scholarly journals The environmental factors limiting the distribution of shallow-water terebratulid brachiopods

Paleobiology ◽  
2020 ◽  
Vol 46 (2) ◽  
pp. 193-217 ◽  
Author(s):  
Diego A. García-Ramos ◽  
Stjepan Ćorić ◽  
Michael M. Joachimski ◽  
Martin Zuschin
Keyword(s):  
Shallow Water ◽  
Oxygen Isotopes ◽  
Seawater Temperature ◽  
High Amplitude ◽  
Grazing Pressure ◽  
Coralline Red Algae ◽  
Secondary Layer ◽  
Temperature Ranges ◽  
Warm Temperate ◽  
Environmental Tolerances

AbstractThe Cenozoic genus Terebratula seems to be an exception to the post-Permian trend in brachiopod retreat to offshore habitats, because it was species rich and numerically abundant in warm-temperate shallow-water environments in the Mediterranean and the Paratethys realms. This was so despite the general dominance of bivalves and the pervasive bioturbation and predation pressure during the Neogene. Terebratula, however, went extinct in the Calabrian (Pleistocene). The optimal environmental conditions for Terebratula during its prime are poorly known. The Águilas Basin (SE Spain) is an ideal study area to investigate the habitat of Terebratula, because shell beds of this brachiopod occur there cyclically in early Pliocene deposits. We evaluate the paleoecological boundary conditions controlling the distribution of Terebratula by estimating its environmental tolerances using benthic and planktic foraminiferal and nannoplanktic assemblages and oxygen isotopes of the secondary layer brachiopod calcite. Our results suggest that Terebratula in the Águilas Basin favored oligotrophic to mesotrophic, well-oxygenated environments at water depths of 60–90 m. Planktic foraminiferal assemblages and oxygen isotopes point to sea-surface temperatures between ~16°C and 22°C, and bottom-water temperatures between 17°C and 24°C. The analyzed proxies indicate that Terebratula tolerated local variations in water depth, bottom temperature, oxygenation, productivity, and organic enrichment. Terebratula was probably excluded by grazing pressure from well-lit environments and preferentially occupied sediment-starved, current-swept upper offshore habitats where coralline red algae were absent. Narrow temperature ranges of Terebratula species might have been a disadvantage during the high-amplitude seawater temperature fluctuations that started about 1 Ma, when the genus went extinct.

scholarly journals Oxygen isotope equilibrium in brachiopod shell fibres in the context of biological control

2008 ◽  
Vol 72 (1) ◽  
pp. 239-242 ◽  
Author(s):  
M. Cusack ◽  
A. Pérez-Huerta ◽  
P. Chung ◽  
D. Parkinson ◽  
Y. Dauphin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Environmental Data ◽  
Ambient Seawater ◽  
Secondary Layer ◽  
Vital Effect ◽  
Vital Effects ◽  
Stable Oxygen ◽  
Isotope Equilibrium

With their long geological history and stable low-Mg calcite shells, Rhynchonelliform brachiopods are attractive sources of environmental data such as past seawater temperature (Buening and Spero, 1996; Auclair et al., 2003; Brand et al., 2003; Parkinson et al., 2005). Concerns about the influence of vital effects on the stable isotope composition of brachiopod shells (Popp et al., 1986), led to isotope analyses of different parts of brachiopod shells in order to identify those parts of the shell that are influenced by any vital effect and those parts that may be suitable recorders of seawater temperature via stable oxygen isotope composition (Carpenter and Lohmann, 1995; Parkinson et al., 2005). Such detailed studies demonstrated that the outer primary layer of acicularcalcite is isotopically light in both δ18O and δ13C while the secondary layer, composed of calcite fibres, is in oxygen-isotope equilibrium with ambient seawater(Fig. 1) (Parkinson et al., 2005).

Relationship between δ18O and minor element composition of Terebratalia transversa

2007 ◽  
Vol 98 (3-4) ◽  
pp. 443-449 ◽  
Author(s):  
Maggie Cusack ◽  
David Parkinson ◽  
Alberto Pérez-Huerta ◽  
Jennifer England ◽  
Gordon B. Curry ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Minor Element ◽  
Oxygen Isotope Composition ◽  
Secondary Layer ◽  
Vital Effects ◽  
Stable Oxygen ◽  
Temperature Proxy ◽  
Isotope Equilibrium

ABSTRACTWith their extensive fossil record and shells of stable low-Mg calcite, rhynchonelliform brachiopods are attractive sources of climate information via seawater temperature proxies such as stable oxygen isotope composition. In Terebratalia transversa (Sowerby) there is a progression towards oxygen isotope equilibrium in the calcite of the innermost secondary layer. This study confirms the lack of any vital effects influencing oxygen isotope composition of T. transversa, even in specialised areas of the innermost secondary layer. Calcite Mg/Ca ratio is another potential seawater temperature proxy, that has the advantage of not being influenced by salinity. Mg concentrations measured by electron microprobe analyses indicate that there is no concomitant decrease in Mg concentration towards the inner secondary layer, associated with the progressive shift towards oxygen isotope equilibrium. Mg distribution is heterogeneous throughout the shell and correlates with that of sulphur, which may be a proxy for organic components, suggesting that some of the Mg may not be in the calcite lattice. It is essential therefore, to determine the chemical environment of the magnesium ions to avoid any erroneous temperature extrapolations in brachiopods or any other calcite biomineral.

Interpreting seawater temperature range using oxygen isotopes and zooid size variation in Pentapora foliacea (Bryozoa)

2010 ◽  
Vol 157 (6) ◽  
pp. 1171-1180 ◽  
Author(s):  
T. Knowles ◽  
M. J. Leng ◽  
M. Williams ◽  
P. D. Taylor ◽  
H. J. Sloane ◽  
...  
Keyword(s):  
Oxygen Isotopes ◽  
Seawater Temperature ◽  
Size Variation ◽  
Temperature Range

scholarly journals Seismic on floating ice on shallow water: Observations and modeling of guided wave modes

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. P1-P13 ◽  
Author(s):  
Tor Arne Johansen ◽  
Bent Ole Ruud ◽  
Gaute Hope
Keyword(s):  
Sea Ice ◽  
Shallow Water ◽  
Seismic Source ◽  
High Amplitude ◽  
Guided Wave ◽  
The Arctic ◽  
Flexural Waves ◽  
Coherent Noise ◽  
Air Gun ◽  
Scholte Waves

Seismic mapping of the shallow, coastal areas of the Arctic is best facilitated in periods when the sea is covered with solid, floating ice. Data from three seismic acquisition campaigns on sea ice floating on shallow water reveal how coherent noise related to guided waves is differently exposed for various source and receiver systems placed on and below the ice. The main coherent noise is due to interference of ice flexural and Scholte waves. The experimental data were overall successfully modeled using a wavenumber integration technique. A seismic source at or near the ice generates high-amplitude, slowly propagating, and highly dispersive flexural waves. Their amplitudes are severely reduced when recorded at hydrophones deployed 5 m or more below the sea ice. The extent of flexural waves generated using an air gun below the ice similarly reduces as the depth of the air gun increases, but then the amplitudes of the seabed Scholte waves increase. Our experiments indicate that an inline line source of detonating cord on the ice combined with hydrophones deployed at the appropriate depth below the ice constitute an efficient setup for reducing the imprints of the ice flexural and Scholte waves on seismic data.

THE GULF OF CARPENTARIA—A NEW BASIN AND NEW EXPLORATION TARGETS

1993 ◽  
Vol 33 (1) ◽  
pp. 297
Author(s):  
V. L. Passmore ◽  
P. E. Williamson ◽  
T. U Mating ◽  
A.R.G. Gray
Keyword(s):  
Shallow Water ◽  
Sedimentary Rocks ◽  
High Amplitude ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Basin Floor ◽  
International Boundary ◽  
Fault Structures ◽  
The One ◽  
Sag Basin

The sparsely explored Gulf of Carpentaria is a shallow water frontier area of stacked basins. The petroleum potential was not tested by the one offshore well drilled in the Gulf in 1984.Recent re-interpretation of offshore seismic in Queensland waters delineated the Bamaga Basin, a new infrabasin below the Carpentaria Basin. This new basin is a northerly trending asymmetrical sag basin that continues north of the international boundary. The Bamaga Basin, containing up to 1.8 seconds of gently folded and faulted sediments, is untested and offers a new exploration objective. Apparent high velocities make the age of the basin uncertain, but Paleozoic reservoir and source rocks, similar to sedimentary rocks in nearby basins, are inferred, although analogue basins are not readily identifiable.Bamaga Basin source rock burial is sufficient to generate hydrocarbons and could source reservoirs in the Bamaga and Carpentaria Basins via migration along faults. Possible direct hydrocarbon indicators increase support for the presence of hydrocarbons in the Gulf.Structural and stratigraphic plays in the Carpentaria Basin that provide new exploration targets include: basal sandstones onlapping areas of higher relief or filling basin floor depressions, sandstone layers within the Wallumbilla Formation draping highs and possible carbonate zones appearing as high amplitude chaotic reflectors. Within the Bamaga Basin, horst, fault structures and anticlinal features are potential structural plays, and termination of units against the main unconformity are possible stratigraphic play targets.

scholarly journals Paleomagnetism of Quaternary sediments from Anholt, Denmark: Onset of the Blake Event and Eem

1995 ◽  
Vol 42 ◽  
pp. 96-104
Author(s):  
Niels Abrahamsen
Keyword(s):  
Shallow Water ◽  
Oxygen Isotopes ◽  
Dipole Field ◽  
Event Correlation ◽  
Quaternary Sediments ◽  
Axial Dipole ◽  
Two Samples ◽  
Normal Polarity ◽  
Termination Date

Trie c. 70 m non-marine Weichselian sands and clays from two consecutive borings, Anholt II and III, show normal polarity and inclinations somewhat shallower (c. 115°) than the axial dipole field value, which may be explained by a moderate compression of the sediment. Most of the marine shallow water silty clays of the Saalian (isotope stage 6) and Eemian (isotope substage 5e) sections (74-81 m) also show normal inclinations, except for two samples at the very top part of the recovered Eemian stage, which are distinctly reversely magnetized. The reversed section of the Pleistocene sediments (in Anholt III) is interpreted to belong to the earliest part of the short reverse geomagnetic Blake event. Correlation via biostratigraphy and oxygen isotopes provides an estimate for the onset of the Blake reversal at about 123 ka which, together with the termination date of 117 ka from Lac de Bouchet, possibly suggest an age of about 123-117 for the Blake reversal.

Seawater Temperature and Wind Speed Dependences and Diurnal Variation of Ambient Noise at the Snapping Shrimp Colony in Shallow Water of Southern Sea of Korea

2012 ◽  
Vol 51 (7S) ◽  
pp. 07GG09 ◽  
Author(s):  
Seom-Kyu Jung ◽  
Bok Kyoung Choi ◽  
Bong-Chae Kim ◽  
Byoung-Nam Kim ◽  
Seong Hyeon Kim ◽  
...  
Keyword(s):  
Wind Speed ◽  
Diurnal Variation ◽  
Shallow Water ◽  
Ambient Noise ◽  
Seawater Temperature ◽  
Snapping Shrimp
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