Conference Agenda

To understand the evolution of lake basins, a robust age-depth model is essential. Usually, such model is created based on core material using various dating techniques (e.g. radiometric dating, magnetostratigraphy, tephra dating/identification, biostratigraphy etc.). However, suitable core material is not always available and other less direct methods have to be applied. In this study, we present an approach to develop an age-depth model based on integrating downhole logging data and seismic survey data from Lake Ohrid to obtain a rough but representative model before core opening. Logging data was acquired during an International Continental Scientific Drilling Program campaign in 2013 and seismic data is from pre-site surveys conducted in 2007 and 2008.

First, the interpretation of seismic data and the use of cyclostratigraphic methods on downhole logging data lead to development of age-depth models derived from direct correlation to the LR04 benthic stack (Lisiecki and Raymo, 2005) at three drill sites at the Lake Ohrid. Based on seismic surveys data, marker horizons are interpreted to support our understanding of accumulation rates. Additional information on sedimentation processes is provided by the evaluation of eccentricity related amplitude modulations using Meyers' timeOptTemplate method (2015, 2019). The use of various, independent methods and the comparison of their age estimations ensures a robust verification of obtained age-depth models.

In a second step, we apply cluster analysis to the physical properties of the sediments, construct artificial lithology logs and integrate them into the age-depth models. This step makes first interpretations of the sedimentological evolution possible.

Precise future predictions of Mediterranean sea surface temperature (SST) variability as one of the most sensitive regions to climate change are hampered by insufficient knowledge of accurate SST reconstructions in resolution relevant for human time-scales from warmer-than-present periods. The Last Interglacial (LIG; ~130,000 to 116,000 years ago) is the most recent period with warmer-than-present climate; however, continuous subdecadal records of LIG SST are unavailable due to a small number of undisturbed sedimentary records and sample-size limitations of conventional methodologies. We circumvent these issues by applying Mass Spectrometry Imaging on finely laminated sapropel S5 sediment deposited in the Eastern Mediterranean; the result is an alkenone-based SST time-series in 1-4 year resolution. These data reveal prominent and rapid decadal SST oscillations in the Eastern Mediterranean with a ~60 years cyclicity that is persistent throughout most of the record, suggesting similar LIG decadal climate oscillations as in the Holocene. We also compare the reconstructed rate of SST change during the LIG to the present-day observational record, and find that LIG temperature change often exceeded the present-day rate of change. On the other hand, comparison of the LIG multidecadal SST to the projected increase in Mediterranean SST until 2100 AD suggests SST increase at the end of the 21^st century to be unprecedented in magnitude and duration. We thus conclude that future warming of the Mediterranean could cause an unrivalled change in the Mediterranean planktonic ecosystems and their biological responses.

We present the findings from our recent paper wherein rock magnetic data record discernible Milankovitch-scale paleoclimatic variability through the Permian Salagou Formation loessite (south-central France). Analysis and modeling of this stratigraphic series (~1000 m of magnetic susceptibility data measured with a portable magnetic susceptibility meter) shows a persistent 10-m-thick cyclicity inferred to represent orbital eccentricity-scale (~100 kyr) variability through the middle to late Cisuralian (ca. 285—275 Ma), and subordinate, higher-frequency cycles (3.3—3.5 and ~1.8 m-thick) that likely represent obliquity and precession-scale variability. Optimal sedimentation rates increase up-section, ranging between 9.4 cm/kyr and 13 cm/kyr. As evinced by laboratory rock magnetic data, the driver of the magnetic signal in the Salagou Formation is hematite, which has generally low magnetic enhancement compared to Eurasian Quaternary loess deposits. If the magnetic signal is pedogenic, then the ~10 m thick cyclicity may represent the thickness of loessite-paleosol couplets in the Salagou Formation. The predominance of hematite (as opposed to magnetite and maghemite) may be attributed to differing conditions of formation such as more arid and/or oxidizing climate conditions than in present Eurasia and/or post depositional oxidation of magnetite and maghemite. This work contributes to a growing evidence for astronomically-forced climate change in Permian loessite at low latitudes.

Groundwater plays an essential role in global water cycles via feedback between groundwater and climate systems. However, the geologic history of groundwater activity remains unclear due to limited data. Sphalerite color banding in the Upper Mississippi Valley District (USA) is apparently caused by variation in oxidation state during sulfide precipitation which is controlled by the penetration of deeply circulating groundwater. Here, time series analysis of the grayscale profile of the Permian sphalerite banding in this district shows the banding correlates with Earth’s eccentricity, obliquity, and precession forcing.

We have found that this astronomical forcing controlled penetration of groundwater into sedimentary hydrothermal fluids which regulated regionally the penetration of groundwater into the ore zone to fixt sphalerite banding. Orbital forcing of climate had a significant impact on a groundwater reservoir at depths near 1 km. The results demonstrate that banding in sphalerite follows the Milankovitch climate frequencies over 10³ – 10⁵ years. Consequently, groundwater oxidation has a major role in depositing the iron-rich bands of the sphalerite and, as a final corollary, that the banding itself can be used to decipher the effects of climate on groundwater variations in the global water cycle.