Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

https://science.sciencemag.org/content/sci/235/4793/1156.full.pdf

Chronology of fluctuating sea levels since the triassic.

An Astronomically Tuned Neogene Time Scale (ATNTS2012) is presented, as an update of ATNTS2004 in GTS2004. The new scale is not fundamentally different from its predecessor and the numerical ages are identical or almost so. Astronomical tuning has in principle the potential of generating a stable Neogene time scale as a function of the accuracy of the La2004 astronomical solution used for both scales. Minor problems remain in the tuning of the Lower Miocene. In GTS2012 we will summarize what has been modified or added since the publication of ATNTS2004 for incorporation in its successor, ATNTS2012. Mammal biostratigraphy and its chronology are elaborated, and the regional Neogene stages of the Paratethys and New Zealand are briefy discussed. To keep changes to ATNTS2004 transparent we maintain its subdivision into headings as much as possible.

The Neogene Period

Proceedings of the Ocean Drilling Program

All Paleocene stages (i.e., Danian, Selandian and Thanetian) have formally ratified definitions, and so have the Ypresian and Lutetian Stages in the Eocene, and the Rupelian Stage in the Oligocene. The Bartonian, Priabonian and Chattian Stages are not yet formally defined. After the global catastrophe and biotic crisis at the CretaceousePaleogene boundary, stratigraphically important marine microfossils started new evolutionary trends, and on land the now flourishing mammals offer a potential for stratigraphic zonation. During the Paleogene the global climate, being warm until the late Eocene, shows a significant cooling trend culminating in a major cooling event in the beginning of the Oligocene, preparing the conditions for modern life and climate. Orbitally tuned cyclic sedimentation series, calibrated to the geomagnetic polarity and biostratigraphic scales, have considerably improved the resolution of the Paleogene time scale. The Paleogene Period - ResearchGate. Available from: http://www.researchgate.net/publication/236611297_The_Paleogene_Period [accessed Mar 23, 2015].

The Paleogene Period

At the boundary between the Palaeocene and Eocene epochs, about 55 million years ago, the Earth experienced a strong global warming event, the Palaeocene–Eocene thermal maximum1,2,3,4. The leading hypothesis to explain the extreme greenhouse conditions prevalent during this period is the dissociation of 1,400 to 2,800 gigatonnes of methane from ocean clathrates5,6, resulting in a large negative carbon isotope excursion and severe carbonate dissolution in marine sediments. Possible triggering mechanisms for this event include crossing a threshold temperature as the Earth warmed gradually7, comet impact8, explosive volcanism9,10 or ocean current reorganization and erosion at continental slopes11, whereas orbital forcing has been excluded12. Here we report a distinct carbonate-poor red clay layer in deep-sea cores from Walvis ridge13, which we term the Elmo horizon. Using orbital tuning, we estimate deposition of the Elmo horizon at about 2 million years after the Palaeocene–Eocene thermal maximum. The Elmo horizon has similar geochemical and biotic characteristics as the Palaeocene–Eocene thermal maximum, but of smaller magnitude. It is coincident with carbon isotope depletion events in other ocean basins, suggesting that it represents a second global thermal maximum. We show that both events correspond to maxima in the ∼405-kyr and ∼100-kyr eccentricity cycles that post-date prolonged minima in the 2.25-Myr eccentricity cycle, implying that they are indeed astronomically paced.

/pdf/astronomical-pacing-of-late-palaeocene-to-early-eocene-1einzptdj9.pdf

Astronomical pacing of late Palaeocene to early Eocene global warming events

Supplementary modification and introduction of code numbers to the low-latitude coccolith biostratigraphic zonation (Bukry, 1973; 1975)

Arctic Ocean Core Fl-422 has been of central importance in Arctic tectonics and paleoceanography because it provides the sole evidence for early Cenozoic marine conditions in the Arctic. The presence of several Eocene and Eocene or Oligocene guide species of silicoflagellates in samples from this core shows that it is no older than middle Eocene, and is not Paleocene as previously reported. There is no evidence of any Paleocene (54 to 65 Ma) siliceous microfossils from Core Fl-422. Paleoceanographic inferences conerning the Cretaceous-Tertiary boundary and the timing of silica deposition in the Arctic have been erroneous because of unsupported biostratigraphic correlations.

Paleogene paleoceanography of the Arctic Ocean is constrained by the middle or late Eocene age of USGS Core Fl-422: Evidence from silicoflagellates

Cretaceous silicoflagellate assemblages from Arctic Ocean USGS Core 437 showVallacerta siderea the most abundant species; most species ofLyramula disappear halfway up the core; onlyL. burchardae, n. sp., persists into the upper sections. These occurrences are untypical of the few documented Cretaceous assemblages from other areas. A Campanian or Maestrichtian age is suggested by correlation, but the uniquely high abundance ofV. siderea and lack ofCorbisema suggests that a difference in both age and general environment could be involved. If Core 437 is latest Maestrichtian, then the evidence from this core would constrain the timing of the ocean-freshening model for the Cretaceous-Tertiary boundary extinctions.

Cretaceous Arctic silicoflagellates

High resolution study (samples every ca. 37 yr) of the diatoms, silicoflagellates, and geochemistry of Kasten Core BAM80 E-17 yields a detailed record of climatic and paleoceanographic change for the past 2,000 years for the eastern Guaymas Basin, a region of very high diatom productivity within the central Gulf of California. Roughly every 200 years, intervals enriched in diatoms alternate with intervals characterized by higher terrigenous material and total organic carbon (TOC), suggesting solar forcing. The record of percent biogenic silica is remarkably similar to the radiocarbon production curve, with increased diatom production occurring during sunspot minima. It is suggested that solar minima coincide with an increase in the strength an/or duration of late fall/winter northwest winds blowing down the Gulf due to atmospheric cooling above northwest Mexico. A prolonged interval of dramatically warmer SST’s that is marked by a two-fold increase (above normal background fluctuations) in the relative abundance of the tropical diatom Azpeitia nodulifera occurs between ca. 910-1140 A.D., corresponding to the Medieval Warm Period. This interval is interrupted by a brief period ( ca. 1020-1100 A.D.) of reduced A. nodulifera and enhanced diatom production.

A 2000-yr-long record of climate from the gulf of california

Biostratigraphic ages determined by planktic coccoliths and benthic foraminifera for the same core samples from the California Continental Borderland suggest that a significant overlap exists among provincial Miocene stages of California and that some of the benthic foraminifera commonly used to recognize these stages are time-transgressive. For example, samples assigned to the middle Miocene Discoaster exilis Zone of coccoliths (∼ 14 ± 1 m.y.) are also assigned to the Relizian, Luisian, and lower Mohnian Stages on the basis of benthic foraminifera. Significantly, most past and current geologic interpretations of Cenozoic marine sequences in California rely heavily on provincial benthic foraminiferal stages and zones. Thus, the apparent overlapping of provincial stages has serious implications for geologic studies of the California Cenozoic and should be further investigated in sections onshore.

David Bukry

Papers

Supplementary modification and introduction of code numbers to the low-latitude coccolith biostratigraphic zonation (Bukry, 1973; 1975)

Paleogene paleoceanography of the Arctic Ocean is constrained by the middle or late Eocene age of USGS Core Fl-422: Evidence from silicoflagellates

Cretaceous Arctic silicoflagellates

A 2000-yr-long record of climate from the gulf of california

Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland