Christian Betzler | University of Hamburg (original) (raw)

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Papers by Christian Betzler

Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial pe... more Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth's orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/K cycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100 kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25 Ma in tandem with the global ice volume benthic δ18O data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130 kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variabili [...]

Geology, 2021

Carbonate platforms are built mainly by corals living in shallow light-saturated tropical waters.... more Carbonate platforms are built mainly by corals living in shallow light-saturated tropical waters. The Saya de Malha Bank (Indian Ocean), one of the world’s largest carbonate platforms, lies in the path of the South Equatorial Current. Its reefs do not reach sea level, and all carbonate production is mesophotic to oligophotic. New geological and oceanographic data unravel the evolution and environment of the bank, elucidating the factors determining this exceptional state. There are no nutrient-related limitations for coral growth. A switch from a rimmed atoll to a current-exposed system with only mesophotic coral growth is proposed to have followed the South Equatorial Current development during the late Neogene. Combined current activity and sea-level fluctuations are likely controlling factors of modern platform configuration.

Palaeogeography, Palaeoclimatology, Palaeoecology, 2019

Earth and Planetary Science Letters, 2019

Progress in Earth and Planetary Science, 2018

Progress in Earth and Planetary Science, 2018

The Depositional Record, 2016

The Maldive archipelago represents one of the largest active carbonate platforms in the world. Th... more The Maldive archipelago represents one of the largest active carbonate platforms in the world. The NEOMA project of universities in Hamburg, Amsterdam, and Houston explores the Neogene development of this system with special regard to the impacts of climatic, paleoceanographic and global sea-level changes. Measurements of sediment geometries as well as the documentation of drowned atoll complexes will help to develop a comprehensive picture of the sedimentary history of the Maldives. Field measurements and drilling operations were performed during the M74-4 cruise of the German R/V METEORin December 2007. First results showed that sedimentation in the Inner Sea, the sedimentary basin situated between the rows of atolls of the Maldives, is controlled by strong N-S and E-W currents (10cm/s). The submarine platform slopes of the individual atolls are steep, reach 200m waterdepth in only two kilometers, and show coarse-grained sediments with e.g. Halimedaand coralline red algae. The sed...

Hydroacoustic data and a piston core were analyzed to decipher sedimentation at a lower slope of ... more Hydroacoustic data and a piston core were analyzed to decipher sedimentation at a lower slope of an atoll of the Maldives carbonate platform. The sediment texture ranges from float- to rudstones with grainstone matrix. The lowermost 3 m of the core are dominated by larger benthic foraminifera (Operculina and Amphistegina) and relict components. The sediment at 9.16 mbsf is dated to 21955 ± 75 cal BP. Followed by an 1.5 m long bioturbated part with minor contents of Halimeda, the upper 7.5 m reveal a successive disappearence of larger benthic foraminifera. In turn, the content of Halimeda increases to more than 50% supported by an increasing content of red algae and planktonic foraminifers towards the surface. The sediment between 6.99 and 0.66 mbsf was deposited with a sedimentation rate between 1.5 to 3.9 mm yr-1. The sediment at 0.66 mbsf reveals a 14C age of 15905 ± 85 cal BP. Acoustic data show a subhorizontally stratified sediment package with internal reflections of medium to ...

Three cores from the shallow Inner Sea of the Maldives carbonate platform have been investigated ... more Three cores from the shallow Inner Sea of the Maldives carbonate platform have been investigated in order to characterize the stratigraphic distribution of Pleistocene carbonate sediments, related to variations in sea level and/or changes in the monsoonal current regime. Synthetic seismograms were established, which were tied to shallow seismic profiles enabling us to model spatial facies distributions on a regional scale. The Maldives carbonate platform is located in the Northern Indian Ocean. Steep outer slopes, expanding far beyond 2,000 m of water-depth, characterize its north-south-trending double-row of atolls. These atolls enclose a relatively shallow sedimentary basin called the “Inner Sea”, which serves as depocenter for sediments shed from the adjacent atolls. Pleistocene sediments from the Maldives consist of fine to coarse-grained periplatform ooze, a mixture of neritic and pelagic skeletal grains. Temporal changes in the ratio of neritic to pelagic components are relate...

International Journal of Earth Sciences

High resolution cyclic records of Sr concentrations in the upper 12-14 m of a muddy periplatform ... more High resolution cyclic records of Sr concentrations in the upper 12-14 m of a muddy periplatform drift in the Maldives Inner Sea (cores M74-4-1120, -1143, and -1144 in about 500 m of water depth) reveal high-frequency sea-level oscillations during late Pleistocene highstands. Export variations of bank-top produced fine aragonite to adjacent slopes and basin floor faithfully record bank-top flooding and exposure, and therefore sea level. Here we present the results of a new analytical method based on Sr concentrations, as a proxy for bank-derived fine aragonite content, measured down the core using a X-ray Fluorescence (XRF) Core Scanner. The three piston cores were analyzed for Sr concentration at 1 cm high resolution spaced intervals. Large cations, such as Sr, are preferentially substituted for Ca in orthorhombic aragonite, whereas small cations such as Mg are preferentially substituted for Ca in rhombohedral calcite. Based on a calibration curve in core M74-4-1143, Sr concentrati...

Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial pe... more Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth's orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/K cycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100 kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25 Ma in tandem with the global ice volume benthic δ18O data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130 kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variabili [...]

Geology, 2021

Carbonate platforms are built mainly by corals living in shallow light-saturated tropical waters.... more Carbonate platforms are built mainly by corals living in shallow light-saturated tropical waters. The Saya de Malha Bank (Indian Ocean), one of the world’s largest carbonate platforms, lies in the path of the South Equatorial Current. Its reefs do not reach sea level, and all carbonate production is mesophotic to oligophotic. New geological and oceanographic data unravel the evolution and environment of the bank, elucidating the factors determining this exceptional state. There are no nutrient-related limitations for coral growth. A switch from a rimmed atoll to a current-exposed system with only mesophotic coral growth is proposed to have followed the South Equatorial Current development during the late Neogene. Combined current activity and sea-level fluctuations are likely controlling factors of modern platform configuration.

Palaeogeography, Palaeoclimatology, Palaeoecology, 2019

Earth and Planetary Science Letters, 2019

Progress in Earth and Planetary Science, 2018

Progress in Earth and Planetary Science, 2018

The Depositional Record, 2016

The Maldive archipelago represents one of the largest active carbonate platforms in the world. Th... more The Maldive archipelago represents one of the largest active carbonate platforms in the world. The NEOMA project of universities in Hamburg, Amsterdam, and Houston explores the Neogene development of this system with special regard to the impacts of climatic, paleoceanographic and global sea-level changes. Measurements of sediment geometries as well as the documentation of drowned atoll complexes will help to develop a comprehensive picture of the sedimentary history of the Maldives. Field measurements and drilling operations were performed during the M74-4 cruise of the German R/V METEORin December 2007. First results showed that sedimentation in the Inner Sea, the sedimentary basin situated between the rows of atolls of the Maldives, is controlled by strong N-S and E-W currents (10cm/s). The submarine platform slopes of the individual atolls are steep, reach 200m waterdepth in only two kilometers, and show coarse-grained sediments with e.g. Halimedaand coralline red algae. The sed...

Hydroacoustic data and a piston core were analyzed to decipher sedimentation at a lower slope of ... more Hydroacoustic data and a piston core were analyzed to decipher sedimentation at a lower slope of an atoll of the Maldives carbonate platform. The sediment texture ranges from float- to rudstones with grainstone matrix. The lowermost 3 m of the core are dominated by larger benthic foraminifera (Operculina and Amphistegina) and relict components. The sediment at 9.16 mbsf is dated to 21955 ± 75 cal BP. Followed by an 1.5 m long bioturbated part with minor contents of Halimeda, the upper 7.5 m reveal a successive disappearence of larger benthic foraminifera. In turn, the content of Halimeda increases to more than 50% supported by an increasing content of red algae and planktonic foraminifers towards the surface. The sediment between 6.99 and 0.66 mbsf was deposited with a sedimentation rate between 1.5 to 3.9 mm yr-1. The sediment at 0.66 mbsf reveals a 14C age of 15905 ± 85 cal BP. Acoustic data show a subhorizontally stratified sediment package with internal reflections of medium to ...

Three cores from the shallow Inner Sea of the Maldives carbonate platform have been investigated ... more Three cores from the shallow Inner Sea of the Maldives carbonate platform have been investigated in order to characterize the stratigraphic distribution of Pleistocene carbonate sediments, related to variations in sea level and/or changes in the monsoonal current regime. Synthetic seismograms were established, which were tied to shallow seismic profiles enabling us to model spatial facies distributions on a regional scale. The Maldives carbonate platform is located in the Northern Indian Ocean. Steep outer slopes, expanding far beyond 2,000 m of water-depth, characterize its north-south-trending double-row of atolls. These atolls enclose a relatively shallow sedimentary basin called the “Inner Sea”, which serves as depocenter for sediments shed from the adjacent atolls. Pleistocene sediments from the Maldives consist of fine to coarse-grained periplatform ooze, a mixture of neritic and pelagic skeletal grains. Temporal changes in the ratio of neritic to pelagic components are relate...

International Journal of Earth Sciences

High resolution cyclic records of Sr concentrations in the upper 12-14 m of a muddy periplatform ... more High resolution cyclic records of Sr concentrations in the upper 12-14 m of a muddy periplatform drift in the Maldives Inner Sea (cores M74-4-1120, -1143, and -1144 in about 500 m of water depth) reveal high-frequency sea-level oscillations during late Pleistocene highstands. Export variations of bank-top produced fine aragonite to adjacent slopes and basin floor faithfully record bank-top flooding and exposure, and therefore sea level. Here we present the results of a new analytical method based on Sr concentrations, as a proxy for bank-derived fine aragonite content, measured down the core using a X-ray Fluorescence (XRF) Core Scanner. The three piston cores were analyzed for Sr concentration at 1 cm high resolution spaced intervals. Large cations, such as Sr, are preferentially substituted for Ca in orthorhombic aragonite, whereas small cations such as Mg are preferentially substituted for Ca in rhombohedral calcite. Based on a calibration curve in core M74-4-1143, Sr concentrati...