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Wyszukujesz frazę "late Miocene" wg kryterium: Temat


Tytuł:
Stratigraphy and geological structure of the Magura Nappe in the south-western part of the Gorce Mountains, Outer Carpathians, Poland
Autorzy:
Szczęch, Mateusz
Waśkowska, Anna
Powiązania:
https://bibliotekanauki.pl/articles/24201044.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Late Cretaceous–Early Miocene
stratigraphy
foraminiferal assemblages
tectonics
highresolution DEM
Opis:
The south-western part of the Gorce Mts (Outer Carpathians) is composed of flysch deposits of the Krynica and Bystrica subunits of the Magura Nappe. The Krynica Subunit includes the Late Cretaceous–Paleocene Ropianka Fm, the Early Eocene Beloveža Fm, the Early Eocene–Oligocene Magura Fm and the Oligocene–Early Miocene Malcov Fm, while the Bystrica Subunit includes the Middle Eocene–?Oligocene Magura Fm, represented mainly by the thick-bedded Magura Sandstone. Thin- and medium-bedded sandstone-shale turbidites predominate in the other formations. The lithostratigraphic units are dated on the basis of foraminifers. The studied deposits accumulated in the southern part of the Magura Basin. Their detrital material was derived from a ridge, bounding the basin in the south. In the study area, the Krynica Subunit overthrusts the Bystrica Subunit. The studied deposits are folded, thrust and cut by numerous faults. The Turbacz Thrust Sheet and the newly identified Kudłoń Thrust Sheet were distinguished in the Krynica Subunit. Faults of different lengths and throws are transverse or oblique. Some of them form complex dislocation zones with lengths of up to several km. In general, the high-resolution digital elevation model DEM contributed significantly to progress in the geological and geomorphological research.
Źródło:
Annales Societatis Geologorum Poloniae; 2023, 93, 2; 103--136
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Climate-driven diversity changes of Mediterranean echinoids over the last 6 Ma
Autorzy:
Borghi, E.
Garilli, V.
Powiązania:
https://bibliotekanauki.pl/articles/31341352.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
Echinoidea
biodiversity
biogeography
paleoclimate
Miocene
salinity crisis
Late Cenozoic
climate change
Mediterranean area
echinoid
Źródło:
Acta Palaeontologica Polonica; 2022, 67, 4; 781-805
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Miocene fluvial distributary system in the northern Danube Basin (Pannonian Basin System): depositional processes, stratigraphic architecture and controlling factors of the Piešťany Member (Volkovce Formation)
Autorzy:
Šujan, M.
Kováč, M.
Hók, J.
Braucher, R.
Rybár, S.
Leeuw, A. de
Powiązania:
https://bibliotekanauki.pl/articles/2060598.pdf
Data publikacji:
2017
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
fluvial distributary system
facies analysis
sediment supply
accommodation
Pannonian Basin System
late Miocene
Opis:
Aim of the study was to investigate the detailed stratigraphic architecture of the alluvial Volkovce Formation, which was deposited in the northern Danube Basin during the interval between 10 and 6 Ma. Two type locality exposures were subject to facies analysis and interpretation of depositional processes and >500 boreholes served for correlation of spatial variability in the character of the formation. The study was focused on the northern Blatné and western Rišňovce depressions, which are partly separated by the Považský Inovec Mountains horst. It was revealed, that a mostly gravelly fluvial distributary system of the Piešťany Member was deposited in the northern Blatné depression, partly confined by the exposed horst and by incised palaeotopography. The sequence is composed of amalgamated braided river channel bodies with no overbank strata, in response to high sediment supply and low accommodation. The palaeo-stream then crossed the horst in its southern part towards the Rišňovce depression, where there was four times more accommodation. The submerged horst acted as a boundary, where the depositional processes changed to a meandering river and significant overbank deposits started to be preserved. Only small streams were present in the northern Rišňovce depression, which led to very low sediment supply compared to the high accommodation there. The depositional system was affected mainly by the incised palaeotopography, by the location of sediment input together with spatial differences in accommodation rate caused by the activity of the Ripňany Fault on the southeastern side of the Považský Inovec Mts.
Źródło:
Geological Quarterly; 2017, 61, 3; 521--548
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new stratigraphic position of some Early Pleistocene deposits in central Poland
Autorzy:
Bujak, Ł.
Woronko, B.
Winter, H.
Marcinkowski, B.
Werner, T.
Stachowicz-Rybka, R.
Żarski, M.
Woźniak, P. P.
Rosowiecka, O.
Powiązania:
https://bibliotekanauki.pl/articles/2060173.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Late Miocene
Early Pliocene
Early Pleistocene
pollen analysis
palaeomagnetism
mineralogy
Central Poland
Opis:
A new borehole in Rożce (SW Mazovian Lowland) drilled in 2012, combined with a wide variety of research methods (palaeomagnetism, palynological analysis, studies of plant macroremains and textural features of deposits) shed new light on the age and stratigraphic position of the Early Pleistocene deposits, formerly assigned as the Lower Pleistocene. The study focuses on the deposits from 50.7-104.0 m depth, between glacial till of the Nidanian Glaciation (ca. 0.9 Ma) and the Poznań Clays (ca. 5.322 Ma). The deposits situated directly underneath the till (50.7-60.2 m) are related to the Nidanian Glaciation and show a reversed polarity and correlate with the end of the Matuyama Epoch. The deposits from 60.2-104.0 m depth were accumulated during the Early Pliocene, i.e. approximately 5.332-4.6 million years ago. They appear to correlate with the middle part of the Gilbert Palaeomagnetic Epoch and thus they are considerably older than previously thought. The cored section indicates a stratigraphic gap of about 3.5 Ma from the Lower Pliocene to the first advance of the Scandinavian ice sheets into Poland, which are thought to have occurred in the early Middle Pleistocene. The analysed deposits accumulated under variable climatic conditions showing two periods with significant aridity alternated with two periods of increased humidity. Deposits of the arid periods contain no pollen, butaeolian sand quartz grains are found. During periods of more humid climate the area was covered by various types of mixed forest.
Źródło:
Geological Quarterly; 2016, 60, 1; 238--251
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Miocene potamarchine rodents from southwestern Amazonia, Brazil - with description of new taxa
Autorzy:
Kerber, L.
Negri, F.R.
Ribeiro, A.M.
Vucetich, M.G.
De Souza-Filho, J.P.
Powiązania:
https://bibliotekanauki.pl/articles/20829.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Late Miocene
Miocene
potamarchine rodent
Mammalia
Rodentia
Caviomorpha
Neogene
Solimoes Formation
rodent
Amazonia
Brazil
Opis:
The fossil rodents from the southwestern Amazonia of Brazil have been studied since the first half of the 20th century. Several caviomorph rodents were reported for the Neogene of this region, mainly neoepiblemids and dinomyids. Until recently, the record of dinomyids in the Solimões Formation (Late Miocene) was predominantly based on a few isolated teeth, which made it difficult to make more accurate taxonomic identifications due to the scarcity of diagnostic characters. Here, new remains, more complete than those previously reported, of potamarchine dinomyids from the Neogene of Brazil are described. A new species of Potamarchus and a new genus and species of a Potamarchinae are erected. In addition, new material of Potamarchus murinus and Potamarchus sp. is identified. These data suggest a higher diversity of dinomyids in in the western Amazonia than previously supposed.
Źródło:
Acta Palaeontologica Polonica; 2016, 61, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Miocene bovids from Serefkoy-2 (SW Turkey) and their position within the sub-Paratethyan biogeographic province
Autorzy:
Kostopoulos, D.S.
Karakutuk, S.
Powiązania:
https://bibliotekanauki.pl/articles/945611.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Late Miocene
Miocene
Bovidae
biogeography
Mammalia
Antilopinae
Turolian
Turkey [geogr.]
Anatolia region
Opis:
We describe new fossil bovid craniodental remains from the Upper Miocene fossil site of Şerefköy-2, Yatağan Basin, SW Turkey. The new material belongs to six species: Gazella cf. G. capricornis, Palaeoryx pallasi, Sporadotragus parvidens, Skoufotragus cf. Sk. schlosseri, Urmiatherium rugosifrons, and ?Sinotragus sp., which together indicate a latest middle–early Late Turolian (Late Miocene) age. Medium-to-large bovid taxa prevail over small ones, and protoryxoid bovids clearly dominate the assemblage. An analysis of the taxonomic structure, size and diet spectra of several Turolian bovid assemblages from Greece and Turkey reveals Şerefköy-2 to be a member of a mammalian palaeocommunity particular to southwestern Anatolia, which in turn forms part of the sub-Paratethyan biogeographic province.
Źródło:
Acta Palaeontologica Polonica; 2015, 60, 1; 49-66
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Miocene capybaras from Argentina: Skull anatomy, taxonomy, evolution, and biochronology
Autorzy:
Vucetich, M.G.
Deschamps, C.M.
Vieytes, E.C.
Montalvo, C.I.
Powiązania:
https://bibliotekanauki.pl/articles/945889.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
Miocene
Late Miocene
capybara
mammalia
Rodentia
Cavioidea
Hydrochoerinae
Argentina
skull
anatomy
taxonomy
evolution
biochronology
morphometry
biostratigraphy
Opis:
Fossil capybaras are morphologically extremely varied, but previous studies have disagreed on whether this diversity reflects intraspecific variation or the existence of multiple species. Here, we review the capybaras from the classic Argentinian Late Miocene localities of Paraná River cliffs (“conglomerado osífero” of the Ituzaingó Formation, Entre Ríos), and Chillhué and Guatraché shallow lakes (Cerro Azul Formation, La Pampa), and perform a morphometric analysis of their upper cheek teeth and the posterior portion of the rostrum. Our results confirm that all of the specimens from the “conglomerado osífero” belong to the single species Cardiatherium paranense. In addition, we refer a specimen from Tupungato (Río de los Pozos Formation, Mendoza) to C. paranense, thus expanding its geographical range. The material from La Pampa represents a different taxon, and is here preliminary referred to Cardiatherium aff. orientalis. Our systematic interpretation of Late Miocene capybaras suggests that the early radiation of this group was not as explosive as previously thought, and was likely constrained by the early acquisition of large size, increasing complexity of the cheek teeth, and probably semi-aquatic habits.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 3; 517-535
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Tortonian bryozoans from Mut Basin, Central Anatolian Plateau, southern Turkey
Autorzy:
Zagorsek, K.
Gordon, D.P.
Powiązania:
https://bibliotekanauki.pl/articles/21300.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Late Tortonian
Tortonian
bryozoan
Mut Basin
Central Anatolian Plateau
Turkey [geogr.]
Bryozoa
Cheilostomata
Basyaylella
Ostrovskia
Eocene
Miocene
Opis:
Sixteen bryozoan species have been identified in the Başyayla section, Mut Basin, southern Turkey. Five of these species are described here, including two new to science representing new genera: Basyaylella elsae gen. et sp. nov. and Ostrovskia triforamina gen. et sp. nov. The other three described species (Exidmonea sp., Biflustra savartii, and Margaretta sp.) show unusual features that have not been reported previously. Based on bryozoan data, the Başyayla sequence represents a tropical to subtropical, normal marine environment, with seafloor composed of fine sedimentary particles in a low−energy setting.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anisodontherium from the Late Miocene of north-western Argentina
Autorzy:
Brandoni, D.
Powell, J.E.
Gonzales, O.E.
Powiązania:
https://bibliotekanauki.pl/articles/20115.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Anisodontherium
Late Miocene
Miocene
paleontology
Argentina
Xenarthra
Megatheriinae
ground sloth
diversity
Upper Miocene
Opis:
The fossil record of Megatheriinae (Tardigrada, Megatheriidae) in Argentina extends from the Colloncuran (Middle Miocene of Patagonia) to the Lujanian (Late Pleistocene–Early Holocene of the Pampean region). In the Late Miocene of north−western Argentina, Megatheriinae is represented by just three species belonging to a single genus, Pyramiodontherium. Here, we describe a partial mandible and the phalanges of a third digit of the manus recovered from the Saladillo Formation (Upper Miocene) of Tucumán Province, and assign them to Anisodontherium sp. Anisodontherium is primarily characterized by mesiodistally compressed molariforms, an anterior margin of the coronoid process located posterior to m4, and a posterior margin of the mandibular symphysis located anterior to m1. While these features can also be observed in A. halmyronomum from the Arroyo Chasicó Formation (Buenos Aires Province, Pampean region), Anisodontherium sp. is smaller and more slender than the former. The shape of each molariform of Anisodontherium affects the total length of the molariform tooth row, and thus the interpretation of some characters used in cladistic and paleobiological analyses. The material described here adds to the knowledge of the mandibular and dental anatomy of early megatheriines. In addition, the occurrence of Anisodotherium in Tucumán Province provides the first record of this genus outside the Pampean region, and increases the diversity of megatheriines during the Late Miocene–Pliocene of north−western Argentina.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neogene karst sinkhole and its deposits from Górażdże Quarry, Upper Silesia : archive for palaeoenvironmental reconstructions
Autorzy:
Szulc, J.
Worobiec, E.
Powiązania:
https://bibliotekanauki.pl/articles/191351.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
palaeokarst
sinkhole deposits
palynology
Late Miocene
Upper Silesia
Opis:
A sinkhole, developed in Middle Triassic limestones and filled with clastic and organic deposits, including lignite, was studied, in terms of its origin and age. The sinkhole represents a solution sinkhole, which originated through the subsidence of surficial deposits into an underlying cave system. The study permitted the recognition of three main stages of sinkhole evolution. During the initial stage, subterranean and surface karstification proceeded concurrently. As a result, a terra rossa cover developed at the surface and a cavern system was formed in the underlying bedrocks. During the second phase, both systems became connected and the soil cover subsided. This, in turn, involved the formation of a depression at the land surface and ponding of the drainage water. The pond was filled with plant debris, later giving rise to lignite formation. During the third and final stage, the sinkhole was filled with quartz sands with kaolinite, derived from eroded, Upper Cretaceous sandstones and marls. Results of pollen analysis from the sinkhole indicate the presence of mesophytic forests and show a significant role of riparian forests and herbaceous vegetation. The occurrence of abundant, freshwater algae and the pollen of aquatic plants evidences sedimentation of the infill in a water body (pond). The apparent dominance of arctotertiary and cosmopolitan, palaeofloristical elements, as well as the occurrence of only sparse, palaeotropical elements (mainly subtropical), indicate a warm-temperate climate (cooler than during the Early and Middle Miocene period). A comparison of the sporomorph association from the sinkhole with those from other Neogene sites provides evidence of its Late Miocene age (Late Pannonian–Early Pontian).
Źródło:
Annales Societatis Geologorum Poloniae; 2012, 82, 4; 371--385
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sexual dimorphism in perissodactyl rhinocerotid Chilotherium wimani from the Late Miocene of the Linxia Basin (Gansu, China)
Autorzy:
Chen, S.
Deng, T.
Hou, S.
Shi, Q.
Pang, L.
Powiązania:
https://bibliotekanauki.pl/articles/23414.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
sexual dimorphism
perissodactyl rhinocerotid
Mammalia
Perissodactyla
Chilotherium wimani
Late Miocene
Miocene
Linxia basin
China
Opis:
Sexual dimorphism is reviewed and described in adult skulls of Chilotherium wimani from the Linxia Basin. Via the analysis and comparison, several very significant sexually dimorphic features are recognized. Tusks (i2), symphysis and occipital surface are larger in males. Sexual dimorphism in the mandible is significant. The anterior mandibular morphology is more sexually dimorphic than the posterior part. The most clearly dimorphic character is i2 length, and this is consistent with intrasexual competition where males invest large amounts of energy jousting with each other. The molar length, the height and the area of the occipital surface are correlated with body mass, and body mass sexual dimorphism is compared. Society behavior and paleoecology of C. wimani are different from most extinct or extant rhinos. M/F ratio indicates that the mortality of young males is higher than females. According to the suite of dimorphic features of the skull of C. wimani, the tentative sex discriminant functions are set up in order to identify the gender of the skulls.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stratigraphic evidence of a Late Maeotian (Late Miocene) punctuated transgression in the Tanais Palaeobay (northern part of the Eastern Paratethys, South-West Russia)
Autorzy:
Ruban, Dmitry A.
Powiązania:
https://bibliotekanauki.pl/articles/94470.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
Late Miocene
Late Maeotian
Eastern Paratethys
transgression
bivalves
późny miocen
późny Maeotian
transgresja
małże
Opis:
The Tanais Palaeobay was located in the northern periphery of the eastern Paratethys Sea during the Late Miocene. New data from the Safianovo section (Rostov Dome, South-West of Russia) confirm that skeletal limestones (coquinites) of the Merzhanovskaja Formation belong to the Congeria (Andrusoviconcha) amygdaloides navicula Zone of the upper Upper Maeotian (the Maeotian is a regional chronostratigraphic unit of the Upper Miocene). Correlation of reference sections of these Upper Maeotian deposits within the Rostov Dome results in pattern of the palaeobay transgression, which was punctuated. The relative importance of local and global controls on this trangsression is not yet clear.
Źródło:
Geologos; 2010, 16, 3; 169-181
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biostratygrafia mikropaleontologiczna utworów kredy górnej i miocenu w wierceniu "Bibice" (okolice Krakowa)
Micropaleontological biostratigraphy of the Upper Cretaceous and Miocene deposits in "Bibice" borehole (Kraków area)
Autorzy:
Zapałowicz-Bilan, B.
Pilarz, M.
Machaniec, E.
Powiązania:
https://bibliotekanauki.pl/articles/183417.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
biostratygrafia
mikropaleontologia
kreda późna
miocen
okolice Krakowa
biostratigraphy
micropaleontology
Late Cretaceous
Miocene
Kraków area
Opis:
Lower Campanian marls and marly opokas with cherts ("Bibice" borehole, Kraków vicinity) are rich in benthic forams (mainly Stensioeina and Gavelinella species) and rare planktic ones (Hedbergella). The overlying Miocene deposits (Kłodnik and Skawina beds), are developed as conglomerates (equivalent of fresh-water marls in Krakow region) which are completely devoid of microfossils, but younger clays are full of the Badenian forams.
Źródło:
Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie; 2009, 35, 2/1; 95-103
0138-0974
Pojawia się w:
Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neogene radiolarian biostratigraphy and faunal evolution rates in the eastern equatorial Pacific ODP Sites 845 and 1241
Autorzy:
Kamikuri, S.-I.
Motoyama, I.
Nishi, H.
Iwai, M.
Powiązania:
https://bibliotekanauki.pl/articles/21655.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Neogene
Radiolaria
biostratigraphy
fauna
evolution rate
Pacific Ocean
Late Miocene
Miocene
Middle Miocene
paleontology
microfossil
Opis:
Radiolarians from Sites 845 and 1241 in the eastern equatorial Pacific were examined in order to evaluate the role of paleoceanographic perturbations upon the general faunal evolutionary pattern of tropical planktonic organisms during the last 17 Ma. Radiolarian appearance and extinction rates indicate no periods of mass extinctions during the past 17 Ma. However, a relatively rapid replacement of the species in the radiolarian assemblages occurs near the middle–late Miocene boundary. This replacement event represents the gradual extinction of a number of radiolarian species and their gradual replacement by evolving new species. The modern equatorial circulation system was formed near the middle–late Miocene boundary due to the closure of the Indonesian seaway. The minor faunal turnover appears to be associated with the formation of the modern equatorial circulation system near the middle–late Miocene boundary. Diatom assemblages in the equatorial Pacific became more provincial in character after about 9 Ma. The appearance and extinction rates of planktic foraminifers were relatively high near the middle–late Miocene boundary, and those of calcareous nannoplankton reached high values in the early late Miocene in the equatorial Pacific Ocean. Thus, faunal evolution from the middle Miocene type to late Miocene types occurred first, being followed by floral evolution. The middle–late Miocene boundary is not a sharp boundary for planktonic microfossils, but marks a time of transition critical for faunal and floral evolution in both siliceous and calcareous microfossil assemblages in the equatorial Pacific Ocean.
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neogene radiolarian biostratigraphy and faunal evolution rates in the easternequatorial Pacific ODP Sites 845 and 1241
Autorzy:
Kamikuri, S.-I.
Motoyama, I.
Nishi, H.
Iwai, M.
Powiązania:
https://bibliotekanauki.pl/articles/945913.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
radiolaria
biostratigraphy
faunal evolution
middle–late miocene boundary
eastern equatorial pacific
Opis:
Radiolarians from Sites 845 and 1241 in the eastern equatorial Pacific were examined in order to evaluate the role of paleoceanographic perturbations upon the general faunal evolutionary pattern of tropical planktonic organisms during the last 17 Ma. Radiolarian appearance and extinction rates indicate no periods of mass extinctions during the past 17 Ma. However, a relatively rapid replacement of the species in the radiolarian assemblages occurs near the middle–late Miocene boundary. This replacement event represents the gradual extinction of a number of radiolarian species and their gradual replacement by evolving new species. The modern equatorial circulation system was formed near the middle–late Miocene boundary due to the closure of the Indonesian seaway. The minor faunal turnover appears to be associated with the formation of the modern equatorial circulation system near the middle–late Miocene boundary. Diatom assemblages in the equatorial Pacific became more provincial in character after about 9 Ma. The appearance and extinction rates of planktic foraminifers were relatively high near the middle–late Miocene boundary, and those of calcareous nannoplankton reached high values in the early late Miocene in the equatorial Pacific Ocean. Thus, faunal evolution from the middle Miocene type to late Miocene types occurred first, being followed by floral evolution. The middle–late Miocene boundary is not a sharp boundary for planktonic microfossils, but marks a time of transition critical for faunal and floral evolution in both siliceous and calcareous microfossil assemblages in the equatorial Pacific Ocean.
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł

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