End Of Maastrichtian Research Articles

Earliest Campanian - latest Maastrichtian sequence stratigraphy based on planktonic foraminifera, Fars province, Zagros, Iran

The Gurpi, Tarbur and Sachun formations have been investigated in the studied section in the Fars Province, in order to determine their sequence stratigraphy. On the basis of done studies on the cores of borehole, four main microfacies have been recognized in four stratigraphic sequence deposited during the Campanian to Maastrichtian. The lowermost sequence, was deposited in the early Campanian-early late Campanian which include wackestone to packestone texture with Globotruncanita elevata Zoneand Globotruncana ventricosa Zonethatrepresentative of the deep marine and outer ramp. The intermediate and uppermost sequences (sequences two, three and four) display well developed deposits formed in the end of the Campanian (Radotruncana calcarata Zoneand Globotruncanella havanensis Zone), formed during the Maastrichtian (Globotruncana aegyptiaca Zoneand Gansserina gansseri Zone) and the end of the Maastrichtian (Omphalocyclus macroporus - loftusia sp assemblage Zone) on pelagic, hemipelagic, outer and middle ramp. On the basis of the sequence stratigraphic chart, the transgression of the upper Cretaceous sea started since the early Campanian and continued gradually until the early Maastrichtian. Then, until the end of Maastrichtian, the area has been emerged. The sequence stratigraphic architecture of Campanian/ Maastrichtian Gurpi, Tarbur and Sachun formations model is in a good agreement with global sea level changes.

Late Cretaceous endemic shallow-marine gastropod genera of the northeast Pacific: biodiversity and faunal changes

Endemic genera of shallow-marine gastropods in the Cretaceous Northeast Pacific Subprovince (NEP), extending from Alaska to northern Baja California Sur, Mexico, are tabulated and discussed in detail for the first time. None are known in Lower Cretaceous or Cenomanian strata, but 43 genera, nearly two-thirds of which are neogastropods, are recognized in Upper Cretaceous strata. Their first appearance was at the beginning of the Turonian, which coincided with the warmest time of the Cretaceous and one of its highest sea-level stands. Fourteen new subtropical endemic genera appeared then, and 10 (71%) were neogastropods. Tethyan-influenced thermophilic mollusks (nerineid, acteonellid, neritid, and cypraeoidean gastropods, as well as rudistid bivalves) were present. A turnover at the Turonian/Coniacian boundary occurred when cooler waters migrated southward, resulting in the subtropical endemics being abruptly and nearly completely replaced by 10 warm-temperate new endemic neogastropods, which commonly had long-living lineages persisting through the Campanian or early Maastrichtian. Eight (80%) of these new genera were neogastropods. During these cooler water times in the Coniacian and nearly all of the Santonian, there was an absence (“gap”) of Tethyan-influenced and other thermophile mollusks. New endemic genera, were added during an origination event in the early Campanian and also during another one in the late Campanian. Fewer and fewer new neogastropod genera appeared during each of these origination events, whereas new endemic genera of non-neogastropods increased. Rudistids and thermophilic mollusks also returned in the Campanian. Most of the post-Turonian endemic genera went extinct at a turnover at the end of the early Maastrichtian (=“Middle Maastrichtian Event”), rather than at the K/Pg boundary mass-extinction event. Two new endemic genera, both neogastropods, originated just before the end of the Maastrichtian. They and three other Cretaceous endemic gastropod genera occur also in the NEP Cenozoic record, thereby imparting a somewhat transitional aspect between these two faunas. The tectonically transported fauna of the middle Albian Alisitos Formation in northern Baja California, Mexico is confirmed to have lived in the tropical-water Caribbean Biotic Province of the Tethyan Realm.

Biostratigraphy and Sequence Stratigraphy of Campanian and Maastrichtian Succession, Qutbabad Well, Zagros (Iran)

The Qutbabad section of the Gurpi, Tarbur and Sachun Formations in the Fars Province (Zagros Basin) has been studied, in order to determinate its microfacies and sequence stratigraphy. On the basis of thin section studies of cores from Qutbabad Well in the Gurpi, Tarbur and Sachun Formations of the Zagros Basin, four main microfacies have been recognized within four stratigraphic sequences deposited during the Campanian to Maastrichtian. Depth and sea level changes were the main controls on the distribution of these microfacies. The microfacies are: Pelagic; Hemi-Pelagic; Outer ramp; and Middle ramp. The lowermost sequence was deposited in the Early Campanian-early Late Campanian and includes wackestone to packestone textures with biozones Globotruncanita elevate and Globotruncana ventricosa representative of the Pelagic, Hemipelagic and Outer (ramp/shelf). The intermediate and uppermost sequences (sequence two, three and four) display well developed deposits formed at the end of the Campanian (Radotruncana calcarata zone and Globotruncanella havanensis zone), beginning of the Maastrichtian (Globotruncana aegyptiaca zone and Gansserina gansseri zone) and the end of the Maastrichtian (Omphalocyclus macroporus - loftusia sp assemblage zone) on the Pelagic, Hemipelagic, Outer and Middle ramp. On the basis of the sequence stratigraphic chart, the transgression of the Upper Cretaceous Sea started from the Early Campanian and continued gradually towards the Early Maastrichtian. Then, until the end of Maastrichtian, has had regression. This resulted that the sequence stratigraphic model of the Campanian- Maastrichtian Gurpi, Tarbur and Sachun Formations has architecture similar to those that have developed from global sea level changes.

Geological еvents at the Cretaceous – Paleogene boundary in Georgia (Caucasus)

A continuous section at Tetrickaro (South Georgia) of Maastrichtian-Danian shallow-marine paleontologically proved carbonate deposits is being described. Within the section, a boundary clay layer, 15 - 20 cm thick, has been established with anomalously high content of Ir (3.46-5.34 ng/g), with shock-quartz grains and reversed polarity corresponding to R-29 zone of the International Paleomagnetic Scale. Mass extinction of representatives of numerous marine macro- and micro-fossil groups has been established at the Maastrichtian-Danian boundary in Georgia. 18 species of inocerams, 16 species from 9 genera of ammonitids, 5 species of bellemnitids, 25 species from 12 genera of echinoidea, 6 species from 3 genera of orbitoids, 9 species from 3 genera of planktonic foraminifers and 60 species from 29 genera of calcareous nannoplankton have disappeared at the end of Maastrichtian.