Reticulate Nummulites (N. fabianii Linage) and Age of the Pellatispira-Beds of the Drazinda Formation, Sulaiman Range, Pakistan

The Eocene shallow marine Pellatispira-beds in the upper part of the Drazinda Formation represent the latest phase of Cenozoic Tethyan marine deposition in the Sulaiman Range, West Pakistan. The unit consists of stratigraphically important taxa as Heterostegina,Silvestriella, Pellatispira, a new Baculogypsina (possibly ancestral to modern Baculogypsina) and reticulate Nummulites implying a latest middle to late Eocene (late Bartonian-Priabonian) age. A more precise age of the unit requires the biometric study of reticulate Nummulites, the evolutionary scheme of which is better known from the peri-Mediterranean region in the Tethys. This group, which was subdivided into a series of successive chrono-species based on the biometry of inner cross-diameter of proloculus and changes in the types of granulation/reticulation on the test surface in the late Eocene-late Oligocene interval, appears to have a significant biostratigraphic potential for a high-resolution biostratigraphy in the peri-Mediterranean region (Western Tethys). The reticulate Nummulites in two samples from Rakhi Nala and Zinda Pir, ZP22 and RNB10, were studied and compared with those from the peri-Mediterranean region. The isolated specimens have a weak surface granulation externally, a distinct small umbonal granule (pile) and typical reticulation. The samples ZP22 and RNB10 from Zinda Pir and and Rakhi Nala sections have an average inner cross diameter of proloculus of 152.0 and 153.0 μm respectively. The reticulate Nummulites in both samples are assigned to N. hormoensis, a chrono-species characteristic for the shallow benthic zone (SBZ 18), referable to latest Bartonian-early Priabonian time interval. Since Heterostegina in peri-Mediterranean region and in Pakistan belongs to different lineages, a correlation of N. hormoensis in the studied samples with the wellestablished evolutionary scheme of Heterostegina reticulata and H.armenica lineages from the Western Tethys was not possible.

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Eocene microplankton from La Meseta Formation, northern Seymour Island

Antarctic Science ◽

10.1017/s0954102092000506 ◽

1992 ◽

Vol 4 (3) ◽

pp. 355-362 ◽

Cited By ~ 33

Author(s):

Christopher D. Cocozza ◽

Ciara M. Clarke

Keyword(s):

Late Eocene ◽

Early Eocene ◽

Shallow Marine ◽

Dinoflagellate Cyst ◽

Two Samples ◽

Low Diversity ◽

La Meseta Formation ◽

Marine System ◽

Near Shore ◽

Seymour Island

Twenty two samples collected from the Tertiary La Meseta Formation of Cape Wiman, Seymour Island, Antarctic Peninsula yielded abundant and moderately diverse assemblages of marine palynoflora, dominated by dinoflagellate cysts, together with acritarchs and chlorophyta. The assemblages can be divided into three association: Association 1, characterized by low diversity dinoflagellate assemblage of late Early Eocene age which are dominated by Enigmadinium cylindrifloriferum; Association 2 characterized by more diverse dinoflagellate cyst assemblages, which show a marked decrease in the dominance of E. cylindrifloriferum, and an increase in relative abundance of Areosphaeridium cf. diktyoplokus; and Association 3 which is characterized by a decrease in dinoflagellate cyst diversity up section. Changes in dinoflagellate cyst dominance and diversity throughout the section suggests a gradation from a stressed, shallow marine palaeoenvironment to a more open near-shore, shallow marine system becoming progressively more nearshore up section. The assemblages are no older than late Early Eocene in age, and possibly as young as Mid–Late Eocene.

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Late Paleogene paleotopographic evolution of the northern Cordilleran orogenic front: Implications for demise of the orogen

Geological Society of America Bulletin ◽

10.1130/b35919.1 ◽

2021 ◽

Author(s):

Majie Fan ◽

Kurt N. Constenius ◽

Rachel F. Phillips ◽

David L. Dettman

Keyword(s):

Initial Phase ◽

Middle Eocene ◽

High Elevation ◽

Late Eocene ◽

Crustal Extension ◽

Late Oligocene ◽

Slab Rollback ◽

Basin Floor ◽

Climate Cooling ◽

High Range

The paleotopographic history of the North American Cordilleran orogen holds the key to understanding mechanisms of orogenesis and subsequent orogenic collapse. It has been suggested that the orogenic front in western Montana (USA) and Alberta (Canada) was more than 4 km high during Late Cretaceous−early Eocene contractional deformation and during the initial phase of extension in the middle Eocene; however, the late Eocene−Oligocene topographic evolution during continued extensional collapse remains poorly constrained. Here we extend the paleotopographic record in the Kishenehn Basin in northwestern Montana and southeastern British Columbia (Canada) to the late Oligocene by studying δ18O values of fossil mollusks and cement and paleosol carbonates. The molluscan taxa changed from three sympatric groups with preferred habitats ranging from tropical wet, semi-arid subtropical, and temperate during the middle and late Eocene, to mainly a single group associated with temperate environment during the Oligocene, reflecting a decline in molluscan biodiversity induced by climate cooling across the Eocene−Oligocene transition. Reconstructed δ18O values of alpine snowmelt and basinal precipitation decreased by 1.4‰ and 3.8‰, respectively, from the middle to late Eocene, reflecting climate cooling and ∼1 km surface uplift of the basin floor. The reconstructed alpine snowmelt δ18O values then increased by 2.9‰ in the Oligocene suggesting a ∼0.5 km drop in elevation of the orogenic front. Collectively, the results of our new and previously published δ18O data chronicle the paleotopographic response to the change from flat-slab subduction to slab rollback over a 45 m.y. period. These data suggest that the orogenic front was characterized by high elevation (>4 km) in the ancestral Lewis-Clark-Livingston ranges during latest Cretaceous−early Eocene (ca. 75−52 Ma) contraction. The initial phase of extension related to the Kishenehn Basin created a lowland basin with a surface elevation of only ∼1.5 km during the early middle Eocene (ca. 46−44 Ma) whereas the ranges remained >4 km high. The high range elevations were sustained for at least 12 m.y. in the middle to late Eocene concurrent with extension, while the basin floor elevation was uplifted to ∼2.5 km by the latest Eocene (ca. 36−34 Ma). Basin aggradation can explain at most half of the 1 km basin floor uplift. The remaining amount (at least 0.5 km) and sustained high range elevation suggest that range denudation and crustal extension was compensated by the isostatic and thermal effects of slab rollback and/or passage of a slab window and infusion of hot asthenosphere beneath the continent. The range elevation in the orogenic front decreased ∼0.5 km by the late Oligocene (ca. 28 Ma), associated with a decrease in rock uplift rate associated with extension. A post-Oligocene elevation drop of ∼1 km resulted in both the ranges and basin floor reaching modern topography in the Kishenehn Basin drainage, likely due to the regional effect of Neogene Basin and Range extension. This study, along with the previous investigation of the Kishenehn Basin by Fan et al. (2017), are the first studies that systematically investigate paleorelief of the orogenic belt by reconstructing paleoelevations of the mountains and the basin at the same time. The results highlight that the Cordilleran orogenic front of northern Montana and southern British Columbia sustained its high elevation edifice for at least 12 m.y. after the start of extension. We suggest that initial crustal extension did not result in orogenic demise because of concurrent thermal and isostatic uplift.

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Fossil and modern sponge fauna of southern Australia and adjacent regions compared: interpretation, evolutionary and biogeographic significance of the late Eocene ‘soft’ sponges

Contributions to Zoology ◽

10.1163/18759866-08501002 ◽

2016 ◽

Vol 85 (1) ◽

pp. 13-35 ◽

Cited By ~ 10

Author(s):

Magdalena Łukowiak

Keyword(s):

New Zealand ◽

Shallow Water ◽

Environmental Context ◽

Late Eocene ◽

Shallow Marine ◽

Marine Communities ◽

Shallow Water Species ◽

Water Species

The late Eocene ‘soft’ sponge fauna of southern Australia is reconstructed based on disassociated spicules and is used to interpret the paleoecology and environmental context of shallow marine communities in this region. The reconstructed sponge association was compared with coeval sponge assemblages from the Oamaru Diatomite, New Zealand, and with the modern ‘soft’ sponge fauna of southern coastal of Australia. Based on the predominance of shallow- and moderately shallow-water species, the late Eocene assemblage is interpreted to have inhabited waters depths of about 100 m. This contrast with the spicule assemblage from New Zealand, which characterized deeper waters based on the presence of numerous strictly deepwater sponge taxa, and the absence of spicules of shallow-water demosponges represented in the Australian material. The southern Australian Eocene sponge assemblages have clear Tethyan affinities evidenced by the occurrence of sponges known today from diverse regions. This distribution suggests much wider geographical ranges of some sponge taxa during the Eocene. Their present distributions may be relictual. The modern sponge fauna inhabiting southern Australian waters shows only moderate differences from these of the late Eocene. Differences are more pronounced at lower taxonomic levels (family and genus).

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Reappraisal of the burrowing lobster Axius (Malacostraca: Decapoda: Axiidea) in the fossil record with notes on palaeobiogeography and description of a new species

BSGF - Earth Sciences Bulletin ◽

10.1051/bsgf/2017175 ◽

2017 ◽

Vol 188 (3) ◽

pp. 12 ◽

Cited By ~ 1

Author(s):

Matúš Hyžný ◽

Sten Lennart Jakobsen ◽

René H. B. Fraaije

Keyword(s):

Fossil Record ◽

Type Species ◽

Morphological Characters ◽

Late Oligocene ◽

The West ◽

Fossil Species ◽

Western Tethys ◽

Preservation Potential ◽

A New Species ◽

Subjective Synonym

The fossil record of the burrowing lobster Axius is reviewed. A diagnosis based on the characters with preservation potential is supplied. Plioaxius lineadactylus Fraaije et al., 2011, from the Pliocene of Belgium and the Netherlands is considered congeneric with the type species of Axius. As a consequence, Plioaxius is considered a junior subjective synonym of Axius. A newly described species, Axius hofstedtae from the late Oligocene of Denmark is considered the oldest unequivocal representative of Axius. Both fossil species, A. hofstedtae n. sp. and A. lineadactylus n. comb., share numerous morphological characters with extant Axius stirhynchus. Scarcity of the Cenozoic Axiidae is ascribed to lack of study of the fossil record of this group rather than to low fossilization potential of its representatives. A preliminary scenario of the migration of Axius based on the scarce fossil record suggests the origin in the Western Tethys and subsequent dispersal westward into the West Atlantic and eastward into the West Pacific.

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New occurrences of Leukadiella and Paroniceras (Ammonoidea) from the Toarcian (Lower Jurassic) of the Canadian Cordillera

Journal of Paleontology ◽

10.1017/s0022336000026949 ◽

1995 ◽

Vol 69 (1) ◽

pp. 89-98 ◽

Cited By ~ 8

Author(s):

G. K. Jakobs

Keyword(s):

North America ◽

Mediterranean Region ◽

Lower Jurassic ◽

Canadian Cordillera ◽

Rare Occurrence ◽

Western Tethys ◽

North American Cordillera ◽

Queen Charlotte Islands ◽

The North ◽

New Occurrences

Previous studies of the Toarcian of the North American Cordillera have mentioned the rare occurrence of Paroniceras in the Queen Charlotte Islands. Recent work has identified the presence of Leukadiella in the Middle Toarcian of the Queen Charlotte Islands, the Spatsizi area, and the Hazelton area. They occur with Rarenodia planulata, Peronoceras pacificum, Peronoceras verticosum, and Phymatoceras cf. P. pseudoerbaense. The Leukadiella specimens are well preserved and generally larger than those found in the Mediterranean region. Taxa present in North America include Paroniceras sternale, Leukadiella ionica, Leukadiella amuratica, Leukadiella aff. L. helenae, and Leukadiella aff. L. ionica. Morphologically Leukadiella is closely related to such genera as Hildaites and Hildoceras and is more suitably placed within the subfamily Hildoceratinae rather than the Bouleiceratinae. The distribution of Leukadiella and Paroniceras indicates the influence of the Hispanic Corridor linking western Tethys and the eastern Pacific during the Middle Toarcian.

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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

Journal of Paleontology ◽

10.1017/s0022336000039263 ◽

1997 ◽

Vol 71 (2) ◽

pp. 348-350 ◽

Cited By ~ 13

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.

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Fossil plant stomata indicate decreasing atmospheric CO<sub>2</sub> prior to the Eocene–Oligocene boundary

Climate of the Past ◽

10.5194/cp-12-439-2016 ◽

2016 ◽

Vol 12 (2) ◽

pp. 439-454 ◽

Cited By ~ 26

Author(s):

Margret Steinthorsdottir ◽

Amanda S. Porter ◽

Aidan Holohan ◽

Lutz Kunzmann ◽

Margaret Collinson ◽

...

Keyword(s):

Late Eocene ◽

Large Shift ◽

Stratigraphic Sequence ◽

Multiple Data ◽

Fossil Leaves ◽

Two Samples ◽

Data Points ◽

Rapid Temperature ◽

Latest Eocene ◽

Climate Mode

Abstract. A unique stratigraphic sequence of fossil leaves of Eotrigonobalanus furcinervis (extinct trees of the beech family, Fagaceae) from central Germany has been used to derive an atmospheric pCO2 record with multiple data points spanning the late middle to late Eocene, two sampling levels which may be earliest Oligocene, and two samples from later in the Oligocene. Using the inverse relationship between the density of stomata and pCO2, we show that pCO2 decreased continuously from the late middle to late Eocene, reaching a relatively stable low value before the end of the Eocene. Based on the subsequent records, pCO2 in parts of the Oligocene was similar to latest Eocene values. These results suggest that a decrease in pCO2 preceded the large shift in marine oxygen isotope records that characterizes the Eocene–Oligocene transition and that when a certain threshold of pCO2 change was crossed, the cumulative effects of this and other factors resulted in rapid temperature decline, ice build up on Antarctica and hence a change of climate mode.

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Peonza: new gastropod genus from the middle Tertiary of Patagonia and Chile

Journal of Paleontology ◽

10.1017/s0022336000022873 ◽

1994 ◽

Vol 68 (2) ◽

pp. 279-286 ◽

Cited By ~ 7

Author(s):

Amalia M. Olivera ◽

William J. Zinsmeister ◽

S. Graciela Parma

Keyword(s):

New Species ◽

Temporal Distribution ◽

Late Eocene ◽

Tierra Del Fuego ◽

Early Miocene ◽

Late Oligocene ◽

Southern Chile ◽

Santa Cruz ◽

Two New Species

A new Tertiary gastropod genus, Peonza n. gen., is described, along with two new species, P. torquata from southern Argentina and P. benjamina from southern Chile. These muricacean gastropods, of uncertain familial status, occur in the late Eocene San Julián Formation and in the late Oligocene to early Miocene? Monte León Formation, Santa Cruz Province, Argentina. They also were recorded in the (probably) Oligocene Magellanian beds in Tierra del Fuego, Argentina, and in early Miocene deposits of the Tres Montes region in the Chilean Canals. In spite of the small number of specimens, Peonza n. gen. seems to have had a wide geographic and temporal distribution.

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Apatite fission-track thermochronology of the Western Pontides (NW Turkey)

Geological Magazine ◽

10.1017/s0016756811000525 ◽

2011 ◽

Vol 149 (1) ◽

pp. 133-140 ◽

Cited By ~ 25

Author(s):

WILLIAM CAVAZZA ◽

ILARIA FEDERICI ◽

ARAL I. OKAY ◽

MASSIMILIANO ZATTIN

Keyword(s):

Fission Track ◽

Late Eocene ◽

Tectonic Activity ◽

Late Oligocene ◽

Apatite Fission Track ◽

Tectonic Events ◽

Fission Track Thermochronology ◽

Nw Turkey ◽

Tectonic Contact ◽

North And South

AbstractThe results of apatite fission-track analyses of the Western Pontides of NW Turkey point to three discrete episodes of Cenozoic exhumation correlatable with major supraregional tectonic events. (1) Paleocene–early Eocene exhumation reflected the closure of the İzmir–Ankara ocean. (2) Late Eocene–earliest Oligocene exhumation was the result of renewed tectonic activity along the İzmir–Ankara suture. (3) Late Oligocene–early Miocene exhumation recorded the onset of northern Aegean extension. Samples collected north and south of the tectonic contact between the two terranes forming the Western Pontides (i.e. İstanbul and Sakarya terranes) record the same cooling events, suggesting that such terranes were amalgamated in pre-Cenozoic times.

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