98 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
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
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
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
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
Holocene Atlantic climate variations deduced from carbonate peri-platform sediments (leeward margin, Great Bahama Bank)
A marine sediment core from the leeward margin of Great Bahama Bank (GBB) was subjected to a multiproxy study. The aragonite dominated core MD992201 comprises the past 7230 years in a decadal time resolution and shows sedimentation rates of up to 13.8 m/kyr. Aragonite mass accumulation rates, age differences between planktonic foraminifera and aragonite sediments, and temperature distribution are used to deduce changes in aragonite production rates and paleocurrent strengths. Aragonite precipitation rates on GBB are controlled by exchange of carbonate ions and CO2 loss due to temperature-salinity conditions and biological activity, and these are dependent on the current strength. Paleocurrent strengths on GBB show high current velocities during the periods 6000β5100 years BP, 3500β2700 years BP, and 1600β700 years BP; lower current speeds existed during the time intervals 5100β3500 years BP, 2700β1600 years BP, and 700β100 years BP. Bahamian surface currents are directly linked to the North Atlantic atmospheric circulation, and thus periods with high (low) current speeds are proposed to be phases of strong (weak) atmospheric circulation
Sub-Milankovitch cycles in periplatform carbonates from the early Pliocene Great Bahama Bank
High-resolution bulk sediment (magnetic susceptibility and aragonite content) and Ξ΄18O records from two different planktonic foraminifera species were analyzed in an early Pliocene core interval from the Straits of Florida (Ocean Drilling Program site 1006). The Ξ΄18O record of the shallow-dwelling foraminifera G. sacculifer and the aragonite content are dominated by sub-Milankovitch variability. In contrast, magnetic susceptibility and the Ξ΄18O record of the deeper-dwelling foraminifera G. menardii show precession cycles. The relationship between the aragonite and the paleoproxy data suggests that the export of sediment from the adjacent Great Bahama Bank was triggered directly by atmospheric processes rather than by sea level change. We propose a climate mechanism that bears similarities with the semiannual cycle component of eastern equatorial Pacific sea surface temperatures under present-day conditions
Carbonate delta drift: a new sediment drift type
Based on high-resolution reflection seismic and core data from IODP Expedition 359 we present a new channel-related drift type attached to a carbonate platform slope, which we termed delta drift. Like a river delta, it is comprised of several stacked lobes and connected to a point source. The delta drifts were deposited at the exit of two gateways that connect the Inner Sea of the Maldives carbonate platform with the open ocean. The channels served as conduits focusing and accelerating the water flow; Entrained material was deposited at their mouth where the flows relaxed. The lobe-shaped calcareous sediment drifts must have formed under persistent water through flow. Sediment supply was relatively high and continuous, resulting in an average sedimentation rate of 17 cm kaβ1. The two delta drifts occupy 342 and 384 km2, respectively; with a depositional relief of approximately 500 m. They have a sigmoidal clinoform reflection pattern with a particular convex upward bending of the foresets. In the Maldives the drift onset marks the transition from a sea-level controlled to a progressively current dominated depositional regime. This major event occurred in the Serravallian about 13 Ma ago, leading to the partial drowning of the carbonate platform and the creation of shallow seaways. The initial bank-enclosed topography resembles an βempty bucketβ geometry which is rapidly filled by the drift sediments that aggrade and prograde into the basin. Thereby the depositional environment of the delta drifts changes from deep water (>500) to shallow-water conditions at their topsets, indicated by the overall coarsening upward trend in grain size and the presence of shallow water large benthic foraminifers at their top
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