Open and filled karst features on the Cayman Islands: implications for the recognition of paleokarst

1988 ◽  
Vol 25 (8) ◽  
pp. 1277-1291 ◽  
Author(s):  
Brian Jones ◽  
Duncan S. Smith
Keyword(s):  
Vadose Zone ◽  
Cayman Islands ◽  
Rock Body ◽  
Terra Rossa ◽  
Local Conditions ◽  
Preservation Potential ◽  
Show Evidence ◽  
Karst Feature ◽  
Two Stages ◽  
Overlying Strata

The dolostones of the Oligocene–Miocene Bluff Formation on the Cayman Islands are characterized by well-developed surficial, interface, and subsurface karst features that are open or filled with speleothems and sediment.Some of the open caves show evidence of a minimum of two stages of development related to dissolution in the phreatic zone and the vadose zone. The development of speleothemic formations (e.g., stalactites, stalagmites, columns) is limited in some caves but extensive in others. Some of the caves have limited amounts of sediment on their floors. In these caves, the speleothems and sediments are still formed of CaCO3 and thus contrast sharply with the dolostone of the Bluff Formation in which they occur. Some of the joints, sinkholes, and caves are filled with breccia, caymanite, terra rossa, terra rossa breccia, pisolitic limestone, and speleothems. Although filled, such karst features are analogous to the open karst features that occur elsewhere on the islands. The filling of joints, sinkholes, or caves is not directly related to the age of the karst development, since caves of the same age may be open or filled. This suggests that local conditions, such as the availability of sediment or the nature of the waters flowing through the caves, played an important role in determining whether a karst feature is filled.Surficial karst features have a low preservation potential, whereas interface and subsurface karst features have a high preservation potential in some circumstances. In the case of sinkholes this assumes that later transgressions did not remove the upper part of the rock body that contained the filled sinkholes. For caves this assumes that they were filled with speleothems and sediment prior to their reaching such a size that collapse of the overlying strata occurred because of the lack of support. If collapse occurs, the presence of caves can only be inferred from the resultant collapse breccias. A potentially valuable criterion for the recognition of paleokarst may lie in the fact that the rocks filling open karst features (e.g., joints, sinkholes, caves) may contrast sharply with the host strata in terms of both lithology and age.

The taphonomic clock in fish otoliths

Paleobiology ◽  
2021 ◽  
pp. 1-17
Author(s):  
Konstantina Agiadi ◽  
Michele Azzarone ◽  
Quan Hua ◽  
Darrell S. Kaufman ◽  
Danae Thivaiou ◽  
...  
Keyword(s):  
Fossil Record ◽  
Radiocarbon Dating ◽  
Pelagic Fish ◽  
Time Averaging ◽  
Target Species ◽  
Local Conditions ◽  
Preservation Potential ◽  
Species Population ◽  
Clock Hypothesis ◽  
Fish Otoliths

Abstract Paleobiological and paleoecological interpretations rely on constraining the temporal resolution of the fossil record. The taphonomic clock, that is, a correlation between the alteration of skeletal material and its age, is an approach for quantifying time-averaging scales. We test the taphonomic clock hypothesis for marine demersal and pelagic fish otoliths from a 10–40 m depth transect on the Mediterranean siliciclastic Israeli shelf by radiocarbon dating and taphonomic scoring. Otolith ages span the last ~8000 yr, with considerable variation in median and range along the transect. Severely altered otoliths, contrary to pristine otoliths, are likely to be older than 1000 yr. For pelagic fish otoliths, at 30 m depth, taphonomic degradation correlates positively with postmortem age. In contrast, no correlation occurs for demersal fishes at 10 and 30 m depth, mostly because of the paucity of very young pristine (<150 yr) otoliths, possibly due to a drop in production over the last few centuries. Contrary to molluscan and brachiopod shells, young otoliths at these depths are little affected and do not show a broad spectrum of taphonomic damage, because those that derive from predation are excreted in calcium- and phosphate-rich feces forming an insoluble crystallic matrix that increases their preservation potential. At 40 m depth, all dated otoliths are very young but rather damaged because of locally chemically aggressive sediments, thus showing no correlation between taphonomic grade and postmortem age. Our results show that local conditions and the target species population dynamics must be considered when testing the taphonomic clock hypothesis.

scholarly journals Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

2013 ◽  
Vol 10 (7) ◽  
pp. 4433-4448 ◽  
Author(s):  
G. Milzer ◽  
J. Giraudeau ◽  
J. Faust ◽  
J. Knies ◽  
F. Eynaud ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climatic Variability ◽  
Intermediate Water ◽  
North Atlantic Current ◽  
Local Conditions ◽  
Bottom Water Temperature ◽  
The North ◽  
Show Evidence ◽  
Matter Flux ◽  
Instrumental Records

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as palaeoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of fresh water and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by the origin (terrigenous vs. marine) of organic matter, local topography-induced variability in organic matter flux at the water–sediment interface, and organic matter degradation. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly vary seasonally and thereby affect water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can be used as proxies of Holocene climatic variability.

Chronicity of Symptoms in Combat Veterans with PTSD Treated by the VA Mental Health System

1994 ◽  
Vol 75 (2) ◽  
pp. 843-848 ◽  
Author(s):  
B. Christopher Frueh ◽  
Robert F. Mirabella ◽  
Keith Chobot ◽  
Mark D. Fossey
Keyword(s):  
Mental Health ◽  
Health System ◽  
Mental Health System ◽  
Combat Veterans ◽  
Self Report ◽  
Time In Treatment ◽  
Show Evidence ◽  
Mississippi Scale ◽  
Two Stages

Self-report questionnaire data, collected at two stages of treatment, are presented for a group of 40 combat veterans with PTSD treated within the VA mental health system. Patients completed the Beck Depression Inventory, Mississippi Scale, and Dissociative Experiences Scale prior to treatment at a PTSD outpatient clinic and at midtreatment follow-up. Patients' symptom reports at follow-up were not correlated with length of time in treatment. Further, results suggest that patients' self-reported symptoms on these measures do not show evidence of improvement after entry into the VA mental health system. Explanations for this apparent chronicity of symptoms are discussed.

Caymanite, a cavity-filling deposit in the Oligocene–Miocene Bluff Formation of the Cayman Islands

1992 ◽  
Vol 29 (4) ◽  
pp. 720-736 ◽  
Author(s):  
Brian Jones
Keyword(s):  
Middle Miocene ◽  
Sediment Load ◽  
Second Phase ◽  
Sediment Source ◽  
Cayman Islands ◽  
Terra Rossa ◽  
Karst Terrain ◽  
Cavity System ◽  
Cavity Filling ◽  
Intercrystalline Pores

Caymanite is a laminated, multicoloured (white, red, black) dolostone that fills or partly fills cavities in the Bluff Formation of the Cayman Islands. The first phase of caymanite formation occurred after deposition, lithification, and karsting of the Oligocene Cayman Member. The second phase of caymanite formation occurred after joints had developed in the Middle Miocene Pedro Castle Member. Caymanite deposition predated dolomitization of the Bluff Formation 2–5 Ma ago.Caymanite is formed of mudstones, wackestone, packstones, and grainstones. Allochems include foraminifera, red algae, gastropods, bivalves, and grains of microcrystalline dolostone. Sedimentary structures include planar laminations, graded bedding, mound-shaped laminations, desiccation cracks, and geopetal fabrics. Original depositional dips ranged from 0 to 60°. Although caymanite originated as a limestone, dolomitization did not destroy the original sedimentary fabrics or structures.The sediments that formed caymanite were derived from shallow offshore lagoons, swamps, and possibly brackish-water ponds. Pigmentation of the red and black laminae can be related to precipitates formed of Mn, Fe, Al, Ni, Ti, P, K, Si, and Ca, which occur in the intercrystalline pores. These elements may have been derived from terra rossa, which occurs on the weathered surface of the Bluff Formation. Caymanite colours were inherited from the original limestone. Stratigraphic and sedimentologic evidence shows that sedimentation was episodic and that the sediment source changed with time. Available evidence suggests that caymanite originated from sediments transported by storms onto a highly permeable karst terrain. The water with its sediment load then drained into the subsurface through joints and fissures. The depth to which these waters penetrated was controlled by the length of the interconnected cavity system. Upon entering cavities, sedimentation was controlled by a complex set of variables.

scholarly journals Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

2013 ◽  
Vol 10 (3) ◽  
pp. 5889-5921 ◽  
Author(s):  
G. Milzer ◽  
J. Giraudeau ◽  
J. Faust ◽  
J. Knies ◽  
F. Eynaud ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climatic Variability ◽  
Intermediate Water ◽  
North Atlantic Current ◽  
Local Conditions ◽  
Bottom Water Temperature ◽  
The North ◽  
Show Evidence ◽  
Matter Flux ◽  
Instrumental Records

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as paleoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of freshwater and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by both the origin (terrigenous vs. marine) of organic matter and local topography-induced variability in organic matter flux at the water-sediment interface. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly varies seasonally and thereby affects water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can therefore be used as proxies of Holocene climatic variability.

scholarly journals Evaluation of the varieties of Chrysanthemum × hortorum from the collection SUBGI UFRC RAS taking into account the direction of use

2021 ◽  
Vol 207 (04) ◽  
pp. 64-73
Author(s):  
Svetlana Denisova ◽  
Antonina Reut
Keyword(s):  
Vegetative Reproduction ◽  
Botanical Garden ◽  
Climatic Conditions ◽  
Comprehensive Assessment ◽  
Local Conditions ◽  
Flowering Duration ◽  
Adverse Conditions ◽  
Perennial Plant ◽  
Economically Valuable Traits ◽  
Two Stages

Abstract. Chrysanthemum × hortorum Bailey is a perennial plant of the Compositae family. Perhaps the most famous and demanded late-flowering culture, which is used both for landscaping the private sector and in the green construction of settlements. However, its use in the soil and climatic conditions of the Bashkir Ural is difficult due to the lack of varieties adapted to local conditions and a reasonable assortment. The aim of the study was a comprehensive assessment of varieties of chrysanthemum from the collection of the South-Ural Botanical Garden of Ufa, taking into account the directions of use. Methods. In accordance with the methodology of E. S. Pidgainaya and other authors plants went through two stages of analysis: at the first stage, the most decorative and stable varieties were identified; on the second, the perspective direction of use of each of them was determined. At the first stage, decorative (decorativeness of a bush, leaves, inflorescences; aroma; variety uniformity; abundance of flowering) and economically valuable (productivity and flowering duration; drought resistance; winter hardiness; resistance to adverse conditions, diseases and pests; intensity of vegetative reproduction) signs were assessed. Results. As a result of the analysis of the decorative qualities of 112 varieties of chrysanthemum, ten were identified (Aktanysh, Anyuta, Belosnezhka, Vecherniye Ogni, Opal, Pektoral, Rozovaya Mechta, Solnechnaya Feyeriya, Solnyshko, Ufimskaya Yubileynaya), which have a high decorative effect of the bush, a weak aroma and are characterized by abundant flowering; they are rated 49–50 points. 84 varieties are rated 40–48 points, they have less abundant flowering and a stronger aroma. According to economically valuable traits, the highest number of points (48–49) was awarded to 4 varieties (Aktanysh, Nezhnaya Muza, Akiwa Yellow, Kurochka Ryaba). The lowest total score (34) belongs to the variety Golden Dukat. As a result of the comprehensive assessment, 106 varieties were classified as highly promising, they scored more than 80 points; six varieties are promising, they are estimated at 60–80 points. Scientific novelty. At the second stage of the analysis, when determining a promising direction of use, it was revealed that most varieties (88) can be recommended for garden use and 25 for container crops.

The Cellular Origin in Atheromatous Lesion

1970 ◽  
Vol 28 ◽  
pp. 202-203
Author(s):  
T. M. Murad ◽  
H. A. I. Newman ◽  
K. F. Kern
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Rabbit Aorta ◽  
Mixed Population ◽  
The Other ◽  
Cellular Origin ◽  
Ultrastructural Studies ◽  
Atherosclerotic Lesions ◽  
Show Evidence ◽  
Early Lesion

The origin of lipid containing cells in atheromatous lesion has been disputed. Geer in his study on atheromatous lesions of rabbit aorta, suggested that the early lesion is composed mainly of lipid-laden macrophages and the later lesion has a mixed population of macrophages and smooth muscle cells. Parker on the other hand, was able to show evidence that the rabbit lesion is primarily composed of lipid-laden cells of smooth muscle origin. The above studies and many others were done on an intact lesion without any attempt of cellular isolation previous to their ultrastructural studies. Cell isolation procedures have been established for atherosclerotic lesions through collagenase and elastase digestion Therefore this procedure can be utilized to identify the cells involved in rabbit atheroma.

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

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