Integrated stratigraphy and palaeoecology of the Lower and Middle Miocene of the Porcupine Basin

2007 ◽  
Vol 145 (3) ◽  
pp. 321-344 ◽  
Author(s):  
STEPHEN LOUWYE ◽  
ANNELEEN FOUBERT ◽  
KENNETH MERTENS ◽  
DAVID VAN ROOIJ ◽  
Keyword(s):  
Continental Margin ◽  
Middle Miocene ◽  
Middle Pleistocene ◽  
Carbonate Mounds ◽  
Dinoflagellate Cyst ◽  
Early Neogene ◽  
Porcupine Basin ◽  
Oceanic Species ◽  
Cooling Phase ◽  
Erosional Event

AbstractA high-resolution palynological analysis and a detailed palaeomagnetic study of a marine sequence recovered during IODP Expedition Leg 307 in the Porcupine Basin southwest of Ireland provide new insights into the regional depositional history and palaeoenvironmental evolution during Early Neogene times. The Hole 1318B studied was drilled on the upper slope of the continental margin in a water depth of 409 m, upslope from a province of carbonate mounds (the Belgica mound province). The diverse and well-preserved dinoflagellate cyst associations consist typically of deep neritic and oceanic species, mixed with a neritic component transported from the shelf, reflecting the deep depositional setting at the continental margin. The palaeomagnetic record together with the ranges of key dinoflagellate cyst species constrain the age of the studied sequence between 16.7 Ma and 12.01 Ma, that is, between the late Burdigalian and late Serravallian. The distinct unconformity terminating the Miocene sequence correlates to the global sequence boundary Ser4/Tor1 dated at 10.5 Ma, and represents, according to previous extensive seismic studies, a basin-wide erosional event. The overlying sediments are of Middle Pleistocene or younger age. Downslope from IODP Site 1318, carbonate mounds root on the erosional surface. The dinoflagellate cyst associations from the Porcupine Basin distinctly mirror the global cooling phase following the Middle Miocene Climatic Optimum. Cooling phase Mi3, a short-lived glaciation, is particularly well expressed and here dated at 13.6 Ma. The palynomorph record furthermore indicates a reduction of the productivity and an increase of oceanic oligotrophic species after 14 Ma, suggesting a reduction or perhaps even a shutdown of the upwelling.

scholarly journals Dinoflagellate cysts and acritarchs from the Miocene Zonderschot sands, northern Belgium: stratigraphic significance and correlation with contiguous areas

2001 ◽  
Vol 3 (1-2) ◽  
pp. 55-65 ◽  
Author(s):  
Stephen LOUWYE
Keyword(s):  
North Sea ◽  
Marine Environment ◽  
Middle Miocene ◽  
Type Locality ◽  
Early Miocene ◽  
Dinoflagellate Cysts ◽  
Shallow Marine ◽  
Dinoflagellate Cyst ◽  
Marine Realm ◽  
Oceanic Species

A palynological investigation of the Miocene Zonderschot Sands (Berchem Formation) from the type locality Zonderschot (northern Belgium) has revealed the presence of a diverse dinoflagellate cyst and acritarch association. The dinoflagellates reflect a shallow marine environment, although the oceanic species Nematosphaeropsis and Impagidinium are prominent in the association and indicate the presence of an oceanic influence. This can be explained only by the depositional area being located at the very southern margin of the relatively isolated North Sea Basin during a period of maximum landward extent of the marine realm. A precise biostratigraphical correlation of the Zonderschot Sands with the Antwerpen Sands (Berchem Formation) from the Antwerp area is established. Biostratigraphical evaluation of key dinoflagellate cyst species indicates a latest Burdigalian (latest Early Miocene) - (earliest?) Langhian (early Middle Miocene) age for the Zonderschot Sands.

Erosion and sedimentation in SE Tibet and Myanmar during the evolution of the Burmese continental margin from the Late Cretaceous to Early Neogene

2021 ◽  
Author(s):  
Peng Zhang ◽  
Lianfu Mei ◽  
Shao-Yong Jiang ◽  
Sihuang Xu ◽  
Raymond A. Donelick ◽  
...  
Keyword(s):  
Continental Margin ◽  
Late Cretaceous ◽  
Early Neogene ◽  
Se Tibet

Distinguishing tectonic versus climatic forcing on landscape evolution: An example from SE Tibetan Plateau

2020 ◽  
Vol 133 (1-2) ◽  
pp. 233-242 ◽  
Author(s):  
Fangbin Liu ◽  
Martin Danišík ◽  
Dewen Zheng ◽  
Kerry Gallagher ◽  
Junsheng Nie
Keyword(s):  
Tibetan Plateau ◽  
Middle Miocene ◽  
Asian Summer Monsoon ◽  
Late Eocene ◽  
Crustal Shortening ◽  
Lateral Extrusion ◽  
Granite Belt ◽  
Cooling Phase ◽  
Forcing Mechanisms ◽  
Exhumation History

Abstract Distinguishing climate from tectonic forcing in shaping the Earth’s surface has been a long-standing issue in the Earth sciences. Great debate exists regarding when and how the SE Tibetan Plateau achieved its current low-relief topography, and both lateral extrusion and lower crust flow have been proposed as the dominant mechanism. Reconstruction of the exhumation history of the SE Tibetan Plateau is key to understanding these formation processes and resolving the significance of different forcing mechanisms. Here we report zircon and apatite (U-Th)/He ages from steep transects across the Lincang granite belt of the SE Tibetan Plateau. Our results reveal a two-stage exhumation history during the Cenozoic with rapid cooling phases in the late Eocene and the middle Miocene. In the late Eocene, the climate was generally dry and there is plenty of evidence for increased extrusion and upper crustal shortening. We suggest tectonic processes are responsible for the first inferred cooling. In contrast, the Asian summer monsoon precipitation increased during the middle Miocene, and we posit the middle Miocene cooling phase records a phase of rapid river incision triggered by the intensified precipitation and associated fault movements. The results are consistent with recent paleo-altimetry work in this region suggesting that the present-day topography of the SE Tibetan Plateau had been largely constructed by the late Eocene. Together, these data suggest that extrusion and/or upper crustal shortening setup the first order topography of the SE Tibetan Plateau, which was then modified by climate-triggered fluvial incision and feedbacks initiated in the middle Miocene.

scholarly journals Re-study of some dinoflagellate cysts from the Oligocene and Miocene of Germany

1984 ◽  
Vol 3 (2) ◽  
pp. 73-94 ◽  
Author(s):  
William A. S. Sarjeant
Keyword(s):  
Middle Miocene ◽  
Type Material ◽  
New Combination ◽  
Late Oligocene ◽  
Dinoflagellate Cysts ◽  
Dinoflagellate Cyst ◽  
Northwest Germany ◽  
Senior Synonym ◽  
First Time

Abstract. The type material of six dinoflagellate cyst species from the Late Oligocene to Middle Miocene of northwest Germany, described originally by Gerlach (1961), is reillustrated and redescribed. It is shown to include representatives of nine species. Areosphaeridium (ex: Baltisphaeridium) pectiniforme is found to be a senior synonym of Areosphaeridium multicornutum Eaton. Systematophora placacantha is considered to be a senior synonym of Cleistosphaeridium (ex: Baltisphaeridium) panniforme (Gerlach). The new combination Rhynchodiniopsis tenuitabulata (Gerlarch) is proposed. Revised diagnoses for these three species and for Leptodinium membranigerum (Gerlach), Achomosphaera triangulata (Gerlach) and Lejeunecysta hyalina (Gerlach) are proposed. The morphology of a form described here for the first time, and tentatively attributed to Phthanoperidinium, is considered perhaps to imply a separate origin for the Phthanoperidiniaceae: for that reason familial, rather than tribal, rank is preferred for that group. The stratigraphical ranges of the nine species here recognised and of two others of Gerlach’s species redescribed in earlier papers are detailed; elimination of misattributed forms means that these ranges are shorter than the published literature suggests.

Shallow marine Lower and Middle Miocene deposits at the southern margin of the North Sea Basin (northern Belgium): dinoflagellate cyst biostratigraphy and depositional history

2000 ◽  
Vol 137 (4) ◽  
pp. 381-394 ◽  
Author(s):  
S. LOUWYE ◽  
J. DE CONINCK ◽  
J. VERNIERS
Keyword(s):  
North Sea ◽  
Depositional Environment ◽  
Middle Miocene ◽  
Depositional History ◽  
Shallow Marine ◽  
Dinoflagellate Cyst ◽  
Southern North Sea ◽  
The North ◽  
Southern Margin ◽  
The North Sea

Detailed dinoflagellate cyst analysis of the Lower–Middle Miocene Berchem Formation at the southernmost margin of the North Sea Basin (northern Belgium) allowed a precise biostratigraphical positioning and a reconstruction of the depositional history. The two lower members of the formation (Edegem Sands and decalcified Kiel Sands) are biostratigraphically regarded as one unit since no significant break within the dinocyst assemblages is observed. The base of this late (or latest) Aquitanian–Burdigalian unit coincides with sequence boundary Aq3/Bur1 as defined by Hardenbol and others, in work published in 1998. A hiatus at the Lower–Middle Miocene transition separates the upper member (the Antwerpen Sands) from the underlying member. The greater part of the Antwerpen Sands were deposited in a Langhian (latest Burdigalian?)–middle Serravallian interval. The base of this unit coincides with sequence boundary Bur5/Lan1. Biostratigraphical correlation points to a diachronous post-depositional decalcification within the formation since parts of the decalcified Kiel Sands can be correlated with parts of the calcareous fossil-bearing section, up to now interpreted as Antwerpen Sands. The dinoflagellate cyst assemblages are dominated by species with a inner neritic preference, although higher numbers of oceanic taxa in the upper part of the formation indicate incursions of oceanic watermasses into the confined depositional environment of the southern North Sea Basin.

scholarly journals Were late Gomphotheres (Plio-Pleistocene) of the Siwaliks at more Stress as Compared to early Gomphotheres (middle to late Miocene)?

2020 ◽  
Vol 7 (4) ◽  
pp. 117-130
Author(s):  
MUHAMMAD AMEEN ◽  
ABDUL MAJID KHAN ◽  
MUHAMMAD TAHIR WASEEM ◽  
RANA MANZOOR AHMAD ◽  
MUHAMMAD IMRAN ◽  
...  
Keyword(s):  
Late Miocene ◽  
Middle Miocene ◽  
Time Span ◽  
Middle Pleistocene ◽  
Faunal Turnover ◽  
Ecological Stress ◽  
Vegetational Change ◽  
Linear Enamel Hypoplasia ◽  
Ecological Changes ◽  
Aridity Indices

Gomphotheres existed in the Siwaliks from the middle Miocene (14.2Ma) to the middle Pleistocene (0.8Ma) and became extinct later on. In this paper, we tried to discuss the reasons of such extinction of gomphotheres in the lower Pleistocene time span by considering Linear Enamel Hypoplasia (LEH) among 114 isolated tooth samples to assess whether ecological changes correlate with the stress factor in gomphotheres. For this purpose, the Siwalik gomphotheres were divided into two Groups viz. early gomphotheres (middle Miocene to late Miocene) and late gomphotheres (Pliocene to middle Pleistocene). We presented the hypothesis, that as the gomphotheres are characterized by the brachydonty and relied on browsing for their feeding while inhabiting the semi forest land setting thus, expected to have higher stress in Plio-Pleistocene time span as vegetational change around ~6 Ma may have exerted stress on late gomphotheres. The results for the occurrence of frequency of LEH indicated severe ecological stress in late gomphotheres (33%). The significant differences were found (P < 0.05) among the early gomphotheres and late gomphotheres which can be correlated to the vegetational change from C3 to C4, higher aridity indices and intensified seasonality after the late Miocene vegetational shift which may have resulted in substantial faunal turnover, extinction and speciation. We assume that such palaeoecological changes forced a competition with more pronounced grazers like of family Elephantidae and Bovidae resulting in extinction of gomphotheres during the late Pleistocene in the Siwaliks of Pakistan.

scholarly journals A review of the lower and middle Miocene of northern Belgium

2020 ◽  
Vol 23 (3-4) ◽  
Author(s):  
STEPHEN LOUWYE ◽  
Jef DECKERS ◽  
JASPER VERHAEGEN ◽  
RIEKO ADRIAENS ◽  
Noël VANDENBERGHE
Keyword(s):  
Middle Miocene ◽  
National Commission ◽  
Geological Correlation ◽  
Dinoflagellate Cyst ◽  
Doctoral Research ◽  
Governmental Organizations ◽  
Roer Valley Graben ◽  
Subsurface Mapping

The stratigraphy, sedimentology and paleogeography of the lower and middle Miocene Berchem and Bolderberg Formations from northern Belgium have been extensively studied during the last decades, a.o. in the framework of doctoral research, as parts of subsurface mapping and interregional geological correlation initiatives by governmental organizations. The last formal stratigraphical revision on formation level, however, almost dates from two decades ago, notwithstanding the fact that a wealth of new data has become available. A compilation and assessment of the stratigraphical data of the lower and middle Miocene has been carried out and a refined stratigraphical framework—based on dinoflagellate cyst stratigraphy—is presented. Recommendations for the National Commission for Stratigraphy of Belgium are proposed. A new member, the Molenbeersel member, is proposed for the glauconite-bearing silts and fine sands in the upper part of the Bolderberg Formation in the Roer Valley Graben.

scholarly journals Late Cenozoic palaeogeography of the eastern North Sea Basin: climatic vs tectonic forcing of basin margin uplift and deltaic progradation

2002 ◽  
Vol 49 ◽  
pp. 145-170
Author(s):  
Mads Huuse
Keyword(s):  
North Sea ◽  
Middle Miocene ◽  
Late Eocene ◽  
Middle Pleistocene ◽  
Tectonic Events ◽  
Erosional Unloading ◽  
Southern Norway ◽  
Uplift And Erosion ◽  
Basin Margin ◽  
Passive Model

The late Eocene to middle Pleistocene development of the eastern North Sea Basin is described by a series of palaeogeographic maps. The maps are based on published information integrated with recent investigations of seismic and well data from the eastern North Sea. The maps provide overviews of the basin geometry at late Eocene, late Oligocene, middle Miocene, late Miocene, late Pliocene and middle Pleistocene time. In post-Eocene time, the eastern and central North Sea Basin was progressively filled by large deltas, which built out from the eastern basin margin. These deltas were fed by ancient rivers from southern Norway (late Paleocene-Oligocene and Pliocene), southern Norway and Sweden (early Miocene), the Baltic region (middle Miocene-early Pleistocene), and finally by rivers flowing northward through the northwest European lowland (middle Pleistocene). It is argued that the Cenozoic evolution of the eastern North Sea Basin may be explained by a ‘self-perpetuating’ passive model. This model involves isostatic uplift of source areas due to erosional unloading of a relief generated by early Palaeogene uplift. The erosional unloading accelerated at the Eocene/Oligocene transition, in the middle Miocene and in the Plio-Pleistocene corresponding to periods of global climatic cooling and long-term eustatic lowering as indicated by δ18O records. The passive model diminishes the need for hypothetical Neogene tectonic events, although the influence of tectonic events cannot be excluded. Previous estimates of Neogene uplift and erosion of the northeastern Danish North Sea of the order of 500–1000 m do not agree with seismic geometries or with the regional palaeogeographic development. This indicates that previous estimates of Neogene uplift and erosion of the northeastern Danish North Sea may be several hundred metres too high.

scholarly journals Foraminiferal biostratigraphy of the post mid-Miocene in two boreholes in the Danish North Sea

1995 ◽  
Vol 12 ◽  
pp. 101-111
Author(s):  
Peter B Konradi
Keyword(s):  
North Sea ◽  
Water Depth ◽  
Middle Miocene ◽  
Middle Pleistocene ◽  
Northwestern Part ◽  
Stratigraphic Subdivision ◽  
Central Trough ◽  
The Subject ◽  
Depth Zonation ◽  
Foraminiferal Biostratigraphy

Cutting samples from two exploration wells, Cleo-1 and Kim-1, in the Central Trough area in the northwestern part of the Danish North Sea, have been investigated for foraminiferal content in the section above the prominent mid-Miocene event. Benthonic foraminifera have been used to produce a stratigraphic subdivision by reference to the standard NSB zonation of King. The NSB 12 to NSB 17 zones (Middle Miocene to Middle Pleistocene) have been identified above the event. These zones can be related to the paleo water depth zonation. Paleoenvironrnental reconstruction shows that sediments from the subject interval from Cleo-1 were deposited in a shallower situation than equivalent deposits in Kim-1. A conspicuous hiatus is identified in Cleo-1 at the Pliocene-Pleistocene boundary.

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