The origin and significance of zigzag microstructure in late Paleozoic Lophophyllidium (Anthozoa, Rugosa)

2003 ◽  
Vol 77 (1) ◽  
pp. 16-30 ◽  
Author(s):  
James E. Sorauf ◽  
Gregory E. Webb
Keyword(s):  
Magnesium Content ◽  
Secular Change ◽  
Late Paleozoic ◽  
Mole Percent ◽  
Rugose Corals ◽  
Magnesian Calcite ◽  
Magnesium Calcite ◽  
Subsequent Loss ◽  
Geochemical Studies ◽  
Buckhorn Asphalt

In late Paleozoic solitary Rugosa, the zigzag microstructure as defined by Schindewolf (1942) is related to presence of an elevated magnesium content within biogenic calcite (intermediate magnesian calcite, IMC) and its subsequent loss during diagenesis by microdissolution and neomorphism. This particular microstructure has been recognized with certainty only in some Carboniferous and Permian rugose corals (e.g., Lophophyllidium spp.). Septal and other skeletal microstructures in those corals are dominantly (oblique) sloping-lamellar, which is also interpreted as diagenetic in origin. Two directions of oblique lamellae commonly occur in thickened skeletal elements, forming chevrons that make up zigzag microstructure with its orientation determined by presence of microdolomite blebs within skeletal calcite. Geochemical studies of corals from the Mississippian Imo Formation of Arkansas, the Pennsylvanian Buckhorn asphalt of Oklahoma and Pennsylvanian Kendrick Shale of Kentucky all indicate that magnesium content in skeletal calcite of the corals was elevated, with a maximum in the neighborhood of six to eight mole percent CaCO3, thereby forming intermediate magnesium calcite. Corals with this zigzag microstructure apparently only occurred during the late Paleozoic interval of “aragonite seas”; as a result, this diagenetic behavior of rugose corals can serve as a proxy for secular change in marine chemistry and/or climate.

scholarly journals THE HIGH-MAGNESIUM CALCITE ORIGIN OF NUMMULITID FORAMINIFERA AND IMPLICATIONS FOR THE IDENTIFICATION OF CALCITE DIAGENESIS

Palaios ◽  
2020 ◽  
Vol 35 (10) ◽  
pp. 421-431
Author(s):  
LAURA J. COTTON ◽  
DAVID EVANS ◽  
SIMON J. BEAVINGTON-PENNEY
Keyword(s):  
Magnesium Content ◽  
Carbonate Diagenesis ◽  
X Ray Diffraction ◽  
Larger Benthic Foraminifera ◽  
X Ray ◽  
Low Magnesium ◽  
Fossil Material ◽  
Magnesium Calcite ◽  
High Magnesium Calcite ◽  
Geochemical Studies

ABSTRACT Nummulites were one of the most abundant and widespread larger benthic foraminifera of the Paleogene, however, confusion remains within the literature as to whether their original test mineralogy was high or low magnesium calcite. As the number of studies using proxies based on Nummulites and related nummulitid geochemistry increase, it is essential to have a firm understanding of test composition to assess preservation within potential samples, and to interpret results. Here we employ a combination of X-ray diffraction, Fourier transform infra-red spectroscopy, and laser ablation ICPMS to determine magnesium content across exceptionally preserved and poorly preserved fossil material as well as modern examples of nummulitids—showing conclusively a primary intermediate to high magnesium calcite composition. This composition appears to be closely related to fluctuating ocean chemistry through the Paleogene. Using these results as an indicator of preservation we examine variation in trace element data across a suite of samples, and introduce the concept of the preservagram, a method of quickly visualizing different styles of carbonate diagenesis. Understanding the original mineralogy of nummulitids and, therefore, the extent to which specimens have been diagenetically altered, is essential as larger foraminifera are increasingly used in geochemical studies.

Probable calcified metaphytes in the latest Proterozoic Nama Group, Namibia: origin, diagenesis, and implications

1991 ◽  
Vol 65 (1) ◽  
pp. 1-18 ◽  
Author(s):  
S. W. F. Grant ◽  
A. H. Knoll ◽  
G. J. B. Germs
Keyword(s):  
Red Algae ◽  
Late Paleozoic ◽  
Lateral Dimension ◽  
Geochemical Evidence ◽  
Magnesian Calcite ◽  
Primary Structures ◽  
Phylloid Algae

Samples from the Huns Limestone Member, Urusis Formation, Nama Group, at two adjacent localities in southern Namibia contain thin foliose to arched, sheet-like carbonate crusts that are 100–500 µm thick and up to 5 cm in lateral dimension. Morphologic, petrographic, and geochemical evidence supports the interpretation of these delicate crusts as biogenic, most likely the remains of calcified encrusting metaphytes. The original sediments of the fossiliferous samples contained aragonitic encrusting algae, botryoidal aragonite cements, and an aragonite mud groundmass. Spherulites within the precursor mud could represent bacterially induced mineral growths or the concretions of marine rivularian cyanobacteria. Original textures were severely disrupted during the diagenetic transition of aragonite to low-magnesian calcite, but some primary structures remain discernible as ghosts in the neomorphic mosaic. Gross morphology, original aragonite mineralogy, and hypobasal calcification indicate that the crusts are similar to late Paleozoic phylloid algae and extant peyssonnelid red algae. Structures interpreted as possible conceptacles also suggest possible affinities with the Corallinaceae.Two species of Cloudina, interpreted as the remains of a shelly metazoan, are also known from limestones in the Nama Group. It is possible, therefore, that skeletalization in metaphytes and animals arose nearly simultaneously near the end of the Proterozoic Eon.

scholarly journals Stable isotopes and predation marks shed new light on ammonoid habitat depth preferences

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marcin Machalski ◽  
Krzysztof Owocki ◽  
Zofia Dubicka ◽  
Oksana Malchyk ◽  
Weronika Wierny
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Late Cretaceous ◽  
Late Paleozoic ◽  
Planktic Foraminifera ◽  
Habitat Depth ◽  
Local Populations ◽  
Isotope Data ◽  
Geochemical Studies ◽  
Stable Isotope Data

AbstractAmmonoids are extinct cephalopods with external shells which predominated in many late Paleozoic and Mesozoic marine ecosystems. Stable isotope data from ammonoid shells constitute primary tools for understanding their palaeohabitats. However, in most sedimentary successions globally the aragonitic shells of ammonoids are dissolved during fossilisation process and therefore not available for geochemical studies. We overcome this taphonomic bias by analysing the better preservable calcitic elements of the ammonoid jaws (aptychi). We study moulds and aptychi of two successive members, temporal subspecies in our interpretation, of a scaphitid evolutionary lineage from a Late Cretaceous chalk succession in Poland. In order to reconstruct their habitat depth preferences, we apply the powerful combination of stable isotope data from aptychi and co-occurring benthic and planktic foraminifera with an analysis of predation marks preserved on scaphitid specimens. On this basis we conclude that the populations of the older subspecies led a nektic, and those of the younger subspecies, a nektobenthic lifestyle. The shift in habitat depth preferences took place probably as a response of local populations to the shallowing of the sea. Previous studies largely assumed stable depth preferences for ammonoid species, genera and even higher clades. Our study casts doubts over such generalizations by pointing out that ammonoids could have been more flexible in their depth-related behaviour than anticipated.

scholarly journals Influence of temporally varying weatherability on CO<sub>2</sub>–climate coupling and ecosystem change in the late Paleozoic

2020 ◽  
Author(s):  
Jon D. Richey ◽  
Isabel P. Montañez ◽  
Yves Goddéris ◽  
Cindy V. Looy ◽  
Neil P. Griffis ◽  
...  
Keyword(s):  
Steady State ◽  
Ice Age ◽  
Secular Change ◽  
Ecosystem Change ◽  
Late Paleozoic ◽  
Relative Role ◽  
C Cycle ◽  
Ecosystem Perturbation ◽  
Atmospheric Pco2

Abstract. Earth's penultimate icehouse, the Late Paleozoic Ice Age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2 : CO2 during the LPIA and its subsequent demise to permanent greenhouse conditions is crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40-Myr interval (~313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2-glaciation linkage, (2) documents synchroneity between major pCO2 and O2 : CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2 : CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources, active during the LPIA and its demise, on steady-state pCO2 using an intermediate complexity climate-C cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangaean Mountains, intensifying aridification, and increasing mafic rock to-granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

Carboniferous biostratigraphy of rugose corals

2021 ◽  
pp. SP512-2021-79
Author(s):  
Xiang-dong Wang ◽  
Sun-rong Yang ◽  
Le Yao ◽  
Tetsuo Sugiyama ◽  
Ke-yi Hu
Keyword(s):  
High Resolution ◽  
The Other ◽  
Ice Age ◽  
Late Paleozoic ◽  
Long Distance ◽  
Distance Correlation ◽  
Rugose Corals ◽  
Rugose Coral ◽  
Late Paleozoic Ice Age ◽  
Coral Composition

AbstractRugose corals are one of the major fossil groups in shallow-water environments. They played an important role in dividing and correlating Carboniferous strata during the last century, when regional biostratigraphic schemes were established and may be useful for long-distance correlation. Carboniferous rugose corals document two evolutionary events. One is the Tournaisian recovery event, with abundant occurrences of typical Carboniferous rugose corals such as columellate taxa and a significant diversification of large, dissepimented corals. The other is the changeover of rugose coral composition at the mid-Carboniferous boundary, which is represented by the disappearance of many large dissepimented taxa with complex axial structures and the appearance of typical Pennsylvanian taxa characterized by compound rugose taxa. The biostratigraphic scales for rugose corals show a finer temporal resolution in the Mississippian than in the Pennsylvanian, which was probably caused by the Late Paleozoic Ice Age that resulted in glacial-eustatic changes and a lack of continuous Pennsylvanian carbonate strata. The Pennsylvanian rugose corals are totally missing in the Cimmerian Continent. High-resolution biostratigraphy of rugose corals has so far only achieved in few regions for the Mississippian time scale. In most regions, more detailed taxonomic works and precise correlations between different fossil groups are needed.

Secular variation in microfossil preservation: causes and consequences of the biogeochemical evolution of the oceans

1992 ◽  
Vol 6 ◽  
pp. 201-201
Author(s):  
Ronald E. Martin
Keyword(s):  
Sea Level ◽  
Habitat Diversity ◽  
Secular Change ◽  
Late Paleozoic ◽  
Calcareous Nannoplankton ◽  
Regulatory Pathways ◽  
Water Column Stratification ◽  
Evolutionary Innovation ◽  
Calcareous Plankton ◽  
Fossil Preservation

Because of their abundance, composition, and widespread occurrence throughout the Phanerozoic, microfossils are ideal subjects for teasing apart the ecological, evolutionary, geochemical, and taphonomic controls on the fossil record, and for testing hypotheses of evolutionary paleoecology against secular change in ocean chemistry as evidenced by patterns of fossil preservation. The history of calcareous plankton is one of interaction between the evolutionary innovation of regulatory pathways in hardpart construction and the paleochemistry of the seas. Diversification of ancestral shelfal calcareous plankton lineages in the Mesozoic was related to sea level transgression, water column stratification, and habitat diversity, as evidenced by major expansions of these groups in association with Oceanic Anoxic Events. In the case of coccolithophorids (calcareous Haptophyceae), the origination of calcified lineages also appears to have been related to nutrient resuspension from bottom sediments and anoxic waters (which may have promoted calcification) advected into the photic zone over shallow shelves during transgressions. Invasion of pelagic habitats by Foraminifera was facilitated by the evolution of test secretory mechanisms (beginning in the Late Paleozoic) that conferred greater cellular control over shell microstructure and density. The beginnings of calcareous nannoplankton, however, are traceable to microfossil “Lagerstätten” that hint at the first attempts at calcification by naked haptophycean lineages much earlier in the Paleozoic. During the Early-Mid Paleozoic greenhouse phase, calcareous nannoplankton assemblages were unlikely to be preserved because high levels of atmospheric (and therefore oceanic) CO2 and extraction of CaCO3 in epeiric seas by calcareous biota resulted in a very shallow CCD. With the advent of the Late Paleozoic icehouse phase (and associated sea level fall), the locus of biogenic limestone deposition shifted seaward and the CCD deepened. Significant accumulations of calcareous pelagic sediments followed in the Late Jurassic in response to diversification of calcareous plankton. As deep pelagic oozes began to accumulate, a new component was added to the global carbon cycle: the metamorphic decarbonation of pelagic limestones that controls long-term (i.e., tens to hundreds-of-millions of years) global warming.

Inter and intraspecific comparisons of the skeletal Mg/Ca ratios of high latitude Antarctic echinoderms

2018 ◽  
Vol 30 (3) ◽  
pp. 160-169 ◽  
Author(s):  
A. Duquette ◽  
K.M. Halanych ◽  
R.A. Angus ◽  
J.B. Mcclintock
Keyword(s):  
Inverse Relationship ◽  
Sea Urchins ◽  
Inverse Correlation ◽  
Magnesium Content ◽  
Sea Stars ◽  
Brittle Stars ◽  
Magnesium Calcite ◽  
High Magnesium Calcite ◽  
The Relationship ◽  
Collection Sites

AbstractEchinoderms are vulnerable to ocean acidification because of their high magnesium calcite skeletons. Here, skeletal Mg/Ca ratios were examined within and between individuals of 20 Antarctic echinoderms representative of the asteroids, ophiuroids and echinoids. The highest mean Mg/Ca ratios occurred in the discs and arms (0.111 and 0.110, respectively) of brittle-stars and the lowest in the spines (0.010) of cidaroid sea urchins. Many taxa (11 of 14 species) from the collection sites showed no intraspecific differences in Mg/Ca ratios between given skeletal components. Exceptions were the spines of two regular sea urchins and the skeletal ossicles of the combined arms and disc of a brittle-star. The relationship between skeletal magnesium content and latitude was further evaluated and an inverse correlation was found between Antarctic echinoderm taxa skeletal magnesium content and latitude across 62° to 76°, indicating that the relationship occurs over relatively narrow latitudes. Upon examination of an even narrower range (70–76° latitude), a region where the mineralogy of echinoderm skeletons has not been investigated, the predicted inverse relationship between Mg/Ca ratio and latitude was still observed in sea-stars, but not in brittle-stars or sea urchins.

Dianulites Eichwald, 1829: An unusual Ordovician bryozoan with a high-magnesium calcite skeleton

1999 ◽  
Vol 73 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Paul D. Taylor ◽  
Mark A. Wilson
Keyword(s):  
Type Species ◽  
Growth Form ◽  
Rugose Corals ◽  
Lower Ordovician ◽  
Magnesium Calcite ◽  
Ultrathin Sections ◽  
High Magnesium Calcite ◽  
Living Tissues ◽  
First Time ◽  
Benthic Animals

The ‘granular’ wall microstructure of the Ordovician stenolaemate bryozoan Dianulites Eichwald, 1829, has been studied using ultrathin sections, scanning electron microscopy (SEM), analytical SEM, and cathodoluminescence. The timing of recrystallization and the presence of microdolomite inclusions in the skeletal walls implies that the original skeleton consisted of high-magnesium calcite (HMC). Although found in some modern cheilostomes, HMC has not been recorded in living stenolaemate bryozoans, but appears to have also been present in Nicholsonella and a few other Ordovician genera traditionally assigned to the trepostomes or cystoporates. The Russian type species of Dianulites, D. fastigiatus Eichwald, 1829, is revised and recorded for the first time in North America from the Fillmore Formation (Lower Ordovician) of Utah. Unusually among bryozoans, D. fastigiatus has turbinate, cone- or horn-shaped colonies, straight to slightly curved, with zooids opening on the flat, broad end of the cone; the sides of the cone comprise calcified exterior walls. This growth-form resembles some solitary rugose corals and other benthic animals thought to have lived with all but their tops buried in soft sediment. Such an interpretation is supported in Dianulites by the scarcity of epibionts on the exterior walls of the cone and by the occurrence of specimens comprising stacks of subcolonies, suggesting periods of partial burial of the living tissues by sediment.

scholarly journals Influence of temporally varying weatherability on CO<sub>2</sub>-climate coupling and ecosystem change in the late Paleozoic

2020 ◽  
Vol 16 (5) ◽  
pp. 1759-1775 ◽  
Author(s):  
Jon D. Richey ◽  
Isabel P. Montañez ◽  
Yves Goddéris ◽  
Cindy V. Looy ◽  
Neil P. Griffis ◽  
...  
Keyword(s):  
Steady State ◽  
Ice Age ◽  
Secular Change ◽  
Ecosystem Change ◽  
Late Paleozoic ◽  
Relative Role ◽  
Carbon Cycle Model ◽  
Ecosystem Perturbation ◽  
Atmospheric Pco2

Abstract. Earth's penultimate icehouse period, the late Paleozoic ice age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, which was under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2∕CO2 ratios during the LPIA and its subsequent demise to permanent greenhouse conditions are crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40 Myr interval (∼313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2–glaciation linkage, (2) documents synchroneity between major pCO2 and O2∕CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2∕CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources active during the LPIA and its demise on steady-state pCO2 using an intermediate-complexity climate–carbon cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangean Mountains, intensifying aridification, and increasing mafic rock to granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

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