Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 83-87). Also available via the Internet.

Th. doct.--Terre, océan, espace--Lyon 1, 1994. / Bibliogr. p. 207-223.

Statistical analyses of palynomorph assemblages from the Upper Cretaceous Bridge Creek Member (Greenhorn Formation) near Pueblo, Colorado suggest that the micritic limestone/organic rich-shale cycles of the Bridge Creek may have been caused by a combination of fluctuating primary productivity and humid/arid climate cycles. Species richness and evenness indices for palynomorph assemblages from 24 Bridge Creek beds were statistically analyzed using Analysis of Variance. The results indicate that assemblages for the limestone beds exhibit greater evenness and richness indices than do assemblage from the shale beds. Because phytoplankton communities typically exhibit lower evenness and richness values in eutrophic conditions, these results are consistent with possible surface water eutrophication during times of shale deposition. During times of high primary productivity, the aerobic oxidation of large amounts of organic matter settling to the sea floor may have consumed the oxygen available at depth creating an anaerobic environment and facilitating the preservation of organic carbon. Riverine input to the seaway also contributed to cycle production. It appears that shale was deposited during humid periods when riverine runoff provided terrigenous material necessary for shale deposition. The flow of isotopically-light fresh water to the seaway during times of shale deposition is supported by lighter 𝛿¹⁸O values in the shale beds. The fluctuating primary productivity and humid/arid cycles may have been caused by Milankovitch Cycle-driven climate change. Climate models indicate that insolation fluctuations driven by the precessional or obliquity cycle may have periodically increased upwelling along the eastern margin of the Cretaceous Interior Seaway and influenced rainfall patterns. At appears that organic rich shale was deposited when upwelling, nutrient-rich bottom water stimulated planktonic productivity and rainfall transported terrigenous material to the seaway. / Master of Science

The Dolomite Alps of northern Italy are a classic field locality in the development carbonate stratigraphic theory. Included in the many discoveries rooted in the geology of the Dolomites is the concept of a hierarchy of stratigraphic forcing in the Alpine Triassic. The hierarchy states that carbonate sedimentation is dominantly a record of eustasy, resulting in organized stacking patterns, and that these stacking patterns reflect the interplay between low frequency (1-10 my) eustatic cycles and their component bundled high-frequency (100 & 20 kyr) eustatic cycles. The overall aim of this study is to further investigate the validity of the hierarchical model after recent dating of Anisian and Ladinian successions called the Milankovitchian periodicity and/or allocyclicity of the cyclic series into question. The study was completed using four sub-studies, 3 based on data collected in the field and a fourth based in cycle theory and computer modeling. First, it can be shown that allocyclic forcing exists in the Anisian/Ladinian platforms of the Dolomites by comparing the stratigraphic sections measured from 2 time-equivalent, independent carbonate platforms, the Latemar and Mendola Pass. Second, computer modeling of Anisian/Ladinian carbonate platform stratigraphy using Milankovitchain solar insolation as a proxy for high-frequency eustasy shows that both pure Milankovitch forcing and mixed Milankovitch/sub-Milankovitch forcing will produce synthetic carbonate platforms with stratigraphic successions comparable to those of the Anisian/Ladinian platforms of the Dolomites. Third, it can be shown that the while the Norian Dolomia Principale (a regional carbonate shelf) was affected by differential subsidence, megacycles systematically increase in their number of component cycles from 2-3:1 in the eastern Dolomites (updip) to 5-6:1 in the western Dolomites (seaward). In conclusion, the concept that carbonate platform stratigraphy is a record of an interplay between eustasy, subsidence, and sedimentation is upheld, while the validity of Milankovitchian forcing acting on all Alpine carbonate cycles is questioned. Instead, cyclic carbonates with sub-Milankovitch periodicities were common in the early and mid-Triassic, while cycles with Milankovitchian periodicities were common in the late Triassic. / text

The Bohemian Cretaceous Basin was a sediment accumulation, which was deposited as an integral part of the central European epicontinental sea during the Late Cretaceous sea level highstand. It acted as a marine strait and was suited for preserving both nearshore coarse- clastic successions and hemipelagic deposits, allowing for the study of interplay between tectonics, eustatic sea level and paleoceanographic conditions. While the north-western part of the basin was extensively studied in the recent years, little information has yet been collected about the coeval along-shore environments. This thesis is aimed at bringing a new insight into these fine-grained deposits through a detailed lithological, multiproxy and time-series analysis investigation of the Late Turonian record in the Bch-1 drill core, Běchary, Czech Republic. The secular onset of carbonate-rich hemipelagic sedimentation coeval to the base of Teplice Formation is characterised by increased micrite content and changes in geochemical proxies, which are interpreted as changes in the pathway of clay distribution and silt source proximity, combined with elevated bioproductivity. Three orders of statistically significant variability were identified by time-series analysis of selected geophysical properties, two of which are carrying the...

Une calibration orbitale du Valanginien et d’une partie de l’Hauterivien (Crétacé inférieur) est présentée au cours de ce travail. Celles-ci sont basées sur l’identification des cycles de l’excentricité à partir d’analyses spectrales menées sur des proxies climatiques mesurés à haute résolution sur des alternances marne/calcaire hémipélagiques.Cinq coupes de référence sont analysées dans le Bassin Vocontien (Sud-Est de la France), couvrant l’ensemble de l’étage du Valanginien. Une durée de 5,08 Ma est proposée pour cet étage à partir de l’identification du cycle de l’excentricité de 405 ka. Le cadre temporel proposé, combiné aux âges radioisotopiques disponibles, montre que la perturbation en 13C du Valanginien moyen (événement Weissert) est antérieure à la mise en place des trapps du Paraná-Etendeka. La forte expression de l’obliquité dans la partie supérieure du Valanginien pourrait refléter la mise en place de calottes polaires de faible extension.La transition Hauterivien-Barrémien de Río Argos (Sud-Est de l’Espagne) est traitée par une analyse multi-proxies (cortèges argileux et susceptibilité magnétique ou SM). Par comparaison avec les bancs calcaires, les interbancs marneux sont enrichis en kaolinite et en illite, appauvries en smectite et possèdent de fortes valeurs de SM. Cela reflète des conditions tropicales humides lors du dépôt des marnes tandis que les calcaires se déposent en climat semi-aride. Les durées des zones d’ammonite à P. ohmi et à T. hugii sont respectivement estimées à 0,78 Ma et 0,54 Ma. L’événement anoxique Faraoni a une durée comprise entre 100 et 150 ka. Par corrélation avec d’autres coupes, Río Argos apparaît être le meilleur candidat GSSP / Orbital floating time scales are proposed for the Valanginian Stage and part of the Hauterivian Stage (Early Cretaceous). These are based on the identification of the eccentricity cycles from spectral analyses performed on high-resolution climatic proxies measured on hemipelagic marl-limestone alternations. Five reference sections were analysed in the Vocontian Basin (SE France), spanning the entire Valanginian. A duration of 5,08 myr is proposed for the Valanginian Stage from the identification of the 405-kyr eccentricity cycle. The time frame proposed, combined with available radiometric ages, shows that the mid-Valanginian 13C positive excursion (namely the Weissert Event) occurs prior to the onset of the Paraná-Etendeka traps. The stronger expression of the obliquity cycles in the upper part of the Valanginian Stage may be caused by the onset of low-extension polar ice. The Hauterivian-Barremian transition of the Río Argos section (SE Spain) was studied by a multi-proxies analysis (clay minerals, magnetic susceptibility or MS). Compared to limestone beds, marl interbeds are enriched in kaolinite and illite, impoverished in smectite and show stronger MS values. This reflect tropical humid conditions during marl deposits while limestone were deposited under semi arid conditions. The durations of the P. ohmi and T. hugii ammonite zones are assessed at 0.78 myr and 0.54 myr, respectively. The duration of the Faraoni anoxic event ranges from 100 to 150 kyr. By correlation with other sections, the Río Argos section appears to be the most valuable candidate for GSSP.

<p>Лес у Војводини има највећу моћност и сматра се за најкомплетнији палеоклиматски архив у Европи. На основу кореалице између две најзначајније лесно-палеоземљишне секвенце, Старог Сланкамена и Тителског брега, створен је синтетички профил коришћен у овој студији. Истраживања Марковића и сарадника (2011) показала су да лесно-палеоземљишна секвенца у Старом Сланкамену има старост од око милион година. С друге стране, високе стопе седиментације и комплетност последњих пет глацијално-интерглацијалних циклуса на Тителском брегу чине овај локалитет најдетаљнијим палеоклиматским архивом у поменутом периоду, у овом делу Европе. Временска скала војвођанског леса формирана је тунирањем резултата магнетног сусцептибилитета према астрономским параметрима, нагибу Земљине осе ротације и прецесије. Овако добијена временска скала показује да је граница између нормалне епохе магнетног поларитета Бринес и епохе реверсног поларитета Метујама значајно старија. Ова граница утврђена је палеомагнетним мерењима у лесном хоризонту V L9. Добијени резултати стоје у доброј корелацији са резултатима палеомагнетних мерења (Marković et al., 2011). &quot;Lock in&quot; ефекат утврђен за војвођански лес знатно је већи у односу на онај у кинеским лесно-палеоземљишним секвенцама, због снажно развијеног коренског система чије постојање је уврђено у V S8 и које се протеже неколико метара у дубину све до лесног хоризонта V L9. Спектрална и вејвлет анализа временске скале војвођанског леса показују присуство орбиталних параметара: ексцентрицитета земљине орбите, промена нагиба Земљине осе ротације и прецесије. Доминантне су компоненте мањих фреквенција, ексцентрицитета, док су краћи орбитални периоди промена нагиба осе ротације и прецесије слабије изражени. Овакви резултати проистичу, пре свега из чињенице да синтетички профил има старост од око милион година и да се само доњи, старији део секвенце може посматрати као део такозваног 41 ky, када доминира фреквенција промена нагиба осе ротације. Вејвлет анализа временског модела показује присуство Средње плеистоцене транзиције, што указује да обитални утицај ексцентрицитета постаје доминантан пре око 650 ky. Резултати стоје у доброј корелацији са секвенцама са Кинеског лесног платоа (Sun et al., 2006)и из Централне Азије(Ding et al., 2002), али такође и са дубокоморским седиментима (Shackleton, 1990). Захваљујући комплетности и старости лесно-палеоземљишне секвенце, омогућено је истраживање палеоклиматске еволуције и утицај орбиталних параметара на палеоклиматске прилике у овом делу Европе. Секвенца се може посматрати и као спојница између западноевропских и азијских лесних профила, значајна за изучавање континенталне и глобалне палеоклиматске еволуције.</p> / <p>Les u Vojvodini ima najveću moćnost i smatra se za najkompletniji paleoklimatski arhiv u Evropi. Na osnovu korealice između dve najznačajnije lesno-paleozemljišne sekvence, Starog Slankamena i Titelskog brega, stvoren je sintetički profil korišćen u ovoj studiji. Istraživanja Markovića i saradnika (2011) pokazala su da lesno-paleozemljišna sekvenca u Starom Slankamenu ima starost od oko milion godina. S druge strane, visoke stope sedimentacije i kompletnost poslednjih pet glacijalno-interglacijalnih ciklusa na Titelskom bregu čine ovaj lokalitet najdetaljnijim paleoklimatskim arhivom u pomenutom periodu, u ovom delu Evrope. Vremenska skala vojvođanskog lesa formirana je tuniranjem rezultata magnetnog susceptibiliteta prema astronomskim parametrima, nagibu Zemljine ose rotacije i precesije. Ovako dobijena vremenska skala pokazuje da je granica između normalne epohe magnetnog polariteta Brines i epohe reversnog polariteta Metujama značajno starija. Ova granica utvrđena je paleomagnetnim merenjima u lesnom horizontu V L9. Dobijeni rezultati stoje u dobroj korelaciji sa rezultatima paleomagnetnih merenja (Marković et al., 2011). &quot;Lock in&quot; efekat utvrđen za vojvođanski les znatno je veći u odnosu na onaj u kineskim lesno-paleozemljišnim sekvencama, zbog snažno razvijenog korenskog sistema čije postojanje je uvrđeno u V S8 i koje se proteže nekoliko metara u dubinu sve do lesnog horizonta V L9. Spektralna i vejvlet analiza vremenske skale vojvođanskog lesa pokazuju prisustvo orbitalnih parametara: ekscentriciteta zemljine orbite, promena nagiba Zemljine ose rotacije i precesije. Dominantne su komponente manjih frekvencija, ekscentriciteta, dok su kraći orbitalni periodi promena nagiba ose rotacije i precesije slabije izraženi. Ovakvi rezultati proističu, pre svega iz činjenice da sintetički profil ima starost od oko milion godina i da se samo donji, stariji deo sekvence može posmatrati kao deo takozvanog 41 ky, kada dominira frekvencija promena nagiba ose rotacije. Vejvlet analiza vremenskog modela pokazuje prisustvo Srednje pleistocene tranzicije, što ukazuje da obitalni uticaj ekscentriciteta postaje dominantan pre oko 650 ky. Rezultati stoje u dobroj korelaciji sa sekvencama sa Kineskog lesnog platoa (Sun et al., 2006)i iz Centralne Azije(Ding et al., 2002), ali takođe i sa dubokomorskim sedimentima (Shackleton, 1990). Zahvaljujući kompletnosti i starosti lesno-paleozemljišne sekvence, omogućeno je istraživanje paleoklimatske evolucije i uticaj orbitalnih parametara na paleoklimatske prilike u ovom delu Evrope. Sekvenca se može posmatrati i kao spojnica između zapadnoevropskih i azijskih lesnih profila, značajna za izučavanje kontinentalne i globalne paleoklimatske evolucije.</p> / <p>Loess in Vojvodinaregion (Northern Serbia) is some of the thickest and most complete in Europe. Synthetic profile was developed based on the interprofile correlation between the two most important loess paleosol sequences, Stari Slankamen and Titel Loess Plateau. Recent study (Marković et al., 2011) showed that loess at Stari Slankamen site spans the last million years. On the other hand, high accumulation rates and the completeness of the last five glacial cycles recorded at Titel Loess Plateau preserve detailed climate proxy archive. Magnetic susceptibility record was tuned to orbital obliquity and precession, thus yielding an improved astronomical time scale for the synthetic loess-paleosol sequence. The time scale indicates much older age for the Bruhnes Matuyama boundary, recorded in loess unit V-L9, whish is in good agreement with the recent results obtained during paleomagnetic measurements (Marković et al., 2011). The lock in effect is much grater than in Chinese loess sequences, due to the strong root channels, which penetrate several meters down through V S8 into V-L9 and probably influence the magnetic properties of the sediments. Spectral and wavelet analysis of tuned magnetic susceptibility record reveal the presence of typical orbital frequencies, corresponding to eccentricity, obliquity and precession. Eccentricity frequencies of solar irradiance are dominant, while relatively short time frame of the investigated profile, since the lower part of sequence can be assigned to the so called 41 ky world. Wavelet analysis reveals the presence of Mid Pleistocene Transition, indicating that the eccentricity parameter becomes dominant from 650 ky. The results are in good agreement with sequences from Chinese Loess Plateau (Sun et al., 2006) and Central Asia (Ding et al., 2002) but also with deep sea sediments (Schackleton, 1990). Spectral and wavlet analysis of tuned magnetic susceptibility record reveal the presence of typical orbital frequencies, corresponding to eccentricity, obliquity and precession. Eccentricity frequencies of solar irradiance are dominant, while relatively short time orbital cycles of obliquity and precession are week. This can be attributed to the time frame of the investigated profile, since the lower part of the sequence can be assigned to the so called 41 ky world.Wavlet analysis reveals the presence of Mid Pleistocene Transition, indicating that the eccentricity parameter becomes dominant from 650 ky. The results are in good agreement with sequences from Chinese Loess Plateau (Sun et al., 2006) and Central Asia (Ding et al., 2002) but also with deep sea sediments (Shackleton, 1990). Due to the completeness and the time frame of studied loess paleosol sequence, the site provides an opportunity for investigating the evolution and climate dynamics in this part of europe. The syntjetic profile can be seen as rare paleoclimate archive that enables the reconstruction of orbital influences over Pannonian Basin and can be seen as link between west European sequences and Asian loess.</p>