Sampling the oxygen minimum zone off Pakistan: glacial-interglacial variations of anoxia and productivity (preliminary results, sonne 90 cruise)

Rad, Ulrich von; Schulz, Hartmut; Khan, Athar Ali; Ansari, Murtaza H.; Berner, Ulrich; Čepek, P.; Cowie, Gregory L.; Dietrich, Peter; Erlenkeuser, Helmut; Geyh, Mebus A.; Jennerjahn, Tim C; Lückge, Andreas; Marchig, Vesna; Riech, Volkher; Rösch, H.; Schäfer, Petra; Schulte, Sonja; Sirocko, Frank; Tahir, Muhammad Aslam; Weiss, W.

doi:10.1016/0025-3227(95)00051-y

Cited by 83 publications

(32 citation statements)

References 6 publications

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“…The sediments recovered, from station depths of ca. 100 to 2900 m, ranged from coarse shelly sands on the shelf to fully laminated (varved) silty clays within the OMZ, to similarly fine but progressively more bioturbated sediments below [28]. Bottom topography on the tectonically active Hab and especially the Makran transects was highly irregular and sediment records were frequently interrupted by local mudflow deposits.…”

Section: Study Area and Samplesmentioning

confidence: 99%

Carbon and Phosphorus Cycling in Arabian Sea Sediments across the Oxygen Minimum Zone

Filippelli¹,

Cowie²

2017

J Oceanogr Mar Res

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Section: Study Area and Samplesmentioning

confidence: 99%

Carbon and Phosphorus Cycling in Arabian Sea Sediments across the Oxygen Minimum Zone

Filippelli¹,

Cowie²

2017

J Oceanogr Mar Res

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“…Successful marine paleomonsoon research rests on two conditions: 1) the retrieval of high quality sediments cores and 2) the development of accurate paleomonsoon proxies. Several scientific cruises to the Indian Ocean and the SCS, including the Ocean Drilling Program (ODP) Leg 117 to the Arabian Sea and Oman Margin (Prell et al 1989), SONNE 90 to the northern Indian Ocean (von Rad et al 1995), SONNE 94 to the SCS (Sarnthein et al 1994), IMAGES (International Marine Past Global Change Studies) Leg III to the SCS (Chen et al 1998a), and ODP Leg 184 to the SCS , made the former possible. Meanwhile, many lithological, micropaleontological, and geochemical tools have been developed to serve as marine monsoon proxies over the past few decades.…”

Section: Introductionmentioning

confidence: 99%

Asian Monsoon Variability Recorded in Other Archives

Cai

Jin

Zhou

et al. 2014

Late Cenozoic Climate Change in Asia

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This chapter provides an extensive review of paleomonsoon variability on millennial-to decadal time scales in various archives other than loess, including speleothems, lake sediments, peat deposits, desert deposits, marine sediments, corals, ice cores, tree rings, pollen archives and historical documents. Case studies will be presented to introduce the major proxy indexes associated with these archives, and the reconstructed history of Asian monsoon variability. Advances in the study of monsoon variability and the peculiarity of different archives will also be introduced in this chapter.Keywords Speleothems · Lake sediments · Peat · Desert · Marine sediments · Coral · Ice cores · Tree ring · Pollen · Historical documents Overview of Various Paleoclimate ArchivesAs described in the previous chapter, the eolian loess sequence, a unique geological archive in the world, plays an important role in studying the climatic and environmental changes in China as it documents the variability of both Asian monsoon and the aridification of inland Asia. It has the advantages of being relatively continuous and long-lasting for studying the monsoon changes and inland aridifications on tectonic and orbital time scales, and even has the potential for studies of monsoon variations on millennial time scales at some sites. However, other geo-biological archives and historical records are also essential in studying the Asian monsoon changes, as they provide indispensable information for fully understanding Asian monsoon changes and its dynamic forces and environmental effects, especially on the millennial to decadal time scales. For example, taking advantage of high-precision absolute U-series dating, speleothems from karst caves, provide the ages of the abrupt events that occurred within the Asian monsoon regions and make it possible to correlate these events with global climate changes, enhancing greatly our understanding of the linkage between Asian monsoon and global climate change. With multiple proxies, lake sediments are good at providing the integrated information on hydrology, weathering processes, biomass and other aspects within the drainage systems. Coral records may indicate the changes in moisture supply from the tropical ocean, ocean circulation, sea surface temperature and other parameters linked closely with monsoon climate. Tree-ring records provide annual changes of regional temperature, precipitation and the hydrological environment, and are the basis to fully describe the present global warming and the anthropogenic contribution. As the direct index of vegetation, pollen assemblages indicate the succession of vegetation associated with monsoon changes, revealing variations in moisture availability and temperature. Therefore, studies of these various archives, as well as peatbogs, ice cores, marine and desert deposits and historical records, greatly expanded our knowledge of the variability of Asian monsoons and their driving forces.This chapter will focus on various archives used in the study of Asian mon...

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“…Winnowing and reworking by slope currents or turbidites was common, which prevented the establishment of continuous long records of annual resolution (Schulz et al, 1996). Instead, cyclic alternations of laminated and bioturbated core sections suggested a spatial variability of the OMZ on longer time scales (von Rad et al, 1995).…”

Section: Laminationsmentioning

confidence: 99%

“…one magnitude higher than in the Arabian Sea. Dilution by seasonal terrigenous sediment input from Pakistan probably accounts for the difference (von Rad et al, 1995).…”

Section: Organic Carbon Accumulation Ratesmentioning

confidence: 99%

“…Laminated sediments have been studied in great detail to unravel the processes forming millimetre-scale interbedded sediments with the perspective that alternations between the varves reflect seasonal, annual or decadal environmental variability (von Stackelberg, 1972;Brodie and Kemp, 1994;Kemp, 1996). In the Arabian Sea, laminated sediments were found between 300 and 900 m water depth whereas the OMZ with oxygen concentrations of < 23 µmol kg −1 impinges the sea floor between 200 and 1200 m depth.…”

Section: Laminationsmentioning

confidence: 99%

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

et al. 2015

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Abstract. 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 < 7 µmol kg −1 under the Peruvian upwelling and < 5 µmol kg −1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 µmol kg −1 . Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 µmol kg −1 , which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm −2 kyr −1 in laminated OAE 2 sections in Tarfaya Basin, Morocco, matching late Holocene accumulation rates of laminated Peruvian sediments under Recent oxygen levels below 5 µmol kg −1 . Sediments deposited at > 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.

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Sampling the oxygen minimum zone off Pakistan: glacial-interglacial variations of anoxia and productivity (preliminary results, sonne 90 cruise)

Cited by 83 publications

References 6 publications

Carbon and Phosphorus Cycling in Arabian Sea Sediments across the Oxygen Minimum Zone

Carbon and Phosphorus Cycling in Arabian Sea Sediments across the Oxygen Minimum Zone

Asian Monsoon Variability Recorded in Other Archives

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

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