Distribusi Foraminifera di Laut Halmahera dari Glasial Akhir Sampai Resen

Mikrofauna foraminifera telah banyak digunakan sebagai proksi dalam penelitian paleoseanografi dan Perubahan iklim purba. Kelimpahan dan komposisi kimia cangkang foraminifera merekam berbagai informasi yang dapat diinterpretasi berkaitan dengan Perubahan lingkungan berdasarkan parameter-parameter paleoseanografi. Paleoseanografi Laut Halmahera sangat penting untuk dikaji karena berpengaruh terhadap dinamika iklim Indonesia dan iklim global. Perubahan-Perubahan parameter oseanografi tersebut mempengaruhi sirkulasi arus global dan interaksi antara air-udara yang berperan terhadap penyebaran uap air ke lintang tinggi. Oleh karena itu tujuan penelitian ini adalah mempelajari distribusi foraminifera untuk rekonstruksi Perubahan paleoseanografi di Laut Halmahera dan sekitarnya. Data foraminifera ini didukung dengan pemodelan umur dan rekonstruksi isotop stratigrafi berdasarkan analisis d18O G. ruber dan C14 radiokarbon dating. Hasil penelitian menunjukkan bahwa kelimpahan foraminifera di Laut Halmahera sangat dipengaruhi oleh iklim global. Kelimpahan foraminifera terutama didominasi oleh G. ruber, G. bulloides, P. obliqueloculata, N. dutertrei, dan G. menardii dari jenis planktonic. Sedangkan jenis bentik didominasi oleh Bulimina spp., Bolivinita quadrilatera, Bolivina spp., dan Uvigerina spp. Biozonasi foraminifera menunjukkan korelasi yang sangat baik dengan data ?18O dan mencerminkan Perubahan – Perubahan iklim di masa lalu yang terjadi sejak 50.000 tahun yang lalu antara lain glasial akhir yang berlangsung sejak zona 1 - 4b, LGM (subzone 4b), deglasiasi (subzona 4c), kondisi seperti YD dari bumi bagian utara atau ACR dari bumi bagian selatan pada awal zona 5, interglasial (pertengahan zona 5), dan Mid Holosen Maksimum pada pertengahan subzona 5a. Kata kunci: Distribusi foraminifera, paleoseanografi, isotop oksigen, Perubahan iklim global, Laut Halmahera. Microfauna foraminifera has been widely used as a potential proxy for paleoceanography and paleoclimatological changes. Its assemblages and its test geochemical composition preserve important data that could interprete various oceanographic parameters related to the paleoenvironmental changes. The paleoceanography dynamic of Halmahera sea is very important to be studied due to its great impact to Indonesian and global climate. The changes of its oceanographic parameters influence the thermohaline circulation and the air-sea interaction that contribute to the water favour distribution to the high latitudes. Therefore this research purpose is to analyze the foraminiferal distribution in order to reconstruct the paleoceanography changes of Halmahera sea and surrounded. This foraminiferal study is supported by the age model reconstruction and isotope stratigraphy analysis based on d18O G. ruber and 14C dating. The result suggests that foraminiferal assemblage was influenced by global climate changes. Planktonic foraminifera is dominated by G. ruber, G. bulloides, P. obliqueloculata, N. dutertrei, and G. menardii. Benthic foraminifera is dominated by Bulimina spp., Bolivinita quadrilatera, Bolivina spp., and Uvigerina spp. Foraminiferal biozonation indicates coherent correlation with ?18O record, and reflects global paleoclimatic changes that occurred since the 50 ka BP. Those paleoclimatic changes are last glacial (zone 1 - subzone 4b), LGM (zone 4b), deglaciation that was started from subzone 4c, condition of YD like of Northern Hemisphere climate or ACR like of the Southern Hemisphere climate (the beginning of zone 5), interglacial (middle of zone 5), and Mid Holocene Maximum at the middle of subzone 5a

Holocene evolution of summer winds and marine productivity in the tropical Indian Ocean in response to insolation forcing: data-model comparison

The relative abundance of <i>Globigerinoides bulloides</i> was used to infer Holocene paleo-productivity changes on the Oman margin and at the southern tip of India. Today, the primary productivity at both sites reaches its maximum during the summer season, when monsoon winds result in local Eckman pumping, which brings more nutrients to the surface. On a millennium time-scale, however, the % <i>G. bulloides</i> records indicate an opposite evolution of paleo-productivity at these sites through the Holocene. The Oman Margin productivity was maximal at ~9 ka (boreal summer insolation maximum) and has decreased since then, suggesting a direct response to insolation forcing. On the contrary, the productivity at the southern tip of India was minimum at ~9 ka, and strengthened towards the present. <br><br> Paleo-reconstructions of wind patterns, marine productivity and foraminifera assemblages were obtained using the IPSL-CM4 climate model coupled to the PISCES marine biogeochemical model and the FORAMCLIM ecophysiological model. These reconstructions are fully coherent with the marine core data. They confirm that the evolution of particulate export production and foraminifera assemblages at our two sites were directly linked with the strength of the upwelling. Model simulations at 9 ka and 6 ka BP show that the relative evolution between the two sites since the early Holocene can be explained by the weakening but also the southward shift of monsoon winds over the Arabian Sea during boreal summer

The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period

Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard–Oeschger (D–O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D–O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73–15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U∕230Th, optically stimulated luminescence (OSL), 40Ar∕39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft AccessTM at https://doi.org/10.1594/PANGAEA.870867

The ACER pollen and charcoal database: A global resource to document vegetation and fire response to abrupt climate changes during the last glacial period

This is the final version of the article. Available from Copernicus Publications via the DOI in this record.Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15ka) with a temporal resolution better than 1000years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U/230Th, optically stimulated luminescence (OSL), 40Ar/39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft Access™ at https://doi.org/10.1594/PANGAEA.870867.The members of the ACER project wish to thank the QUEST-DESIRE (UK and France) bilateral project, the INQUA International Focus Group ACER and the INTIMATE-COST action for funding a suite of workshops to compile the ACER pollen and charcoal database and the workshop on ACER chronology that allow setting the basis for harmonizing the chronologies. Josué M. Polanco-Martinez was funded by a Basque Government postdoctoral fellowship (POS_2015_1_0006) and Sandy P. Harrison by the ERC Advanced Grant GC2.0: unlocking the past for a clearer future

High resolution compressional wave velocity measurements in Pleistocene sediments of the Ceara Rise (western equatorial Atlantic): implications for orbital driven sedimentary cycles

International audienceCores from Ocean Drilling Program Sites 927 and 928, retrieved in water depths of 3315 m and 4012 m on the northern ßank of the Ceara Rise, were examined to provide continuous time series of compressional-wave velocity for the Pleistocene (0-1.2 Ma), to evaluate the responses of these records to climate change in the time and frequency domain and to study the effect of carbonate dissolution on P-wave velocity changes. Comparisons with other high-resolution sediment physical property measurements (GRAPE density, magnetic susceptibility) and sedimentological parameters (CaCO 3 content, coarse fraction) demonstrate that velocity changes at Sites 927 and 928 are the result of glacial/interglacial changes in coarse-fraction grain size, with velocity increasing as grain size increases during interglacial periods. The grain-size distribution in turn is controlled by carbonate productivity and dissolution changes. This signal, however, is diluted by abundant input of Þne-grained terrigenous sediments from the Amazon Fan that contain magnetic minerals and thus lead to an inverse relationship between velocity and magnetic susceptibility. Spectral analysis of P-wave velocity and related parameters reveals that spectral energy is concentrated at orbital frequencies in the precession, obliquity, and eccentricity band, and, therefore, conÞrms the potential of velocity records as a paleoceanographic tool. Marked differences between variance density spectra of the velocity and preservation index records at Site 927 indicate that velocity changes in sediments deposited well above the present lysoclineÑapart from the dilution effectÑmost probably reßect foraminifer productivity changes. At Site 928, enhanced dissolution close to the lysocline affects the velocity time series and leads to maxima of concentration in variance density between obliquity and precessional frequency bands

Life cycle(s) of sediment physical properties, Ceara Rise

International audienceSediments recovered during Leg 154 exhibit an unusually wide variation of interbedded lithologies down to the deepest layers recovered (900-m burial depth). We report here on relations of properties as a function of lithology and burial depth. Lithologies have been characterized by a large number of carbonate determinations on samples used for discrete physical properties measurements. Carbonate determinations have been supplemented by quartz determinations using infrared spectroscopy, and by shipboard determinations of biogenic opal content. Physical properties show coherent patterns with carbonate content over discrete zones that average several hundred meters of thickness. The relation between seismic velocities and carbonate content is strong enough to detect a velocity calibration problem for an interval of Site 925 shipboard measurements. The shallowest Ceara Rise sediments show a weak positive dependency of bulk density and a more pronounced positive relationship of seismic velocities on carbonate content. The difference between bulk-density and carbonate relations on Ceara Rise and well-known relations established in siliceous settings can be explained by the high quartz contents (15%-16% on a carbonate-free basis) of the Pleistocene section. For each type of physical property, inversions are encountered, where the sense of the correlation between property and lithology changes. For example, both bulk densities and seismic velocities become negatively correlated to carbonate content at depths of 100-250 meters below seaßoor on the Ceara Rise, but then become positively correlated on further burial. These inversions are interpreted to result from the competition between mechanical and chemical compaction in pelagic sediments. Bulk density, in particular, shows a complex evolution with depth that often results in a parabolic relation of density to carbonate content in more deeply buried Ceara Rise sediments. Nevertheless, the relations between physical properties and carbonate content on Ceara Rise are sufÞciently systematic that predictive models can be generated to relate lithology to signals sensed by borehole logging tools and by seismic imaging

d18O and trace element calibrations for 3 deep-dwelling planktonic foraminifera species : potential recorders of past thermocline temperature

Most previous paleoceanographic studies focused on past surface water or deep-water conditions by analysing surface-dweller or benthic organisms. However, little information is available on temperature variations in the upper 500 m of the water column, where most of the energy storage and heat transport occur. Deep-dwelling planktonic foraminifers, which inhabit the top few hundred meters of the ocean constitute potential recorders of thermocline conditions. We measured the oxygen isotopic composition of the deep-dwelling foraminiferal species Globorotalia inflata, G. truncatulinoides dextral and sinistral, and Pulleniatina obliquiloculata in 29 modern core tops raised from the North Atlantic Ocean. We compared calculated isotopic temperatures with atlas temperatures and developed ecological models for each species. All species live preferentially at the base of the seasonal thermocline but under temperature stress (when the base of the seasonal thermocline is warmer than 16°C) G. inflata and G. truncatulinoides live deeper in the main thermocline. In the same set of core-tops, we measured Mg/Ca and Sr/Ca ratios of these deep-dwelling species and of surface-dwelling foraminiferal species Globigernoides ruber and Globigerinoides bulloides. We analyzed the thermo-dependence of those trace element ratios relative to isotopic temperatures. Mg incorporation in the test is a function of temperature in all species but only G. inflata and G. truncatulinoides show a good correlation between Sr/Ca and temperature. Our calibrations of the Mg/Ca thermometer in G. ruber and G. bulloides fit well with the published relations for these species, respectively by Elderfield and Ganssen [2000] and Anand et al. [2003]. Species-specific calibrations showed that incorporation of Mg and Sr have similar sensitivity to temperature for the three deep-dwelling species. Given the current knowledge on these proxies we to group those data to establish multi-deep-dwelling relationships with significant coefficient correlations. These calibrations areas are as precise as species-specific relations and provide thermocline temperature estimates with with an error of ± 1.8°C for Mg/Ca ratio and ± 1.4°C for Sr content as long as Sr geochemistry in ocean is constant though time

Crystallinity of foraminifera shells: A proxy to reconstruct past bottom water CO(3)(=) changes?

The reconstruction of past changes in bottom water CO(3)(=) is central to evaluating competing oceanic scenarios that deal with long-term variations in atmospheric pCO(2). In search of a quantitative bottom water CO(3)(=) proxy, we analyzed the variations of calcite crystallinity of planktonic foraminifera Globigerinoides ruber shells picked from core top samples along three depth transects: Ontong Java Plateau and the northeast margin of Irian Jaya, in the western equatorial Pacific, and the Sierra Leone Rise, in the eastern tropical Atlantic. The strong empirical relationship between calcite crystallinity ( inferred from the full width at half maximum (FWHM) of calcite (104) X-ray diffraction peak) and bottom water saturation relative to calcite (DeltaCO(3)) shows that foraminifera calcite crystallinity could be a promising proxy for the reconstruction of upper Pleistocene bottom water carbonate ion concentration

DISTRIBUSI FORAMINIFERA DI LAUT HALMAHERA DARI GLASIAL AKHIR SAMPAI RESEN

Mikrofauna foraminifera telah banyak digunakan sebagai proksi dalam penelitian paleoseanografi dan perubahan iklim purba. Kelimpahan dan komposisi kimia cangkang foraminifera merekam berbagai informasi yang dapat diinterpretasi berkaitan dengan perubahan lingkungan berdasarkan parameter-parameter paleoseanografi. Paleoseanografi Laut Halmahera sangat penting untuk dikaji karena berpengaruh terhadap dinamika iklim Indonesia dan iklim global. Perubahan-perubahan parameter oseanografi tersebut mempengaruhi sirkulasi arus global dan interaksi antara air-udara yang berperan terhadap penyebaran uap air ke lintang tinggi. Oleh karena itu tujuan penelitian ini adalah mempelajari distribusi foraminifera untuk rekonstruksi perubahan paleoseanografi di Laut Halmahera dan sekitarnya. Data foraminifera ini didukung dengan pemodelan umur dan rekonstruksi isotop stratigrafi berdasarkan analisis d18O G. ruber dan C14 radiokarbon dating. Hasil penelitian menunjukkan bahwa kelimpahan foraminifera di Laut Halmahera sangat dipengaruhi oleh iklim global. Kelimpahan foraminifera terutama didominasi oleh G. ruber, G. bulloides, P. obliqueloculata, N. dutertrei, dan G. menardii dari jenis planktonic. Sedangkan jenis bentik didominasi oleh Bulimina spp., Bolivinita quadrilatera, Bolivina spp., dan Uvigerina spp. Biozonasi foraminifera menunjukkan korelasi yang sangat baik dengan data ?18O dan mencerminkan perubahan – perubahan iklim di masa lalu yang terjadi sejak 50.000 tahun yang lalu antara lain glasial akhir yang berlangsung sejak zona 1 - 4b, LGM (subzone 4b), deglasiasi (subzona 4c), kondisi seperti YD dari bumi bagian utara atau ACR dari bumi bagian selatan pada awal zona 5, interglasial (pertengahan zona 5), dan Mid Holosen Maksimum pada pertengahan subzona 5a. Kata kunci: Distribusi foraminifera, paleoseanografi, isotop oksigen, perubahan iklim global, Laut Halmahera. Microfauna foraminifera has been widely used as a potential proxy for paleoceanography and paleoclimatological changes. Its assemblages and its test geochemical composition preserve important data that could interprete various oceanographic parameters related to the paleoenvironmental changes. The paleoceanography dynamic of Halmahera sea is very important to be studied due to its great impact to Indonesian and global climate. The changes of its oceanographic parameters influence the thermohaline circulation and the air-sea interaction that contribute to the water favour distribution to the high latitudes. Therefore this research purpose is to analyze the foraminiferal distribution in order to reconstruct the paleoceanography changes of Halmahera sea and surrounded. This foraminiferal study is supported by the age model reconstruction and isotope stratigraphy analysis based on d18O G. ruber and 14C dating. The result suggests that foraminiferal assemblage was influenced by global climate changes. Planktonic foraminifera is dominated by G. ruber, G. bulloides, P. obliqueloculata, N. dutertrei, and G. menardii. Benthic foraminifera is dominated by Bulimina spp., Bolivinita quadrilatera, Bolivina spp., and Uvigerina spp. Foraminiferal biozonation indicates coherent correlation with ?18O record, and reflects global paleoclimatic changes that occurred since the 50 ka BP. Those paleoclimatic changes are last glacial (zone 1 - subzone 4b), LGM (zone 4b), deglaciation that was started from subzone 4c, condition of YD like of Northern Hemisphere climate or ACR like of the Southern Hemisphere climate (the beginning of zone 5), interglacial (middle of zone 5), and Mid Holocene Maximum at the middle of subzone 5a.Keywords: Foraminiferal distribution, paleoceanograhy, oxygen isotope, global climate changes, Halmahera sea