William A. Berggren

Eocene-Oligocene Climatic and Biotic Evolution

The transition from the Eocene to the Oligocene epoch was the most significant event in Earth history since the extinction of dinosaurs. As the first Antarctic ice sheets appeared, major extinctions and faunal turnovers took place in the land and in the sea, eliminating forms adapted to a tropical world and replacing them with the ancestors of most of our modern animal and plant life. Through a detailed study of climatic conditions and of organisms buried in Eocene-Oligocene sediments, this volume shows that the separation of Antarctica from Australia was a critical factor in changing oceanic circulation and ultimately world climate. In this book, contributors examine the full range of Eocene and Oligocene phenomena. Their articles cover nearly every major group of organisms in the ocean and on land and include evidence from palaeontology, stable isotopes, sedimentology, seismology and computer climatic modelling. The volume concludes with an update of the geochronological framework of the late Palaeogenic period.

Late Neogene chronology: New perspectives in high-resolution stratigraphy

We present an integrated geochronology for late Neogene time (Pliocene, Pleistocene, and Holocene Epochs) based on an analysis of data from stable isotopes, magnetostratigraphy, radiochronology, and calcareous plankton biostratigraphy. Discrepancies between recently formulated astronomical chronologies and magnetochronologies for the past 6 m.y. have been resolved on the basis of new, high-precision Ar/Ar ages in the younger part of this interval, the so-called Brunhes, Matuyama, and Gauss Epochs (5 Chrons C1n‐C2An; 0‐3.58 Ma), and revised analysis of sea floor anomalies in the Pacific Ocean in the older part, the so-called Gilbert Epoch (5 Chron C2Ar‐C3r; 3.58‐5.89 Ma). The magneto- and astrochronologies are now concordant back to the Chron C3r/C3An boundary at 5.89 Ma. TheNeogene(Miocene,Pliocene,Pleistocene, and Holocene) and Paleogene are treated here as period/system subdivisions oftheCenozoicEra/Erathem,replacements for the antiquated terms Tertiary and Quaternary.TheboundarybetweentheMiocene and Pliocene Series (Messinian/Zanclean Stages),whoseglobalstratotypesectionand point (GSSP) is currently proposed to be in Sicily,islocatedwithinthereversedinterval just below the Thvera (C3n.4n) Magnetic Polarity Subchronozone with an estimated age of 5.32 Ma. The Pliocene/Pleistocene boundary, whose GSSP is located at Vrica (Calabria,Italy),islocatednearthetopof the Olduvai (C2n) Magnetic Polarity Subchronozone with an estimated age of 1.81 Ma. The 13 calcareous nannoplankton and 48 planktonic foraminiferal datum events for the Pliocene, and 12 calcareous nannoplankton and 10 planktonic foraminiferal datum events for the Pleistocene, are calibrated to the newly revised late Neogeneastronomical/geomagneticpolarity time scale.

The Geology of the Darien, Panama, and the late Miocene-Pliocene collision of the Panama arc with northwestern South America

The geology of the Darien province of eastern Panama is presented through a new geologic map and detailed biostratigraphic and paleobathymetric analysis of its Upper Cretaceous to upper Miocene sediments. The sequence of events inferred from the stratigraphic record includes the collision of the Panama arc (the southwestern margin of the Caribbean plate) and South American continent. Three tectonostratigraphic units underlie the Darien region: (1) Precollisional Upper Cretaceous–Eocene crystalline basement rocks of the San Blas Complex form a series of structurally complex topographic massifs along the northeastern and southwestern margins of the Darien province. These rocks formed part of a >20 m.y. submarine volcanic arc developed in a Pacific setting distant from the continental margin of northwestern South America. The northerly basement rocks are quartz diorites, granodiorites, and basaltic andesites, through dacites to rhyolites, indicating the presence of a magmatic arc. The southerly basement rocks are an accreted suite of diabase, pillow basalt, and radiolarian chert deposited at abyssal depths. Precollisional arc-related rocks, of Eocene to lower Miocene age, consist of 4000 m of pillow basalts and volcaniclastics, and biogenic calcareous and siliceous deep-water sediments. They consist of the Eocene-Oligocene Darien Formation, the Oligocene Porcona Formation and the lower-middle Miocene Clarita Formation. Postcollisional deposits are mostly coarse- to fine-grained siliciclastic sedimentary rocks and turbiditic sandstone of upper middle to latest Miocene age. This 3000 m thick sedimentary sequence is deformed as part of a complexly folded and faulted synclinorium that forms the central Chucunaque-Tuira Basin of the Darien. The sedimentary package reveals general shallowing of the basin from bathyal to inner neritic depths during the 12.8−7.1 Ma collision of the Panama arc with South America. The sediments are divided into the upper middle Miocene Tapaliza Formation, the lower upper Miocene Tuira and Membrillo Formations, the middle upper Miocene Yaviza Formation, and the middle to upper Miocene Chucunaque Formation. The precollisional open marine units of Late Cretaceous–middle Miocene age are separated from the overlying postcollisional sequence of middle to late Miocene age by a regional unconformity at 14.8−12.8 Ma. This unconformity marks the disappearance of radiolarians, the changeover of predominantly silica deposition from the Atlantic to the Pacific, the initiation of the uplift of the isthmus of Panama, and the onset of shallowing upward, coarser clastic deposition. This pattern is also recorded from the southern Limon Basin of Caribbean Costa Rica to the Atrato Basin of northwestern Colombia. By the middle late Miocene, neritic depths were widespread throughout the Darien region, and a regional unconformity suggests completion of the Central American arc collision with South America by 7.1 Ma. No Pliocene deposits are recorded from either the Darien or the Panama Canal Basin, and no sediments younger than 4.8 Ma have been identified in the Atrato Basin of Colombia, suggesting rapid uplift and extensive emergence of the Central American isthmus in the latest Miocene. Northward movement of the eastern segment of the Panama arc along a now quiescent Panama Canal Zone fault during Eocene-Oligocene time may have dislocated the pre-collision arc. Since collision, the portion west of this fault (Chorotega Block) has remained stable, without rotation; to the east, in the Darien region, compression has been accommodated through formation of a Panama microplate with convergent boundaries to the north (North Panama deformed belt) and south (South Panama deformed belt), and suturing with South America along the Atrato Valley. Deformation within the microplate has been accommodated in the Darien province by several major left-lateral strike-slip faults that were active until the early Pliocene, since when the plate has behaved rigidly.

The Neogene: Part 2: Neogene geochronology and chronostratigraphy

Summary We present a revised Neogene geochronology based upon a best fit to selected high temperature radiometric dates on a number of identified magnetic polarity chrons (within the late Cretaceous, Paleogene, and Neogene) which minimizes apparent accelerations in sea-floor spreading. An assessment of first order correlations of calcareous plankton biostratigraphic datum events to magnetic polarity stratigraphy yields the following estimated magnetobiochronology of major chronostratigraphic boundaries: Oligocene/Miocene (Chron C6CN): 23.7 Ma; Miocene/Pliocene (slightly younger than Gilbert/Chron 5 boundary): 5.3 Ma; Pliocene/Pleistocene (slightly younger than Olduvai Subchron): 1.6 Ma. Changes to the marine time-scale are relatively minor in terms of recent and current usage except in the interval of the middle Miocene where new DSDP data reveal that previous correlations of magnetic anomalies 5 and 5A to magnetic polarity Chrons 9 and 11, respectively, are incorrect. Our revized magnetobiostratigraphic correlations result in a 1.5-2 m.y. shift towards younger magnetobiochronologic age estimate in the middle Miocene. Radiometric dates correlated to bio- and magnetostratigraphy in continental section generally support the revized marine magnetobiochronology presented here. Major changes, however, are made in marine-non-marine correlations in the Miocene in Eurasia which indicate African-Eurasian migrations through the Persian Gulf as early as 20 Ma. The 12.5 Ma estimate of the Hipparion datum is supported by recent taxonomic revisions of the hipparions and magnetobiostratigraphic correlations which show that primitive hipparions first arrived in Eurasia and North Africa at c. 12.5 Ma and a second wave in the tropics (i.e. Indian and central Africa) at c. 10 Ma.

Paleogene tropical planktonic foraminiferal biostratigraphy and magnetobiochronology

Confusion has arisen over the connotation and correlation of two competing tropical-subtropical Paleogene planktonic foraminiferal zonations (Berggren 1969; Blow 1979). This derives from the fact that the former scheme, when originally published, was viewed as provisional and precise definitions were not given for the zonal system. We review here the development of these two zonal schemes in a historical context, present a definition, in part revised and updated, of the P-zonation system of Berggren (1969), and correlate this and related zonal schemes to a magnetostratigraphic and, ultimately, magnetobiochronologic framework to the extent possible.

The late Miocene Panama isthmian strait

Miocene sediments of the Caribbean Gatun and Chagres formations, Panama Canal basin, were deposited within an archipelagic strait that connected Caribbean and Pacific waters. Shallow-water (∼ 25 m) benthic foraminifera of the Gatun Formation have a strong Caribbean affinity, indicating that a significant interoceanic, biogeographic barrier had formed at ∼ 8 Ma. However, benthic foraminifera of the overlying Chagres Formation are bathyal and markedly Pacific in affinity, indicating that at ∼ 6 Ma, waters of the Panama isthmian strait deepened to ∼ 200–500 m and Pacific bathyal waters flowed into the Caribbean. The Chagres Formation crops out at the Caribbean entrance to the Panama Canal in a large wedge of cross-laminated sandstone and coquina. The cross-laminations and coarse grain size indicate high-energy currents atypical of bathyal settings. We infer that a jet of the Pacific North Equatorial Countercurrent–Equatorial Undercurrent passed through the Panama isthmian strait to deposit these sediments on the Caribbean side. This later entry of Pacific taxa into the Caribbean had no apparent effect on the subsequent composition of Caribbean faunas.

Introduction to marine micropaleontology

Marine micropaleontology: an introduction (W.A. Berggren). Calcareous Microfossils. Foraminifera (A. Boersma). Calcareous nannoplankton (B.U. Haq). Ostracodes (V. Pokomy). Pteropods (Y. Herman). Calpionellids (J. Remane). Calcareous algae (J.L. Wray). Bryozoa (K. Brood). Siliceous Microfossils. Radiolaria (S.A. Kling). Marine diatoms (L.H. Burckle). Silicoflagellates and ebridians (B.U. Haq). Phosphatic Microfossils. Conodonts and other phosphatic microfossils (K.J. Muller). Organic-Walled Microfossils. Dinoflagellates, acritarchs and tasmanitids (G.L. Williams). Spores and pollen in the marine realm (L. Heusser). Chitinozoa (A. Jansonius, W.A.M. Jenkins).

Plate tectonics and paleocirculation — Commotion in the ocean☆

Abstract Oceanic circulation is dependent upon dynamically interrelated aspects of geography and climate. Sequential changes in these two parameters during the past 200 m.y. have resulted in a complex history of oceanic circulation. Certain paleogeographic and climatic events have played a critical role in the evolution of global circulation patterns. The general picture is of deposition in tranquil oceanic environments during the Mesozoic under the influence of equable climates and oceanic thermal-haline homogeneity. In the Cenozoic, continued continental dispersal and climatic deterioration (and latitudinal thermal heterogeneity) due to high latitude cooling (beginning 40 m.y. ago but particularly the last 10 m.y.), led to accelerated surface and bottom water circulation, especially along western margins of ocean basins and the development of erosion and redeposition as a major sedimentary process. The Cenozoic activity taken in its entirety is referred to here as “commotion in the ocean”.

Jurassic to Paleogene: Part 2 Paleogene geochronology and chronostratigraphy

Summary We present a revised Paleogene geochronology based upon a best fit to selected high temperature radiometric dates on a number of identified magnetic polarity chrons (within the late Cretaceous, Paleogene and Neogene) which minimizes apparent accelerations in sea-floor spreading. An assessment of first order correlations of calcareous plankton biostratigraphic datum events to magnetic polarity stratigraphy yields the following estimated magnetobiochronology of major chronostratigraphic boundaries: Cretaceous-Tertiary boundary (Chron C29R), 66.4 Ma; Paleocene-Eocene (Chron C24R), 57.8 Ma; Eocene-Oligocene (Chron C13R), 36.6 Ma; Oligocene-Miocene (Chron C6CN), 23.7 Ma. The Eocene is seen to have expanded chronologically (~ 21 m.y.) at the expense of the Paleocene (~ 9 m.y.) and is indeed the longest of the Cenozoic epochs. In addition, magnetobiostratigraphic correlations require adjustments in apparent correlations with standard marine stage boundaries in some cases (particularly in the Oligocene). Finally, we present a correlation between standard Paleogene marine and terrestrial stratigraphies.

Formation of the Isthmus of Panama

Independent evidence from rocks, fossils, and genes converge on a cohesive narrative of isthmus formation in the Pliocene. The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.