Different Degrees Of Preservation Research Articles

Oxygen Isotope Analysis of Animal Bone Phosphate: Method Refinement, Influence of Consolidants, and Reconstruction of Palaeotemperatures for Holocene Sites

A new method to isolate phosphate from bones for oxygen isotope analysis was developed and tested. A graphite-reduction technique introduced by O'Neil et al. (1994;Israel Journal of Earth Sciences43, 203–212) is much simpler and quicker than conventional fluorination techniques and was refined in this study. Problems that may arise during the preparation of bone tissue with high organic content were solved by adding two steps of pre-treatment to remove organic substances before complete dissolution of the bone. The reproducibility of δ18O values is very good, not only for commercial silver phosphate (±0·25‰) and synthetic hydroxyapatite (±0·22‰) but also for modern and fossil bones with different degrees of preservation (±0·16‰). Interlaboratory comparisons were made with NIST-120c, NIST-120b, and the University of Michigan Standard-1. The values for all standards are in good agreement with values obtained both with conventional fluorination and the graphite-reduction method (δ18Op: 21·7; 20·0; 12·2‰ versus SMOW, respectively). Additionally, the influence of consolidants on the preparation and oxygen isotope analysis was investigated. This investigation was deemed necessary, because fragile and brittle animal remains from archaeological and palaeontological sites are often preserved with these materials before samples can be taken for isotopic analysis. Modern and fossil bones of different degrees of preservation were treated with Mowilith, Shellac, Zaponlack, and Ponal, and subsequently, oxygen isotope analyses were performed in the normal way. No measurable effect of these consolidants was observed on the analyses for δ18Op.The new procedure has been successfully used to analyse oxygen isotope ratios of cattle and pig bones from Holocene archaeological sites in different climate zones. Calculations of the δ18O values of meteoric water and of mean temperatures using the δ18Opvalues illustrate that isotopic compositions of bones from these terrestrial mammals reflect the climatic conditions of their environment very precisely.

Sedimentary organic matter in condensed sections from distal oxic environments: examples from the Mesozoic of SE France

A detailed analysis of sedimentary organic matter (or palynofacies) was carried out on thermally immature to early mature Upper Jurassic and Hauterivian condensed intervals in deep‐sea carbonate–marl alternations outcropping in the Vocontian Basin (SE France). All the condensed sections studied are characterized by intense bioturbation and very low organic carbon content (< 0·25 wt.%), indicative of oxic depositional conditions.Oxic condensed sections display variable palynofacies signatures, which are best illustrated by: (1) the ratio of continental to marine constituents; (2) the ratio of opaque to translucent phytoclasts (i.e. woody debris) and (3) the preservation of palynomorphs (based on fluorescence intensity and morphological preservation state in transmitted light microscopy). Both of the ratios increase with the degree of palynomorph degradation, which shows that phytoclasts, especially the opaque ones, become relatively concentrated in the most degraded facies. These observations lead to the classification of oxic condensed sections into three organic facies types showing different degrees of preservation and palynofacies signatures. Type 1 organic facies display intense degradation and are characterized by high values of the ratio of continental to marine fraction. They record unfavourable depositional environments for preservation of organic matter. Type 2 organic facies are most common and are characterized by a decreasing value of the ratio of continental to marine fraction. Type 3 organic facies display the same trend of the ratio of continental to marine fraction as type 2, but the palynomorph assemblage is better preserved. Type 1 and type 3 organic facies are relatively rare.Recognizing these organic facies types is important when analysing the relationship between sedimentary organic matter and sequence stratigraphy, because it allows the use of the appropriate palynofacies parameters. In particular, the use of the ratio of continental to marine constituents, usually a very good indicator of regressive–transgressive trends, becomes questionable in highly degraded intervals. Moreover, distinguishing between well‐preserved or highly degraded palynofacies in condensed intervals provides valuable information on the oxicity of the depositional environment.

Separation and Artificial Maturation of Macerals from Type II Kerogen

Immature Type II kerogen (HI = 660 mg/g) from the Lower Toarcian of the Paris Basin was separated into an alginite concentrate (HI = 952 mg/g) and an amorphous organic matter (AOM) concentrate (HI = 573 mg/g) by density centrifugation. The flash pyrolysate of the alginite is characterized by high relative concentrations of several series of n-alkanones and n-alkenones (including mid-chain alkyl ketones), in addition to n-alkanes, n-alk-1-enes, and n-alkadienes. To our knowledge, this Toarcian alginite is the oldest example of marine organic matter whose pyrolysate contains mid-chain alkanones in such high relative concentrations. In sharp contrast, the AOM produced predominantly alkylbenzenes, alkylthiophenes, n-alkanes, and n-alk-1-enes upon pyrolysis. Micro-FTIR spectroscopy indicated that the alginite was enriched in aliphatic C-H (particularly CH2) and depleted in aromatic C=C, relative to the AOM, consistent with the pyrolysis results. Aliquots of the concentrates were heated separately in gold tubes (24 h, 70 MPa) at fixed temperatures ranging between 250 and 375 °C. Yields of liquid products as a function of temperature were initially greater for the AOM, reaching a maximum at 325 °C. In contrast, the alginite yielded little liquid product at low temperatures, attaining its maximum at 350 °C, at which temperature its yield greatly surpassed that of the AOM. This kerogen is a heterogeneous assemblage of fossil organic matter, exhibiting different degrees of preservation and petroleum potential. The alginite is fossilized marine algaenans with alkyl chains cross-linked by ether bridges, while the AOM component is at least in part a geopolymer with thioether linkages, the thermally labile nature of which is responsible for its lower temperature peak liquid generation. It is evident that the alginite concentrate is chemically distinct from its companion AOM in this kerogen and that the full extent of its uniqueness would not have been revealed without the density separation step.

Membrane distribution in dividing endosperm cells of Haemanthus.

Membranes in cell-wall-free dividing endosperm cells of Haemanthus were examined after postfixation with osmium tetroxide-potassium ferrocyanide. We found that preservation and staining of membranes in metaphase cells was highly variable. Even adjacent cells often showed different degrees of preservation of membrane. However, this method does reveal a much more extensive membrane system in the mitotic spindle of Haemanthus than has been revealed previously using glutaraldehyde-osmium fixation. At prometaphase a system of membranes becomes associated with the kinetochore bundles. By metaphase, membranes constitute a prominent feature of kinetochore bundles, terminating near the kinetichores. Minipoles, identified by converging microtubules and associated membranes, are distributed in a zone extending laterally across the polar regions of the cell. The microtubules appear to terminate at the minipoles, whereas the membrane system becomes oriented generally perpendicular to the spindle axis and interfaces distally with a region of amorphous electron-dense material, helical polyribosomes, and cell organelles. The role of this extensive membrane system, if any, in chromosome movement is unknown. However, its distribution is coincident with the distribution of calcium-rich membranes and kinetochore fibers at metaphase in these cells (Wolniak, S. M., P. K. Hepler, and W. T. Jackson, 1981, Eur. J. Cell Biol., 25:171-174). Thus, these membranes may function in creating calcium domains that, in turn, may play a regulatory role in chromosome movement.

Protein synthesis in plant mitochondria: III. Characterization of mitochondria and the microsomal fractionm of the seedlings of vigna sinensis

1. 1. Glucose-6-phosphatase (EC 3.1.3.9) activity was considerable in the microsomal fraction but was absent in the mitochondria cell from Vigna sinesis. Ribonucleic acid in the microsomal fraction was sensitive to exogenous ribonuclease (EC 2.7.7.16) while that in mitochondria remained unaffected. 2. 2. Electron-microscopy of the microsomal fraction revealed prepoderance of particle (110–160 Å in diameter), with relatively rare occurrence of membranes, polyribosome-like structures and other small particles (60–70 Å) of considerably greater electron density. 3. 3. Electron-microscopy of the mitochondrial pellet revealed typical structures of mitochondria with different degrees of preservation. Ribosomes, whole cells or nuclei were absent. Mitochondia in the “five-times-washed” pellets had greater number of well preserved cristae and less heterogenous matrix than those in the “once-washed” pellets. 4. 4. These observations have been discussed in the light of the earlier finding that mitochondria were more active than the microsomal fraction in incorporating amino acid into their protein.