The early magmatic chronology of Fuerteventura, Canary Islands

1986 ◽  
Vol 123 (3) ◽  
pp. 287-298 ◽  
Author(s):  
M. J. Le Bas ◽  
D. C. Rex ◽  
C. J. Stillman
Keyword(s):  
Canary Islands ◽  
Late Cretaceous ◽  
Middle Miocene ◽  
Early Miocene ◽  
Volcanic History ◽  
Early Tertiary ◽  
Ring Complex ◽  
High Level

AbstractEight new K-Ar determinations are presented which, together with field relations and previous studies, are used to construct a chronology of the volcanic build-up of Fuerteventura. The earliest island-building volcanics are late Cretaceous to early Tertiary alkaline basaltic volcaniclastic sediments, and these may be correlated with the early gabbro/pyroxenite intrusions which were probably subvolcanic to the early edifice. This was followed by a carbonatitic subvolcanic complex then by two later high-level gabbro/pyroxenite plutons, the latter being early Miocene or older. The emplacement of a subsequent middle Miocene gabbro/syenite ring complex caused widespread resetting of the Ar contents of the earlier rocks, but nevertheless consideration of the mineralogy of the rocks in conjunction with the field relations enables the long volcanic history (c. 80 Ma) to be reconstructed.

scholarly journals Geomorphological observations on Sermersôq. A contribution to the geomorphology of S. Greenland

1965 ◽  
Vol 62 ◽  
pp. 1-41
Author(s):  
O.I Soen
Keyword(s):  
Late Cretaceous ◽  
Vertical Movements ◽  
The Third ◽  
Base Level ◽  
Early Tertiary ◽  
Glacial Stage ◽  
High Level ◽  
Mountain Glaciation ◽  
Erosion Surface ◽  
Coastal Platform

On the island of Sermersôq four erosion surfaces have been recognized, which are of regional importance in S Greenland. Their development is related to three cycles of erosion, interrupted by two glacial stages. The high-level erosion surface at altitudes above 1000 m is the remnant of an old peneplane, which was formed during the oldest erosion cycle and uplifted in late Cretaceous or early Tertiary times. This uplift initiated a second erosion cycle in the course of which a main glacial stage intervened. In this glacial stage the icelevel in the main valleys (the present fjords) acted as the effective base level of erosion and this resulted in the formation of stretches of an intermediate-level erosion surface, which now occur along the main fjords at altitudes between 400 m and 650 m. An important lowering of effective base level of erosion occurred when in the subsequent interglacial stage the sea-level resumed its role as the effective base level of erosion. This event initiated a third erosion cycle in the course of which the low-level erosion surface, between 100 m and 250 m altitude, and the strandflat, a coastal platform below 50 m, were formed. The third erosion cycle was interrupted by a second glacial stage, which on Sermersôq has the localized character of a mountain glaciation; it is during this second glacial stage that the present day fretted upland morphology of central Sermersôq originated. Post-glacial vertical movements causing the emergence of the strandflat induced a rejuvenation of erosion and consequently the incision of this coastal platform and valley floors by recent rivers.

Rediscovery of Choroterpes atramentum in Costa Rica, type species of Tikuna new genus (Ephemeroptera: Leptophlebiidae: Atalophlebiinae), and its role in the "Great American Inter-change"

Zootaxa ◽  
2005 ◽  
Vol 932 (1) ◽  
pp. 1 ◽  
Author(s):  
HARRY M. SAVAGE ◽  
R. WILLS FLOWERS ◽  
WENDY PORRAS V.
Keyword(s):  
Costa Rica ◽  
Central America ◽  
Late Cretaceous ◽  
Type Species ◽  
New Genus ◽  
South American ◽  
Early Tertiary ◽  
Geological Formation

A new genus, Tikuna, is described based on recent collections of adults and nymphs of Choroterpes atramentum Traver from western Costa Rica. All recent collections are from streams on or near the Nicoya Complex, the oldest geological formation in Lower Central America. Tikuna belongs to a lineage of South American Atalophlebiinae (Leptophlebiidae: Ephemeroptera) whose origin is hypothesized to have been in the late Cretaceous–early Tertiary. Some implications of the distribution of Tikuna for theories on the origin of Costa Rica’s biota are discussed.

Foraminifera Biostratigraphy of Two Wells in Niger Delta

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Dairo VA
Keyword(s):  
Niger Delta ◽  
Middle Miocene ◽  
Early Miocene ◽  
Orbulina Universa ◽  
Exploratory Wells ◽  
Stratigraphic Range

Biostratigraphic studies of foraminifera were carried out on two exploratory wells drilled in the Eastern Niger Delta to establish the age, biozonation and paleoenvironment of the foraminifera present in the strata penetrated by the wells. A total of 80 ditch cutting samples retrieved at 60ft intervals from AX-1 and AX-2 Wells at the depth of 3,600ft to 6,000ft and 4,200ft to 6500ft. respectively were subjected to micropaleontological analysis which involves picking and identification of the foraminifera present. The resulting data were loaded into the Stratabug software and interpreted. The foraminifera recovered and identified from the two wells are made up of both benthic and planktic species. The marker species, whose stratigraphic range are well established were used to describe the biozonation and these includes Heterostegina sp, Catapsydrax stainforthi, Chiloguembelina victoriana, Orbulina universa/suturalis, Praeorbulina sicana,Buliminella subfusiformis, Nonion centrosulcatum, Catapsydrax dissimilis, Globigerinoides bisphericus and Globigerinoides sicanus. Four biozones of foraminifera made up of N8, N7-N8, N6-N7 and N5-N6 were recognised based on the zonation scheme of Grandstein; with their stratigraphic age ranging from early Miocene to middle Miocene. Furthermore, the environment of deposition prevailing in the Formations penetrated by the two wells are predominantly middle neritic with similarity in their ages as observed from the correlation of the biozones from the two wells

Middle Miocene recovery of Caribbean reef corals: New data from the Tamana Formation, Trinidad

2001 ◽  
Vol 75 (3) ◽  
pp. 513-526 ◽  
Author(s):  
Kenneth G. Johnson
Keyword(s):  
Middle Miocene ◽  
New Records ◽  
Early Miocene ◽  
Early Pleistocene ◽  
Reef Corals ◽  
Rigorous Description ◽  
Caribbean Coral Reef ◽  
The Caribbean ◽  
Stratigraphic Ranges ◽  
Biotic Change

Caribbean coral reef communities were restructured by episodes of accelerated biotic change during the late Oligocene/early Miocene and the late Pliocene/early Pleistocene. However, rigorous description of the effects of rapid biotic change is problematic because preservation and exposure of coral-bearing deposits is not consistent in all stratigraphic intervals. In the Caribbean, early and middle Miocene exposures are more rare than late Miocene and Pliocene exposures. One exception is the late early to early middle Miocene Tamana Formation of Trinidad, and old and new collections from this unit were studied to determine the timing of recovery after the Oligocene/Miocene transition. A total of 41 species of zooxanthellate corals were recovered from the unit, including 21 new records. Within these assemblages, species first occurrences outnumber species last occurrences by a factor of four (31 first occurrences and eight last occurrences). The extension of the stratigraphic ranges of species previously first recorded in Pliocene sediments has reduced an apparent Pliocene pulse of origination, indicating that the Pliocene/Pleistocene transition was largely a result of accelerated extinction against a background of near-constant origination. The fact that few species last occur in the Tamana fauna indicates that the Oligocene/Miocene transition was complete by the end of the early Miocene.

Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, North Cascade Range, Washington and British Columbia

1991 ◽  
Vol 103 (10) ◽  
pp. 1297-1307 ◽  
Author(s):  
RALPH A. HAUGERUD ◽  
PETER VAN DER HEYDEN ◽  
ROWLAND W. TABOR ◽  
JOHN S. STACEY ◽  
ROBERT E. ZARTMAN
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Cascade Range ◽  
Gneiss Complex ◽  
Early Tertiary

Roof modification of a high level granite, Jos-Bukuru Younger Granite Ring Complex, Nigeria

1974 ◽  
Vol 111 (1) ◽  
pp. 43-47 ◽  
Author(s):  
P. K. Webb
Keyword(s):  
Mineral Assemblage ◽  
Intrusive Body ◽  
Jos Plateau ◽  
Ring Complex ◽  
High Level

SummaryThe Rayfield-Gona granite of the Jos Plateau, Nigeria, formerly regarded as an independent intrusive body, is now thought to be a roof facies of the Ngell granite. This explains several phenomena, such as the gradational contact between the two, and the distinctive mineral assemblage of the former.

scholarly journals Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt

GeoArabia ◽  
2003 ◽  
Vol 8 (1) ◽  
pp. 91-124 ◽  
Author(s):  
Adel R Moustafa ◽  
Ati Saoudi ◽  
Alaa Moubasher ◽  
Ibrahim M Ibrahim ◽  
Hesham Molokhia ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Tectonic Evolution ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Western Desert ◽  
Normal Faults ◽  
Surface Mapping ◽  
Early Mesozoic ◽  
Hydrocarbon Fields ◽  
Stable Area

ABSTRACT An integrated surface mapping and subsurface study of the Bahariya Depression aided the regional subsurface interpretation. It indicated that four major ENE-oriented structural belts overlie deep-seated faults in this part of the ‘tectonically stable’ area of Egypt. The rocks of the Bahariya area were deformed in the Late Cretaceous, post-Middle Eocene, and Middle Miocene-and subsurface data indicated an early Mesozoic phase of normal faulting. The Late Cretaceous and post-Middle Eocene deformations reactivated the early normal faults by oblique slip and formed a large swell in the Bahariya region. The crest was continuously eroded whereas its peripheries were onlapped by Maastrichtian and Tertiary sediments. The tectonic evolution of the Bahariya region shows great similarity to the deformation of the ‘tectonically unstable’ area of the northern Western Desert where several hydrocarbon fields have been discovered. This similarity may indicate that the same phases of deformation could extend to other basins lying in the ‘tectonically stable’ area, such as the Asyut, Dakhla, Nuqura, and El Misaha basins.

scholarly journals A mid-miocene age for the Slanci formation near Belgrade (Serbia), based on a record of the primitive antelope Eotragus cf. Clavatus from Visnjica

2007 ◽  
pp. 53-59
Author(s):  
der van ◽  
Slobodan Knezevic ◽  
Ivan Stefanovic
Keyword(s):  
Middle Miocene ◽  
Lacustrine Sediments ◽  
Early Miocene

In a borhole at Veliko Selo near Belgrade in the Miocene lacustrine sediments Slanci, which are locally known as the Slanacka Serija, a mammal tooth was found. The age of these deposits is under discussion. The fossil is here described and attributed with a query to the primitive antelope Eotragus clavatus (GERVAIS, 1850), which is suggestive of a Early Serravallian ("upper Badenian") or Early Middle Miocene age for these deposits, whereas an Aquitalian or Eggenburgian ("Egerian" or "Eggenburgian") (Early Miocene) age can be ruled out.

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