Catastrophe

In analyzing the differences between the evolutionary history of plants and animals, Traverse (1988a) asserted that major plant extinctions have not been synchronous with animal extinctions in the geologic past, and that changes in floras through time have been due to gradual replacement, not mass extinction. He cogently argued that this is because as a group, plants are resilient organisms able to survive extrinsic stresses much better than animals. Reasons for this include plants' ubiquity on...

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UlmipollenitesSubtr iporopoll.Rhoipites assemb lage CedripitesP odocarpidites rilobosporites UlmipollenitesP odocarpiditestkngsupollis subassemblage PterisisporitesEphedr ipites subassemblage Rugubivesiculitestknghanpollis subassemblage GothanipollisGabonispor is subassemblage Classopollis Exesipollenites Schizaeoisporites Assemblage Figure 8.8 The K-T boundary interval in Jiangsu Province, China, with a possible approximate position of the boundary indicated by the horizontal line and question...

Info On On Fossil Plants

Iii mil i i i i i ml i i i 11 ml i . i i i i 10-1 100 101 102 Angiosperm pollen fern spores 10-1 100 101 102 Angiosperm pollen fern spores Figure 5.7 Iridium concentrations (black dots) and ratios of angiosperm pollen to fern spores (triangles) in the York Canyon Core major deflections mark the K-T boundary (from Orth et al. 1981). Reprinted by permission. horizon at the outcrop localities (Figure 5.8). Realizing that data points as far apart as New Mexico and Montana were evidence of a...

Info

Palynological assemblages, not on the extinction event. Sweet and Braman documented occurrences and relative abundances of some individual species and several broader groups of palynomorphs (pollen, spores, and algal cysts) through the stratigraphic intervals at all 12 of their localities. They proposed a sweeping revision of the interpretation of the K-T boundary event and its effects on plants. Their new scenario centered on emplacement of the boundary clay-stone layer, which they interpreted...

New evidence accumulates

In the decade following publication of the Alvarez et al. (1980) impact hypothesis, the Raton Basin of Colorado and New Mexico (Figure 4.3) was a focus of studies of the palynological and paleobotanical records of the K-T extinctions. These studies were conducted in conjunction with a search for new localities at which the iridium anomaly was present in nonmarine rocks. The new evidence developed in the Raton Basin contributed supporting data for the impact hypothesis and played a role in the...

The development of palynology

As reviewed by Traverse (1988b), stratigraphic palynology had its beginning as a field of study (originally called pollen analysis) in the early 1900s with the microscopic investigation of Pleistocene peat deposits in Europe. The development of palynology in pre-Pleistocene stratigraphy began in the 1940s, but its application to studies of Cretaceous and Paleogene rocks in North America did not take place until later with the research of Rouse (1957) and Stanley (1965). By the late 1960s it had...

Impact scenario

The extraterrestrial impact scenario for the extinctions at the K-T boundary introduced by Alvarez et al. (1980) is the one that is best supported by more than 25 years of research. The evidence for the impact having occurred is overwhelming. It includes the globally distributed, anomalous concentration of iridium at the K-T boundary (Alvarez et al. 1980, Alvarez et al. 1984) shocked quartz and other mineral grains produced at the impact site and deposited at the boundary (Bohor et al. 1984,...

Africa

In their paper on global palynofloristic provinces, Herngreen and Chlonova (1981) listed the characteristic taxa of the Palmae Province, which existed in Africa and northern South America in Senonian (Coniacian through Maastrichtian) time. Most noteworthy among them are the palm pollen genera Psilamonocolpites, Retimonocolpites, Proxapertites, and Spinizonocolpites. Assemblages in which palm pollen is prominent characterize upper Senonian strata, but angio-sperm pollen becomes increasingly...

The study of palynoflora

Palynofloras are essential to studies of the K-T boundary in nonmarine rocks. Numerous aspects of the nature of palynofloras must be considered when using them in such studies. These include taxonomy (pollen or spore species vs. botanical species), preservation and preparation, sample size, facies effects, reworking or redeposition, stratigraphic resolution, and geographic coverage. These topics are covered in depth in textbooks on palynology (e.g., Traverse 1988b, Jansonius and McGregor 1996,...

Akmetiev Laboratori

We both have been fascinated by the Cretaceous-Paleogene (K-T) boundary since the late 1970s. The Alvarez discovery galvanized our individual research efforts and we have worked together on this problem since we met in 1983. Our research has focused on western North America, so our data and interpretations are largely based on field work and laboratory analyses in this region. We have also studied terrestrial K-T boundary sections in Russia, China, and New Zealand and searched, unsuccessfully,...

Leaf architecture and the systematic utility of leaves

American paleobotany had grown from European roots and its practitioners followed the nomenclatural lead of Heer, Saporta, von Ettinghausen, and Brongniart. As a result, the basionyms of many of the species described by Lesquereux, Knowlton, Berry, Newberry, and Ward were from Europe or the Arctic. In North America, the naming and sorting of these taxa took place as these paleobotanists were caught up in the tangled web ofthe Laramie Problem. The result was a snarl of poor or missing type...

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Figure 7.16 Palynostratigraphy and magnetostratigraphy of the Kiowa Core showing position of the K-T boundary at 993.85 0.05 ft 302.93 0.015 m and magnetic polarity subchrons identified depths in feet D1 and D2 sequence terminology after Raynolds 2002 . In the Kiowa Core, the uppermost 3 mm of the Cretaceous strata yielded a diverse, angiosperm-dominated assemblage from the Wodehouseia spinata Assemblage Zone that includes seven characteristically Maastrichtian species not found in the 3-mm...

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Golden Cretaceous Boundary

Figure 7.10 Diagrams showing the stratigraphic relationship of the fern-spore spike to the boundary claystone layer and coal beds at three localities in the Raton Basin. a - City of Raton, b - Starkville South, c - Sugarite modified from Nichols and Fleming 1990 . Reprinted by permission. from clastics to coal or as at Pyramid Butte in the Williston Basin from coal to clastics. Comparison of the lithology and palynology of the Starkville South, Sugarite, and City of Raton localities shows that...

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Geology Powder River Basin

Figure 7.17 The K-T boundary interval at the West Bijou Site showing sample positions for palynology and iridium analyses, fern-spore spike as percentages of fern spores in samples, and relative abundance of shocked quartz in samples X marks from Barclay et al. 2003 . Reprinted by permission. Figure 7.18 Lower Paleocene leaves from the distal part of the Denver Basin. a - Cornophyllum newberryi DMNH 23481 , b - Paranymphaea crassifolia DMNH 23515 , c - Cissites panduratus DMNH 26144 , d -...

Plants And The K-t Boundary

Paleocene coal Shocked quartz and peaWr KT boundar y claystone Maastrichtian mudstone Figure 2.2 The K-T boundary at the scale of the impactite level showing the iridium anomaly and fern-spore spike at the Sussex locality in the Powder River Basin see Section 7.4 . Enlarged detail below shows microstratigraphy of the boundary interval including mudstone bearing Maastrichtian pollen overlain by impactite deposits beneath coal of earliest Paleocene age. Peak iridium anomaly and most shocked...

Overview

South Dakota Williston Map Basin

The uppermost Maastrichtian and lowermost Paleocene rocks in the Williston Basin of western North Dakota, northwestern South Dakota, and eastern Montana contain the best exposed and most studied nonmarine record of the terminal Cretaceous event in the world. This region contains 41 39 of the known terrestrial K-T boundary sections see Table 2.1 and Appendix . The Williston Basin is a large structural depression occupying much of North Dakota and parts of South Dakota, Montana Figure 6.1 , and...

Raton Basin Colorado and New Mexico

Boundary Visible Colorado

The first iridium-bearing terrestrial K-T boundary sections were discovered in the Raton Basin of southeastern Colorado and northeastern New Mexico Figure 7.2 . The K-T boundary is preserved in the Raton Formation, an entirely nonmarine unit of Maastrichtian and early Paleocene age Figure 7.3 . The Raton Formation is composed of sandstone, siltstone, mudstone, coal, and minor conglomerate. Thin to thick coal beds are common in the lower and upper parts of the formation, but are scarce to absent...

New Zealand

The K-T boundary in New Zealand has been known in marine rocks since the publication of Alvarez et al. 1980 , and about 20 localities are now known Hollis 2003 . The Woodside Creek locality on the South Island of New Zealand was one of the three localities in the world where anomalous concentrations of iridium were first detected at the paleontologically defined K-T boundary - the level of extinction of marine foraminifera. The boundary in nonmarine rocks in New Zealand took a great deal longer...

The central role of plants as evidence

Sketch Fossil Record

As succinctly stated by Hickey 1984 , land plants form a central element in any comprehensive inquiry into possible causes of extinctions at the K-T boundary because they are a conspicuous and exposed part of the terrestrial biota. Plants are speciose and common on terrestrial landscapes. They are primary producers, composing the base of the food chain. The fate of terrestrial animals depends upon them, either directly or indirectly, as food sources and for shelter thus, the collapse of plant...

The study of megaflora

Megaflora includes identifiable macroscopic plant particles the most commonly studied are leaves, fruits, seeds, and wood. To date, most work on the K-T boundary has focused on fossil leaf floras because leaves are the most commonly preserved macroscopic plant organs in this age rock although European workers have focused more on fruits and seeds and Indian workers have concentrated on wood . Numerous aspects of fossil leaves must be considered when using them to study the K-T boundary. These...

Dakota Formation In New Mexico

Figure 7.32 Stratigraphic nomenclature for the Maastrichtian and Paleocene of parts of Alberta and southern Saskatchewan. Figure 7.32 Stratigraphic nomenclature for the Maastrichtian and Paleocene of parts of Alberta and southern Saskatchewan. North Dakota lies within the upper part of magnetostratigraphic subchron C29r. The extinction of Aquilapollenites pollen marked the boundary. Lerbekmo 1985 repeated these results in the Frenchman Valley Cypress Hills area locality 75 in Saskatchewan....

Early Paleocene vegetation

Paleocene Reconstruction

Paleocene vegetation is best known from the Rocky Mountains and Great Plains of North America, northeastern Asia, and Greenland. Isolated Paleocene sites have been discovered or described in Europe, the Canadian Arctic, Antarctica, New Zealand, India, Colombia, Chile, and Argentina. Africa and Australia are poorly known, with essentially no Paleocene megafloras. The North American Paleocene is so well sampled from nearly a thousand fossil localities that knowledge of Paleocene megafloras is...

Eastern Montana

Sketch Map Creek

The western part of the Williston Basin is present in eastern Montana. The strata in this area are exposed in badlands along the banks and tributaries of the Missouri River in Garfield and McCone counties and adjacent to the Yellowstone River between Miles City and Glendive. The Missouri River is dammed at Fort Peck and the Fort Peck Reservoir is surrounded by these extensive badlands Figure 6.26 . The same stratigraphic units known in western North Dakota are present in eastern Montana the...

South America

Echitriporites Trianguliformis Picture

In latest Cretaceous time, northern South America lay within the Palmae palynologic province Herngreen and Chlonova 1981 . Characteristic pollen included species of the genera Psilamonocolpites, Retimonocolpites, Proxapertites, and Spinizonocolpites the species S. echinatus is said to be identical with pollen of the living palm Nypa fruticans . Muller et al. 1987 presented a comprehensive palynostratigraphy of the Cretaceous through Holocene of northern South America. Their study areas included...

Polle Maastrichtian

Maastrichtian

Proteacidites Tschudypollis thalmannii Figure 8.13 Data on palynostratigraphic zones in the Zeya-Bureya Basin from Markevich 1994 . Both the older and newer stratigraphic nomenclature Figure 8.10 are shown. Palynomorph taxa listed are those that are known in both the Russian Far East RFE and North America NA . Ages shown in the third column are from Markevich 1994 alternative ages shown in the fifth column are our interpretations based on occurrences of taxa in common between the RFE and NA....

Late Cretaceous vegetation

Wodehouseia

Paleobotanists divide Phanerozoic time into three eras the Paleophytic, Mesophytic, and Cenophytic Traverse 1988b . The Mesophytic-Cenophytic boundary lies nowhere near the Mesozoic-Cenozoic boundary. Because it is defined by the first appearance of the angiosperms, the Cenophytic begins in the earliest stages of the Cretaceous, some 60-70 million years before the K-T boundary. Angiosperm evolution was rapid in the Cretaceous and global summaries based on megafloral and palynofloral data Crane...

Eurasia

Diagram Fossil Layer Occurence

The quality of published K-T boundary terrestrial data diminishes dramatically outside of North America. Of the 20 non-North American K-T boundary sections, only one scored as much as 10 points on Table 2.1. Our evaluation of these sections begins with the 14 localities known from Eurasia, which we subdivide based on the data available into Europe, Japan, China, and the Russian Far East. Each of these regions is discussed in its own section in this chapter. Two of the first three places in the...

The fernspore spike

A unique feature of earliest Paleocene vegetation is an anomalous concentration of fern spores just above the level of palynological extinction. This anomalous palynological assemblage is known as the fern-spore spike. It is evidence that plant communities of the earliest Paleocene were pioneer communities numerically dominated by ferns, in most places of a single species. An artist's conception is on the cover of this book. The first report of this exceptional palynological assemblage was that...

The KT controversy and the Alvarez challenge

A paper published in 1980 in the journal Science revolutionized the science of geology. Coauthored by Nobel laureate in physics Luis Alvarez, his geophysicist son Walter, and two colleagues, the paper presented data from the esoteric field of neutron activation analysis. These data suggested that the Earth had been struck by a large extraterrestrial object an asteroid or possibly a comet some 65 million years ago, precisely at the moment in time that marked the boundary between the Mesozoic and...