Obliquity Cycles Research Articles

Chemical weathering characteristics of the Late Cretaceous Nenjiang Formation from the Songliao Basin (Northeastern China) reveal prominent Milankovitch band variations

The Songliao Basin (SLB) in Northeast China has a succession of terrestrial sedimentary deposits that span much of the Cretaceous. The sedimentary records recovered from SLB allow us to investigate the relationship between astronomically forced climate and clastic sediment accumulation in a terrestrial setting from the mid to high latitudes. Here, we compiled high-resolution X-Ray Fluorescence (XRF) datasets (K/Ti, Rb/Sr, Ca/Ti), and gamma ray (GR) logging data from Member 2 of the Nenjiang Formation in the SK-1n borehole. Power spectral analysis of the GR data revealed that sedimentary cycles had wavelengths of 27.4 m, 6.56 m, 2.60 m, and 1.27 m. These wavelengths are interpreted as the orbital cycles of long-eccentricity, short-eccentricity, obliquity, and precession, respectively. We established an astronomical time scale by assuming that the 27.4 m cycles represent ~405 kyr eccentricity. We also applied correlation coefficient (COCO) analysis to identify the astronomical forcing periods. The chemical weathering history was classified by the relative changes of Rb/Sr and K/Ti ratios. The lower Rb/Sr and higher K/Ti values correspond to weak weathering, interpreted as arid periods, and vice versa. Ca/Ti ratios correlate with the humid periods and we attribute this correspondence to a salinity control on Ca/Ti. Furthermore, the unconventional 173-kyr obliquity cycle associated with the secular frequency interference of orbital inclinations between Earth and Saturn was recognized and manifested by humid/arid cliamtic oscillations, suggesting that high obliquity contributed to strengthening the hydrological cycles in SLB and bringing more precipitation and runoff towards the basin. The unique paleogeographic location and the existing paleoclimate simulations of SLB further demonstrated the existence of paleomonsoon variations in East Asia during the Late Cretaceous.

Astronomically paced climate evolution during the Late Paleozoic icehouse-to-greenhouse transition

Late Paleozoic deglaciation is Earth's first icehouse-to-greenhouse transition with extensive vegetation, but the response of tropical climate to this transition has not yet been fully addressed. Here, cyclostratigraphic analysis was conducted on the magnetic susceptibility (MS) record of a deep marine carbonate succession in South China to construct the astrochronology of late Cisuralian (Early Permian), and decipher the evolutionary response to the climate transition in the MS and δ13Ccarb time series. The constructed astronomical time scale indicates an age of 272.83 ± 0.2 Ma for the Cisuralian–Guadalupian boundary in South China. Synchronizing global records demonstrates a complicated linkage between low and high latitudes, involving secular changes in atmospheric pCO2, ice volume, tropical climate and carbon cycling. In the final stage of the Early Permian icehouse (~290–288.2 Ma), the delivery of moisture from low to high latitudes was reduced in comparison with that in the icehouse apex. A more humid climate facilitated the development of tropical coal forests and more storage of 12C on land. In a full greenhouse condition (~281–272 Ma), the tropical responses to a rise in atmospheric pCO2 involved continental drying and ocean stagnation. On a shorter time scale, the nodes of 1.36 Myr obliquity cycles triggered ice-sheet expansion and enhanced tropical precipitation during an icehouse condition. With the gradual transition to an arid greenhouse, the insolation-climate relationship began to change at ~285.1 Ma, and the obliquity nodes became associated instead with terrestrial aridity and marine anoxia. These results bring into a focus pattern of shifting dynamics involving Earth's astronomical parameters and climate change for icehouse and greenhouse worlds in the Late Paleozoic Era.

Middle Miocene-Pleistocene Magneto-Cyclostratigraphy from IODP Site U1501 in the Northern South China Sea

Site U1501 of International Ocean Discovery Program (IODP) Expedition 368 locates on a broad regional basement high in the northern margin of the South China Sea (SCS). This study refines the chronostratigraphy of the upper 160 m sedimentary succession from Hole U1501C using paleomagnetic measurements and cyclostratigraphic analysis on the Natural Gamma Radiation (NGR) data. Rock magnetic analysis displays that the magnetic signal of the sediments is mainly carried by single-domain (SD) and multi-domain (MD) magnetite. A total of 12 geomagnetic reversals are identified and correlated to the geomagnetic polarity time scale (GPTS) in Geologic Time Scale 2020 (GTS 2020), combining biostratigraphic data and planktonic foraminiferal oxygen records. The Milankovitch cycles of 405-kyr long orbital eccentricity, ∼100-kyr short orbital eccentricity, and obliquity cycles are identified in the NGR profile. A 15.54 Myr astronomical time scale is constructed by tuning the short eccentricity cycles filtered from the NGR profiles to the La2010 astronomical solution with the constraints of the magnetostratigraphic results, biostratigraphic age datum and planktonic foraminiferal oxygen records. This new high-resolution age model provides a new temporal constraint on the tectonic and paleoenvironmental evolution in the South China Sea.

Tectonic and Orbital Imprints in the Redox History of Japan Sea Since the Pliocene

AbstractOxygen content in the deep ocean plays a vital role in biogeochemical processes and has significant impacts on the global carbon cycle. The Japan Sea is a semiclosed basin with only shallow water connection to the Western North Pacific, and its redox history has been sensitively affected by tectonic and climatic changes in the past. Studies of paleo‐redox changes in the Japan Sea focused on the tectonic and orbital scales since the Pliocene remain scarce to date. Here, we present two high‐resolution paleo‐redox records during the last 4 Ma at IODP Sites U1425 and U1430 drilled in the Japan Sea. Our authigenic U (uranium) and U/Al records suggest remarkable changes of Japan Sea redox history from relatively oxic to periodic oxic‐anoxic conditions at ∼1.7 Ma. This was mainly caused by the restricted input of North Pacific oxygen‐rich water due to the uplift of northeastern Japan during late Pliocene and early Pleistocene, and opening of the Tsushima Strait and the periodic intrusion of Tsushima Warm Current following sea level change during glacial‐interglacial cycles since ∼1.7 Ma. Orbital changes of Japan Sea redox history suggest the existence of a long eccentricity cycle of 400 ka associated with East Asian summer monsoon rainfall evolution throughout the last 4 Ma. Changes of the amplitude of sea level and inflow of Tsushima Warm Current combined with the East Asian monsoon evolution produced eccentricity and obliquity cycles in Japan Sea redox environment after ∼1.7 Ma, as well as a transition from relatively oxic to anoxic conditions during glacials before and after Middle Pleistocene Transition.

The 173‐kyr Obliquity Cycle Pacing the Asian Monsoon in the Eastern Chinese Loess Plateau From Late Miocene to Pliocene

AbstractWe conduct magnetostratigraphy and cyclostratigraphy on an eolian red clay sequence spanning 7–3.1 Ma in the eastern Chinese Loess Plateau. We pay more attention to the unconventional 173‐kyr obliquity modulated cycle which is associated with the secular frequency interference of orbital inclinations between Earth and Saturn. Similar to the 405‐kyr eccentricity cycles, the 173‐kyr obliquity band proved to be an important orbital driving component by the latest astronomical findings, and can serve as a chronometer of terrestrial air circulation reconstruction back to 7 Ma. Comparison with magneto‐cyclo‐bio‐stratigraphic timescales of another noted eolian sequence from the adjacent area, the 173‐kyr cycle is exceptionally presented as a robust recognition of the cyclical sedimentary patterns for the East Asia monsoon deposits.

Machine learning approach reveals strong link between obliquity amplitude increase and the Mid-Brunhes transition

The Mid-Brunhes Transition (MBT) refers to the change in the amplitude of glacial-interglacial cycles around 430 ka BP, with more pronounced, warmer interglacials after ca. 430 ka BP. Despite the advances in the understanding of glacial cycles, the cause and mechanism of the MBT are still not entirely clear. In this study we examine (i) whether the MBT is caused by a change in the intrinsic dynamics of glacial cycles and (ii) how important the systematic changes of the orbital elements across the MBT are for the occurrence of the MBT. In order to address these questions, we take a pure machine-learning approach. We develop an artificial neural network model which provides a skilful 21-ka ahead prediction of glacial-interglacial changes in the LR04 benthic δ18O stack record as well as a sea level reconstruction obtained by an inverse model. This allows us to predict the interglacial levels from glacial conditions. Although the neural network model is trained over a pre-MBT period of 900–450 ka BP, it exhibits the intensification of interglacials after 450 ka BP. This suggests that the dynamical characteristics generating the stronger post-MBT interglacials is inherent already before the MBT. When the neural network model is forced by a hypothetical insolation for which the amplitude of the obliquity cycles is kept at pre-MBT level, the MBT-like phenomenon does not appear in our simulations. In line with earlier suggestions, our results thus give quantitative evidence that the MBT is caused by amplitude changes of the obliquity forcing. For comparison, our results suggest that the change in the mean eccentricity level across the MBT has a smaller impact on the appearance of the MBT.

The 173-kyr obliquity cycle pacing the Asian monsoon in the eastern Chinese Loess Plateau from Late Miocene to Pliocene

The 173-kyr obliquity cycle pacing the Asian monsoon in the eastern Chinese Loess Plateau from Late Miocene to Pliocene

Trends and Rhythms in Climate Change During the Early Permian Icehouse

AbstractLate Paleozoic deglaciation is the first icehouse‐to‐greenhouse transition in a world with expansive tropical forests, but the detailed process of this climatic upheaval is still debated due to lack of high‐precision global correlation. Here, based on the cyclostratigraphic analysis of a deep‐marine succession of Naqing in South China, chronostratigraphic correlation was achieved between Paleo‐Tethyan deep‐marine carbonate cyclicity and U‐Pb zircon age‐calibrated cyclothems from the Pangaean paleotropics. Refining the global chronostratigraphy indicates ages of 294.1 ± 0.2 Ma and 290.1 ± 0.2 Ma for the base of the Sakmarian and Artinskian stages, respectively. We juxtapose the climatic proxies and indicators across blocks and latitudes to decipher the trends and rhythms in climate change during a period from the apex of the Late Paleozoic ice age (LPIA) to the initial deglaciation. On the multiple‐million‐year time scale, the polar and equatorial climates were linked through the atmospheric pCO2 control. A rise in pCO2 promoted Gondwanan deglaciation and tropical aridification. The disparity in the inferred polarity of tropical climate changes during glacials and interglacials has been confirmed on the million‐year time scale. The meridional flux of moisture was enhanced during the minima of the ∼1.2 Myr obliquity cycle, periodically resulting in Gondwanan glaciation, glacio‐eustatic sea‐level lowerings, and reduced moisture availability in the tropical Pangaean and Paleo‐Tethyan regions. Our study provides an improved temporal resolution and understanding of the apex of the LPIA.

New Constraints on Pluto’s Sputnik Planitia Ice Sheet from a Coupled Reorientation–Climate Model

Abstract We present a coupled reorientation and climate model, to understand how true polar wander (TPW) and atmospheric condensation worked together to create the Sputnik Planitia (SP) ice sheet and reorient it to its present-day location on Pluto. SP is located at 18°N, 178°E, very close to the anti-Charon point, and it has been previously shown that this location can be explained by TPW reorientation of an impact basin as it fills with N2 ice. We readdress that hypothesis while including a more accurate treatment of Pluto’s climate and orbital obliquity cycle. Our model again finds that TPW is a viable mechanism for the formation and present-day location of SP. We find that the initial impact basin could have been located north of the present-day location, at latitudes between 35°N and 50°N. The empty basin is constrained to be 2.5–3 km deep, with enough N2 available to form at most a 1–2 km thick ice sheet. Larger N2 inventories reorient too close to the anti-Charon point. After reaching the final location, the ice sheet undergoes short periods of sublimation and recondensation on the order of 10 m of ice, due to Pluto’s variable obliquity cycle, which drives short periods of reorientation of a few kilometers. The obliquity cycle also has a role in the onset of infilling; some initial basin locations are only able to begin accumulating N2 ice at certain points during the obliquity cycle. We also explore the sensitivity of the coupled model to albedo, initial obliquity, and Pluto’s orbit.

Organic carbon burial is paced by a ~173-ka obliquity cycle in the middle to high latitudes.

Earth's climate system is complex and inherently nonlinear, which can induce some extraneous cycles in paleoclimatic proxies at orbital time scales. The paleoenvironmental consequences of these extraneous cycles are debated owing to their complex origin. Here, we compile high-resolution datasets of total organic carbon (TOC) and stable carbon isotope (δ13Corg) datasets to investigate organic carbon burial processes in middle to high latitudes. Our results document a robust cyclicity of ~173 thousand years (ka) in both TOC and δ13Corg The ~173-ka obliquity-related forcing signal was amplified by internal climate feedbacks of the carbon cycle under different geographic and climate conditions, which control a series of sensitive climatic processes. In addition, our new and compiled records from multiple proxies confirm the presence of the obliquity amplitude modulation (AM) cycle during the Mesozoic and Cenozoic and indicate the usefulness of the ~173-ka cycle as geochronometer and for paleoclimatic interpretation.

Stability of Atmospheric Redox States of Early Mars Inferred from Time Response of the Regulation of H and O Losses

Abstract The ratio of total losses of H and O from the atmosphere is crucial for determining the Martian atmospheric redox state. The H and O escapes are shown to be regulated in a stoichiometric 2:1 ratio in a converged model of present-day Mars over a timescale of ∼105 yr, which is called self-regulation. Self-regulation timescales under different atmospheric conditions on early Mars are not well understood. Here we use a 1D photochemical model to calculate the timescales of self-regulation for denser CO2 atmospheres with various surface temperatures as benchmark cases for early Mars. Self-regulation is driven by variations in the amount of O2 or CO in the atmosphere, depending on the atmospheric redox state. Self-regulation timescales are likely to be controlled by the net redox balance. A 1 bar CO2 atmosphere with a surface temperature of 240 K has a self-regulation timescale of a few million years. Denser atmospheres of early Mars have a longer regulation timescale and are less redox-stable than the atmosphere of present-day Mars. Obliquity variations cause atmospheric CO2 fluctuations, producing a difference in the self-regulation timescale between high and low obliquity. Because an increase in CO2 suppresses H escape, the net effect of the obliquity cycle could have driven the atmospheric redox states to be more reducing. Our results also suggest the possibility of a CO-dominated atmosphere of 10–100 mbars at 3 Ga. The redox state of ancient Mars might have fluctuated more easily than that of the present.

Coals peripheral to opening and closure of the northern Western Interior Seaway: depositional signatures recording interplay between Milankovitch orbital forcing and salt dissolution collapse-subsidence structures with responsiveness to craton deformation and eustatic sea-level

Aptian paralic and Paleocene intracratonic mires that bracket the northern reaches of the Western Interior Seaway preserve Milankovitch orbital forcing cycle signals and record the dynamic interplay with craton-linked salt dissolution tectonism in the Alberta Basin foreland and the adjoined intracratonic Williston Basin to the southeast. These mires, now lignite-bearing strata, along the northern Seaway provide a proxy record for Milankovitch orbital signals that would not have been otherwise recorded because of the voluminous clastic sediments accumulated along the western Canadian portion of the Cretaceous Seaway, in contrast to pervasive orbital forcing signals recorded by organic-rich cyclic carbonate deposits accumulated along the central and southern reaches of the Seaway. Prior to opening of the northern segment of the Seaway, the base levels of the paralic mires of the lower McMurray Formation (Aptian) were hydraulically linked to the rising sea-level fluctuations resulting from southward transgression of the Boreal Sea. In contrast, inland fluvial-margin peats of the Paleocene Ravenscrag and Fort Union formations accumulated following the closure of the Cretaceous Seaway. These mires were increasingly sensitive to aquifer-eustatic controls on the water table–mire relationship. Orbital forcing signals were preserved in the central Williston Basin mires in contrast to their masking by salt dissolution collapse-subsidence structures that exerted dominant control on peat mire configurations across the northern Williston Basin. Paralic mires accumulated at the top of the lower McMurray Formation record short-term orbital forcing, possibly representing an obliquity cycle recorded by lithotype sequencing in petrographic profiles. Mires accumulated along the coastal areas during the transition from a lowstand system tract to an early transgressive system tract. The linkage of sea level with coastal water table fluctuations permitted pervasive accumulations of paralic mires at the top of the lower McMurray Formation. Internal mire cycles resulted in coal lithotype profiles responsive to Milankovitch fifth-order and higher sub-cycles. In contrast, concurrent cataclysmic sinkhole collapses and differential fault block displacements were responsive to underlying salt removal patterns. The sea level/water table linkage was punctuated by the salt tectonism and orbital forcing signals were masked, resulting in sinkholes infilled with different coal lithotype sequences. Following the closure of the Western Interior Seaway, inland Paleocene fluvial-margin mires across the northern intracratonic Williston Basin were responsive to larger scale salt removal events in the subsurface. The collapse-subsidence structures were propagated several km up-section, diffused but sufficient to control mire configurations and mask orbital forcing signals. Southward into the central and southwestern Williston Basin, these strong salt dissolution tectonism patterns were out-of-phase with the repetitive mire accumulations, permitting the recognition of the markedly weaker signals of the 100 kyr orbital eccentricity cycle.

Facies analysis and stratigraphy across the Jurassic-Cretaceous boundary in a new basinal Tithonian–Berriasian section of the Vaca Muerta Formation, Las Tapaderas, Southern Mendoza Andes, Argentina

This paper presents a multidisciplinary study of a new basinal section of Tithonian-Berriasian the Vaca Muerta Formation at Las Tapaderas area, including detailed, biostratigraphic, sedimentologic, sequence stratigraphic and cyclostratigraphic analysis. Biostratigraphy based on ammonite, calpionellids and calcareous dinoflagellate cysts indicate that Las Tapaderas section spans through the Lower Tithonian - lowermost Upper Berriasian, however, its upper part is covered through an erosive unconformity by Pleistocene volcaniclastic deposits, and therefore Las Tapaderas section could reach the Lower Valanginian. Two facies associations were identified, corresponding to basinal and distal outer ramp subenvironments. Recognition of flooding surfaces allowed the identification of three composite depositional sequences and eight high-frequency depositional sequences, which can be correlated with other sections throughout the basin. Cyclostratigraphic analysis based on the recognition of marlstone/limestone couples (elementary cycles) allowed to build a time series based on bed thickness. Fourier analysis indicates the characteristic mid latitude precession-eccentricity syndrome, with 220 precessional cycles (~20.4 and ~23 kyr), 53 low frequency eccentricity cycles (~79, ~90 and ~140 kyr) and 11 high frequency eccentricity cycles (~400 kyr). Spectral analysis also allowed to recognize the presence of the obliquity cycle (38.5 kyr), which has been erratically recorded in the Vaca Muerta Formation. Our data allowed the construction of an orbital scale, calibrated by cosmopolitan markers (calpionellids and calcareous dinoflagellate cysts), for this section. The precise bio- and cyclostratigraphic location of the Jurassic-Cretaceous boundary was established for this section. The sedimentation rate was studied at the scale of the precession cycle, showing values between 0.6 and 3 cm/kyr, while at the low-frequency eccentricity scale it shows values between 1 and 2 cm/kyr.

The transient impact of the African monsoon on Plio-Pleistocene Mediterranean sediments

Abstract. Over the Plio-Pleistocene interval a strong linkage exists between northern African climate changes and the supply of dust over the surrounding oceans and continental runoff towards the Mediterranean Sea. Both these signatures in the sedimentary record are determined by orbital cycles influencing glacial variability on the one hand and northern African monsoon intensity on the other hand. In this paper, we use the intermediate-complexity model CLIMBER-2 to simulate African climate during the Plio-Pleistocene between 3.2 and 2.3 million years ago (Ma) and compare our simulations with existing and new climate reconstructions. The CLIMBER-2 model is externally forced with atmospheric CO2 concentrations, ice sheet topography, and orbital variations, all of which strongly influence climate during the Pliocene and Pleistocene. Our simulations indicate that the records of northern Africa climate oscillate in phase with climatic precession. For the Earth's obliquity cycle, the time lag between the 41 000-year component in insolation forcing and the climatic response increased after inception of Northern Hemisphere (NH) glaciation around 2.8 Ma. To test the outcome of our simulations, we have put emphasis on the comparison between the simulated runoff of grid boxes encompassing the Sahara desert and the Sahel region and the sedimentary records of marine sediment cores from ODP Site 659 (Atlantic Ocean) and ODP Site 967 (Mediterranean). In this study we will show for the first time an extended Ti∕Al record of Site 967 down to 3.2 Ma. This record strongly correlates with runoff in the Sahara and Sahel regions, whereas correlation with the dust record of Site 659 is moderate and slightly improves after NH ice sheet inception. We investigated the transient variability of the individual and combined contributions of the Sahel and Sahara regions and found significant transient behaviour overlapping the inception of NH ice sheets (2.8 Ma) and the Plio-Pleistocene transition (2.6 Ma). Prior to 2.8 Ma, a larger contribution from the Sahara region is required to explain the variability of Mediterranean dust input. After this transition, we found that a more equal contribution of the two regions is required, representing an increased influence of Sahel runoff and wet periods.

A high-resolution timescale for the Miocene Shanwang diatomaceous shale lagerstätte (China): development of Wavelet Scale Series Analysis for cyclostratigraphy

The Miocene aged Shanwang Formation from the Shanwang National Geopark in China represents a succession of lacustrine diatomaceous shales containing an abundant and diverse biota with lagerstatte fossilization of soft tissues. To date, the Shanwang Formation has not been investigated for cyclostratigraphy nor has it been dated with high precision methods. Now we use thorium data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic analysis. A new and simple cyclostratigraphic method, Wavelet Scale Series Analysis (WSSA) is developed to recognize Milankovitch cycles. A total of three short eccentricity and fifteen precession cycles are identified; obliquity cycles are not apparent. In the sedimentary succession, the corresponding precession and short eccentricity cycles are 1.17 m and 4.98 m thick respectively, with this verified by Correlation Coefficient (COCO) analysis and Multitaper-Method (MTM) spectral analysis. We estimate the studied interval was deposited over a duration of 0.3 Myr with a depositional rate of c. 5.7 cm/kyr. Paleomagnetic and radio isotope dating data shows that the diatomaceous shale was deposited during Chron C5En, which places it at approximately 18.5 Ma during the Burdigalian stage of the Early Miocene, rather than in the Middle Miocene as previously thought. The Shanwang lagerstatte biota therefore predates the Middle Miocene Climate Optimum (MMCO) and did not form within it. The geological time scale with a high resolution of 20 kyr was set accordingly.

Characteristics of Milankovitch cycles recorded in Eocene strata in the eastern depression of North Yellow Sea Basin, North China

As cyclical orbital movements of Earth, Milankovitch cycles can be recorded in sedimentary strata. The time they reflect can be used to accurately divide and compare strata. Milankovitch cycles recorded in strata enrich the stratigraphic theory, especially the theories of cycle stratigraphy, and thus they are widely used in geological survey engineering nowadays. This study explored the characteristics of the Milankovitch cycles recorded in the eastern depression of the North Yellow Sea Basin, highlighting their control over high-frequency stratigraphic sequences. The Eocene Milankovitch cycles in the depression were calculated based on the method proposed by J. Laskar, and their parameters primarily include eccentricity cycles of 125 ka and 99 ka, obliquity cycles of 51 ka and 39 ka, and precession cycles of 23 ka and 19 ka. Spectral analysis of gamma-ray (GR) and spontaneous potential (SP) log curves of the Eocene strata was carried out to divide and compare stratigraphic sequences, revealing that the spectral peaks correspond well to astronomical cycles. This indicates that the strata in the depression fully record Milankovitch cycles. Furthermore, there are long-, medium-, and short-term stratigraphic cycles in the eastern depression, with a thickness of 13.03–15.89 m, 3.70–5.21 m, and 2.17–2.94 m, respectively. The sedimentation rates of the Eocene strata were calculated to be 121.2–127.12 m/Ma accordingly. From the uplift to the center of the lacustrine basin along the slope in the eastern depression, both the sedimentation duration and the sediment thickness increase, while the sedimentation rate remains relatively stable. The Eocene strata can be divided into six stages of high-frequency sequences by continuous wavelet transformation, namely E6–E1 from bottom to top. The sedimentation duration and sedimentation rates of the sequences were calculated using spectral analysis with each of the sequences as a separate window. Moreover, the impacts of climate change on the sedimentary environment in the eastern depression were analyzed. It can be concluded that E6 was a lowstand system tract, E5 and E4 were lacustrine expansion system tracts, E3 was a highstand system tract, and E2 and E1 were lacustrine contraction system tracts. All these verify that Milankovitch cycles serve as an effective approach for the analysis of sedimentary cycles.

Possible obliquity-forced warmth in southern Asia during the last glacial stage

Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced ~100,000-year global ice-age cycles and monsoon influenced ~23,000-year low-latitude hydroclimate variations. However, the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes. Here, we report paired mean annual air temperature (MAAT) and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China. While summer monsoon intensity follows the ~23,000-year precession beat found also in previous studies, we identify previously unrecognized warm periods at 88,000–71,000 and 45,000–22,000 years ago, with 2–3 °C amplitudes that are close to our recorded full glacial-interglacial range. Using advanced transient climate simulations and comparing with forcing factors, we find that these warm periods in our MAAT record probably depends on local annual mean insolation, which is controlled by Earth’s ~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes. The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.

Astronomical Cycles of the Late Permian Lopingian in South China and Their Implications for Third-Order Sea-Level Change

The late Permian (Lopingian) was a crucial climate transition period from the late Paleozoic Ice Age to the early Triassic of exceptionally high temperatures. However, the origins of the third-order sea-level changes during the Lopingian Epoch remain unclear. Here, we presented astronomically calibrated gamma-ray (GR) log and non-U GR (computed gamma ray or CGR) curves from the clastic and carbonate successions of well GFD-1 in the Pingle Depression of South China for studying the sea-level oscillations during the Lopingian. Spectral analyses of the 405 kyr-calibrated GR and CGR time data revealed periodicities close to about 405, about 100, about 44.2, about 35.1, about 21, and about 17.5kyr, supporting the existence of Milankovitch forcing in the sedimentary records. A high-resolution astronomical time scale and high-resolution sedimentation rate curve of the Lopingian from well GFD-1 were constructed by cyclostratigraphic analysis. The eccentricity and obliquity amplitude modulation cycles suggested long periodicities of about 2.4 and about 1.2 myr, respectively. In the Wuchiapingian greenhouse of the Lopingian, the about 2.4 myr eccentricity oscillation controlled’ weak’ glacio-eustasy and/or aquifer eustatic changes related to the global third-order sea-level changes and that a lowstand (W2) was initiated by an eccentricity oscillation minimum. In contrast, during the Changhsingian, which exhibited a cooling event, an about 1.2 myr obliquity cycle was probably strong, with the sea-level records highlighting the link between the ‘icehouse’ sea-level lowering (C2 and C1) and the obliquity nodes. Moreover, dynamic sedimentary noise model as an indicator of sea-level showed local third-order sea-level variations, the coevolution trends in the orbital power, global and local sea-level changes, and sedimentation rate had significant implications for establishing the global nature and synchronicity of these million-year-scale eustatic records and reconstructing the temporal depositional history at a regional scale. In addition, the volcanism and tectonism that continued into the early-middle Wuchiapingian probably led to a series of climate changes that drove the hydrological cycles not paced by the Milankovitch cycles.

Interglacials of the Quaternary defined by northern hemispheric land ice distribution outside of Greenland

Glacial/interglacial dynamics during the Quaternary were suggested to be mainly driven by obliquity (41-kyr periodicity), including irregularities during the last 1 Myr that resulted in on average 100-kyr cycles. Here, we investigate this so-called Mid-Pleistocene Transition via model-based deconvolution of benthic δ18O, redefining interglacials by lack of substantial northern hemispheric land ice outside of Greenland. We find that in 67%, 88% and 52% of the obliquity cycles during the early, middle and late Quaternary, respectively, a glacial termination is realized leading to irregular appearances of new interglacials during various parts of the last 2.6 Myr. This finding suggests that the proposed idea of terminations leading to new interglacials in the Quaternary as obliquity driven with growing influence of land ice volume on the timing of deglaciations during the last 1 Myr might be too simple. Alternatively, the land ice-based definition of interglacials needs revision if applied to the entire Quaternary.

Jurassic – Cretaceous boundary record in Carpathian sedimentary sequences

An integrated study of micro- and nannoplankton distribution, O and C isotopes and palaeomagnetic record of nine Carpathian sections provided a key interpretation tool to characterize the Jurassic–Cretaceous (J/K) boundary transition. Biostratigraphy supported by saccocomids, radiolarians, calpionellids, dinoflagellates and nannofossils helped to distinguish biostratigraphic zones which could have been correlated both with stable isotopes and with magnetostratigraphy. The Alpina Event (lorica size change) accompanied by Nannoconus wintereri and N. steinmannii minor FO's designates the J/K boundary.Sedimentary model in N Mediterranean Tethys margin consists of elevated blocks with slow (1–2 mm/ka) Rosso Ammonitico carbonate sedimentation separated by dysoxic depressions. Tectonic instability has been indicated by Upper Jurassic fluxoturbidites.Late early Tithonian (M21n to M20r) saccocomid abundance increases with positive δ18O isotope ratios, similar excursion between M20n and M19r accompanied late Tithonian crassicollarian boom. The δ13C variation (>0.2‰) confronted with microplankton quantity variations: positive excursion occurred both during early Tithonian Saccocoma sp., and during late Tithonian calpionellid and nannoconid blooms. Higher up in the Berriasian “Maiolica” sequence, lighter δ13C values prevailed.During late Tithonian (Praetintinnopsella-to earliest Crassicollaria zones; M20n1n to M19r), Saccocoma microfacies has been substituted by a calpionellid one. Reorganization of Tethyan oceanic currents during opening of the Hispanic corridor started planktonic carbonate particle „rain“ resulting in the Maiolica facies dominance. Sedimentary rate raised ten times. Calpionella alpina lorica size change event was synchronneous with FO's of Nannoconus wintereri and N. steinmannii minor and with negative δ18O trend of latest Tithonian (Colomi Subzone) warming. Expressiveness of eccentricity and obliquity cycles indicates climatic optimum conditions.