Geochemical and paleomagnetic constraints on mid-Proterozoic mafic dyke emplacement events in southern Finland

Keskiproterotsooiset mafiset juoniparvet eteläisessä Suomessa liittyvät rapakivimagmatismiin. Näitä juoniparvia kutsutaan ”subjotunisiksi” (1,64–1,54 Ga), koska ne edeltävät jotunisia hiekkakiviä. Tässä työssä tutkittiin mafisia juonia viidestä eri juoniparvesta, jotka sijaitsevat Ahvenanmaalla, Satakunnassa, Hämeessä, Suomenniemellä ja Sipoossa. Yhteensä 110 kivinäytteelle, jotka oli aiemmin kerätty 101 mafisesta juonesta ja yhdestä mafisesta intruusiosta, tehtiin röntgenfluoresenssianalyysi (XRF). Samoja näytteitä oli aiemmin käytetty paleomagneettisissa tutkimuksissa. Yleistäen eteläisen Suomen subjotuniset mafiset juonet ovat hypersteeni-normatiivisia tholeiittisia basaltteia ja basalttisia andesiitteja. Joillakin juonilla on alkalisia piirteitä, jotka ilmenevät kohonneina alkalipitoisuuksina ja/tai Nb/Y-arvoina. Juonien MgO pitoisuudet ovat vaihtelevia (3–15 wt%), ja niiden normatiivinen koostumus vaihtelee kvartsinormatiivisista oliviininormatiivisiin tyyppeihin. Ahvenanmaan juonet jakautuvat kahteen geokemialliseen ryhmään, joilla on pääsääntöisesti myös erilaiset magneettiset polariteetit ja virtuaalisten geomagneettisten napojen sijainnit. Nämä havainnot viittaavat kahteen eri-ikäiseen magmaattiseen tapahtumaan Ahvenanmaalla. Satakunnan juonet muodostavat kaksi geokemiallista ryhmää. Toiseen ryhmään kuuluu oletettavasti svekofennisiä juonia, joilla on selkeästi korkeammat Nb/Y-arvot tietyillä Zr/Y-arvoilla kuin subjotunisilla juonilla. Hämeen juonet muodostavat kolme geokemiallista ryhmää. Joillakin Suomenniemen juonilla on geokemiallisia ja paleomagneettisia yhteneväisyyksiä Hämeen juonien kanssa, mutta todennäköisesti Suomenniemen juonet edustavat läheisen Hämeen juoniparven synnyttäneestä tapahtumasta erillistä magmaattista tapahtumaa. Sipoon juonet muodostavat hyvin homogeenisen geokemiallisen ryhmän, joka erottuu selkeästi muiden subjotunisten juonien geokemiasta. Sipoon juonien voidaan tässä mielessä ajatella edustavan magmaattista intruusiota, joka on erillinen niistä tapahtumista, jotka muodostivat muut tämän tutkimuksen juoniparvet. Niillä eteläisen Suomen subjotunisilla juonilla, joiden on ajateltu muodostuneen >1,63 Ga (Hämeen, Suomenniemen ja Sipoon parvet Etelä- ja Kaakkois-Suomessa), on yleisesti ottaen korkeammat Nb/Y- ja Zr/Y-arvot kuin niillä juonilla, joiden on ajateltu kuuluvan nuorempiin, <1,58 Ga muodostuneisiin parviin (Ahvenanmaan ja Satakunnan juoniparvet Lounais-Suomessa). Osalla Satakunnan juonista on kuitenkin geokemiallisia ja/tai paleomagneettisia ominaisuuksia, jotka viittaavat niiden olevan vanhempia subjotunisia kuin Satakunnan iätetty 1,57 Ga juoni. Näiden juonien ikien varmistamiseksi tulisi kuitenkin tehdä uusia tarkkoja iänmäärityksiä Satakunnan juoniparvelle. Monilla tämän tutkimuksen juonilla on havaittu sekundäärisen magnetoituman komponentti, ”B-komponentti”, jonka suunta on aina lähellä (mutta selkeästi eriävä) Maan magneettikentän tämänhetkistä suuntaa kullakin näytteenottopaikalla. Tässä tutkimuksessa ei havaittu yhteneväisyyksiä B-komponentin ja tietyn magmatyypin välillä. Sen sijaan B-komponentin havaittiin esiintyvän erityisesti hyvin muuttuneilla juonilla. Tämä tutkimus tukee aiempien tutkimusten havaintoja siitä, että B-komponentin synty liittyy kivien hydrotermiseen muuttumiseen ja siitä johtuvaan uusien magneettisten mineraalien syntyyn.Mid-Proterozoic mafic dyke swarms in southern Finland are associated with rapakivi magmatism. The dyke swarms are commonly referred to as “Subjotnian” (1.64–1.54 Ga), being older than the rift-filling Jotnian sandstones. Mafic rocks from five dyke swarms located in Åland, Satakunta, Häme, Suomenniemi and Sipoo were studied in this thesis. An X-ray fluorescence (XRF) analysis was made of 110 rock samples from 101 mafic dykes and one mafic intrusion. The analyses were made of the same rock samples as previous paleomagnetic studies. Overall, the Subjotnian mafic dykes in southern Finland are hyperstene-normative tholeiitic basalts or basaltic andesites with varying MgO contents (3–15 wt%). Some dykes show alkaline features with higher total alkali and/or Nb/Y values. They vary from quartz- to olivine-normative types. The dykes of the Åland swarm form two geohemical groups. The division is accompanied with a switch in magnetic polarity and distinct virtual geomagnetic pole positions. These observations imply that two separate magmatic events/pulses that have an age difference have taken place in Åland. The Satakunta dykes form two geochemical groups of which the other includes presumably Svecofennian dykes that show high Nb/Y values at given Zr/Y ratios. The dykes of the Häme swarm form three geochemical groups. Although some Suomenniemi dykes show geochemical and paleomagnetic affinities to Häme dykes, they probably represent a distinct igneous event of the event that formed the nearby Häme swarm. The Sipoo dykes are very homogeneous in their geochemistry and can be distinguished from the emplacement events that formed the other Subjotnian swarms. The Subjotnian dyke swarms in southern Finland that are believed to have emplacement ages of >1.63 Ga (Häme, Suomenniemi and Sipoo swarms in S-SE Finland) generally have higher Nb/Y (and Zr/Y) values than the dyke swarms that are believed to record younger magmatic events at <1.58 Ga (Åland and Satakunta swarms in SW Finland). Some Satakunta dykes, however, have geochemical and/or paleomagnetic implications that suggest they have an older Subjotnian age than the dated 1.57 Ga dyke in Satakunta. Further chronological work on the Satakunta dyke swarm is needed to verify the age of the dykes. Many of the Subjotnian dykes show a secondary magnetization component, called the “B-component”, whose direction is always close to, but distinct of, the Present Earth Field (PEF) at the sampling location. There was no correlation between the B-component and the magma types of the dykes. The B-component occurs mostly in dykes that are very altered. Thus, the results support previous suggestions that the B-component formed due to hydrothermal alteration of the rocks and the subsequent formation of new magnetic minerals

The provenance of late Cenozoic East Asian Red Clay : Tectonic-metamorphic history of potential source regions and a novel combined zircon-rutile approach

Constraining the provenance of aeolian mineral dust is critical in understanding past climate changes, atmospheric dust activity, circulation, and sediment generation. On the Chinese Loess Plateau (CLP), use of detrital zircon U-Pb age data as source tracers for the dust has seen a huge growth and lead to breakthroughs in understanding dust provenance. However, significant ambiguities remain especially regarding the provenance of the aeolian Neogene Red Clay (RC). To address this, here we review the state of the art of understanding of Neogene RC provenance, with a focus on single-grain analyses, and introduce detrital rutile geochemistry as a tool to complement zircon U-Pb dating. Furthermore, to better utilise the link between the detrital minerals and their primary origin, we compile primary source region geologic background and single-grain data relevant for use of geochronological and metamorphic provenance proxy minerals. We discuss four major tectonic divisions in northern China and southern Mongolia: North China Craton (NCC), Tarim Craton (TC), Central China Orogen (CCO), parts of the Central Asian Orogenic Belt (CAOB), and briefly summarize the Tibetan-Himalayan orogen. Many of these regions have been tectonically active during the same time periods in the Earth's history, and our analysis demonstrates how use of zircon age data alone has limitations in differentiating between a number of key potential dust sources to the CLP. Addition of a metamorphic source tracer such as rutile allows some of these possible source areas to be distinguished. For example, the proximal northern NCC regions that show high-/ ultrahigh-temperature metamorphic conditions can potentially be diagnostic of a northerly source component to CLP dust. Our combined zircon-rutile data analysis of ca. 4 Ma Nihewan RC in northern CLP verifies the utility of the novel rutile provenance proxy in sourcing CLP sediments. The zircon and rutile data suggest similar dust provenance: the dominant sources are proximal areas on the NCC, while contributions from the dry areas in parts of the CAOB, central deserts, and the Yellow River are also likely. Our results also hint at a minor source component deriving from distal western source regions in the TC, and/or in the central parts of the CCO, but rutile data from potential secondary source areas are needed to verify this possibility. We also conclude that multi-proxy single-grain provenance analyses are needed for more reliable provenance analyses.Peer reviewe

Age, geochemistry, and origin of the mid-Proterozoic Häme mafic dyke swarm, southern Finland

We have reappraised the age and composition of the mid-Proterozoic Häme dyke swarm in southern Finland. The dominant trend of the dykes of this swarm is NW to WNW. Petrographic observations and geochemical data indicate uniform, tholeiitic low- Mg parental magmas for all of the dykes. Nevertheless, the variability in incompatible trace element ratios, such as Zr/Y and La/Nb, provides evidence of changing mantle melting conditions and variable crustal contamination. Our ID-TIMS 207Pb/206Pb ages for four low-Zr/Y-type dykes indicate emplacement at 1639 ± 3 Ma, whereas the most reliable previously published ages suggest emplacement of the high-Zr/Y-type dykes at 1642 ± 2 Ma. We propose that the Häme dyke swarm, and possibly also the other mid- Proterozoic mafic dyke swarms in southern Finland, records a progressive decrease in Zr/Y values due to magma generation under developing areas of thinned lithosphere. We consider that the formation of mafic magmas was most probably associated with the upwelling of hot convective mantle in an extensional setting possibly related to the nearby Gothian orogeny. The generation of tholeiitic magmas below continental lithosphere was probably promoted by the elevated mantle temperature underneath the Nuna supercontinent. We speculate that the origin of most of the relatively small mid-Proterozoic mafic dyke swarms, anorthosites, rapakivi granites, and associated rocks found across Nuna was similarly triggered by extensional plate tectonics and the convection of anomalous hot upper mantle below the supercontinent.Peer reviewe

Neogene global climate change and East Asian dust sources: Combined rutile geochemistry and zircon U-Pb analysis from the northern Chinese Loess Plateau

Peer reviewe

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Provenance of the pre-Quaternary aeolian dust deposits of East Asia

Atmospheric mineral dust is a key component in the climate system, but its effect on and response to climate changes are poorly understood, especially over long timescales. This thesis investigates the sources of late Paleogene and Neogene dust deposits that formed under warmer-than-present global climates in the northern Chinese Loess Plateau (CLP) region in mid-latitude East Asia. Provenance research on wind-blown (aeolian) dust is one of the few available methods to constrain past wind directions, dust sources and transport pathways, which is crucial for understanding regional paleoclimate and its changes during global climate transitions. Aeolian dust deposits from three sites are analysed here: the late Paleogene (35–27 Ma) Ulantatal dust sequence, the late Neogene (7–2.6 Ma) Baode Red Clay, and a c. 4 Ma sample from the Nihewan Red Clay. A joint single-grain analysis of detrital zircon (DZ) U-Pb geochronology and detrital rutile (DR) trace element analysis was applied to trace provenance. This thesis is the first use of DR geochemistry as a provenance indicator for CLP dust, and the thesis therefore summarizes the tectonic history of potential primary source regions and presents DR data from 14 potential secondary/sedimentary dust source regions, for comparison to dust deposits. The results highlight the importance of multimineral single-grain analysis, as some provenance signals were not evident from DZ data alone. Fundamentally, the results demonstrate the long-term stability of overall atmospheric circulation in Central-East Asia, with modern-type atmospheric components existing since the late Paleogene. Dust was mostly transported by Siberian High pressure system (SH) -induced northwesterly winds, and planetary mid-latitude circulation -driven westerly winds from primary source regions of the Central Asian Orogenic Belt and Northern Tibetan Plateau, respectively. The results also show provenance changes at the Eocene-Oligocene, Miocene-Pliocene, and Pliocene-Pleistocene boundaries, indicating a long-term link between the Central-East Asian dust cycle and global cooling events. This thesis further argues that overall, both the dust provenance, and possibly the formation of northern CLP region dust deposits since the latest Eocene in general, were controlled by the Northern Hemisphere glaciations via the SH and northwesterly winds. The results shed light on the long-term environmental history of Central-East Asia and demonstrate the link between the regional dust cycle and global cooling. The findings of this thesis provide important constraints to guide future modelling work on dust-climate interactions under warmer-than-present global climates in Central-East Asia, one of the most populated regions on Earth.Double Doctorate Degree</p

Provenance of the pre-Quaternary aeolian dust deposits of East Asia

Atmospheric mineral dust is a key component in the climate system, but its effect on and response to climate changes are poorly understood, especially over long timescales. This thesis investigates the sources of late Paleogene and Neogene dust deposits that formed under warmer-than-present global climates in the northern Chinese Loess Plateau (CLP) region in mid-latitude East Asia. Provenance research on wind-blown (aeolian) dust is one of the few available methods to constrain past wind directions, dust sources and transport pathways, which is crucial for understanding regional paleoclimate and its changes during global climate transitions. Aeolian dust deposits from three sites are analysed here: the late Paleogene (35–27 Ma) Ulantatal dust sequence, the late Neogene (7–2.6 Ma) Baode Red Clay, and a c. 4 Ma sample from the Nihewan Red Clay. A joint single-grain analysis of detrital zircon (DZ) U-Pb geochronology and detrital rutile (DR) trace element analysis was applied to trace provenance. This thesis is the first use of DR geochemistry as a provenance indicator for CLP dust, and the thesis therefore summarizes the tectonic history of potential primary source regions and presents DR data from 14 potential secondary/sedimentary dust source regions, for comparison to dust deposits. The results highlight the importance of multimineral single-grain analysis, as some provenance signals were not evident from DZ data alone. Fundamentally, the results demonstrate the long-term stability of overall atmospheric circulation in Central-East Asia, with modern-type atmospheric components existing since the late Paleogene. Dust was mostly transported by Siberian High pressure system (SH) -induced northwesterly winds, and planetary mid-latitude circulation -driven westerly winds from primary source regions of the Central Asian Orogenic Belt and Northern Tibetan Plateau, respectively. The results also show provenance changes at the Eocene-Oligocene, Miocene-Pliocene, and Pliocene-Pleistocene boundaries, indicating a long-term link between the Central-East Asian dust cycle and global cooling events. This thesis further argues that overall, both the dust provenance, and possibly the formation of northern CLP region dust deposits since the latest Eocene in general, were controlled by the Northern Hemisphere glaciations via the SH and northwesterly winds. The results shed light on the long-term environmental history of Central-East Asia and demonstrate the link between the regional dust cycle and global cooling. The findings of this thesis provide important constraints to guide future modelling work on dust-climate interactions under warmer-than-present global climates in Central-East Asia, one of the most populated regions on Earth.Double Doctorate Degree</p

Provenance of the pre-Quaternary aeolian dust deposits of East Asia

Atmospheric mineral dust is a key component in the climate system, but its effect on and response to climate changes are poorly understood, especially over long timescales. Aeolian dust (loess) deposits provide an important record to study the interactions between dust, climate, and tectonics in the geologic past. The thickest, longest, and most continuous terrestrial dust deposits on Earth are on the Chinese Loess Plateau (CLP) in mid-latitude East Asia. While the CLP mostly consists of Quaternary loess, older dust deposits are also preserved in the region. These pre-Quaternary dust deposits offer a unique opportunity to better understand the dust cycle under warmer-than-present global climates of the late Paleogene and Neogene. Furthermore, investigating the provenance of these sediments allows a thorough understanding of the whole dust cycle from dust emission to transport to deposition to be obtained. Provenance research on aeolian dust is also one of the few available methods to constrain past wind directions, which is crucial for understanding regional paleoclimate and its changes during global climate transitions. This thesis investigates the provenance of late Paleogene and late Neogene aeolian dust deposits in the northern CLP region and aims to shed light on the controlling factors behind the Central-East Asian dust cycle over both longer (Paleogene-Neogene) and shorter (~1 Myr) timescales. In addition, this thesis also aims to understand the atmospheric circulation patterns in the region during varying global climate states. Moreover, this work introduces a new method, detrital rutile (DR) geochemistry, to the provenance toolkit of the CLP region to enhance the reliability of future CLP provenance analyses. Aeolian dust deposits from three sites are analysed: the late Paleogene (35–27 Ma) Ulantatal dust sequence, the late Neogene (7–2.6 Ma) Baode Red Clay, and a c. 4 Ma sample from the Nihewan Red Clay. This applied approach uses joint single-grain analysis of detrital zircon (DZ) U-Pb geochronology and DR trace elements in provenance tracing. As DR trace element geochemistry is used for the first time as a provenance indicator in sourcing the CLP dust deposits, this thesis also summarizes the tectonic history of potential primary source regions for the CLP dust and presents DR data from 14 potential secondary/sedimentary dust source regions for comparison to dust deposits. In addition, the Ulantatal provenance analysis is combined with anisotropy of magnetic susceptibility for detecting past surface wind directions. Furthermore, to compare the provenance results to the present-day dust cycle, source contribution models of modern dust are provided for the Baode and Ulantatal sites. The results of this thesis demonstrate the applicability of the joint DZ-DR analysis in sourcing the northern CLP dust. DR data are particularly useful in detecting the very high-temperature metamorphic source rocks in the CLP-proximal North China Craton and the very low-temperature rocks in potential distal western primary source areas of Tianshan and North Qilian Mts. However, DR data may not be diagnostic in sites such as Ulantatal, which do not seem to receive material from these exceptional metamorphic potential source regions. The results of this thesis, however, highlight the importance of multimineral single-grain analysis that targets both metamorphic and igneous minerals in sourcing the CLP dust, as in general some provenance signals were not evident from DZ data alone. Fundamentally, the results demonstrate the long-term stability of overall atmospheric circulation in Central-East Asia, with modern-type atmospheric components existing since the late Paleogene. Dust was mostly transported by Siberian High pressure system (SH) -induced northwesterly winds, and planetary mid-latitude circulation -driven westerly winds from the potential primary sources of the Central Asian Orogenic Belt and Northern Tibetan Plateau, respectively. The results indicate provenance changes at the Eocene-Oligocene, Miocene-Pliocene, and Pliocene-Pleistocene boundaries, indicating a long-term link between the Central-East Asian dust cycle and global cooling. However, the long-term provenance trends in the late Neogene Baode Red Clay are disturbed by shorter time interval changes that are most likely related to tectonic uplift of the Northern Tibetan Plateau, Yellow River evolution and/or relatively high Pliocene climate variability. Furthermore, as a response to global cooling, dust transport from distal western sources to Baode may have been enabled at c. 4 Ma. This thesis argues that long-range silt-sized dust transport and deposition to the CLP may be feasible when (zonal) westerly jet axis movement is coupled with an intensified East Asian summer monsoon, allowing wet deposition from the upper troposphere. Modelling results for modern dust source contributions to Baode and Ulantatal are consistent with the nearly identical combined DZ source signals obtained from these two sites, and reinforces the use of modern analogues to explain the past dust cycle. This thesis concludes that since the Eocene-Oligocene transition, the SH and long-term positive phase of Arctic Oscillation -like conditions dominated northwesterly and planetary westerly dust transporting winds, respectively. By contrast, the warmhouse Eocene favoured a long-term negative phase of Arctic Oscillation -like conditions, which allowed planetary circulation to dominate both the northwesterly and westerly dust transport pathways to the northern CLP region. This thesis further argues that overall, both the dust provenance, and possibly the formation of northern CLP region dust deposits since the latest Eocene in general, were controlled by the Northern Hemisphere glaciations (NHG) via the SH and northwesterly winds. During periods of high NHG, the SH is strengthened, the northwesterly winds intensified, and the regions under the SH were possibly more arid. During such periods, the provenance signals from the northwest/north/northeast from the Central Asian Orogenic Belt and/or the North China Craton increase. Such provenance signals are especially pronounced at the Pliocene-Pleistocene transition towards the Quaternary icehouse conditions. In contrast, during low NHG, northwesterly winds weaken, westerly winds dominate the dust transport, and sources from the west, e.g., the Northern Tibetan Plateau, increase in the provenance signals. However, if dust availability in the western source regions is increased, source contributions from the west may be high despite increased NHG and strong northwesterly winds. This thesis provides essential background information and data for a sediment provenance analysis in the CLP region using methods that target geochronology or geothermometry of single detrital minerals. Moreover, the results shed light on the long-term environmental history of Central-East Asia and demonstrate the link between the regional dust cycle and global cooling. The findings of this thesis provide important constraints to guide future modelling work on dust-climate interactions under warmer-than-present global climates in Central-East Asia, one of the most populated regions on Earth.Ilmakehän mineraalipöly on keskeinen ilmaston osatekijä, jonka vaikutukset ja vasteet ilmastonmuutoksiin tunnetaan huonosti. Tässä työssä tutkitaan Kiinan lössiylängölle kerrostuneen pölyn lähdealueita myöhäispaleogeenin ja -neogeenin aikana, jolloin maapallon ilmasto oli nykyistä lämpimämpi. Lössiylängön paksut, tuulenkuljettamat pölykerrostumat ovat tärkeitä ilmastoarkistoja. Pölyn lähdealuetutkimuksen avulla voidaan määrittää muinaisten tuulten kulkureittejä ja ymmärtää globaalien ilmastonmuutosten vaikutuksia Keski- ja Itä-Aasian ilmastoon. Väitöskirjassa analysoitiin kolmen eri tutkimuskohteen pölykerrostumia: 35–27 miljoonaa vuotta vanhoja Ulantatalin kerrostumia, Baoden punaisen saven (’Red Clay’) kerrostumia (7–2,6 miljoonaa vuotta) sekä noin neljän miljoonan vuoden ikäistä Red Clay -näytettä Nihewanista. Päätutkimusmenetelminä käytettiin raskasmineraalien (zirkonit ja rutiilit) yksittäisraeanalyyseja. Näistä rutiilien hivenaineanalyysejä sovellettiin ensimmäistä kertaa lössiylängön pölyjen lähdealuetutkimuksissa. Lisäksi työhön sisältyy kirjallisuuskatsaus pölyn mahdollisten lähdealueiden tektoniseen historiaan sekä 14 sekundääri-tai sedimenttilähdealueen DR-verrokkiaineisto. Tutkimuksen tulokset korostavat monimineraalianalyysin tärkeyttä Kiinan lössiylängön lähdealuetutkimuksissa, sillä osa lähdealueisiin liittyvistä piirteistä oli heikosti havaittavissa pelkän zirkoniaineiston avulla. Tulokset osoittivat Keski- ja Itä-Aasian ilmakehän kiertoliikkeen pitkän aikavälin vakauden ja nykyistenkaltaisten ilmakehän ilmiöiden olemassaolon jo myöhäispaleogeenista lähtien. Pölyä kulkeutui pääosin Siperian korkeapaineen aiheuttamien luoteistuulten sekä planetaaristen länsituulten mukana Keski-Aasian orogeeniselta vyöhykkeeltä ja Tiibetin ylängön pohjoisosista. Tulokset osoittivat myös, että Keski- ja Itä-Aasian pölyn kiertokulku muuttui maailmanalaajuisten ilmaston viilenemisjaksojen aikana eoseeni-oligoseeni- (n. 34 milj. v. sitten), mioseeni-plioseeni- (n. 5,3 milj. v. sitten) sekä plioseeni-pleistoseeniepookkien (n. 2,6 milj. v. sitten) rajoilla. Lisäksi tutkimuksessa esitetään, että sekä pölyn lähdealueiden muutokset että mahdollisesti myös lössiylängön pohjoisosien muodostuminen, liittyvät pohjoisen pallonpuoliskon jäätiköitymiseen Siperian korkeapaineen ja luoteistuulten välityksellä

Detrital zircon U-Pb age from the late Neogene Baode Red Clay sequence, Chinese Loess Plateau

The data consist of detrital zircon U-Pb ages of the 4.04–2.64 Ma Baode Red Clay (four samples from the Pliocene Jingle Formation and one sample from the 2.64 Ma Transitional Unit). The data were collected using Nu Plasma AttoM single collector ICP-MS (Nu Instruments Ltd., Wrexham, UK) connected to an Analyte Excite 193 ArF laser ablation system (Photon Machines, San Diego, USA) at the Geological Survey of Finland