African origin of caviomorph rodents is indicated by incisor enamel microstructure

Paleobiology ◽  
1994 ◽  
Vol 20 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Thomas Martin
Keyword(s):  
North American ◽  
Late Eocene ◽  
South American ◽  
Late Oligocene ◽  
African Origin ◽  
Enamel Microstructure ◽  
The North ◽  
Early Oligocene ◽  
Caviomorph Rodents

The same three subtypes of derived multiserial Hunter-Schreger bands are found in the incisor enamel of African phiomorph rodents from the late Eocene-early Oligocene and the oldest South American Caviomorpha from the Deseadan (late Oligocene). The synapomorphies contained therein, especially arrangement and orientation of interprismatic matrix, make an African origin of the Caviomorpha very probable. A North American origin of the Caviomorpha is thus rejected, as only primitive pauciserial Hunter-Schreger bands have been observed in possible ischyromyoid caviomorph ancestors. A multiserial Schmelzmuster apparently never evolved in the North American rodent fauna.

Tertiary extension and tilting in the Queen Charlotte Islands, evidence from dyke swarms and their paleomagnetism

1992 ◽  
Vol 29 (9) ◽  
pp. 1878-1898 ◽  
Author(s):  
E. Irving ◽  
J. G. Souther ◽  
J. Baker
Keyword(s):  
North American ◽  
Late Eocene ◽  
North American Plate ◽  
Western Margin ◽  
Queen Charlotte Islands ◽  
The North ◽  
Early Oligocene ◽  
Magnetic Stability ◽  
Transform Margin ◽  
Dyke Swarms

The Queen Charlotte Islands form the western margin of the Tertiary Queen Charlotte Basin, which is situated on the western margin of the North American Plate. They contain seven major dyke swarms of Late Eocene to Miocene age, a period when the relative motions of the Pacific and the North American plates in this region were dominantly dextral strike slip (transform margin), with intervals of highly oblique divergence and convergence. Within each swarm, dykes have a systematic trend. However, trends vary from swarm to swarm, indicating that the stress field varied. A total of 678 cores (1352 specimens) were collected from 129 dykes in six swarms over a distance of about 200 km. Magnetic stability is variable. One hundred and one dykes yielded records of the paleofield. Data are also reported from an Oligocene pluton (5 sites, 27 cores, 52 specimens) and Miocene lavas (8 sites, 52 cores, 101 specimens). Both normal and reversed magnetizations occur, but irrespective of sign, the mean directions of remanent magnetization of each swarm and of the pluton and the lavas have systematically steeper inclinations than the value calculated from coeval rocks in North America. To explain this it is proposed that, after dyke emplacement, the sampling areas were tilted to the north or northwest by amounts that vary between 9 and 16°. Apparently, crustal tilting, similar in magnitude and direction, extended over distances of approximately 200 km. This cannot reflect tilting of a single block. Instead, it is argued that at least the southern Queen Charlotte Islands underwent considerable northerly or north-northwesterly directed extension and normal block faulting, which followed and in part was concurrent with the formation of widespread mid-Tertiary dyke swarms, plutons and lava flows. Making use of the fact that dykes propagate perpendicular to the direction of extension, and combining previously measured dyke orientations with paleomagnetic data, three stages of extension are proposed: east–west extension sometime during the Late Eocene to Early Oligocene; north–south extension sometime in the interval Late Oligocene to Early Miocene; and northwest–southeast extension sometime during Late Miocene or later time.

scholarly journals Paleoecology of Late Eocene-Oligocene foraminiferal assemblages in a two-well transect across the North-East Newfoundland shelf

1991 ◽  
Vol 10 (1) ◽  
pp. 57-67
Author(s):  
F. C. Thomas
Keyword(s):  
North Sea ◽  
Late Eocene ◽  
Western Boundary ◽  
Late Oligocene ◽  
North East ◽  
The North ◽  
Early Oligocene ◽  
The North Sea ◽  
Relationship Of ◽  
The Relationship

Abstract. Core samples from the Paleogene of the Bonavista C-99 well on the northeast Newfoundland shelf and cuttings from downdip Blue H-28 contain foraminiferal assemblages which enable reconstruction of paleoenvironments along a downslope transect in Eocene through Late Oligocene-Miocene time. Comparison with coeval assemblages in North Sea wells with respect to structure and grain size of agglutinated taxa between the two areas reveal inter-basin differences.Reconstruction of the paleobathymetry derived from foraminiferal analysis, confirms seismic evidence for shallowing at the Bonavista site beginning in the Early Oligocene. The relationship of the Bonavista assemblages to contour currents is explored with reference to modern regional analogues. Species such as Reticulophragmium amplectens, Haplophragmoides walteri, Eponides umbonatus and Uvigerina ex. gr. miozea-nuttalli persist stratigraphically higher in the deeper Blue site.The paleoslope of this two-well transect is determined as approximately 0.48° during the Middle to Late Eocene and 0.68° during the Late Oligocene-Early Miocene. The bottom water hydrography of the transect can be evaluated by reference to these assemblages and a comparison to flysch-type agglutinated assemblages from a transect in the North Sea. The presence of an Upper Eocene-Middle Miocene hiatus at the Blue site contrasting with apparently continuous Tertiary deposition at Bonavista places a theoretical upper limit of 500–1000 m on the depth of the early Cenozoic western boundary undercurrent.

Diversification of the North American Doellingeria-Eucephalus Clade (Astereae: Asteraceae) Inferred from Molecular and Morphological Evidence

2019 ◽  
Vol 44 (4) ◽  
pp. 930-942
Author(s):  
Geraldine A. Allen ◽  
Luc Brouillet ◽  
John C. Semple ◽  
Heidi J. Guest ◽  
Robert Underhill
Keyword(s):  
North American ◽  
Sequence Data ◽  
Phylogenetic Analyses ◽  
Sister Group ◽  
Morphological Evidence ◽  
South American ◽  
New Combinations ◽  
The North ◽  
Hybridization Event ◽  
Ancient Hybridization

Abstract—Doellingeria and Eucephalus form the earliest-diverging clade of the North American Astereae lineage. Phylogenetic analyses of both nuclear and plastid sequence data show that the Doellingeria-Eucephalus clade consists of two main subclades that differ from current circumscriptions of the two genera. Doellingeria is the sister group to E. elegans, and the Doellingeria + E. elegans subclade in turn is sister to the subclade containing all remaining species of Eucephalus. In the plastid phylogeny, the two subclades are deeply divergent, a pattern that is consistent with an ancient hybridization event involving ancestral species of the Doellingeria-Eucephalus clade and an ancestral taxon of a related North American or South American group. Divergence of the two Doellingeria-Eucephalus subclades may have occurred in association with northward migration from South American ancestors. We combine these two genera under the older of the two names, Doellingeria, and propose 12 new combinations (10 species and two varieties) for all species of Eucephalus.

scholarly journals Late oligocene–early miocene shortening in the Thrace Basin, northern Aegean

2021 ◽  
Author(s):  
Ümitcan Erbil ◽  
Aral I. Okay ◽  
Aynur Hakyemez
Keyword(s):  
Large Scale ◽  
Middle Eocene ◽  
Early Miocene ◽  
Fold Axis ◽  
Late Oligocene ◽  
The Balkans ◽  
Sedimentary Sequences ◽  
The North ◽  
Early Oligocene ◽  
Thrace Basin

AbstractLate Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

The youngest record of fossil land mammals from Antarctica; its significance on the evolution of the terrestrial environment of the Antarctic Peninsula during the late Eocene

1997 ◽  
Vol 71 (2) ◽  
pp. 348-350 ◽  
Author(s):  
S. F. Vizcaino ◽  
M. Bond ◽  
M. A. Reguero ◽  
R. Pascual
Keyword(s):  
Antarctic Peninsula ◽  
Present Note ◽  
Late Eocene ◽  
South American ◽  
Terrestrial Environment ◽  
Shallow Marine ◽  
Early Oligocene ◽  
La Meseta Formation ◽  
The Antarctic ◽  
Seymour Island

The record of fossil land mammals from Antarctica has been restricted previously to the middle levels of the Eocene-?early Oligocene La Meseta Formation in Seymour Island, Antarctic Peninsula. This mostly shallow-marine sequence was divided informally into seven subunits (Tertiary Eocene La Meseta or TELM 1 to 7) by Sadler (1988). Land mammals, representing South American lineages of marsupials, edentates, and ungulates were recovered from TELM 3, 4, and 5 (Marenssi et al., 1994; Vizcaíno et al., 1994). The purpose of the present note is to report the discovery of a well-preserved ungulate tooth from the uppermost level of the La Meseta Formation (TELM 7) and to discuss its paleoenvironmental implications.

Grossplots: a Method for Estimating the Temperature State of the Earth and of Australia, Cretaceous to Middle Miocene

1997 ◽  
Vol 45 (3) ◽  
pp. 359 ◽  
Author(s):  
L. A. Frakes
Keyword(s):  
Middle Miocene ◽  
Global Climate ◽  
Interval Data ◽  
Late Eocene ◽  
Space Distribution ◽  
Mean Annual Temperature ◽  
The North ◽  
Early Oligocene ◽  
Time Space ◽  
Temperature State

Grossplots are compilations of globally distributed palaeotemperature data onto latitude versus age plots, which are then contoured. The results specifically show the distribution of temperature over the globe and its variations over the Cretaceous to Middle Miocene interval. Data for continents and oceans are plotted separately in this investigation, and each such grossplot is in accord with the known climate changes of this time. The general scarcity of quantitative palaeotemperature information for Australia can be rectified by deriving, from the global continental grossplot, the relationship between mean annual temperature and latitude. When these are applied to the latitude band progressively occupied by Australia, the following observations can be made: (1) during the Early Cretaceous, the south-east of the continent was subjected to freezing wintertime temperatures; (2) peak warming of northern Australia was attained in the Turonian–Santonian, but this was followed by cooling later in the Cretaceous; (3) Early Tertiary warming until the Late Eocene particularly affected the northern half of the continent, but this region then underwent the most severe cooling in the Early Oligocene; (4) subsequently, the whole of the continent cooled uniformly from conditions only slightly warmer than at present. Despite Australia’s equatorward march, the Late Cretaceous to Palaeocene climates of the continent have been influenced more effectively by changes in the global climate state. However, global cooling since the Eocene has been less effective than drift in controlling the warming climate of Australia. The time–space distribution of precipitation over Australia is estimated from the global relationship between terrestrial temperature and rainfall. The Eocene experienced the heaviest rainfall (> 1560 mm year-1, in the north only), and the Eocene to Middle Miocene experienced moderately high rates (> 500 mm year-1 in the northern three-quarters of the continent). Tertiary brown coals in southern regions were formed in proximity to areas of high rainfall. Continentwide low rates (< 500 mm year-1; semi-arid) are suggested for the Cretaceous, except for wet conditions in the north during the Albian–Santonian and the Late Maastrichtian. Estimates of precipitation are subject to factors such as continentality and location of moisture sources, which cannot be evaluated at present.

ON THE GEOGRAPHICAL DISTRIBUTION OF NORTH AMERICAN LEPIDOPTERA

1886 ◽  
Vol 18 (11) ◽  
pp. 213-220
Author(s):  
Aug. R. Grote
Keyword(s):  
Geographical Distribution ◽  
North American ◽  
North American Species ◽  
South American ◽  
Seasonal Temperature ◽  
The South ◽  
Old World ◽  
The North

Again, the genera Citheronia and Eacles are a South American element in our fauna, while the typical Attacinæ, such as Actias, probably belong to the Old World element in our fauna, together with all our Platypteryginœ. Among the Hawk Moths the genera Philampelus and Phlegethontius are of probable South American extraction, though represented now by certain strictly North American species. Mr. Robert Bunker, writing from Rochester, N. Y., records the fact that Philampelus Pandorus, going into chrysaiis Augnst 1, came out Sept. 10 as a moth, showing that in a warmer climate the species would become doublebrooded. And this is undoubtedly the case with many species the farther we go South, where insect activities are not interrupted so long and so strictly by the cold of winter. Since the continuance of the pupal condition is influenced by cold, a diminishing seasonal temperature for ages may have originally affected, if not induced, the transformations of insects as a whole. Butterflies and Moths which are single brooded in the North become double brooded in the South.

Pre-Priabonian Palaeogene formations in southwestern Bulgaria and northern Greece: stratigraphy and tectonic implications

1998 ◽  
Vol 135 (1) ◽  
pp. 101-119 ◽  
Author(s):  
IVAN S. ZAGORCHEV
Keyword(s):  
Late Cretaceous ◽  
Middle Eocene ◽  
Regional Metamorphism ◽  
Late Eocene ◽  
Thin Layers ◽  
The South ◽  
Northern Greece ◽  
The North ◽  
Early Oligocene ◽  
Metamorphic Core

The Paril Formation (South Pirin and Slavyanka Mountains, southwestern Bulgaria) and the Prodromos Formation (Orvilos and Menikion Mountains, northern Greece) consist of breccia and olistostrome built up predominantly of marble fragments from the Precambrian Dobrostan Marble Formation (Bulgaria) and its equivalent Bos-Dag Marble Formation (Greece). The breccia and olistostrome are interbedded with thin layers of calcarenites (with occasional marble pebbles), siltstones, sandstones and limestones. The Paril and Prodromos formations unconformably cover the Precambrian marbles, and are themselves covered unconformably by Miocene and Pliocene sediments (Nevrokop Formation). The rocks of the Paril Formation are intruded by the Palaeogene (Late Eocene–Early Oligocene) Teshovo granitoid pluton, and are deformed and preserved in the two limbs of a Palaeogene anticline cored by the Teshovo pluton (Teshovo anticline). The Palaeocene–Middle Eocene age of the formations is based on these contact relations, and on occasional finds of Tertiary pollen, as well as on correlations with similar formations of the Laki (Kroumovgrad) Group throughout the Rhodope region.The presence of Palaeogene sediments within the pre-Palaeogene Pirin–Pangaion structural zone invalidates the concept of a ‘Rhodope metamorphic core complex’ that supposedly has undergone Palaeogene amphibolite-facies regional metamorphism, and afterwards has been exhumed by rapid crustal extension in Late Oligocene–Miocene times along a regional detachment surface. Other Palaeogene formations of pre-Priabonian (Middle Eocene and/or Bartonian) or earliest Priabonian age occur at the base of the Palaeogene sections in the Mesta graben complex (Dobrinishka Formation) and the Padesh basin (Souhostrel and Komatinitsa formations). The deposition of coarse continental sediments grading into marine formations (Laki or Kroumovgrad Group) in the Rhodope region at the beginning of the Palaeogene Period marks the first intense fragmentation of the mid- to late Cretaceous orogen, in particular, of the thickened body of the Morava-Rhodope structural zone situated to the south of the Srednogorie zone. The Srednogorie zone itself was folded and uplifted in Late Cretaceous time, thus dividing Palaeocene–Middle Eocene flysch of the Louda Kamchiya trough to the north, from the newly formed East Rhodope–West Thrace depression to the south.

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