scholarly journals Gradual Morphological Evolution in a Late Cretaceous Lineage of Planktonic Foraminifera

1996 ◽  
Vol 8 ◽  
pp. 225-225
Author(s):  
Michal Kucera ◽  
Björn. A. Malmgren
Keyword(s):  
Late Cretaceous ◽  
Morphological Evolution ◽  
Planktonic Foraminifera

Differences between evolution of mean form and evolution of new morphotypes: an example from Late Cretaceous planktonic foraminifera

Paleobiology ◽  
1998 ◽  
Vol 24 (1) ◽  
pp. 49-63 ◽  
Author(s):  
Michal Kucera ◽  
Björn A. Malmgren
Keyword(s):  
Natural Selection ◽  
Late Cretaceous ◽  
Gradual Increase ◽  
Accumulation Rate ◽  
Morphological Evolution ◽  
Rapid Development ◽  
Planktonic Foraminifera ◽  
Shell Morphology ◽  
Gradual Change ◽  
Change In Mean

Morphological evolution in the Late Cretaceous (Maastrichtian) Contusotruncana lineage of planktonic foraminifera was studied at DSDP Sites 525 (South Atlantic) and 384 (North Atlantic). A multivariable approach was used to separate aspects of form controlled by geographical variation (size, spiral roundness of the test, percentage of kummerform specimens) from those due to changes that occurred simultaneously in geographically distant populations of the lineage (shell conicity, number of chambers in the last whorl).A gradual increase in mean shell conicity was observed over the last 3 million years of the Cretaceous. It arose from the combination of a rapid development of highly conical shells after 68.5 Ma and a long-term trend of progressive disappearance of the ancestral morphotype. Therefore, despite the gradual change in “mean form,” the morphological evolution in the Contusotruncana lineage differs from the classical image of phyletic gradualism. The gradual increase in mean shell conicity in the lineage was accompanied by a remarkable decrease in its absolute abundance (shell accumulation rate), suggesting that the changes in shell morphology might not have been neutral with respect to natural selection. Apparently, gradual change in “mean form” of fossil lineages does not require an equally gradual development of morphological novelties. It may be caused by natural selection operating on a constant range of variation in populations living in environments without geographical barriers.

The crucial boundaries in the development of the late cretaceous biota of plankton foraminifers in the southern part of the Indian ocean

2019 ◽  
Vol 59 (6) ◽  
pp. 1074-1085
Author(s):  
E. A. Sokolova
Keyword(s):  
Indian Ocean ◽  
Species Composition ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Planktonic Foraminifera ◽  
The Indian Ocean ◽  
Systematic Composition ◽  
Climatic Series

The article analyzes own data on the species composition of shells of planktonic foraminifera from the Upper Cretaceous sediments of the Indian Oceans, as well as from the sections of the offshore seas of Australia. The species of planktonic foraminifera are grouped and arranged in a climatic series. An analysis of the change in the systematic composition of foraminifers made it possible to distinguish periods of extreme and intermediate climatic states in the Late Cretaceous.

The Ecological Balance of Nature: Identifying Stasis and Growth in Late Cretaceous Planktonic Foraminifera from ODP Hole 690C (Weddell Sea)

2020 ◽  
Vol 50 (3) ◽  
pp. 313-317
Author(s):  
Martin A. Buzas ◽  
Lee-Ann C. Hayek ◽  
Brian T. Huber
Keyword(s):  
Species Richness ◽  
Late Cretaceous ◽  
Planktonic Foraminifera ◽  
Sampling Time ◽  
Weddell Sea ◽  
Species Evenness ◽  
Data Set ◽  
Balance Of Nature ◽  
Ecological Balance ◽  
Do So

ABSTRACT The ecological balance of nature is defined as an equilibrium between species richness (S) and species evenness (E) such that diversity (H) remains constant with time. Based on this definition, our approach identifies growth or decline in communities as perturbations from stasis and has successfully done so for benthic foraminiferal communities. Here, we examine whether this approach is appropriate for planktonic foraminifera. To do so, we utilized planktonic foraminiferal counts (39 samples, 66% recovery) from Maastrichtian sediments in the Weddell Sea from ODP Hole 690C. A total of 24 species were observed and both >63-µm and >150-µm fractions were counted. In the >63-µm fraction, nine communities were recognized while in the >150-µm fraction, there were 12. In both fractions at 70.45 Ma, a boundary was recognized and immediately after this boundary, a community in growth was identified. A trend of increasing diversity upcore was substantiated by regression on individual samples. For our purposes, the >150-µm fraction in this data set is sufficient to recognize community trends. The >150-µm fraction in Hole 690C has 82% of the sampling time in stasis and an average time per community is 0.85 Ma. The >63-µm fraction has 73% of the sampling time in stasis and an average time per community of 1.02 Ma.

scholarly journals New evidence on the origin of non-spinose pitted–cancellate species of the early Danian planktonic foraminifera

2013 ◽  
Vol 64 (3) ◽  
pp. 237-251 ◽  
Author(s):  
Ignacio Arenillas ◽  
Jose Antonio Arz
Keyword(s):  
Morphological Evolution ◽  
Planktonic Foraminifera ◽  
Middle Part ◽  
External Morphology ◽  
Evolutionary Trends ◽  
Test Size ◽  
Evolutionary Path ◽  
Origin And Evolution ◽  
Large Pore ◽  
New Evidence

Abstract Intermediate forms identified in some of the most continuous lower Danian sections allow a better understanding of the origin and evolution of pitted (Globanomalina) and cancellate (Praemurica) planktonic foraminifera. Both Globanomalina and Praemurica are part of a major Paleocene lineage, namely the “non-spinose lineage”, which started to diverge in the early Danian. Transitional specimens strongly suggest the evolution from Parvularugoglobigerina to Globanomalina, and then to Praemurica. These evolutionary turnovers were quite rapid (probably lasting less than 10 kyr), and seem to have begun in the time equivalent of the lower part of the E. simplicissima Subzone, namely the middle part of the standard Zone Pa. The initial evolutionary trends within this non-spinose lineage were the increase of test size and lip thickness, and the evolution from tiny pore-murals to large pore-pits, and from smooth to pitted and finally cancellate walls. Biostratigraphic data suggest that evolution of the wall texture preceded the morphological evolution within each genus. The oldest species of both Globanomalina and Praemurica, namely G. archeocompressa and Pr. taurica, initially retained the external morphology of the ancestral Parvularugoglobigerina eugubina. Since their divergence, Globanomalina and Praemurica followed a separate evolutionary path, evolving into morphologically different species.

Successive Paleocene and Eocene infillings of polyphase paleokarsts within the Cretaceous limestones of the Empordà thrust sheets (Catalan Pyrenees, Spain) : relationships between tectonics and karstification

2007 ◽  
Vol 178 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Bernard Peybernès ◽  
Marie-José Fondecave-Wallez ◽  
Pierre-Jean Combes ◽  
Michel Seranne
Keyword(s):  
Late Cretaceous ◽  
Root Zone ◽  
Planktonic Foraminifera ◽  
Thrust Sheet ◽  
Tectonic Events ◽  
Karst Formation ◽  
Early Paleocene ◽  
Thrust Sheets

Abstract The Mesozoic series of the southern units of the Pyrenean Empordà thrust sheets (Montgrí and Figueres nappes, Catalonia, Spain) were finally emplaced over the autochthonous basement and its Cenozoic cover during Eocene times. However, they have originally been folded by the “Laramian” compressional event (Late Cretaceous/Early Paleocene), while they were still in their root zone more than 50 km to the N-NE. Postdating the Santonian, the emersion of the Cretaceous tectorogen induced karst formation at the expense of Berriasian to Santonian limestone sequences. Karst cavities of this paleokarst 1 (lapiaz and canyons) were subsequently coated with a fine, red or black, Microcodium-bearing, continental silt, and infilled with marine chaotic breccias. Following a new episode of emersion then erosion, the original paleokarst 1 was cross-cut by newly formed cavities of the paleokarst 2, filled with Lutetian-Bartonian marine breccias. Both types of marine breccias (Paleocene then Eocene in age) are now relatively well dated by means of planktonic foraminifera (Globigerinacea) occurring within the argillaceous-sandy matrix, and for the older ones, within the argillaceous-sandy or carbonate, finely laminated, interbedded hemipelagites, that mark the top of marine sequences tens of centimetres thick. The relationships of the “Laramian” and “Pyrenean” compressional tectonic events, occurring from latest Cretaceous to Bartonian, with the development of paleokarsts 1 and 2 are analysed in the perspective of the progressive southwards emplacement of the Montgrí thrust sheet, during Eocene time.

First sedimentary record of the pre-obduction convergence in New Caledonia: formation of an Early Eocene accretionary complex in the north of Grande Terre and emplacement of the ‘Montagnes Blanches’ nappe

2011 ◽  
Vol 182 (6) ◽  
pp. 479-491 ◽  
Author(s):  
Pierre Maurizot
Keyword(s):  
Late Cretaceous ◽  
New Caledonia ◽  
Sedimentary Cover ◽  
Planktonic Foraminifera ◽  
Foreland Basin ◽  
Late Eocene ◽  
Passive Margin ◽  
Early Eocene ◽  
Accretionary Complex ◽  
The North

Abstract New Caledonia lies at the northern tip of the Norfolk ridge, a continental fragment separated from the east Gondwana margin during the Late Cretaceous. Stratigraphic data for constraining the convergence that led to ophiolitic nappes being obducted over Grande Terre during the Eocene are both few and inaccurate. To try and fill this gap and determine the onset of the convergence, we investigated the lithology, sedimentology, biostratigraphy and geodynamic context of the Late Cretaceous – Palaeogene sedimentary cover-rock succession of northern New Caledonia. We were able to establish new stratigraphic correlations between the sedimentary units, which display large southwest-verging overfolds detached along a basal argillite series, and reinterpret their interrelationships. The sediments from the Cretaceous-Paleocene interval were deposited in a post-rift pelagic environment and are mainly biogenic with minimal terrigenous input. From the base up, they comprise black organic-rich sulphide-bearing argillite, black chert (silicified equivalent of the argillite), micritic with chert, and micrite rich in planktonic foraminifera. These passive-margin deposits are found regionally on the Norfolk Ridge down to New Zealand, and on the Lord Howe Rise, and were controlled primarily by regional or global environmental factors. The overlying Eocene deposits mark a change to an active-margin regime with distal calciturbidite and proximal breccia representing the earliest Paleogene flysch-type deposits in New Caledonia. The change from an extensional to a compressive regime marks the beginning of the pre-obduction convergence and can be assigned fairly accurately in the Koumac–Gomen area to the end of the Early Eocene (Late Ypresian, Biozone E7) at c 50 Ma. From this period on, the post-Late Cretaceous cover in northern New Caledonia was caught up and recycled in a southwest-verging accretionary complex ahead of which flysch was deposited in a flexural foreland basin. The system prograded southwards until the Late Eocene collisional stage, when the continental Norfolk ridge entered the convergence zone and blocked it. At this point the autochthonous and parautochthonous sedimentary cover and overlying flysch of northern New Caledonia was thrust over the younger flysch to the south to form a newly defined allochthonous unit, the ‘Montagnes Blanches’ nappe, that is systematically intercalated between the flysch and the obducted ophiolite units throughout Grande Terre.

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