Conference Agenda

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Session Overview
Session
2.2-1 The imprint of astronomical climate forcing: geochronometer and paleoclimate archive
Time:
Monday, 24/Aug/2020:
10:20am - 12:20pm

Location: Room 2.02

Session Abstract

by Christian Zeeden1, Diederik Liebrand2, Anna-Joy Drury3, Stefanie Kaboth-Bahr4, Qiang Fang5

1: Leibniz Institute for Applied Geophysics, Hanover, Germany; 2: MARUM, Bremen, Germany; 3: University College London, London, UK; 4: University of Potsdam, Potsdam, Germany; 5: China University of Geosciences, Beijing, China

The pacing of the global climate system by variations in orbital parameters is clearly demonstrated in the timing and specific patterns of e.g. sapropels and glacial-interglacial cycles beside many other examples. The imprint of astronomical cycles can be used as high-precision geochronometer, and as paleoclimatic information. We invite contributions utilizing the imprint of Milankovic cycles as preserved in the geological record in any way. This includes the often not very well understood mechanisms that translate this forcing into geoarchives. Submissions exploring proxy data and/or modelling work are welcome; we aim to bring together proxy-based, theoretical and modelling studies focused on global and regional climate responses to astronomical forcing at different time scales.


Presentations
10:20am - 10:35am
ID: 246
Invited Virtual Presentation | Keynote

Astronomical climate forcing of ~2.5 Ga banded iron formations

Margriet L. Lantink1, Joshua H. F. L. Davies2,3, Rick Hennekam4, Frederik J. Hilgen1, David McB. Martin5, Paul R. D. Mason1, Gert-Jan Reichart1,4, Urs Schaltegger2

1Utrecht University; 2Université du Québec à Montréal; 3University of Geneva; 4Royal Netherlands Institute for Sea Research, and Utrecht University; 5Geological Survey of Western Australia

Large-scale banded iron formations (BIFs) were deposited during Neoarchean to early Paleoproterozoic and have been mainly linked to hydrothermal plume activity and the rise of oxygen in the ocean and atmosphere. However, the potential influence of astronomical “Milankovitch” forcing on their deposition has been largely neglected so far and was hindered by large uncertainties in BIF depositional rates. In a recent study, we showed that outcrops of the ~2.5 Ga Kuruman Banded Iron Formation (BIF) in South Africa reveal a characteristic pattern in weathering profile that can be laterally traced over ~250 km (Lantink et al., 2019)*. Cyclostratigraphic analysis combined with high-precision U-Pb dating indicated that this pattern reflects a hierarchy of two superimposed cycles linked to the 405 kyr and a 1.2 - 1.6 Myr eccentricity cycle. This pattern is mirrored in magnetic susceptibility and high-resolution XRF core scan data of a new drill-core through the Kuruman BIF, providing insight into the chemical variations and may be used for cyclostratigraphic correlations to the broadly time-equivalent6 Australian Dales Gorge Member BIF. Furthermore, the dominance of eccentricity implies that precession-related cycles should be visible as well within the BIF stratigraphy and may be used to reconstruct the Precambrian evolution of the Earth-Moon distance.

*https://doi.org/10.1038/s41561-019-0332-8

Lantink-Astronomical climate forcing of ~25 Ga banded iron formations_Info.pdf


10:35am - 10:50am
ID: 166
Virtual Presentation | ECS

Stratigraphic gaps and durations of the carbon isotope events during the Middle-Late Ordovician in Yichang, South China

Chuan zhen Ren1,2, Qiang Fang1,2, Huaichun Wu1,2

1State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; 2School of Ocean Sciences, China University of Geosciences, Beijing 100083, China

The Middle-Late Ordovician transition is one of the most important periods of the environmental changes and biotic turnovers throughout the earth's history. Here, we used magnetic susceptibility as the paleoclimate proxy to conduct cyclostratigraphic analysis on the Zhenjin and Puxihe sections in Yichang, South China, to understand the astronomical forcing in the paleoclimate changes against a refined astro-chronostratigraphy. Spectra analyses of the magnetic susceptibility sequence shows that the ratios of different sedimentary cycles in Kunuitan, Miaopo and Pagoda formations, are consistent with those of Milankovitch cycles during the Mid-Late Ordovician. A ~7.94 Myr floating astronomical time scale (ATS) is constructed based on the 405 kyr long eccentricity cycles calibration, which indicates the durations of partial middle Darriwilian isotope carbon excursion (MDICE) and Guttenberg isotope carbon excursion (GICE) are ~460 kyr and ~700 kyr, respectively. High-precision continental correlation between Yichang area in South China and the Dawangou section in Tarim reveals that the duration of hiatus on the top of the Kunuitan Formation is ~2.87 Myr. Alignment of minimum of amplitude of obliquity and 405 kyr eccentricity may trigger the MDICE.

Ren-Stratigraphic gaps and durations of the carbon isotope events during the Middle-Late Ordovician_Info.pdf


10:50am - 11:05am
ID: 159
Virtual Presentation | ECS

Orbital forcing of Triassic megamonsoon activity documented in lacustrinesediments from Ordos Basin, China

Runjian Chu1, Huaichun Wu1, Rukai Zhu2, Qiang Fang1

1China University of Geosciences (Beijing), China, People's Republic of; 2Research Institute of Petroleum Exploration & Development, PetroChina, Beijing, China

The “hothouse” Triassic climate provides a key window to study megamonsoon systems. However, high-quality paleoclimate proxy records are rarely reported from the Tethys realm, where the seasonal meridional migration of the intertropical convergence zone (ITCZ) should be the most remarkable. Here, continuous and well-dated proxy records are used to study monsoon activity in the northeastern Tethys from the Middle Triassic lacustrine sediments (Ch7 black shale, Yanchang Formation) in the Ordos Basin (China). The proxies, including natural
gamma-ray intensity, magnetic susceptibility, and element concentrations and ratios (U, K, Zr/Al, Zr/Rb and Sr/Rb), document a strong precession signal in the sediments. We propose that the periodic deposition of the Ch7 black shale occurred in response to intensifications in a monsoon-driven climate enhanced by the early Ladinian warming event. Climate variability in the Ordos Basin (~25°N) reflects the harmonics of ~100 kyr, ~20 kyr and ~10 kyr cycles and is highly coherent with solar insolation at 9° latitude, suggesting that this monsoon system might have been modulated by tropical solar insolation. The dominance of tropical climate processes in this midlatitude monsoon region can be attributed to the dramatic dynamics of the ITCZ and intense monsoon circulation in the Tethys realm.

Chu-Orbital forcing of Triassic megamonsoon activity documented_Info.pdf


11:05am - 11:20am
ID: 319
Virtual Presentation | ECS

Reconstruction of high-resolution lake level and its astronomical forcing during the Paleogene

Meng Wang1, Mingsong Li2

1School of Earth Resources, China University of Geosciences, Wuhan 430074, Hubei, PR China; 2Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA

Challenges in continental sequence stratigraphy and typically limited resolution in geochronology hinder the understanding of paleolake evolution and hydrocarbon exploration in terrestrial basins. The Dongpu Depression in North China is a lacustrine basin with abundant hydrocarbon resources. An accurate geochronology for the Paleogene stratigraphy in the Dongpu Depression is lacking, and the mechanism of lake-level variations remains unclear.

We utilize high-resolution gamma ray logs to conduct a cyclostratigraphic analysis of the Shahejie Formation, which is a Paleogene succession in the Dongpu Depression characterized by sandstones and dark mudstones interbedded with thin salt rocks. Time series analysis reveals evidence for 405 kyr eccentricity cycles in the gamma ray series. Tuning of the gamma ray data to this 405 kyr eccentricity cyclicity enables a 14.37-Myr-long astronomical time scale. This astrochronology is anchored to the recalibrated age of the Dongying Formation/Shahejie Formation boundary (28.86 Ma) in the Bohai Bay Basin, providing an absolute timescale for the studied interval that extends from 28.86 Ma to 43.59 Ma. Furthermore, based on a recently established sedimentary noise model for inferring sea level change in marginal marine settings, we propose that variations in sedimentary noise in paleolake environments can be linked to lake level fluctuations. Sedimentary noise modeling of the tuned gamma ray series reveals high-resolution sedimentary noise changes indicative of lake-level variations linked to million-year scale astronomical forcing. These inferred changes in lake level are supported by previously published sequence stratigraphic interpretations. Moreover, an evolutionary correlation coefficient (eCOCO) analysis of the gamma ray series also indicates recurrent distortions in sedimentation that may link to lake level changes. This study provides new methods for the assessment of paleolake level variations and provides insights into the connection between astronomical forcing over long-time scales and lake evolution in terrestrial basins.

Wang-Reconstruction of high-resolution lake level and its astronomical forcing during the Paleogene_Info.pdf


11:20am - 11:35am
ID: 275
Virtual Presentation

Preliminary cyclostratigraphy on planktonic foraminifera from IODP-Hole U1406A

Alessio Fabbrini1, Luca Foresi2, Fabrizio Lirer3

1University College London, United Kingdom; 2Department of Physical Sciences, Earth and Environment, Siena, Italy; 3Marine Science Institute (ISMAR) -CNR,Napoli, Italy

Cyclostratigraphy reconstructs astronomical-periodic signals in quantitative data from climate-sensitive proxies, as microfossils, carbonate content, isotopic data or any physical properties measurable at sufficient resolution. The astronomical cycles strongly influence the climate changes at a long time scale. The deep link between climate, sedimentation and orbitally forced insolation can be detected at a smaller scale and it allows the tuning of sedimentary sequences using foraminifera. This study investigated the interval 23.40-21.17 Ma within IODP Site U1406 in the North Atlantic Ocean, detecting periodicities longer than 40 Ky. The spectral analysis on Paragloborotalia siakensis, Globigerina bulloides, Globoturborotalita and Catapsydrax provided the most reliable results, All signals resulted stronger in the upper portion of the succession and weaker in the lower one, highlighting problems on the first paleomagnetic age model of this site. Paragloborotalia siakensis shows the strongest correspondence with the 110 Ky, 400 Ky and 1.2 Ma eccentricity cycles. Thus, it was selected to elaborate the second age model. Iteratively using the 400 Ky periodicity as an additional checking tool, the P. siakensis filtered curve has been adjusted to achieve the final age model, correlating each peak of its distribution to the eccentricity curve Laskar2004. The abundance of G. bulloides seems paced by 110 Ky, 400 Ky and 1.2 Ma eccentricity cycles in antiphasic relation to P. siakenisis. Globigerina bulloides and Trilobatus group show unexpectedly a similar sensitivity to astronomical cycles, possibly explained by different paleoecological affinity of T. primordius in respect with the other taxa of the Globigerinoides plexus.

Fabbrini-Preliminary cyclostratigraphy on planktonic foraminifera_Info.pdf


11:35am - 11:50am
ID: 146
Virtual Presentation

Studying glacial/interglacial cycles from downhole logging data: an application to the ICDP drilling project Lake Junín, Peru

Simona Pierdominici1, Christian Zeeden2, Jochem Kück1, Donald Rodbell3, Marc Abbott4

1Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ, Germany; 2Leibniz Institute for Applied Geophysics, Hannover, Germany; 3Union College, Schenectady, NY 12308, USA; 4Dep. Of Geology and Planetary Science, University of Pittsburg, PA 15260-3332, USA

Can the history of the lake records covering the glacial-interglacial cycles be reconstructed from downhole logging data without the high-resolution data derived from core analysis? To answer this question, we present a study reconstructing glacial-interglacial sediment variability and an estimate of lacustrine sedimentation rates based only on downhole logging data from the ICDP Lake Junín drilling project. We use a suite of cyclostratigraphic methods. Lake Junín is located at 4082 m in the Andes and is characterized by a thick sediment package dominated by alternating units of carbonates and glaciogenic silts with thin peat and organic-rich mud layers. The first step of our study was to investigate the consistency of cyclic sediment behavior and see that the interval from ~30-90 m shows a rather stable cyclicity with a wavelength of ca. 10 m. Natural and spectral gamma ray logging data were used for cyclostratigraphic analysis, and the astronomical spectral misfit (ASM) method was used to reconstruct the sedimentation rate. The results indicate a sedimentation rate of between 5 and 20 cm/kyr. For the second step, the TimeOpt method was applied to test for a fit of precession amplitude with eccentricity; it results in an average sedimentation rate of 15 cm/kyr. This method suggests a good fit of the precession amplitude and an eccentricity filter when applying an average sedimentation rate of 14-15 cm/kyr. Based on these information on sedimentation rate, the final step was to correlate the spectral gamma ray data with the LR04 benthic isotope stack.

Zeeden-Studying glacialinterglacial cycles from downhole logging data_Info.pdf


11:50am - 12:05pm
ID: 176
Virtual Presentation | ECS

Orbital and glacial/interglacial forcing reflected by integrated environmental magnetic and colorimetric parameters of a loess-palaeosol sequence in the middle Danubian Basin for the last 430 ka

Christian Laag1,2,3, Christian Zeeden2, Ulrich Hambach3,4, Mladjen Jovanovic5, Slobodan Marković5,6

1Université de Paris, Institut de Physique du Globe de Paris, CNRS, 1 rue Jussieu, 75005 Paris, France; 2Leibniz Institute for Applied Geophysics, Section 5, Stilleweg 2, 30655 Hannover, Germany; 3Chair of Geomorphology, University of Bayreuth, 95440 Bayreuth, Germany; 4BayCEER, University of Bayreuth, 95440 Bayreuth, Germany; 5Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia; 6Serbian Academy of Sciences and Arts, Knez Mihajlova 35, 11000 Belgrade, Serbia

Loess-palaeosol sequences (LPSs) are valuable records of Quaternary environmental change especially in the northern hemisphere. In Eurasian LPS, the alternation of loess and palaeosol intervals reflects the uninterrupted but fluctuating dust deposition during the Quaternary and the fluctuations of temperature and precipitation responsible for the formation of palaeosol horizons. At Zemun (Middle Danube Basin, Serbia), a studied LPS covers four interglacial-glacial cycles. We use standard colorimetric data, containing luminance (L*), redness (a*) and blueness (b*), backscattered wavelength intensities of the visible light spectrum (400-700 nm), and first derivatives of the measured spectra indicative for assessing relative hematite and goethite contents. Environmental magnetic data comprise indicators for intensity of pedogenesis (frequency dependence of the magnetic susceptibility) and for magnetic mineralogy (high- and low-field susceptibilities) of 490 samples.

Age models of LPSs are often created by the direct correlation of low-frequency susceptibility records with global paleoclimate stacks (in particular the LR04 stack, Lisiecki & Raymo, 2005) and global ice models (Imbrie & Imbrie 1980), especially when absolute dating techniques are limited. Here we apply several spectral analysis techniques for investigating orbital forcing at the Zemun site. The resulting age model goes back to ~430 ka, and shows distinct differences between proxy records. These differences are presumably caused by different sensitivities of the employed palaeoenvironmental proxy parameters reflecting their non-linear response to changing climate conditions.

Laag-Orbital and glacialinterglacial forcing reflected_Info.pdf


12:05pm - 12:20pm
ID: 200
Virtual Presentation

Applying astrochronology to reconstruct sedimentation rate and time from downhole logging data at Lake Chalco, Central México

Mehrdad Sardar Abadi, Christian Zeeden, Arne Ulfers, Katja Hesse, Thomas Wonik

LIAG, Leibniz Institute for Applied Geophysics, Germany

Understanding the evolution of lower latitude climate from the most recent glacial period of the latest Pleistocene to post glacial warmth in the continental tropical regions has been obstructed by a lack of continuous time series. Here we present results from a lacustrine record from tropical North America. Specifically, we examine sediments from Lake Chalco, located in the Valley of Mexico, central Mexico (19°30’N, 99°W). The basin represents a hydrological closed system surrounded by the Trans-Mexican Volcanic Belt aging from the Oligocene to the present. In order to elucidate changes in sedimentation rate across the Quaternary, we used borehole logging to conduct a cyclostratigraphic analysis of the Lake Chalco sediments. More than 400 m were logged for several geophysical properties including magnetic susceptibility and spectral gamma radiation. In order to obtain a fast understanding of such borehole logging datasets, including data from complex settings as lakes, a good understanding of the potential and specifics of relevant (time/depth) evolutive methods in cyclostratigraphy are an essential prerequisite. Therefore, we apply a suite of evolutive cyclostratigraphic methods to the Lake Chalco logging data, with a focus on gamma ray data. The high-resolution gamma ray results suggest that the Lake Chalco sediments contain several rhythmic cycles with a quasi-cyclic pattern, allowing us to calculate the time span of Lake Chalco sediment deposition. Here we present initial results from the full succession in this sedimentary archive. Tephra layers are manifest, but do not prevent a successful cyclostratigraphic analysis. The alterations between carbonates and diatomites are especially evident in the logging data and can be interpreted in a quasi-cyclic way. By using cyclostratigraphic analysis on data captured by geophysical downhole logging, we demonstrate the potentially broad applicability of this method for well logging data and provide further insight into the sedimentation history of Lake Chalco.

Sardar Abadi-Applying astrochronology to reconstruct sedimentation rate and time_Info.pdf