Lower Cretaceous benthic foraminifera of the Indian Ocean

A comprehensive documentation of Berriasian to Albian benthic foraminiferal assemblages from Indian Ocean DSDP and ODP sites is compiled, which provides a unified taxonomic data base for the Indian Ocean. The benthic foraminiferal assemblages are strongly cosmopolitan, but differ from typical low latitude Tethyan assemblages by the rarity or absence of some characteristic Tethyan lineages. Marked faunal differentiation or endemism is suggested in the Cuvier Basin by the unique composition of agglutinated assemblages at Site 263, which include five new species and numerous taxa not recorded at other Indian Ocean sites. The chronostratigraphy of DSDP and ODP Indian Ocean sites is revised. New ages are determined, which considerably improve the stratigraphic resolution of intervals, previously dated as undifferentiated Aptian or Albian. An older Valanginian to Barremian age is also established for the base of Hole 263. None of the existing benthic foraminiferal zonal schemes are found to be applicable in the Lower Cretaceous of the Indian Ocean. A new biostratigraphic scheme is proposed, which enables the correlation of Lower Cretaceous sedimentary sequences in the Indian Ocean. Palaeoecological interpretations, derived from quantitative analyses of benthic foraminiferal distribution patterns and morphogroup analyses, indicate a marked differentiation in palaeoenvironments along the western and northwestern margins of Australia. Diversity and specific distribution appear strongly influenced by margin subsidence, oceanic circulation patterns, and inferred changes in the depth of the CCD during the Early Cretaceous. Three main transgressive pulses are detected in the Barremian, late Aptian and late early Albian. Productivity fluctuations in the Aptian and Albian probably reflect changes in deep-water circulation and in the nutrient and oxygen budget of an ocean already susceptible to dysoxia. Well ventilated conditions became established during the late early to mid Albian, when a significant drop in CCD occurred, before dysoxic conditions returned to some marginal sites in the late Albian

Minimal influence of recrystallization on middle Miocene benthic foraminiferal stable isotope stratigraphy in the eastern equatorial Pacific

Stable carbon and oxygen isotopes (δ13C and δ18O) of foraminiferal tests are amongst the most important tools in paleoceanography, but the extent to which recrystallization can alter the isotopic composition of the tests is not well known. Here we compare three middle Miocene (16–13 Ma) benthic foraminiferal stable isotope records from eastern equatorial Pacific sites with different diagenetic histories to investigate the effect of recrystallization. To test an extreme case, we analyzed stable isotope compositions of benthic foraminifera from Integrated Ocean Drilling Program Site U1336, for which the geochemistry of bulk carbonates and associated pore waters indicates continued diagenetic alteration in sediments > 14.7 Ma. Despite this diagenetic overprinting, the amplitudes and absolute values of the analyzed U1336 stable isotopes agree well with high-resolution records from better preserved Sites U1337 and U1338 nearby. Our results suggest that although benthic foraminiferal tests of all three sites show some degree of textural changes due to recrystallization, they have retained their original stable isotope signatures. The good agreement of the benthic foraminiferal stable isotope records demonstrates that recrystallization occurred extremely rapidly (< 100 kyr) after deposition. This is confirmed by the preservation of orbital cyclicities in U1336 stable isotope data and δ18O values being different to inorganic calcite that would precipitate from U1336 pore waters during late recrystallization. The close similarity of the benthic foraminiferal stable isotope records between the sites allows the well-resolved paleomagnetic results of Site U1336 to be transferred to Sites U1337 and U1338 improving the global geological timescale

Evidence for Indonesian Throughflow slowdown during Heinrich events 3-5

We present sea surface and upper thermocline temperature records (60-100 year temporal resolution) spanning marine isotope stage 3 (similar to 24-62 ka B. P.) from International Marine Global Change Study core MD01-2378 (121 degrees 47.27'E and 13 degrees 04.95'S; 1783 m water depth) located in the outflow area of the Indonesian Throughflow within the Timor Sea. Stable isotopes and Mg/Ca of the near-surface-dwelling planktonic foraminifer Globigerinoides ruber (white) and the upper thermocline-dwelling Pulleniatina obliquiloculata reveal rapid changes in the thermal structure of the upper ocean during Heinrich events. Thermocline warming and increased delta O-18(seawater) (P. obliquiloculata record) during Heinrich events 3, 4, and 5 reflect weakening of the relatively cool and fresh thermocline flow and reduced export of less saline water from the North Pacific and Indonesian Seas to the tropical Indian Ocean. Three main factors influenced Indonesian Throughflow variability during marine isotope stage 3: (1) global slowdown in thermohaline circulation during Heinrich events triggered by Northern Hemisphere cooling, (2) increased freshwater export from the Java Sea into the Indonesian Throughflow controlled by rising sea level from similar to 60 to 47 ka, and (3) insolation-related changes in the Australasian monsoon with associated migration of hydrological fronts between Indian Ocean- and Indonesian Throughflow-derived water masses at similar to 46-40 ka

Oxygen minimum zone-type biogeochemical cycling in the Cenomanian-Turonian Proto-North Atlantic across Oceanic Anoxic Event 2

Highlights • We present a 5 myr record of biogeochemical cycling in a Cretaceous upwelling area. • A novel quantitative approach for the evaluation of Fe speciation proxies was applied. • Ferruginous proxy signature reflects intense chemical weathering rather than anoxia. • Water column redox conditions evolved from oxic to nitrogenous to euxinic before OAE2. • Smaller seawater nitrate inventory facilitated sedimentary H2S release and euxinia. Abstract Oceanic Anoxic Events (OAEs) in Earth's history are regarded as analogues for current and future ocean deoxygenation, potentially providing information on its pacing and internal dynamics. In order to predict the Earth system's response to changes in greenhouse gas concentrations and radiative forcing, a sound understanding of how biogeochemical cycling differs in modern and ancient marine environments is required. Here, we report proxy records for iron (Fe), sulfur and nitrogen cycling in the Tarfaya upwelling system in the Cretaceous Proto-North Atlantic before, during and after OAE2 (∼93 Ma). We apply a novel quantitative approach to sedimentary Fe speciation, which takes into account the influence of terrigenous weathering and sedimentation as well as authigenic Fe (non-terrigenous, precipitated onsite) rain rates on Fe-based paleo-redox proxies. Generally elevated ratios of reactive Fe (i.e., bound to oxide, carbonate and sulfide minerals) to total Fe (FeHR/FeT) throughout the 5 million year record are attributed to transport-limited chemical weathering under greenhouse climate conditions. Trace metal and nitrogen isotope systematics indicate a step-wise transition from oxic to nitrogenous to euxinic conditions over several million years prior to OAE2. Taking into consideration the low terrigenous sedimentation rates in the Tarfaya Basin, we demonstrate that highly elevated FeHR/FeT from the mid-Cenomanian through OAE2 were generated with a relatively small flux of additional authigenic Fe. Evaluation of mass accumulation rates of reactive Fe in conjunction with the extent of pyritization of reactive Fe reveals that authigenic Fe and sulfide precipitation rates in the Tarfaya Basin were similar to those in modern upwelling systems. Because of a smaller seawater nitrate inventory, however, chemolithoautotrophic sulfide oxidation with nitrate was less efficient in preventing hydrogen sulfide release into the water column. As terrigenous weathering and sediment flux determine how much authigenic Fe is required to generate an anoxic euxinic or ferruginous proxy signature, we emphasize that both have to be taken into account when interpreting Fe-based paleo-redox proxies

Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones

Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of 10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions

Croatian Liberal Press about Reform Movement of Part of Catholic Lower Clergy (1918—1923)

Kraj Prvog svjetskog rata značio je prekretnicu u hrvatskoj nacionalnoj povijesti. S druge strane Crkva u Hrvata suočila se s pokretom nižeg katoličkog klera koji je zahtijevao poboljšanje svoga materijalnog statusa. Ovaj pokret prerastao je s vremenom u reformni pokret ili tzv. "žuti pokret" koji je u svojim zahtjevima zalazio u crkvenu disciplinu tražeći velike reformske zahvate na tom području. Dok je službeni i poluslužbeni katolički tisak oštro nastupao prema reformnom pokretu liberalni tisak je s neskrivenim simpatijama gledao na sam pokret i otvoreno ga podržavao. Zahtjevi članova reformnog pokreta usko su se podudarali s liberalnim pogledom na Crkvu te su liberalne novine toga vremena veliki prostor davali reformaπima i njihovim zahtjevima. Ovo otvoreno podržavanje reformnog pokreta od strane hrvatskog liberalnog tiska bilo je neupitno sve do donošenja Vidovdanskog ustava u lipnju 1921. godine. Zbog potpore koju je pokret uživao od strane tiska bliskog Pribićevićevoj Samostalnoj demokratskoj stranci hrvatski liberalni tisak potpuno mijenja svoj odnos prema reformnom pokretu. Od otvorene podrške na njega se sada gleda kao produženu ruku beogradske vlade kojom se želi oslabiti hrvatski nacionalni korpus, u kojem katolicizam ima bitnu ulogu. Osnivanje Hrvatske starokatoličke crkve krajem 1923. godine liberalni tisak popratiti će poprilično nezainteresirano.The end of First World War was turning-point of in Croatian national history. Catholic Church in Croatia was in this period confronted with movement of part of lower clergy which had demanded improvement of his material status. This movement had become Reform movement also called flYellow movement« which had in his demands frequenting deep in the discipline maters of Catholic Church. Demands of Reform movement had correspond with liberal view on Church maters so Croatian liberal press of that time had given to the movement his full support. This support of Croatian liberal press to the Reform movement was strong until the June 1921 when the Vidovdan Constitution was voted. Because of support which Reform movement had from Pribičević’s Independent Democratic Party Croatian liberal press completely changes his attitude to movement. From strong support they now write about Reform movement like extended hand of Belgrade government for languishment of Croatian national being, in which Catholic Church had strong position. About foundation of Croatian Old Catholic Church at the end of 1923 liberal press will wrote with indifference

The Middle to Late Miocene “Carbonate Crash” in the Equatorial Indian Ocean

We integrate benthic foraminiferal stable isotopes, X‐ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2 million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2 Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7 Ma, coincides with the middle to late Miocene carbonate crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Interocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10 Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the carbonate crash. An increase in U1443 Log (Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2 Ma, which predates the global onset of the biogenic bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon

Temperature gradients across the Pacific Ocean during the middle Miocene

Abstract: Sea surface temperatures (SSTs) of the tropical Pacific Ocean exert powerful controls on regional and global climates. Previous studies have suggested that during warm climate phases, the east‐west temperature gradient collapsed. To date, there has been no high‐resolution reconstruction of sea surface conditions in both the east and west Pacific Ocean during the Miocene Climate Optimum (MCO) and across the middle Miocene climate transition (MMCT); therefore, our understanding of the mean oceanographic state during this major global climatic shift is limited. Here, we present new SST reconstructions for the eastern Pacific Ocean (15.5–13.3 Ma) which show a clear east‐west temperature gradient of ∼4°C during the warmest interval of the Neogene, implying that the oceanographic processes that produce the modern gradient were present and active. There is no shift in the east‐west gradient across the MMCT indicating that the gradient was not impacted by global cooling and ice growth. We find a 2°C sea surface cooling in the eastern equatorial Pacific, that lags the benthic foraminiferal δ18O positive shift by 150 kyr, indicating that tropical temperature did not decrease synchronously with the expansion of the Antarctic ice sheet. Reconstructed variations in the δ18O composition of seawater, determined by combining our Mg/Ca and δ18O records, reveal a freshening in the eastern Pacific Ocean after 13.8 Ma, suggesting changes in the hydrological cycle and in tropical fronts in response to the new icehouse regime

Middle Pleistocene re-organization of Australian Monsoon

The sensitivity of the Australian Monsoon to changing climate boundary conditions remains controversial due to limited understanding of forcing processes and past variability. Here, we reconstruct austral summer monsoonal discharge and wind-driven winter productivity across the Middle Pleistocene Transition (MPT) in a sediment sequence drilled off NW Australia. We show that monsoonal precipitation and runoff primarily responded to precessional insolation forcing until ~0.95 Ma, but exhibited heightened sensitivity to ice volume and pCO2 related feedbacks following intensification of glacial-interglacial cycles. Our records further suggest that summer monsoon variability at the precessional band was closely tied to the thermal evolution of the Indo-Pacific Warm Pool and strength of the Walker circulation over the past ~1.6 Myr. By contrast, productivity proxy records consistently tracked glacial-interglacial variability, reflecting changing rhythms in polar ice fluctuations and Hadley circulation strength. We conclude that the Australian Monsoon underwent a major re-organization across the MPT and that extratropical feedbacks were instrumental in driving short- and long-term variability