approach7,8, using palaeolatitudes derived from Pacific guyots. Contrary to predictions from TPW models, these data suggest only minor latitudinal shifts of Pacific hotspots during the Cretaceous period. Instead of TPW, relative motion between the Atlantic and Pacific hotspot groups9 is required at a velocity of approximately 30 mm yr−1, more than 50% larger than previously proposed5.

Insight on the formation of Pacific guyots from ODP Leg 144

Guyots are flat‐topped seamounts that are most common on Mesozoic‐age Pacific oceanic crust. Dredging of the Pacific guyots, of which over 300 are known, commonly revealed the existence of mid‐Cretaceous rudist reefs and other shallow‐water carbonate facies, now submerged to depths on the order of 1000‐1500 m, capping volcanic edifices [Lincoln et al., 1993].The intriguing question of how guyots originate played a major role in the development of concepts of seafloor spreading, hot spots, thermal subsidence and crustal thinning, and superswells [e.g., Hess, 1962; Detrick and Crough, 1978; Menard, 1964, 1984]. However, key questions remain, such as why a tropical carbonate platform would suddenly cease to keep pace with subsidence after constructing a massive carbonate cap up to 1000‐m thick and tens of kilometers in diameter, or why the apparent ages of the underlying volcano and of the shallow‐water carbonate cap as determined from dredge samples appeared to lack the coherent patterns predicted from hot‐spot and subsidence theories.

Facies of sunken early cretaceous atoll reefs and their capping Late Albian drowning succession (Northwestern Pacific)

Since first described in detail byHamilton (1956), the causes and timing of the drowning of several hundred guyots in the northwestern Pacific is a puzzling question. Thus, the northwestern Pacific is one of the key areas in deciphering the demise of flat-topped platforms throughout the earth’s history. Based on older paleontological data and the newly found shallow-water benthic foraminifera, the atoll reefs probably had a major period of vertical aggradation during the Barremian and the Aptian into the Late Albian depending on the stage of atoll development (type of guyot). New sedimentologic and stratigraphic data suggest a strong fall in sea level, leading to karstification and the formation of lowstand fringing reefs, prior to an even rapid rise of greater amplitude in the Late AlbianRotalipora appenninica zone ultimately causing drowning. After climatic relaxation, a sea level rise led to the final formation of small barrier reefs, rimming the top of many guyots in the Japanese Group, the Wake Group and the Mid-Pacific Mountains. They can be interpreted as “give-up” structures indicating a final shallow-water carbonate production on top of the atolls during drowning. The facies of the syn- and post-drowning sediments on the guyot tops are strikingly similar even when vast distances apart. This and the biostratigraphic data suggest a synchronous drowning of many seamounts investigated up to now. Biotic composition and facies of the final Albian reefs are very similar to Albian caprinid-dominated reefs in the Caribbean region, indicating comparable environmental controls. In the case of the northwestern Pacific guyots, the simultaneous demise of reefs could be due to a short-term cooling event in the Late Albian, connected with a strong regressive-transgressive cycle with an amplitude of about 180 m. This event is also known from the Tethys and the Atlantic. Climatic disturbances triggering short-term cooling and inducing a high amplitude regressive-transgressive sea level cycle, might be responsible not only for the Late Albian event, but also perhaps for other reef drownings throughout the earth’s history.