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Orbital cyclicity is a fundamental pacemaker of Earth's climate system. The Newark-Hartford Basin (NHB) lake sediment record of eastern North America contains compelling geologic expressions of this cyclicity, reflecting variations of climatic conditions in tropical Pangea during the Late Triassic and earliest Jurassic (~233 to 199 Ma). Climate modeling enables a deeper mechanistic understanding of Earth system modulation during this unique greenhouse and supercontinent period. We link major features of the NHB record to the combined climatic effects of orbital forcing, paleogeographic changes, and atmospheric

This paper presents the results of a paleoenvironmental study of two Hauterivian–Aptian adjacent sections (Transnordestina A/B) of the Iguatu Basin using ostracods and aided by X-ray fluorescence (XRF), total organic carbon (TOC), total sulfur (S), and spectral analyses. Cluster analysis divided the 10 genera found into two main groups: one composed of Alicenula-Pattersoncypris?-Brasacypris-Hastacypris-Ilyocypris?, and the second composed of Cypridea-Looneyellopsis-Rhinocypris?. The first group is interpreted as representing paleoenvironments with permanent waterbodies, such as lakes, and the second as being indicative of ephemeral settings, such as temporary pools in an inundation plain. XRF analysis using the positive peaks of Ca/Ti and Ca/ΣTi, Fe, Al ratios show a few dry periods, particularly in the lower and middle part of Transnordestina A, between 0 to 175 m and 385 to 475 m, which also display a small number of ostracods. Total S shows several high peaks which might be indicative of gypsum deposition during droughts. Spectral analysis of molar Ti/Al ratio shows two intervals with different sedimentation rates, between 0 and 233 m, and 233 to 836 m. For the first interval, six 100 ka eccentricity cycles were identified; the low number of ostracods for the interval and highly variable Ca/Ti and Ca/ΣTi, Fe, Al values indicate a different sedimentation rate in a drier environment. For the second interval, ten 405 ka cycles were identified; its higher ostracod count and more stable Ca/Ti and Ca/ΣTi, Fe, Al values could be indicative of increasing humidity.

Orbital cyclicity is a fundamental pacemaker of Earth’s climate system. The Newark–Hartford Basin (NHB) lake sediment record of eastern North America contains compelling geologic expressions of this cyclicity, reflecting variations of climatic conditions in tropical Pangea during the Late Triassic and earliest Jurassic (~233 to 199 Ma). Climate modeling enables a deeper mechanistic understanding of Earth system modulation during this unique greenhouse and supercontinent period. We link major features of the NHB record to the combined climatic effects of orbital forcing, paleogeographic changes, and atmospheric p CO 2 variations. An ensemble of transient, orbitally driven climate simulations is assessed for nine time slices, three atmospheric p CO 2 values, and two paleogeographic reconstructions. Climatic transitions from tropical humid to more seasonal and ultimately semiarid are associated with tectonic drift of the NHB from ~ 5 ° N to 20 ° N . The modeled orbital modulation of the precipitation–evaporation balance is most pronounced during the 220 to 200 Ma interval, whereas it is limited by weak seasonality and increasing aridity before and after this interval. Lower p CO 2 at around 205 Ma contributes to drier climates and could have led to the observed damping of sediment cyclicity. Eccentricity-modulated precession dominates the orbitally driven climate response in the NHB region. High obliquity further amplifies summer precipitation through the seasonal shifts in the tropical rainfall belt. Regions with other proxy records are also assessed, providing guidance toward an integrated picture of global astronomical climate forcing in the Late Triassic and ultimately of other periods in Earth history.

A 55 meters thick section at Cuchia, Basque-Cantabrian Chain, North Spain, mainly formed by Lower Cretaceous Wealden facies, has been intensively investigated from the micropalaeontological viewpoint. The carbonate beds intercalated within this series yield a rich and diverse charophyte assemblages of high biostratigraphic interest, which could be studied for the first time after successful preparation following the acetolysis method.Twenty-two charophyte taxa were identified forming two distinct charophyte assemblages belonging to two successive charophyte biozones. The first charophyte assemblage, from the lower part of the studied section, is composed of Echinochara lazarii, Atopochara trivolvis var. triquetra, Globator mallardii var. trochiliscoides, Clavator grovesii var. gautieri, Clavator harrisii var. dongjingensis, C. harrisii var. harrisii, C. calcitrapus var. jiangluoensis, C. calcitrapus var. calcitrapus, Ascidiella stellata var. stellata, A. triquetra, Hemiclavator neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, Mesochara voluta gr. voluta and Favargella sp. According to Pérez-Cano et al. (2021), such a charophyte assemblage belongs to the new Eurasian “Hemiclavator neimongolensis var. neimongolensis” biozone, late early Barremian–early late Barremian in age as calibrated by Sr isotope stratigraphy and by correlation with marine biostratigraphy.The second charophyte assemblage, which occurs in the upper part of the studied section is composed of the species E. lazarii, A. trivolvis var. triquetra, A. trivolvis var. trivolvis, C. grovesii var. jiuquanensis, C. harrisii var. dongjingensis, C. harrisii var. harrisii, C. harrisii var. reyi, Ascidiella cruciata, H. neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, Mesochara voluta gr. voluta, Munieria grambastii, Clavatoraxis sp., Charaxis sp. and Tolypella sp. vel. Mesochara sp. According to Pérez-Cano et al. (2021), such a charophyte assemblage belongs to the new Eurasian “Clavator grovesii var. jiuquanensis” biozone, late Barremian–early Aptian in age as calibrated by Sr isotope stratigraphy and by correlation with marine biostratigraphy.As the overlaying succeeding limestones is early Aptian in age, our results allow constraining the chronostratigraphy of the Wealden series at Cuchia section to the late early Barremian– late Barremian, instead of Hauterivian–Barremian (Najarro et al., 2011) as previously thought, leading for a more detailed stratigraphic correlation of the Cuchia section to equivalent units of the Iberian plate, especially from the Iberian Chain and the Pyrenees.References.Najarro, M., Rosales, I., Martin-Chivelet, J. (2011). Major palaeoenvironmental perturbation in an Early Aptian carbonate platform: Prelude of the Oceanic Anoxic Event 1a. Sedimentary Geology 235, 50–71. https://doi.org/10.1016/j.cretres.2021.104934Pérez-Cano, J., Bover-Arnal, T., Martín-Closas, C. (2021). Barremian–early Aptian charophyte biostratigraphy revisited. Newsletters on Stratigraphy (in press). DOI: 10.1127/nos/2021/0662

Micropalaeontological investigations of the Bouhedma Formation in the Jebel Majoura section from the southern Central Tunisian Atlas revealed four successive ostracod associations (in total 16 species of 13 genera) of higher palaeoenvironmental, and thus far limited biostratigraphic and palaeobiogeographic utility due to poor preservation. The most notable of these is a new upper Hauterivian?–Barremian non-marine Wealden-type ostracod assemblage of high diversity from the Lower Member of the Bouhedma Formation, the first one documented from the southern Central Tunisian Atlas, which consists of 9 species: Cypridea cyrtorostralis, Cypridea aff. tenuis, Cypridea aff. insulae, Cypridea sp., Theriosynoecum cf. fittoni, Vecticypris polita, Alicenula? leguminella, as well as Klieana sp. and Fabanella sp. The subsequent two ostracod assemblages from the Lower Member are characterized by the brackish species Rehacythereis? sp., Fabanella sp., Ilyocypris sp., and Schuleridea? sp. indicating transition to lagoonal environment. The subsequent ostracod assemblage from two levels of the Middle Member of the Bouhedma Formation is exclusively composed of the euryhaline marginal marine Paracypris sp., and the marine species Antepaijenborchella praealta, Protocythere cf. bedoulensis and Metacytheropteron aff. grosdidieri, reflecting a marine incursion event. The biostratigraphic utility, particularly that based on the non-marine fauna, is limited thus far but the results are consistent with an upper Hauterivian?–Barremian age previously assigned to the Bouhedma Formation from the southern Central Tunisian Atlas, facilitating its regional stratigraphic correlation with coeval series from the northern part of this palaeogeographic domain. The discovery of Tunisian Wealden-type non-marine ostracods from the southwestern margin of the Tethys (North Africa) sheds new light on the dispersal patterns and palaeobiogeography of these ostracods, their potential utility as biostratigraphic tool, as well as on the significance of the north Gondwanan continental basins and peri-Tethyan islands of the Central Tunisian Atlas for recording Early Cretaceous non-marine microfaunas and -floras.