Retraversing the Highs and Lows of Cenozoic Sea Levels

Correlation and cyclicity of stratigraphic sequence boundaries and chronostratigraphic stage boundaries of the last 253 My: Synchrony of tectonism, sea level, climate and biotic change

Calcareous nannofossils, stable isotopes, and cyclostratigraphy of the upper Qom Formation (Burdigalian, Central Iran): Implications for paleoclimate and paleoecology

Marine strontium isotopes preserved in fossil shark teeth calibrate Neogene land mammal evolution

Calcareous Nannofossils, Stable Isotopes, and Cyclostratigraphy of the Upper Qom Formation (Burdigalian, Central Iran): Implications for Paleoclimate and Paleoecology

Recent updates to the reconstructions of Cenozoic environmental changes (global sea level, temperature, and atmospheric carbon dioxide content) have made it intriguing to compare them to paleontological records for original interpretations. Paleogene brachiopods have remained in the shadow of their Paleozoic–Mesozoic predecessors, and the reactions of their diversity to the Earth’s dramatic changes are poorly understood. The present work aims to fill this gap via a comparison of several diversity and paleoenvironmental curves. The generic diversity was established by stages with two essentially different paleontological datasets, and several fresh paleoenvironmental reconstructions were adopted. It was observed that neither Paleogene eustatic fluctuations nor changes in the atmospheric carbon dioxide content correspond well to the generic diversity dynamics of brachiopods. The changes in the total number of genera and the global temperatures demonstrate similarity at the Danian–Ypresian interval, but not later. The fluctuations in the brachiopod diversity are near the same level during the Eocene–Oligocene, despite strong paleoenvironmental changes, implying the intrinsic resistivity of these organisms to external influences. Additionally, the Cretaceous/Paleogene mass extinction, the Paleocene–Eocene thermal maximum, and the Early Eocene optimum could enhance the diversity dynamics together with the long-term temperature changes. In contrast, the influences of the Late Danian warming event and the Oi-1 glaciation were not observed.

Abstract Early Miocene land mammals from eastern North America are exceedingly rare. Over the past several decades a small, but significant, vertebrate fauna has been recovered by paleontologists and citizen scientists from the Belgrade Formation at the Martin Marietta Belgrade Quarry in eastern North Carolina. This assemblage has 12 land mammal taxa, including beaver (Castoridae), stem lagomorph, carnivorans (Mustelidae, Ailuridae), horses (Equidae), rhinoceros (Rhinocerotidae), tapir (Tapiridae), peccary (Tayassuidae), anthracothere (Anthracotheriidae), entelodont (Entelodontidae), and protoceratid (Protoceratidae). Taken together, the biochronology of this Maysville Local Fauna indicates a late Arikareean (Ar3/Ar4) to early Hemingfordian (He1) North American Land Mammal Age (NALMA). This interval, which includes the Runningwater Chronofauna, documents numerous important Holarctic immigrants, including Amphictis, Craterogale, and cf. Menoceras found at this locality. Strontium isotope stratigraphy (SIS) of shark teeth collected in situ from the Belgrade Formation yield an age of 21.4 ± 0.13 Ma, which validates the age of interbedded land mammals within this unit. It also is consistent with the late Arikareean (Ar3/Ar4) biochronology and Aquitanian Neogene marine stage. New SIS analyses of oysters (Striostrea gigantissima) and clams (Chione) from this mine, previously assigned to late Oligocene or Late Miocene, are significantly older (28.0 ± 0.22 Ma and 27.6 ± 0.26 Ma, respectively) than the land mammals. Depending upon stratigraphic interpretations, these may confirm an older marine facies within the Belgrade Formation. This locality is important because of its marine and terrestrial tie-ins that facilitate intercalibration of both NALMAs and Cenozoic marine stages.

The Onil and Ibi sections (Prebetic Zone, Betic Cordillera: Alicante, SE Spain) record a late Ypresian (Cuisian) to early Lutetian (~51 to ~43 Myr) carbonate platform succession, dated using larger benthic foraminifera (LBF) and planktonic foraminifera. Seven field lithofacies (L1 to L7) and five thin-section microfacies (Mf1–Mf5) were identified, indicating inner- to mid-ramp environments (from seagrass meadows to Maërl-LBF-dominated) in warm-water and low-latitude conditions. A distinctive feature of these platforms is their dominance by LBF in association with rhodophyceae, contrasting with typical coral reef factories. We propose a novel carbonate production model, “TC-factory”, to describe these warm-temperate systems. Integrated field logging, drone imagery, and microfacies data allowed us to define a sequence stratigraphic framework comprising five lower-frequency sequences (LFS: ~2 Myr average duration), each of them nesting various numbers of high-frequency sequences (HFS: ~0.25 to ~1 Myr). The LFSs belong to a higher-rank sequence bounded by regional unconformities. The five LFSs only broadly match the upper Ypresian and lower Lutetian cycles in global eustatic curves (~51 to ~43 Myr), indicating that other regional or local controls were important. The number of HFSs being fewer than expected also suggests additional controls, such as local tectonics, erosion during lowstands, or carbonate production feedback.

An exposed sedimentary succession, ca 115 m of a total of 1000 m, from the Eastern Carpathian foredeep was, for the first time, analyzed using facies analysis and scale- and time-independent sequence stratigraphy methods to reveal the depositional environment and its cyclic sedimentation. The outcropping deposits, belonging to the Șomuz Formation, dated on the basis of molluscs, foraminifera, and ostracods, are uppermost Volhynian (upper Serravalian). The three recurrent facies associations we have distinguished indicate a storm-dominated shoreface–offshore transition environment. Five-decametre-thick high-frequency sequences (HFS1–5), at most of 4th order, bounded by maximum regressive surfaces, were defined in the studied interval. The maximum thickness of the Volhynian deposits in the area, known both from well sites and outcrops, allowed us to estimate the sedimentation rate at ca 1.5 m/kyr. The fossil content shows that the entire sedimentary succession was deposited in very shallow to shallow water during the whole Volhynian (12.65 - ca 12.01 Ma). The time interval we studied was estimated at ca 75 kyr, so the average time of one HFS is ca 15 kyr. At this scale, considering that both high subsidence and Eastern Paratethys sea-level rise added to accommodation, the sediment supply must have been the main control of cyclic sedimentation, which, in turn, must have been controlled by precession climatic changes in the source area. The estimated time of an HFS is shorter than a precession cycle, but better dating might support or refute this hypothesis. This paper may awaken the interest of the owners of better data, especially from subsurface (seismic, well logs), to complete the data from natural exposures.

MICROPALEONTOLOGICAL EVIDENCE OF A SUBMARINE FAN IN THE LOWER COALEDO FORMATION, SOUTHWESTERN OREGON, USA: REPLY

Late Eocene to Early Miocene environments, vegetation and climate in Southeastern France documented by palynology