Latest Oligocene to Earliest Pliocene Benthic Foraminiferal Biofacies of the Northeastern Gulf of Mexico

We use benthic foraminifers to reconstruct the Neogene Paleobathymetric history of the Marion Plateau, Queensland Plateau, Townsville Trough, and Queensland Trough on the northeastern Australian margin (Ocean Drilling Program Leg 133). Western Queensland Plateau Site 811/825 (present depth, ~938 m) deepened from the neritic zone (0-200 m) to the upper bathyal zone (200-600 m) during the middle Miocene (-13-14 Ma), with further deepening into the middle bathyal zone (600-1000 m) occurring during the late Miocene (-7 Ma). A depth transect across the southern Queensland Plateau shows that deepening from the outer neritic zone (100-200 m) to the upper bathyal zone began during the latest Miocene (~6 Ma) at the deepest location (Site 813, present depth, 539.1 m), whereas the shallower Sites 812 and 814 (present depths, 461.6 and 520.4 m, respectively) deepened during the late Pliocene (-2.7 and -2.9 Ma). At Marion Plateau Site 815 (present depth, 465.5 m), water depth increased during the late Miocene (-6.7 Ma) from the outer neritic to the upper bathyal zone. Nearby Site 816 (present water depth, 437.3 m) contains Pliocene upper bathyal assemblages that directly overlie middle Miocene shallow neritic deposits; the timing of the deepening is uncertain because of a late Miocene hiatus. On the northern slope of the Townsville Trough (Site 817, present depth, 1015.8 m), benthic foraminifers and sponge spicules indicate deepening from the lower upper bathyal (400-600 m) to the middle bathyal zone in the late Miocene (by -6.8 Ma). Benthic foraminiferal faunas at nearby Site 818 (present water depth, 752.1 m) do not show evidence of Paleobathymetric change; however, a late Pliocene (-2-3 Ma) increase in downslope transport may have been related to the drowning of the Queensland Plateau. Site 822 (present depth, 955.2 m), at the base of the Great Barrier Reef slope, deepened from the upper bathyal to the middle bathyal zone during the late Pliocene (by -2.3 Ma). Queensland Trough Site 823 (present depth, 1638.4 m) deepened from the middle bathyal to the lower bathyal (1000-2000 m) zone during the late Miocene (-6.5 Ma). Benthic foraminiferal faunal changes at these Leg 133 sites indicate that rapid deepening occurred during the middle Miocene (-13-14 Ma), late Miocene (6-7 Ma), and late Pliocene (2-3 Ma) along the northeastern Australian margin.

Miocene of the S.E. United States: A model for chemical sedimentation in a peri-marine environment

Orogeny in Action: Tectonic Evolution and Stratigraphy of Sabah, Seismic and Outcrop Evidence

":La Formación Uscari (en los ríos Torito y Calvario, y las secciones 3X, Peralta y Alto Guayacán), muestrauna somerización desde zonas batiales inferiores hasta zonas neríticas durante el Mioceno Temprano. En el MiocenoMedio cambia nuevamente a zonas batiales no tan profundas como las alcanzadas en el área de 3X, durante el intervaloanterior.Durante el Mioceno Temprano las zonas batiales estuvieron caracterizadas por ambientes eutróficos a mesotróficosdepositadas bajo condiciones de surgencia oceánica y flujos de turbidez, a excepción de 3X que muestra una fauna másestable. La somerización hacia zonas neríticas se caracterizó por ambientes oligotróficos, con sustratos duros y arenososde alta energía, con presencia de arrecifes, algas y aguas cálidas. Durante el Mioceno Medio, las zonas batiales eranoligotróficas y presentaban la menor diversidad de todas las muestras, debido posiblemente a una mayor predación oa un cambio en la circulación de las aguas intermedias por la influencia del Componente de Agua Norte (North Com-ponent Water, NCW), precursor de la actual Agua Profunda del Atlántico Norte (North Atlantic Deep Water, NADW),caracterizada por aguas oxigenadas, ricas en carbonatos y pobre en nutrientes.La zona batial del área de estudio se correlaciona con la parte inferior de la quebrada Terciopelo y el Mioceno Tempranodel río Reventazón. Tanto los depósitos batiales y abisales de la sección río Reventazón, y el batial medio de la secciónquebrada Terciopelo estuvieron sujetas a turbiditas y a la introducción de taxones someros en agua profunda. Durante elMioceno Temprano Tardío y el Mioceno Medio Temprano, la parte media y superior de la sección quebrada Terciopelo,resultó en la transición de pendiente superior a ambientes de plataforma. La sección tipo del Mioceno Medio tempranode la quebrada Uscari fue depositada en la plataforma continental y se correlaciona tentativamente con la parte superiorde la quebrada Terciopelo."

Upper abyssal to lower bathyal benthic foraminifera from Ocean Drilling Program Sites 689 (present water depth 2080 m) and 690 (present water depth 2914m) on Maud Rise (Antarctica) recorded changes in deep-water characteristics at high southern latitudes during the Cenozoic. The benthic foraminiferal faunas show only minor differences as a result of the difference in water depths between the sites, and changes in faunal composition were coeval. These changes occurred at the early/late Paleocene boundary (±61.6 Ma), in the latest Paleocene (±57.5 Ma), in the middle early Eocene (±55.0 Ma), in the middle middle Eocene (±46.0 Ma), in the earliest Oligocene (±36.5 Ma) and in the early middle Miocene (±14.5 Ma). The faunal change at the end of the Paleocene was the most important and has been recognized world-wide. On Maud Rise, the diversity decreased by 50% and many common species became extinct over a period of less than 20 000 years. Diversity increased again during the early Eocene, and reached the same values as in the Paleocene by the middle Eocene. In the middle Eocene the diversity started to decrease, and continued to decrease until the middle Miocene. From the beginning of the middle Miocene until today biosiliceous oozes accumulated and calcareous benthic foraminifera were generally absent, with the exception of part of the late Miocene (±8.5–7.5 Ma) and the Quaternary. Changes in composition of the benthic foraminiferal faunas over a wide depth range (upper abyssal-lower bathyal) probably indicate periods of major changes in the formational processes of the deep waters in the oceans. The earliest Eocene faunas, living just after the major extinction at the end of the Paleocene, are characterized by low diversity and high relative abundance of small species that probably migrated downslope into the deep waters. These faunas, and to a lesser degree those in the early middle Eocene, are characterized by high relative abundance of biserial and triserial species. In contrast, older and younger faunas have high relative abundances of spiral species. This suggests that bottom waters on Maud Rise were poor in dissolved oxygen in the latest Paleocene through early middle Eocene, and that the major extinction of benthic foraminifera at the end of the Paleocene might have resulted from a decrease in availability of dissolved oxygen as a result of warming of the deep waters. Warming might have been caused by a change in sources of deep waters, possibly as a result of plate-tectonic activity. The overall decrease in diversity from middle Eocene through Miocene probably reflects continual cooling of the deep waters. Benthic foraminiferal faunas thus indicate that Cenozoic changes in the deep oceanic waters at high latitudes did not consist of gradual progression from Cretaceous circulation to the present-day patterns of formation of deep water: the benthic faunal changes occurred in discrete steps. Benthic faunal composition indicates that deep water most probably formed at high latitudes during the Maastrichtian—early Paleocene, and from the middle Eocene to Recent, with episodes of deep water formation at low latitudes (warm, salty deep water) during the latest Paleocene and early Eocene.

Benthic foraminiferal proxy evidence for the Neogene palaeoceanographic history of the Southwest Pacific, east of New Zealand

The Cenozoic Niger Delta formed after the separation of the African and South American plates.An integrated micropaleontology analysis was employed based on foraminifera studies  to determine age, biostratigraphic zonation, paleowaterdepth, paleosalinity and sea-level history of the well interval based on ditch cutting samples. Foraminifera preparation was based on standard micropaleontology preparation techniques and identification, which showed a high diversity and abundance of both planktonic and benthonic foraminifera occurrence. The planktonic foraminifera: Globigerinoides bulloidues, Globigerinoides primordius, Globorotalia obesa, Globigerinoides sp.,Catapsydrax stainforthi showed the entire deposition took place during the early to late Miocene (N6-N17) based on the First Downhole Occurrence (FDO) and Last Downhole Occurrence (LDO).The boundary resolution between the Early and Middle Miocene was identified based on the FDO of Catapsydrax stainforthi and the boundary between Middle and Late Miocene based on the FDO Globorotalia obesa. Two benthic biozones are proposed for the well interval equivalent to the N11-N17 and N6-N11 based on bioevents of chronostratigrahically significant benthonic foraminifera and whose stratigraphic range were well established in the Niger Delta and worldwide. Three third-order sea-level rises and falls occurred during the Early to Late Miocene within the Niger Delta, with a corresponding paleo-waterdepth from transitional to outer neritic based on biofacies such as ; Ammonia beccarii, Quinqueloculina microcostata, Poritextularia panamensis, Uvigerina subperegrina, Brizalina mandoroveensis, Lenticulina grandis and Eponides eshira.The maximum flooding surfaces shown by,the Chiloguembelina-3 Shale (16.0 Ma), Dodo Shale (11.6 Ma) and the Uvigerina-8 Shale (9.2 Ma), were associated with transgression. The 15.5 Ma SB of Depositional Sequence 1(Early Miocene), 10.5 Ma SB of Depositional Sequence 2(Middle Miocene) and 8.5 Ma SB of Depositional Sequence 3(Late Miocene) due to progradation, resulting in three depositional sequences established within the study interval. This showed  that the study interval was exposed to three local depositional cycles (cycle 6,9and 10), three regional cycles (cycles 2.3,2.6 and 3.1) within the TB2  and TB3 super cycles, correlated to the Niger Delta chronostratigraphic sea-level chart, which indicated that the sedimentary cyclic pattern was due to tectonics, eustatic and climatic conditions. Based on the triangular plot of the foraminifera test type (arenaceous, porcelaneous and hyaline), suggests a transition from the brackish marginal marine environment to open neritic conditions. The study interval is said to have penetrated sediments of the parallic Early to Late Miocene Agbada formation. Keywords: Biostratigraphy, Early-Late Miocene, Planktonic Foraminifera, Benthic Foraminifera, sedimentary cyclic pattern

Late cretaceous to recent palaeoenvironments of the Saudi Arabian Red Sea

Miocene Climatic Oscillation Recorded in the Lakes Entrance Oil Shaft, Southern Australia: Benthic Foraminiferal Response on a Mid-Latitude Margin

The benthic foraminiferal faunas from the Pliocene and Pleistocene sections of ODP Hole 625B (889m depth), drilled in the DeSoto Canyon area of the northeast Gulf of Mexico were examined from samples representing climatic maxima and minima according to the Joyce et al. (1990) 61 O record. The Pliocene and Pleistocene sections of four Eureka boreholes, two from the eastern Gulf of Mexico (E66-83A, 769m; E68-139, 1852m) and two from the western Gulf of Mexico (E66-40D, 776m; E67-116A, 1229m) were examined in less detail. The fossil faunas from these cores resemble closely those of the present-day Gulf of Mexico. The benthic faunas of the early Pliocene (about 5 Ma to 2.4 Ma) of all cores were very uniform. The respective fossil faunas are usually closer in composition to modem faunas that are deeper than the present coring sites. Faunal composition changed sharply at 2.4 Ma in the interglacial series of samples from Hole 625B, the time of the onset of Northern Hemisphere glaciations: several species that are indicative of very high biological productivity and/or moderate oxygen deficiency (e.g., Bulimina aculeata, Bulimina mexicana, Bulimina exilis) flooded the samples. This fauna occurs in three pulses during the late Pliocene and Pleistocene interglacial sample series: from 2.4 to l.9Ma, from 1.3 to 0.7 Ma, and from 0.4 Ma to the present. The intervening sections exhibit faunas that are essentially similar to the early Pliocene associations. An equivalent change in the faunas of the glacial series of samples from Hole 625B occurred 0.8 m.y. later, from about 1.6 Ma to 1.2 Ma in the early Pleistocene, persisting until about 0.4 Ma. The faunas of the Eureka boreholes closely follow the faunal evolution in Hole 625B. Discrepancies between faunal compositions of 625B and approximately coeval Eureka samples occur particularly in late Pliocene and Pleistocene intervals. These discrepancies originate from the chance recovery of Eureka samples they may represent intermediate climatic stages. Samples from Hole 625B were analyzed in three size fractions: 74 to 125pm, 125 to 150,um, and >150gm. The effect of different size fraction upon faunal composition is slight between the 125 to 150gm and the >150gm fraction. However, the contrast between the faunas of the fine fraction (74 to 125gm) and the coarse fraction (>125gm) is drastic. Exclusively small species belong primarily to the genera of Bolivina and Eponides, which are often indicators of very high biological productivity and/or oxygen deficiency. INTRODUCTION The microfaunas on the deep ocean floor live in an extremely stable environment, an environment that does not experience the drastic fluctuations that surface organisms have to endure. Deep sea benthic foraminifers show a remarkably slow rate of faunal turnover (Douglas and Woodruff 1981) that is inherent from the slow, random process of genetic mutation, which only occasionally receives direction from environmental change. One such environmentally forced event occurred during the late Eocene (Corliss et al. 1984), when the global deep ocean circulation switched from warm and salty low latitude source areas to cold high latitude areas. Boltovskoy and Boltovskoy (1988) argue that this was the one turnover during which the deep sea microfauna, that had its origin during the Mesozoic, became essentially moder. The difference between Oligocene and moder faunas, they argue, lies mostly in historically developed errors of taxonomic usage. However, many authors document another, perhaps lesser, faunal turnover during the late middle Miocene (e.g. Berggren 1972; Schnitker 1979b, 1986; Boersma 1986; Thomas 1986; Woodruff and Savin 1989; Miller et al. 1992). This Miocene faunal turnover is usually ascribed to the additional cooling of deep ocean water, coincident with the build-up of a permanent ice cap on Antarctica. However, Thomas and Vincent (1987) suggest that the faunal change predated the ice-cap formation and cooling. Very large climatic changes occurred during the last five million years that have also affected the deep ocean environment: the sudden beginning of intermittent ice sheet occurrences in the northern hemisphere at 2.4 Ma (Shackleton et al. 1984). It would be reasonable to expect significant faunal turnover at these climatic and oceanographic forcing points as well. Studies of late Quaternary piston cores (e.g., Streeter 1973; Schnitker 1974, 1979a) clearly demonstrated that the deep faunas rearranged themselves drastically in response to glacial/interglacial deep water changes. Several works on the PlioPleistocene sequences of DSDP and ODP holes (Schnitker 1984, 1986; Boersma 1985; Thomas 1986; Loubere and Banonis 1987; Boltovskoy and Boltovskoy 1988; Kurihara and Kennett 1988) also found a drastic change in the composition of the benthic faunas, but hardly any extinctions or occurrences of new species.

Miocene Climatic Oscillation Recorded in the Lakes Entrance Oil Shaft, Southern Australia: Reappraisal of the Planktonic Foraminiferal Record

Summary Deep marine basins began to form along the continental margin of central California in late Oligocene time as a result of the initiation of a translational plate boundary. Deposition of transgressive shallow-marine sand (Vaqueros Formation) was followed by deposition of a thick (> 500 m) massive clay unit (Rincon Shale). Rapid subsidence (> 2000 m) coincident with rising sea-level created sediment-starved basins by late early Miocene time ( c. 18 Ma). Typical of many of these borderland basins was the Santa Barbara basin, located at least 50 km from the Miocene strandline. In this basin, between late early and latest Miocene time (18–5.5 Ma), was deposited a heterogeneous sequence of highly biogenous sediment (Monterey Formation) consisting of mixed diatomaceous, foraminiferal-coccolithic, and terrigenous debris generally rich in organic matter (mean 8%). Overlying latest Miocene and Pliocene sediments (Sisquoc Formation) contain increasingly abundant clay debris. The Miocene biogenous sequence reflects hemipelagic sedimentation from highly productive coastal waters during an extended period of generally low terrigenous influx. Accumulation of terrigenous debris decreased markedly in the early Miocene (from 11 to 1 g/cm 2 ·10 3 yr) and was low throughout the middle Miocene, increasing somewhat at about 8 Ma and markedly after 5.5 Ma; this pattern is partly related to global sea-level changes but also resulted from high rates of subsidence and tectonic events. Biogenous silica accumulation peaked (mean 2.5 g/cm 2 ·10 3 yr) in the late early Miocene (18–15 Ma) and again in the late Miocene and early Pliocene (8–3.5 Ma) and was 5 to 25 times slower in the interval 15–11 Ma; these variations are thought to reflect primarily variations in the intensity of upwelling and associated production of diatoms. Accumulation rates of biogenous calcite gradually declined from a late early Miocene peak through the early late Miocene and virtually ceased in latest Miocene (8–5.5 Ma), probably due to dissolution. Massive stratification indicates that bottom waters were oxygenated until latest early Miocene time ( c. 16 Ma), when expansion of the oxygen-minimum zone or tectonic formation of a sill within the oxygen-minimum zone produced marked lowering of oxygen levels resulting in the dominance of laminated stratification between 16 and 5.5 Ma. Abundance of organic matter is closely associated with the abundance of clay and of calcite but is inversely correlated with silica content. Organic matter is also about twice as abundant in massive or discontinuously laminated beds (indicating good to moderate oxygenation) than in associated beds with varve-like lamination (indicating minimal oxygenation). These relations indicate that grain-size outweighed the influence of low-oxygen bottom waters in preserving organic matter.

Deep sea Cenozoic paleoceanographic evolution was studied using quantitative analysis of benthic foraminifera from ODP Sites 757 and 758 (Ninetyeast Ridge) and Site 747 (Kerguelen Plateau), on the south-north transect of the Indian Ocean. Bathyal Site 747 records high latitude paleoceanography and Sites 757 and 758 record midto lowlatitude bathyal and abyssal paleoceanography respectively. Benthic foraminiferal assemblages reflect global paleoceanographic changes, but the faunal changes are not all coeval, due to the different paleodepths and paleolatitudes. At Site 747, Southern Component Water (SCW) developed in the Oligocene and middle Miocene; Northern Component Water (NCW) and SCW developed in the Oligocene and the late Miocene. At bathyal Site 757, the following periods of paleoceanographic change were recognized: early to middle Eocene (-52 Ma), late middle Eocene (-42 Ma), latest Eocene (-38 Ma), early Oligocene (-32 Ma), middle Miocene (-12 Ma), and late Miocene (-8 Ma). At abyssal Site 758, the paleoceanographic changes are complex, with both NCWand SCW-allied assemblages occurring in the Oligocene and the middle Miocene to Pliocene (-33-29, -26-24, -9, -6-4, -3 Ma). Comparison of the benthic foraminiferal assemblages with the modern distribution of foraminiferal species and with oxygen and carbon isotopic data suggests the following paleoecological conditions at Sites 757 and 758: Cold water and high organic matter-exploiting assemblages appeared from the late Miocene to Pleistocene; warm water and lower organic matter-exploiting assemblages occurred from the early Eocene to middle Miocene. Resistant to high carbonate corrosion-type assemblages developed during the Oligocene and from the late Miocene to Pliocene at Site 747. Temperature decrease and changes in the food resource (phytodetritus) level of deep water are important factors for the benthic faunal changes throughout the Cenozoic. Faunal changes at bathyal depths before the middle Miocene occurred during a lower food resource level and those from the middle Miocene onward occurred in an enriched phytodetritus flux in deep water. The modern deep water is formed at -2 Ma in the Indian Ocean at Sites 757 and 758. The cold-water and carbonate corrosion-type assemblages are more dominant at Subantarctic Site 747.

Lufengpithecus keiyuanensis from the Xiaolongtan Coal Mine is the earliest known Miocene fossil hominoids in southern China, yet its chronological context has long been subjected to disputes, in being either of late Middle Miocene or early Late Miocene age. This controversy is largely due to the uncertainty of the exact positions of previously discovered fossils in the outcrops, and the different chronological interpretations for some proboscidean and suid fossils from associated fossil faunal assemblages. Here we report the first discovery of Stegolophodon latidens from Xiaolongtan with an unambiguous stratigraphic provenance, which provides important evidence in constraining the age of Lufengpithecus keiyuanensis . Stegolophodon has a very high evolutionary rate of dental morphology, and exhibits a pronounced evolutionary trend with time: from the pentalophodont m3 of the Early Miocene or early Middle Miocene, to the pentalophodont M3 and hexalophodont m3 of the late Middle Miocene, to the 5.5-lophed (five principal lophs followed by an extreme well-developed cingulum) M3 and hexa- to heptalophodont m3 of the early Late Miocene, and to the hexalophodont M3 and hepta- to octalophodont m3 of the middle Late Miocene. The newly discovered Stegolophodon latidens bears a 5.5-lophed M3 and a heptalophodont m3, the second and subsequent lophs/lophids show a slight chevron structure, and the pretrite mesoconelets shift mesially and fuse with the corresponding pretrite anterior central conules, forming a “Y-shape”. These traits are similar to, or even slightly more derived than those of Stegolophodon from the lower part of the Dhok Pathan Formation (9.3−8.3 Ma) in the Middle Siwaliks of the Indian Subcontinent. The materials described here can all be assigned to Stegolophodon latidens which was originally discovered from the Yenangyaung fauna, the lower Irrawaddy Formation of Myanmar, deemed of early Late Miocene age. Revisions on the other proboscidean and suid materials also support an early Late Miocene age for Xiaolongtan Fauna. The new fossils were discovered from the upper part of the lignite layers, close to the bottom of the greyish marls of the Buzhaoba Formation. Based on the original records in the geological reports of the Xiaolongtan Coal Mine, the descriptions of the previous publications, as well as the accounts of the fossil finders, the Xiaolongtan coal mine possesses only one fossiliferous layer, which locates in the upper part on the Xiaolongtan Formation (lignite layers). Therefore, the new fossils situate possibly in the same layer as Lufengpithecus keiyuanensis that were found in the 1950’s and 1980’s. From the recent palaeomagnetic investigations, the age of this fossil layer should be 11.6/11.7 Ma, close to the boundary between the Middle and the late Miocene; however, seems to be slightly older than Stegolophodon latidens from the Siwaliks. Further investigations should be carried out to resolve this inconsistency.

Correlation of pollen sequences in the Neogene palynofloristic regions of China