234 research outputs found
ΠΡΠΈΡΠ΅ΡΠΈΠΈ ΠΈ ΡΡΠ΅Π΄ΡΡΠ²Π° ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΠΎΠ³ΠΎ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠ΅Π½ΠΈΡ Π΄Π»Ρ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ²ΡΡ ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΠΉ
ΠΠ±ΡΡΠΆΠ΄Π°ΡΡΡΡ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ Π°Π½Π°Π»ΠΈΠ·Π° ΠΏΡΠΈΠΌΠ΅Π½ΠΈΠΌΠΎΡΡΠΈ ΠΈ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΡΡ
ΡΠΈΡΡΠ΅ΠΌ Π²Π΅Π΄ΡΡΠΈΡ
Π·Π°ΡΡΠ±Π΅ΠΆΠ½ΡΡ
ΠΈ ΠΎΡΠ΅ΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΡ
ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΡΠ΅Π»Π΅ΠΉ, ΠΊΡΠ»ΡΡΠΈΠ²ΠΈΡΡΠ΅ΠΌΡΡ
Π½Π° ΡΡΠ½ΠΊΠ΅ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠΎΠ½Π½ΡΡ
ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ Π΄Π»Ρ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ²ΡΡ
ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΠΉ. Π‘ΡΠΎΡΠΌΡΠ»ΠΈΡΠΎΠ²Π°Π½Ρ ΠΊΡΠΈΡΠ΅ΡΠΈΠΈ ΠΎΡΠ΅Π½ΠΊΠΈ Π±Π°Π·ΠΎΠ²ΡΡ
ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΡΡ
ΡΠΈΡΡΠ΅ΠΌ, ΠΊΠΎΡΠΎΡΡΠΌΠΈ ΡΠ»Π΅Π΄ΡΠ΅Ρ ΡΡΠΊΠΎΠ²ΠΎΠ΄ΡΡΠ²ΠΎΠ²Π°ΡΡΡΡ ΠΏΡΠΈ ΠΎΠ±ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ Π²ΡΠ±ΠΎΡΠ°. ΠΠ°Π½ΠΎ ΡΠΎΡΠΌΠ°Π»ΠΈΠ·ΠΎΠ²Π°Π½Π½ΠΎΠ΅ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠ΅ ΡΠ»ΠΎΠΆΠ½ΡΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² Π³Π΅ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΈ Π³ΠΈΠ΄ΡΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ²ΡΡ
ΠΌΠ΅ΡΡΠΎΡΠΎΠΆΠ΄Π΅Π½ΠΈΠΉ Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΡΠΈΡΡΠΎΠ²ΡΡ
3D-ΠΌΠΎΠ΄Π΅Π»Π΅ΠΉ ΠΈ ΠΏΠΎΠ΄Π΄Π΅ΡΠΆΠΈΠ²Π°ΡΡΠΈΡ
ΠΈΡ
ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΡΡ
ΡΠΈΡΡΠ΅ΠΌ
Holocene reef growth and recent carbonate production in the Red Sea
Holocene reef growth, present date bioerosion .and recorded
carbonate production were studied in the fringing
reef at Aqaba, Red Sea. Water depth, wave impact as well
as nutrient availability were considered.
The carbonate production was measured for several coral
samples. Samples of Porites-colonies were collected from
several depths and sites near the Marine Science Station at
Aqaba. Growth rate depends on water depth, size and age
of colonies. Within the coral optimum of water depth growth
rates vary between 5 and 16 mm/yr. Coral carbonate production
was calculated on the base of annual growth increments
and skeletal density using transects from shallow
subtidal down to 40 m water depth. High resolution stable
isotope data were measured to prove the origin of growth
increments. Long-term trends of sea surface temperature
and carbon isotope shift (1800-today) fit to the known global
deviations.
Bioerosion rates were determined using standard dead
coral substrates exposed in different water depths and environmental
settings. Rates vary between 0.6 and
1.4 kg/m2yr. Sediment export evaluated by means of simple
sediment traps ranges between 0.3 and 0.7 kg/m2yr.
Gross carbonate production, mainly built up by scleractinian
corals, amounts to ca. 1.57 kg/m2yr. Bioerosion alters
approx. 1.3 kg/m2yr of hard substrates into sediment. Sediment
export is estimated to be ca. 0.4-0.6 kg/m2yr. Thus a
net production of ca. 0.7 to 0.9 kg/m2yr should remain in the
present reef, which is proved by the recorded carbonate
production (reef drillings). Net production preserved in the
reef can be given with ca. 800 kg/m2kyr (=0.8 kg/m2yr)
Meeresspiegelschwankungen und ihre geologische Γberlieferung im Karbonatsystem
The dependency between carbonate sediment production on a carbonate platform and its relation to sea-level changes is discusses here. The topography of the upper slope plays an important role in determining the way in which sedimentation continues during lowstands in sea level. The mineralogy and composition of sediments produced on the platform can clearly be related to those found in sediments deposited in the adjacent basin. Two examples from the Recent are described: (1) Sanganeb Atoll (Red Sea), and (2) Pedro Bank (caribbean). The applicability of the "highstand shedding" principle is shown for ancient carbonate platforms
ΠΠ½Π°Π»ΠΈΠ· ΠΈ ΠΈΠ½ΡΠ΅ΡΠΏΡΠ΅ΡΠ°ΡΠΈΡ Π³ΠΈΠ΄ΡΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ Π΄Π»Ρ Π΄Π²ΡΡ ΡΠ°Π·Π½ΠΎΠ³ΠΎ ΠΏΠΎΡΠΎΠΊΠ° (Π²ΠΎΠ΄Π°-Π½Π΅ΡΡΡ)
ΠΠΎΠΊΠ°Π·Π°Π½Ρ ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ, Π²ΠΎΠ·Π½ΠΈΠΊΠ°ΡΡΠΈΠ΅ ΠΏΡΠΈ ΠΈΠ½ΡΠ΅ΡΠΏΡΠ΅ΡΠ°ΡΠΈΠΈ ΠΈ Π°Π½Π°Π»ΠΈΠ·Π΅ Π΄Π°Π½Π½ΡΡ
Π³ΠΈΠ΄ΡΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ, ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½Π½ΡΡ
Π½Π° ΡΠΊΠ²Π°ΠΆΠΈΠ½Π°Ρ
Ρ ΠΎΠ±Π²ΠΎΠ΄Π½Π΅Π½Π½ΠΎΡΡΡΡ, ΠΎΡΠ»ΠΈΡΠ½ΠΎΠΉ ΠΎΡ Π½ΡΠ»Ρ. Π Π°Π·ΠΎΠ±ΡΠ°Π½Ρ ΠΏΡΠ΅ΠΈΠΌΡΡΠ΅ΡΡΠ²Π° ΠΈ Π½Π΅Π΄ΠΎΡΡΠ°ΡΠΊΠΈ ΠΏΡΠΈΠΌΠ΅Π½ΡΠ΅ΠΌΡΡ
ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² ΠΈΠ½ΡΠ΅ΡΠΏΡΠ΅ΡΠ°ΡΠΈΠΈ ΠΈ Π°Π½Π°Π»ΠΈΠ·Π°. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½ Π½ΠΎΠ²ΡΠΉ ΠΌΠ΅ΡΠΎΠ΄ Π½ΠΎΡΠΌΠ°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΏΠΎΠ΄Π²ΠΈΠΆΠ½ΠΎΡΡΠΈ Π΄Π»Ρ Π°Π½Π°Π»ΠΈΠ·Π° ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² Π³ΠΈΠ΄ΡΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΡΠΊΠ²Π°ΠΆΠΈΠ½
A test of the biogenicity criteria established for microfossils and stromatolites on quaternary tufa and speleothem materials formed in the βTwilight zoneβ at Caerwys, UK
Β© 2015, Mary Ann Liebert, Inc. The ability to distinguish the features of a chemical sedimentary rock that can only be attributed to biology is a challenge relevant to both geobiology and astrobiology. This study aimed to test criteria for recognizing petrographically the biogenicity of microbially influenced fabrics and fossil microbes in complex Quaternary stalactitic carbonate rocks from Caerwys, UK. We found that the presence of carbonaceous microfossils, fabrics produced by the calcification of microbial filaments, and the asymmetrical development of tufa fabrics due to the more rapid growth of microbially influenced laminations could be recognized as biogenic features. Petrographic evidence also indicates that the development of "speleothem-like" laminae was related to episodes of growth interrupted by intervals of nondeposition and erosion. The lack of any biogenic characteristics in these laminae is consistent with their development as a result of variation in the physicochemical parameters that drive calcite precipitation from meteoric waters in such environmental settings
Are spherulitic lacustrine carbonates an expression of large-scale mineral carbonation? : A case study from the East Kirkton Limestone, Scotland
BP Exploration Co. is thanked for funding, and particularly the Carbonate Team for supporting this research and for fruitful discussions. West Lothian Council and Scottish Natural Heritage are thanked for allowing access and permission for sampling the site. The Core Store Team at BGS Keyworth is particularly acknowledged for their assistance. Mark Anderson, Tony Sinclair (University of Hull), and Bouk Lacet (VU University Amsterdam) are thanked for technical support. Anne Kelly (SUERC) for carrying out the Strontium Isotope analyses. Mark Tyrer is thanked for his advice on PHREEQC modelling.Peer reviewedPostprin
The surface energy balance during foehn events at Joyce Glacier, McMurdo Dry Valleys, Antarctica
The McMurdo Dry Valleys (MDV) are a polar desert, where glacial melt is the main source of water to streams and the ecosystem. Summer air temperatures are typically close to zero, and therefore foehn events can have a large impact on the meltwater production. A 14-month record of automatic weather station (AWS) data on Joyce Glacier is used to force a 1D surface energy balance model to study the impact of foehn events on the energy balance. AWS data and output of the Antarctic Mesoscale Prediction System (AMPS) on a 1.7βkm grid are used to detect foehn events at the AWS site. Foehn events at Joyce Glacier occur under the presence of cyclones over the Ross Sea. The location of Joyce Glacier on the leeward side of the Royal Society Range during these synoptic events causes foehn warming through isentropic drawdown. This mechanism differs from the foehn warming through gap flow that was earlier found for other regions in the MDV and highlights the complex interaction of synoptic flow with local topography of the MDV. Shortwave radiation is the primary control on melt at Joyce Glacier, and melt often occurs with subzero air temperatures. During foehn events, melt rates are enhanced, contributing to 23β% of the total annual melt. Foehn winds cause a switch from a diurnal stability regime in the atmospheric surface layer to a continuous energy input from sensible heat flux throughout the day. The sensible heating during foehn, through an increase in turbulent mixing resulting from gustier and warmer wind conditions, is largely compensated for by extra heat losses through sublimation. Melt rates are enhanced through an additional energy surplus from a reduced albedo during foehn.</p
Synchroneity of major late Neogene sea level fluctuations and paleoceanographically controlled changes as recorded by two carbonate platforms
Shallow-water carbonate systems are reliable recorders of sea level fluctuations and changes in ambient seawater conditions. Drilling results from Ocean Drilling Program (ODP) Legs 133 and 166 indicate that the timing of late Neogene sedimentary breaks triggered by sea level lowerings is synchronous in the sedimentary successions of the Queensland Plateau and the Great Bahama Bank. This synchrony indicates that these sea level changes were eustatic in origin. The carbonate platforms were also affected by contemporary, paleoceanographically controlled fluctuations in carbonate production. Paleoceanographic changes are recorded at 10.7, 3.6, and 1.7β2.0 Ma. At the Queensland Plateau, sea surface temperature shifts are documented by shifts from tropical to temperate carbonates (10.7 Ma) and vice versa (3.6 Ma); the modern tropical platform was established at 2.0β1.8 Ma. At Great Bahama Bank, changes were registered in compositional variations of platform-derived sediment, such as major occurrence of peloids (3.6 Ma) and higher rates of neritic carbonate input (1.7 Ma). The synchroneity of these changes attests to the far-field effects of modifications in the oceanographic circulation on shallow-water, low-latitude carbonate production
Changing distributions of sea ice melt and meteoric water west of the Antarctic Peninsula
The Western Antarctic Peninsula has recently undergone rapid climatic warming, with associated decreases in sea ice extent and duration, and increases in precipitation and glacial discharge to the ocean. These shifts in the freshwater budget can have significant consequences on the functioning of the regional ecosystem, feedbacks on regional climate, and sea-level rise. Here we use shelf-wide oxygen isotope data from cruises in four consecutive Januaries (2011β2014) to distinguish the freshwater input from sea ice melt separately from that due to meteoric sources (precipitation plus glacial discharge). Sea ice melt distributions varied from minima in 2011 of around 0 % up to maxima in 2014 of around 4β5%. Meteoric water contribution to the marine environment is typically elevated inshore, due to local glacial discharge and orographic effects on precipitation, but this enhanced contribution was largely absent in January 2013 due to anomalously low precipitation in the last quarter of 2012. Both sea ice melt and meteoric water changes are seen to be strongly influenced by changes in regional wind forcing associated with the Southern Annular Mode and the El NiΓ±oβSouthern Oscillation phenomenon, which also impact on net sea ice motion as inferred from the isotope data. A near-coastal time series of isotope data collected from Rothera Research Station reproduces well the temporal pattern of changes in sea ice melt, but less well the meteoric water changes, due to local glacial inputs and precipitation effects
The surface energy balance during foehn events at Joyce Glacier, McMurdo Dry Valleys, Antarctica
The McMurdo Dry Valleys (MDV) are a polar desert, where glacial melt is the main source of water to streams and the ecosystem. Summer air temperatures are typically close to zero, and therefore foehn events can have a large impact on the meltwater production. A 14-month record of automatic weather station (AWS) data on Joyce Glacier is used to force a 1D surface energy balance model to study the impact of foehn events on the energy balance. AWS data and output of the Antarctic Mesoscale Prediction System (AMPS) on a 1.7 km grid are used to detect foehn events at the AWS site. Foehn events at Joyce Glacier occur under the presence of cyclones over the Ross Sea. The location of Joyce Glacier on the leeward side of the Royal Society Range during these synoptic events causes foehn warming through isentropic drawdown. This mechanism differs from the foehn warming through gap flow that was earlier found for other regions in the MDV and highlights the complex interaction of synoptic flow with local topography of the MDV. Shortwave radiation is the primary control on melt at Joyce Glacier, and melt often occurs with subzero air temperatures. During foehn events, melt rates are enhanced, contributing to 23 % of the total annual melt. Foehn winds cause a switch from a diurnal stability regime in the atmospheric surface layer to a continuous energy input from sensible heat flux throughout the day. The sensible heating during foehn, through an increase in turbulent mixing resulting from gustier and warmer wind conditions, is largely compensated for by extra heat losses through sublimation. Melt rates are enhanced through an additional energy surplus from a reduced albedo during foehn
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