Jiří Laurin

Climate-controlled changes in eustatic sea level (ESL) are linked to transfers of water between ocean and land, thus offering a rare insight into the past hydrological cycle. In this study, we examine the timing and phase of Milankovitch-scale ESL cycles in the peak Cretaceous greenhouse, the early Turonian (~93-94 million years, Myr, ago). A high-resolution astronomical framework established for the Bohemian Cretaceous Basin (central Europe) suggests a ~400-kyr pace and a distinct asymmetry of interpreted ESL cycles. The rising limbs of ESL change constitute only 20-30% of the cycle, and are encased entirely within the falling phase of the 405-kyr eccentricity; the intervening ESL falls (≤6 m in magnitude) are more protracted, starting within 70 kyr prior to the eccentricity minima and culminating ~60 kyr after the 405-kyr eccentricity maxima. Despite similarities to the sawtooth shape of ~100-kyr glacioeustatic oscillations of the Late Pleistocene, the time scales and phasing are unparalleled in the Pleistocene icehouse. A similar, 405-kyr pace is found in ice-volume variations of the early Miocene, but the timing of glacioeustatic change relative to eccentricity forcing is incompatible with the phase of greenhouse sea-level oscillations. The phasing points to major differences in the geographic location and insolation sensitivity of the key hydrological reservoirs under icehouse and greenhouse regimes. The inferred structure of greenhouse eustasy points to low- or middle-latitude water storage, likely aquifers, that charge (expand) with rising seasonality variations and discharge (contract) with declining seasonality amplitudes on the 405-kyr scale. The net volume of water transferred on these time scales is within 2.2 x106 km3, equivalent to ≤10 % of the present-day storage in the uppermost 2 km of continental crust; potential additive interference with steric eustasy, proportionally relevant during greenhouse regimes, could reduce the volumes required for continental storage.

The Early Turonian interval represents a unique confluence of climatic and oceanographic conditions including peak surface temperatures, high greenhouse-gas concentrations and maximum Phanerozoic sea level. The susceptibility of this climate mode to astronomical insolation forcing remains poorly understood partly due to a limited time control and unknown phasing of astronomical cycles in this interval. Here we offer a refined astrochronology of the Early Turonian based on laterally consistent precession signals preserved in offshore strata of the Bohemian Cretaceous Basin (central Europe). Pristine amplitude modulation verified through interference patterns in depth-frequency plots provides a robust indication of ~100-kyr and 405-kyr eccentricity phases (maxima and minima) that are pinned to ammonite biozones and new carbon-isotope data from two cores. The Early Turonian is estimated as 885 ±41 (2s) thousand years (kyr) in duration, with the Cenomanian/Turonian boundary predating the first Turonian 405-kyr maximum (no. 232 in the Geological Time Scale 2020) by 82 ±70 (2s) kyr. The results support a possible link of the recovery from Oceanic Anoxic Event II to increasing magnitude of seasonal insolation extremes due to rising eccentricity on 405-kyr and million-year (Myr) time scales. Superimposed upon this trend are small-scale carbon-isotope anomalies the pacing of which passes from ~110 kyr, resembling short eccentricity, to ~170-kyr, possibly related to obliquity modulation. This eccentricity-to-obliquity transition, paralleling the rising phase of Myr-scale eccentricity, suggests decoupling of the carbon-cycle perturbations from low-latitude seasonal insolation and involvement of mid- to high-latitude carbon reservoirs.  

Oceanic Anoxic Event 2 (OAE2; c. 94.5-93.9 Ma) offers insight into the mechanisms of past climate change linked to organic productivity and carbon sequestration. It has been studied extensively, but the vast majority of data come from marine records, thus providing an incomplete view of past climate dynamics. Here we integrate new high-resolution data and published records on depositional environments, the carbon-isotope composition of bulk organic carbon (δ13Corg) and plant cuticles (δ13Ccut), and stomatal-index values, a proxy for pCO2, in well-preserved terrestrial through marginal-marine archives of the initial phase of OAE2. The study area is located on the western margin of the Western Interior Seaway (southwestern Utah). Age constraints are based on a new U-Pb bentonite age and correlation to an orbitally calibrated interval of the Bridge Creek Limestone. n-Alkane abundance suggests predominance of terrestrial contributions to bulk organic carbon for most samples. Despite similarities between carbon-isotope variations and transgressive-regressive shoreline movements, it is argued that δ13Corg and δ13Ccut are not strongly affected by local variables. A series of negative, ~2‰ carbon-isotope excursions is identified and attributed to changes in the size and isotopic value of the atmospheric CO2 reservoir. The temporal spacing of these anomalies (80-120 kyr) is consistent with changes in insolation modulated by orbital eccentricity. A systematic, phase-shifted relationship between the negative carbon-isotope excursions and transgressive increments further suggests a link between carbon-cycle perturbations and meter-scale sea-level change on astronomical time scales. A conceptual model involving insolation-controlled aquifer charge/discharge and biomass burial/degradation in the monsoonal belt is proposed. The framework presented here is available to facilitate further research on the interplay of terrestrial and oceanic carbon reservoirs during OAE2.

Cretaceous oceanic anoxic event 2 (OAE2) is thought to have been contemporary with extensive volcanism and the release of large quantities of volcanic CO 2 capable of triggering marine anoxia through a series of biogeochemical feedbacks. High-resolution reconstructions of atmospheric CO 2 concentrations across the initiation of OAE2 suggest that there were also two distinct pulses of CO 2 drawdown coeval with increased organic carbon burial. These fluctuations in CO 2 likely led to significant climatic changes, including fluctuations in temperatures and the hydrological cycle. Paleofire proxy records suggest that wildfire was a common occurrence throughout the Cretaceous Period, likely fueled by the estimated high atmospheric O 2 concentrations at this time. However, over geological time scales, the likelihood and behavior of fire are also controlled by other factors such as climate, implying that CO 2-driven climate changes should also be observable in the fossil charcoal record. We tested this hypothesis and present a high-resolution study of fire history through the use of fossil charcoal abundances across the OAE2 onset, and we compared our records to the estimated CO 2 fluctuations published from the same study sites. Our study illustrates that inferred wildfire activity appears to relate to changes in CO 2 occurring across the onset of OAE2, where periods of CO 2 drawdown may have enabled an increase in fire activity through suppression of the hydrological cycle. Our study provides further insight into the relationships between rapid changes in the carbon cycle, climate, and wildfire activity, illustrating that CO 2 and climate changes related to inferred wildfire activity can be detected despite the estimated high Cretaceous atmospheric O 2 concentrations.

Isotopic mass balance models are employed here to study the response of carbon isotope composition (δ 13 C) of the ocean-atmosphere system to amplitude-modulated perturbations on Milankovitch time scales. We identify a systematic phase distortion, which is inherent to a leakage of power from the carrier precessional signal to the modulating eccentricity terms in the global carbon cycle. The origin is partly analogous to the simple cumulative effect in sinusoidal signals, reflecting the residence time of carbon in the ocean-atmosphere reservoir. The details of origin and practical implications are, however, different. In amplitude-modulated signals, the deformation is manifested as a lag of the 405 kyr eccentricity cycle behind amplitude modulation (AM) of the short (~100 kyr) eccentricity cycle. Importantly, the phase of AM remains stable during the carbon cycle transfer, thus providing a reference framework against which to evaluate distortion of the 405 kyr term. The phase relationships can help to (1) identify depositional and diagenetic signatures in δ 13 C and (2) interpret the pathways of astronomical signal through the climate system. The approach is illustrated by case studies of Albian and Oligocene records using a new computational tool EPNOSE (Evaluation of Phase in uNcertain and nOisy SEries). Analogous phase distortions occur in other components of the carbon cycle including atmospheric CO 2 levels; hence, to fully understand the causal relationships on astronomical time scales, paleoclimate models may need to incorporate realistic, amplitude-modulated insolation instead of monochromatic sinusoidal approximations. Finally, detection of the lagged δ 13 C response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.

Major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods, amplitudes and phases of the ‘Milankovitch cycles’ of precession, obliquity and eccentricity.  While numerous quantiative approaches exist for the identification of these astronomical cycles in stratigraphic data, limitations in radioisotopic dating, and instability of the theoretical astronomical solutions beyond ~50 Myr ago, can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies. Here we demonstrate that interference patterns accompanying frequency modulation (FM) of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data. One- and two-dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the FM method, and indicate that pristine eccentricity FM can be readily distingushed in paleo-records. Apart from paleoclimatic implications, the FM approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions, and for refining chronologies for the deep past.

We present two case studies that use the FM approach to evaluate major carbon-cycle perturbations of the Eocene and Late Cretaceous. Interference patterns in the short-eccentricity band reveal that Eocene hyperthermals ETM2 (‘Elmo‘), H2, I1 and ETM3 (X; ~52–54 Myr ago) were associated with maxima in the 405-kyr cycle of orbital eccentricity. The same eccentricity configuration favored regional anoxic episodes in the Mediterranean during the Middle and Late Cenomanian (~94.5–97 Myr ago).  The initial phase of the global Oceanic Anoxic Event II (OAE II; ~93.9–94.5 Myr ago) coincides with maximum and falling 405-kyr eccentricity, and the recovery phase occurs during minimum and rising 405-kyr eccentricity. On a Myr scale, the event overlaps with a node in eccentricity amplitudes. Both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times.

Hemipelagic rhythmites of the Bohemian Cretaceous Basin and two-dimensional numerical modelling of coexisting hemipelagic and siliciclastic depositional systems reveal important details on hemipelagic sequence stratigraphy. Lowstand systems tracts of c. 400 ka sequences are marked by distinct (up to 100 ka) phase lags between maxima in bottom shear stress (omission surfaces) and maxima in siliciclastic deposition (mudstone intercalations) in the shallowest zone of this hemipelagic setting. Importantly, sediment redistribution caused by local differences in bathymetry induces up to 100 ka shifts in lithological markers, thus changing the hemipelagic expression of sea-level falls. Both results underscore the frequently neglected fact that lithological and geochemical data on siliciclastic fluxes (e.g. quartz contents, Ti ⁄ Al) provide nonlinear proxies of eustatic and relative sea-level changes. Hemipelagic records of climatic and orbital forcings can be markedly distorted in phases and magnitudes. Two-dimensional model- ling can be instrumental in extracting unbiased signals.

The Cenomanian–Turonian interval of the Sevier foredeep, western U.S.A., is examined in order to (1) establish a high-resolution stratigraphic framework for marginal-marine strata of this interval and (2) test for the existence of high- frequency (tens of kyr-scale) cycles of continental runoff or sea-level change predicted by the hemipelagic record and climate models. High rates of sediment accumulation in marginal-marine environments of southwestern Utah (up to 210 m/Myr, compacted) and a northward translation of the major Sevier thrusting made possible the preservation of a highly detailed record of shoreline movements. The coeval Bridge Creek Limestone, linked with the study interval using biostratigraphic and bentonite-stratigraphic data of previous authors, provides an unprecedented, high-resolution orbital time scale. Three orders of transgressive–regressive cycles defined as genetic sequences are identified in the upper Cenomanian (S. gracile and N. juddii Zones) through lower Turonian (W. devonense through M. nodosoides Zones). The longest sequence (S. gracile Zone through V. birchbyi Zone) spans approximately 800 kyr and is penecontemporaneous with the d13Corg positive excursion that defines Oceanic Anoxic Event II (OAE II). Medium-term and short-term sequences show durations of c. 65–160 kyr and c. 20–40 kyr, respectively. Features suggesting regression due to relative sea-level fall are described from some of the 20–40 kyr cycles in the lowermost S. gracile Zone (possibly including the uppermost M. mosbyense Zone). The data provide the first physical evidence globally of Cenomanian–Turonian changes in shoreline position and relative sea level, whose recurrence interval was as short as a few tens of kyr. These processes provide a viable depositional link between the rhythmic deposition of the Bridge Creek Limestone and the primary orbital forcing of insolation and climate. Although the possible tectonic influence is difficult to unravel, the study area represents an important reference point for climate and oceanographic modeling of the Cenomanian– Turonian greenhouse and OAE II.

Many ancient rhythmic hemipelagic sequences have been interpreted to record orbital variations, but the exact nature of the climatic and depositional transfer functions re- sponsible for this link remains poorly understood. Two-dimensional numerical simulations were used to explore selected aspects of orbital signal distortion in linked siliciclastic and hemipelagic systems. The models suggest that transfer of multiorder (e.g., 20, 100, and 400 k.y.) oscillations in relative sea level into the hemipelagic record produces an inherent amplitude distortion of the shorter-period (e.g., 20 k.y.) cycle. This distortion gives rise to amplitude modulation (AM), which is qualitatively similar to AM of orbitally driven changes in insolation (e.g., eccentricity modulation of precession-driven cycles). However, unlike the orbitally driven AM, synthesized AM is distinctly phase shifted relative to the stratigraphic record of the long-period (e.g., 100 k.y., 400 k.y.) cycle as a result of sea- level–driven changes in the storage capacity of nearshore through alluvial parts of the source siliciclastic system. Hence, multiorder changes in sea level can leave a distinct AM signature in dilution-affected hemipelagic records, thus making hemipelagic rhythms due to eccentricity-forced sea-level changes distinguishable from other types of orbitally driven hemipelagic cyclicity.

The Bohemian Cretaceous Basin combines features of a shallow-water (mostly < 100 m) epicontinental seaway formed during a global transgression with those of a tectonically active, transtensional setting. The basin formed under a greenhouse climate and was affected by strong axial currents. Dense well-log coverage, combined with locally high-quality exposures and biostratigraphic control, make it possible to examine in three dimensions the geometries of genetic sequences and interpret their controlling variables. Sand-dominated deltas formed sequences at several spatial scales that reflect nested transgressive–regressive cycles with durations ranging from tens of thousands of years to millions of years. Progradation directions and distances, thicknesses and internal geometry of the individual sequences were controlled primarily by intrabasinal faulting, basin-scale changes in subsidence rate, eustatic fluctuations and localized bathymetric changes due to successive filling of the basin. Along-strike change in sediment input from different parts of the source area and a short-lived uplift of a secondary clastic source provided additional controls on the sequence geometry. Efficient hypopycnal transport combined with redeposition of fine clastics in shallow water promoted development of steep slopes of sand-dominated deltas while preventing downlap of muddy clinoforms; most of the suspended load became deposited downcurrent in subhorizontal or gently dipping bottomsets. Long- term accommodation rates were low during the Early to Middle Turonian, with minor intrabasinal faulting, but became accelerated in the Late Turonian and Early Coniacian. This acceleration was caused at least partly by increased subsidence rate accompanied by structural partitioning of the depocentre and partly compensated by increased sediment input indicating increased uplift rates in the Western Sudetic Island source area. This event probably reflected an increase in the regional strain rate in Central Europe. The succession of two major flooding events in the Early Turonian and late Early Coniacian, separated by a low-accommodation interval in the Middle Turonian, shows a close similarity to published estimates of long-term eustatic curves. However, the eustatic component of accommodation rate in the Bohemian Late Turonian and Coniacian is difficult to separate from accelerated subsidence. In several cases, evidence for short-term (100 kyr scale) forced regressions, independent of basinal structural activity, suggests small-scale eustatic falls at rates which, as presently understood, cannot be explained other than by a glacio-eustatic mechanism.

This study interprets the controls on cyclic and secular changes in a shallow-water hemipelagic system of the Bohemian Cre- taceous Basin using (i) spatial and temporal changes in facies and ge- ometries of the hemipelagic succession and (ii) correlation of the hem- ipelagic cycles with the coeval nearshore siliciclastic sequences. Three orders of hemipelagic rhythms, characterized by changes in lithology between foram-dominated limestones (􏰇 70% CaCO3) and mudstones (􏰆 30% CaCO3), are recognized: couplets, first-order bun- dles, and second-order bundles. The hemipelagic bundles are inter- preted to reflect changes in siliciclastic flux that followed transgressive– regressive movements of the adjacent shoreline. Upward-muddying in- tervals correspond to regressive trends whereas downward-muddying intervals are interpreted as due to transgressions. The upward-mud- dying and downward-muddying intervals of the second-order hemi- pelagic bundles display offlapping and onlapping internal geometries, respectively, suggesting that the transgressive–regressive cycles were coupled with changes in potential accommodation in the hemipelagic system. These relationships may point to sea-level forcing of the sec- ond-order hemipelagic bundles. Finally, spectral analyses of gamma- ray signatures of the hemipelagic strata suggest that the second-order hemipelagic bundles were driven primarily by the Milankovitch cycles of ‘‘long’’ eccentricity (c. 400 kyr), whereas the first-order hemipelagic bundles record an interplay of the cycles of ‘‘short’’ eccentricity (c. 100 kyr) and obliquity (c. 40 kyr). Thus, the transgressive–regressive, and possibly sea-level, cycles acted as mediators of Milankovitch-driv- en changes in insolation.
The secular onset of carbonate-dominated conditions in the distal part of the basin does not follow any secular transgressive trend but coincides with a major change in differential subsidence/uplift pattern of the study area. It is interpreted to reflect an increase in the back- ground carbonate production in the basin due to a tectonically and/or climatically induced change in circulation and associated acceleration of water-mass exchange with the pelagic-carbonate factory of north- western Europe. In summary, processes related to relative sea-level changes and transgressive–regressive shoreline movements are capable of producing hemipelagic rhythms, but it is the interplay of these processes with ‘‘background’’ oceanographic conditions (regional circulation pat- terns, open-marine trophic resource levels, etc.) that controls the actual character of the hemipelagic rhythms (e.g., whether carbonate or clas- tic dominated). Thus, changes in hemipelagic conditions as expressed in the rock record are rarely proportional to either changes in sea level and terrigenous input alone or changes in the ‘‘background’’ ocean- ography alone. Sequence stratigraphic analysis of hemipelagic strata must consider the spatial and temporal variability in the local ocean- ographic conditions that result from a combination of the above pro- cesses.

This study presents a synthesis of currently available data on the distribution of Cenomanian-age palaeodrainage sys- tems in the Bohemian Cretaceous Basin, filled by fluvial and estuarine strata, and an interpretation of their relationships to the basement units and fault systems. Much of the progress, compared to previous studies, was made possible by a re- cent basin-scale evaluation of Cenomanian genetic sequence stratigraphy. Several local palaeodrainage systems devel- oped in the basin, separated by drainage divides of local importance and one major divide – the Holice-Nové Město Palaeohigh – which separated the drainage basins of the Tethyan and Boreal palaeogeographic realms. The locations and directions of palaeovalleys were strongly controlled by the positions of inherited Variscan basement fault zones, whereas the bedrock lithology had the subordinate effect of narrowing or broadening valleys on more vs. less resistant substratum, respectively. The intrabasinal part of the palaeodrainage network followed the slopes toward the Labe (Elbe) System faults and was strongly dominated by the conjugate, NNE-trending, Jizera System faults and fractures. Outlet streams – ultimate trunk streams that drained the basin area – are interpreted to have followed the Lužice Fault Zone toward the Boreal province to the Northwest, and the Železné hory Fault Zone toward the Tethyan province to the Southeast. At both the northwestern and southeastern ends of the Bohemian Cretaceous Basin, shallow-marine or estuarine conditions are proven to have existed during the early Cenomanian. Direct evidence for syn-depositional sub- sidence during the early to mid-Cenomanian, fluvial to estuarine phase is very rare, and the onset of deposition by fluvial backfilling of the palaeodrainage systems was driven mainly by the long-term rise in global sea level. Subtle surface warping, mostly without detectable discrete faulting, is inferred to have been a response to the onset of the palaeostress regime that later, with further stress accumulation, led to subsidence in fault-bounded depocentres of the Bohemian Cre- taceous Basin and uplift of new source areas.

A large freshwater lake formed (lake area > 5000 km2) during the Stephanian B (~304 My) period of the Late Pennsylvan- ian in the central-east equatorial Pangaea and covered a substantial part of the continental Late Palaeozoic basins in the central Bohemian Massif (the Czech Republic). Lacustrine mudstones of the Mšec Member were acquired from two shallow boreholes 80 km apart and were analysed for lamination structure and periodicity, mineral composition and dis- persed organic matter, in order to obtain more detailed information on the palaeoenvironmental change with a near an- nual resolution. Two hydrological states of the lake were identified, including high lake-level periods with dysoxic con- ditions on the lake floor, under a permanently thermally stratified hypolimnion favouring organic matter production and storage during periods of condensed sedimentation producing an irregular lamination pattern. A series of continuous regular couplet lamination reflect conditions of partially, possibly seasonally stratified hypolimnion with advanced lake-water mixing and organic matter oxidation. The couplet lamination results from an alternation of organic-clay laminae, consisting of variable proportions of autochthonous algal and microbial organic remnants, with detrital silt laminae accompanied by authigenic siderite and humified or burnt terrestrial plant debris. Similarly as in some modern tropical lakes, such regular high-frequency variations in sediment supply suggest seasonal changes in rainfall to be re- sponsible for couplet formation. Couplet thickness distribution shows statistically significant periodicities, resembling multiannual to multidecadal scales observed in recent sediment archives, and so indirectly supports seasonality in pre- cipitation in Pangaean low-latitudes, at least during part of the Stephanian B.

ABSTRACT Understanding to climate dynamics requires identification of orbital forcing as a piece of a jigsaw puzzle. High-frequency climate changes could be the reason of discrepancies among Miocene climate reconstructions from sediment archives. Nearly all continental sediment sequences have some repetitive patterns, of which causes can be manifold; orbital forcing (climatic cycles) is only one option. There are two main reasons for this uncertainty: 1) recording mechanisms of climate changes in a real sediment basin are site-specific and ambiguous (and usually not known, or not reported) and 2) autocyclic behaviour (inherent chaos) and tectonics can also produce repetitive patterns and statistics itself is not capable to reveal that their nature is not climatic. On the other hand, most paleontological climatic reconstructions have temporal resolution in order of Myr (or at best in tenths of Myr), which cannot really reflect the expected climate dynamics. We have studied about 250 m thick clastic syn-rift sediment sequence in the Most Basin in the Ohře Graben (Czech Republic). In the mature-rift stage, a basin-wide lake existed there for &amp;lt;1 Myr during the late Burdigalian (before Mid-Miocene Climate Optimum). The palaeogeography of the lake watershed changed due to rift evolution, which is an important but still only roughly described variable. Tectonic pulses probably affect the accomodation space, a network of feeding rivers and/or a basin outflow pathway during the lake existence. The clear and well-correlated variations in Sr and K concentrations in the sediments suggest orbital components (multitaper spectral estimation and misfit relative to theoretical Milankovitch frequencies). There is a question, whether the formal statistics (without understanding the actual recording mechanism and excluding other repetitive environmental changes) is sufficient to confirm climatic basis for these variations, although such approach can be found in numerous current studies. The proof that we really handle Milankovitch cycles in the Most Basin lacustrine mudstones is a consistency of cyclostratigraphy-based sedimentation rate (16-20 cm/kyr) which allowed assignment of one complete inverse magnetozone (100 m thick monotonous lacustrine mudstones) to C5Cr or C5Dr chrons in the late Burdigalian (there are no other plausible options respecting the small mammal biozone MN3a in the early rifting stage). The simplest interpretation of the Milankovitch cycles in our sediment succession is variability in precipitation in Central Europe at a scale of tens to hundreds kyr.

ABSTRACT In the W to NW of the Czech Republic there are remnants of sedimentary basins (Cheb, Sokolov and Most Basins), which were part of the European Cenozoic Rift System. These basins were filled during the Burdigalian in purely terrestrial environment. Extensive peatlands (which produced economically important coal measures) in the Most Basin were covered by whole-basin Libkovice Lake after increase of the basin subsidence, and finally the lake covered more than 1000 km2. The sedimentation was terminated in the upper Early Miocene probably shortly before the Middle Miocene climatic optimum (MMCO). The resulting monotonous, siliciclastic, fossil-barren deltaic and lacustrine sediments have total thickness of up to 250 m; there is no datable material in them and hence their age is based on biostratigrahy of the basin fill. The detailed stratigraphy including correlation over the entire Most Basin (dimensions about 20x50 km), has not yet been established. We have started our research to extract its palaeoenvironmental information content from the Most Basin. The first step of our work was a chemostratigraphic correlation of the sediments obtained from five long cores (~200 m) provided by Severoceske doly (a coal-mining company). We use EDXRF element analysis and chemical analysis by ion exchange with [Cu(trien)]2+. Analysis of exchangeable/water soluble cations revealed that the Libkovice Lake was freshwater with only moderately mineralized water. Slight and smooth variations of major element content proved very stable sedimentary environment. Variations in K/Al element ratio, changes in the expandable clay mineral content (CEC), and Sr accumulations allow a detailed correlation of boreholes from different parts of the basin. Three crandallite-containing horizons formed by alteration of volcaniclastic fallouts (or mass flows) were found that supports our chemostratigraphic correlation. Spectral analysis suggests that Sr and K/Al variations possibly record orbitally driven changes in insolation. The orbital interpretation implies sedimentation rates up to 16 - 20 cm/ky during the major lacustrine phase (Libkovice Lake).. These sedimentation rates make it possible to obtain high-resolution data on depositional, volcanic and climatic changes during the Early Miocene in Central Europe.