Nature and origin of carbonate particles along a transect on the western margin of Great Bahama Bank (Middle Miocene): sedimentary processes and depositional model

2008 ◽  
Vol 179 (3) ◽  
pp. 231-244 ◽  
Author(s):  
Mélanie Turpin ◽  
Laurent Emmanuel ◽  
Maurice Renard
Keyword(s):  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
Calcareous Nannofossils ◽  
Western Margin ◽  
Great Bahama Bank ◽  
Permeable Sediments ◽  
Low Magnesium ◽  
Carbonate Sedimentation ◽  
Depositional Processes ◽  
Magnesium Calcite

Abstract During ODP Leg 166, Middle Miocene sediments were collected along the western margin of the Great Bahama Bank (GBB) at four sites, distributed along a proximal-distal transect. Site 1006 is located in the basin, Site 1007 at the toe-of-slope and Sites 1003 and 1005 on the mid and upper slope. The carbonate slope deposits of GBB consist of periplatform oozes, an admixture of platform-derived aragonite and high-magnesium calcite particles, and pelagic low-magnesium calcite. An assessment of carbonate sedimentation is made in order to estimate the proportion of platform-derived versus pelagic components. The originality of this study is based on the application of a separation method giving access to homogeneous granulometric fractions, ranging from 63 to 3 μm in grain diameter. This method, associated with a multidisciplinary approach (micropaleontology, optical and electronic microscopy, mineralogy – X-ray diffractometry, and trace elements geochemistry – strontium and magnesium), allows the quantification and characterization of different kinds of carbonate particles. In Miocene sediments, three types of particles display a biogenic structure: planktonic foraminifera, calcareous nannofossils and fragments of neritic organisms. Two types of particles do not exhibit any structures that allow for a determination of their origin. Based on their size and their mineralogy, we have distinguished macroparticles (calcite and dolomite) and microparticles (calcite and aragonite). The detailed study of the composition of the separated fractions highlights major differences in carbonate ooze composition between the different sites along the transect. The unlithified samples of Sites 1006 and 1007 are dominated by pelagic components (planktonic foraminifera and calcareous nannofossils) and contain aragonite microparticles. In contrast, lithified sediments of Sites 1003 and 1005 (and 1007) are characterized by higher proportions of neritic debris and particles without biologic structure, the pelagic phase is impoverished and aragonite needles are absent. The origin of particles without biological structure has been demonstrated by their spatial distribution and by mineralogical as well as geochemical criteria. The rhombohedral calcitic microparticles mainly occur at slope sites. Their high magnesium contents support a formation on the bank implying an allochthonous origin. This suggests that calcitic microparticles correspond to the bank micrite exported towards slope environments. Rhomboedral calcitic macroparticles, which fill sediment voids, originate from in situ transformations of metastable carbonates due to pore fluids, which preferentially flow in the slope permeable sediments. Two sedimentary sources are proposed: 1) an autochthonous pelagic source with low-magnesium calcitic components and 2) an allochthonous neritic source with both aragonitic and calcitic components. Export and depositional processes can be differentiated for the allochthonous particles. The neritic debris and calcitic microparticles in slope Sites 1003 and 1005 (and less frequently in Site 1007) were probably exported by gravity currents whereas the aragonite microparticles, due to their shape and granulometry, were perhaps transported as suspension and deposited at the distal Sites 1006 and 1007.

scholarly journals <i>Bolboforma</i> (Phytoplankton Incertae Sedis), <i>Bachmayerella</i> and other Calciodinelloidea (Phytoplankton) from the Middle Miocene of the Alpine–Carpathian Foredeep (Central Paratethys)

2004 ◽  
Vol 23 (2) ◽  
pp. 139-152 ◽  
Author(s):  
Silvia Spezzaferri ◽  
Fred Rögl
Keyword(s):  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
High Latitudes ◽  
Calcareous Nannofossils ◽  
Geological Time ◽  
Incertae Sedis ◽  
Sedimentary Sequences ◽  
Unicellular Organisms ◽  
First Time

Abstract. Bolboforma is a microfossil of uncertain origin with affinities to protophytic algae. It generally occurs at high latitudes and/or in cool and temperate waters and has a high stratigraphic potential especially for the Miocene. Calcareous cysts of dinoflagellates represent the ‘benthic cyst stage’ of unicellular organisms belonging to the marine phytoplankton.The occurrence of Bolboforma, Bachmayerella is documented here and, for the first time, some calcareous cysts of dinoflagellates tentatively attributed to Alasphaera and Pithonella from Badenian (Langhian–Middle Miocene) sediments in Austrian and Moravian localities. Alasphaera and Pithonella were previously described from Cretaceous and Danian sediments only, therefore, their range has been extended into the Paratethyan Middle Miocene.Correlation of Bolboforma bioevents with standard geological time-scales allows confirmation, and in some cases refinement, of age assignments based on other microfossil groups, such as foraminifera and calcareous nannofossils, in Paratethyan areas. In particular, this paper presents a case study of the biostratigraphy of the Grund Formation outcropping at its type locality in Lower Austria. Age attribution of the Grund Formation has been uncertain for some time. The recovery of Praeorbulina glomerosa circularis and Uvigerina macrocarinata, associated with Bolboforma reticulata, allows the correlation of the Grund Formation with the Early Badenian (Middle Miocene). As planktonic foraminifera are generally very rare or absent in shelf deposits of many other Austrian and Moravian Middle Miocene sedimentary sequences, Bolboforma, and in particular B. reticulata, remains an important biomarker to identify lower Badenian sediments.Additionally, the new species Bolboforma gneixendorfensis Spezzaferri &amp; Rögl is described. It is generally double-chambered with a weakly reticulate wall texture and is associated with Bolboforma reticulata, B. bireticulata and/or B. moravica.

scholarly journals Mg/Ca Ratios in Synthetic Low-Magnesium Calcite: An Experimental Investigation

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1158
Author(s):  
Jeremy M. Weremeichik ◽  
Rinat I. Gabitov ◽  
Aleksey Sadekov ◽  
Aleksandra Novak ◽  
Angel Jimenez ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Partition Coefficients ◽  
Planktonic Foraminifera ◽  
Calcite Precipitation ◽  
Low Magnesium ◽  
Magnesium Calcite ◽  
Set Up

The work presented sought to determine the effects of Mg/Ca ratios in solution have on Mg partitioning (KMg) between precipitated abiotic low-Mg calcite and solution. Experiments were set up so that Mg/Ca in precipitated abiotic calcite would match the Mg/Ca in planktonic foraminifera. This research intended to investigate the effect of Mg/Ca(Fluid) on KMg when the molar value of Mg/Ca(Fluid) was below 0.5, which is below the previously reported Mg/Ca range. The values of pH, salinity, and aqueous Mg/Ca were monitored during calcite precipitation, and Mg/Ca of calcite was determined at the end of experiments. Partition coefficients of Mg were evaluated as a ratio of Mg/Ca in calcite to the averaged ratio of aqueous Mg/Ca for each experiment.

scholarly journals Late Neogene evolution of modern deep-dwelling plankton

2021 ◽  
Author(s):  
Flavia Boscolo-Galazzo ◽  
Amy Jones ◽  
Tom Dunkley Jones ◽  
Katherine A. Crichton ◽  
Bridget S. Wade ◽  
...  
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
Euphotic Zone ◽  
Biological Pump ◽  
Calcareous Nannofossils ◽  
The Past ◽  
Late Neogene ◽  
Global Cooling

Abstract. The fossil record of marine microplankton provides insights into the evolutionary drivers which led to the origin of modern deep-water plankton, one of the largest component of ocean biomass. We use global abundance and biogeographic data combined with depth habitat reconstructions to determine the environmental mechanisms behind speciation in two groups of pelagic microfossils over the past 15 million years. We compare our microfossil datasets with water column profiles simulated in an Earth System model. We show that deep-living planktonic foraminiferal (zooplankton) and calcareous nannofossil (mixotroph phytoplankton) species were virtually absent globally during the peak of the middle Miocene warmth. Evolution of deep-dwelling planktonic foraminifera started from subpolar-midlatitude species during late Miocene cooling, via allopatry. Deep-dwelling species subsequently spread towards lower latitudes and further diversified via depth sympatry, establishing modern communities stratified hundreds of meters down the water column. Similarly, sub-euphotic zone specialist calcareous nannofossils become a major component of tropical and sub-tropical assemblages through the latest Miocene to early Pliocene. Our model simulations suggest that increased organic matter and oxygen availability for planktonic foraminifera, and increased nutrients and light penetration for nannoplankton, favored the evolution of new deep water niches. These conditions resulted from global cooling and the associated increase in the efficiency of the biological pump over the last 15 million years.

scholarly journals The evolution of the Carpathian Foredeep Basin during the latest Badenian and Sarmatian (Middle Miocene): inferences from micropalaeontological data

2020 ◽  
Vol 64 (4) ◽  
Author(s):  
Simina Dumitriţa DUMITRIU ◽  
Zofia DUBICKA ◽  
Sergiu LOGHIN ◽  
Mihaela Carmen MELINTE-DOBRINESCU ◽  
Jolanta PARUCH-KULCZYCKA
Keyword(s):  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
Foreland Basin ◽  
Taxonomic Composition ◽  
Calcareous Nannofossils ◽  
Central Paratethys ◽  
Carpathian Foredeep ◽  
The Republic ◽  
Significant Regression ◽  
Matter Flux

Seven Middle Miocene (Upper Badenian to Lower Sarmatian) sedimentary sections of the Central Paratethys, two from the Polish Carpathian Foredeep Basin (PCFB) and five from the Eastern Carpathian Foreland Basin (ECFB) of Romania and the Republic of Moldova have been analysed micropalaeontologically to better constrain the Badenian-Sarmatian Extinction Event, characterized by significant taxonomic impoverishment of both foraminifers and ostracods. Our studies show significant palaeoenvironmental changes in the basin including depth, salinity, oxygenation, and organic matter flux. The occurrence of moderately diverse planktonic foraminifera (Globigerina, Globigerinita, Globorotalia, Trilobatus, Orbulina, Velapertina) in the Upper Badenian deposits of the PCFB as well as in the ECFB and their rarity in the lowermost Sarmatian indicate an almost fully marine environment during the latest Badenian, followed by a significant regression and possible appearance of much more restricted marine conditions across the boundary. The taxonomic composition of the Sarmatian foraminifera, ostracoda and calcareous nannofossils indicate that during this interval the salinity fluctuated strongly, with the water regime varying from brackish to normal marine. In addition, the identified micropalaeontological assemblages identified show palaeoenvironmental similarity across different basins of the Central Paratethys. This supports a hypothesis of possible connections during the latest Badenian between different areas of the Central Paratethys, as well as of the existence of a gateway between the Central Paratethys and the Mediterranean realm

scholarly journals Age determinations of Neogene sediments from the English Channel and Western Approaches

1986 ◽  
Vol 5 (1) ◽  
pp. 5-6
Author(s):  
D. Graham Jenkins ◽  
Erlend Martini
Keyword(s):  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
English Channel ◽  
Calcareous Nannoplankton ◽  
Lower Miocene ◽  
Published Evidence ◽  
Neogene Sediments ◽  
Age Range ◽  
Age Determinations

Abstract. Original published evidence indicated an age range of early Lower Miocene to early Middle Miocene for Globigerina silt samples from the English Channel and the Western Approaches. Suggested younger ages for these samples are refuted on the basis of planktonic foraminifera and calcareous nannoplankton.

scholarly journals The calcareous nannofossil <i>Prinsiosphaera</i> achieved rock-forming abundances in the latest Triassic of western Tethys: consequences for the δ<sup>13</sup>C of bulk carbonate

2013 ◽  
Vol 10 (5) ◽  
pp. 7989-8025 ◽  
Author(s):  
N. Preto ◽  
C. Agnini ◽  
M. Rigo ◽  
M. Sprovieri ◽  
H. Westphal
Keyword(s):  
Global Ocean ◽  
Late Triassic ◽  
Calcareous Nannofossils ◽  
Calcareous Nannofossil ◽  
Western Tethys ◽  
Carbonate Sedimentation ◽  
History Of ◽  
Calcareous Plankton ◽  
Inorganic Carbon Cycle

Abstract. The onset of pelagic biomineralization marked a milestone in the history of the long term inorganic carbon cycle: as soon as calcareous nannofossils became major limestone producers, the pH and supersaturation state of the global ocean were stabilized (the so-called Mid Mesozoic Revolution). But although it is known that calcareous nannofossils were abundant already by the end of the Triassic, no estimates exist on their contribution to hemipelagic carbonate sedimentation. With this work, we estimate the volume proportion of Prinsiosphaera, the dominant Late Triassic calcareous nannofossil, in hemipelagic and pelagic carbonates of western Tethys. The investigated Upper Triassic lime mudstones are composed essentially of microspar and tests of calcareous nannofossils, plus minor bioclasts. Prinsiosphaera became a significant component of lime mudstones since the late Norian, and was contributing up to ca. 60% of the carbonate by the late Rhaetian in periplatform environments with hemipelagic sedimentation. The increasing proportion of Prinsiosphaera in upper Rhaetian hemipelagic lime mudstones is paralleled by a increase of the δ13C of bulk carbonate. We interpreted this isotopic trend as related to the diagenesis of microspar, which incorporated respired organic carbon with a low δ13C when it formed during shallow burial. As the proportion of nannofossil tests increased, the contribution of microspar with low δ13C diminished, determining the isotopic trend. We suggest that a similar diagenetic effect may be observed in many Mesozoic limestones with a significant, but not yet dominant, proportion of calcareous plankton.

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