RE: Precise K-T boundary dating

All rights reserved. New insights about the asteroid thought to have killed off the dinosaurs suggest it may have just been the final blow, and that the reptiles were already suffering from a finicky climate prompted by volcanic eruptions long before the meteorite struck. The research, detailed in the February 8 issue of the journal Science , adds to the ongoing scientific debate over what exactly killed off the dinosaurs. That debate, which once revolved around the question of whether the culprit was an asteroid or volcano-induced climate changes, has evolved to consider the possibility that perhaps multiple environmental factors were involved. Using a high-precision dating technique on tektites—pebble-sized rocks formed during meteorite impacts—from Haiti that were created during the event, the team concluded that the impact occurred 66,, years ago—slightly later than previously thought. When error limits are taken into account, the new date is the same as the date of the extinction, the team says, making the events simultaneous. Renne said the new findings should lay to rest any remaining doubts about whether an asteroid was a factor in the dinosaurs’ demise.

Refining the date of the K/T boundary and the dinosaur extinction

Detection of a new form of carbon in volcanic rock samples from Anjar town in Gujarat in western India has revived the debate on what killed the dinosaurs. Dinosaurs and almost 80 per cent of Earth’s other organisms were wiped out 65 million ears ago at the so-called K-T boundary KTB that marks the end of Cretaceous K , and beginning of Tertiary T periods in the geological calendar.

Some say it was the result of extraterrestrial objects hitting the earth, a theory originally proposed by the Nobel physicist Luis Alvarez. Others blame it on vast clouds of climate-altering gases released by eruptions that buried western India under layer upon layer of basaltic lava flows nearly 3, meters thick. Now, researchers from India’s three national laboratories have joined the fray.

Tylosaurus and the K-T impact event at the end of the survivors of the Cretaceous extinction event (known as the K-T boundary) at the end.

Skip to main content Skip to table of contents. This service is more advanced with JavaScript available. Encyclopedia of Paleoclimatology and Ancient Environments Edition. Contents Search. How to cite. The end result is a crater tens to hundreds of kilometers in size. Although the existence of large impact structures on Earth is undisputed, the possible climatic effects of an impact were not seriously considered until , when a team led by the famous physicist Luis Alvarez and his son, the geologist Walter Alvarez, suggested that the profound end-Cretaceous mass extinction might have been caused by the impact of a km diameter asteroid or comet Alvarez et al.

Dated to 65 million years ago, this extinction is the last of the large, known mass extinctions on Earth and defines a major geologic boundary between the Cretaceous and Tertiary or Paleogene, as

K-T Boundary

The Cretaceous—Paleogene K—Pg boundary , formerly known as the Cretaceous—Tertiary K-T boundary , [a] is a geological signature , usually a thin band of rock. K , the first letter of the German word Kreide chalk , is the traditional abbreviation for the Cretaceous Period and Pg is the abbreviation for the Paleogene Period. Its age is usually estimated at around 66 Ma million years ago , [2] with radiometric dating yielding a more precise age of The K—Pg boundary is associated with the Cretaceous—Paleogene extinction event , a mass extinction which destroyed a majority of the world’s Mesozoic species, including all dinosaurs except for birds.

However, improvements in rock-dating techniques and in understanding the The scale of change leading up to the K-Pg boundary pales in.

This formation forms the striking, massive, m high vertical cliffs along the south side of the San Juan River on the south side of the city of Farmington in the west-central part of the basin Figure 1. The Ojo Alamo is a coarse-grained, conglomeratic sandstone that crops out around the periphery of most of the New Mexico part of the San Juan Basin but is absent in the northern part mostly in Colorado, Figure 1.

The Ojo Alamo was deposited on a basin-wide erosion surface in early, but not quite earliest, Paleocene time by south-to-southeasterly flowing, high energy, braided streams Fassett , Fassett et al. A hiatus of nearly 8 m. The Ojo Alamo is a multi-storied conglomeratic sandstone with highly varied internal architecture and thicknesses throughout the basin Fassett et al. Conglomerate clasts range from near-boulder size in the northwest part of the basin to small pebbles and grit in the southeast part.

A dating success story: genomes and fossils converge on placental mammal origins

Scientists at the University of California, Berkeley, and the Berkeley Geochronology Center have pinpointed the date of the dinosaurs’ extinction more precisely than ever thanks to refinements to a common technique for dating rocks and fossils. The argon-argon dating method has been widely used to determine the age of rocks, whether they’re thousands or billions of years old.

Nevertheless, the technique had systematic errors that produced dates with uncertainties of about 2. Renne and his colleagues in Berkeley and in the Netherlands now have lowered this uncertainty to 0. As a result, argon-argon dating today can provide more precise absolute dates for many geologic events, ranging from volcanic eruptions and earthquakes to the extinction of the dinosaurs and many other creatures at the end of the Cretaceous period and the beginning of the Tertiary period.

THE KT-BOUNDARY IMPACTPaintings and text copyright William K. from the Cenozoic Era, dating 65 My ago, they found an excess of the element iridium.

A number of radiometric methods of dating rocks are used by Geologists. These techniques rely on measuring the rate of decay of certain isotopes contained with rock and mineral samples. As certain isotopes are known to decay at a constant rate, measuring the levels and ratios of isotopes within a rock sample can provide evidence of how old the rock is. One of the most common methods used is the argon-argon dating method. It can be used to date rocks that are millions or even billions of years old.

This dating method is particularly suitable for dating volcanic materials igneous rocks.


Few episodes in geologic history are as widely recognized as the Cretaceous-Paleogene, or K-Pg, boundary 66 million years ago. Mention it to science-interested laymen, meanwhile, and they may conjure images of tyrannosaurs peering over their shoulders in anguish as they flee from streaking meteors. These catastrophic events make for a compelling and, aside from artistic liberties taken in some recountings, mostly truthful tale. Paleontologists have long recognized from the fossil record that more than half of the species inhabiting Earth perished at the end of the Mesozoic — the most emblematic of course being the remaining nonavian dinosaurs, like T.

The Cretaceous/Tertiary boundary that marks the end of the Mesozoic and the beginning of the Cenozoic had been dated to around

According to abundant geological evidence, an asteroid roughly 10 km 6 miles across hit Earth about 65 million years ago. This impact made a huge explosion and a crater about km roughly miles across. Many asteroids of this type are now known; their orbits pass through the inner solar system and cross Earth’s orbit. Some of these could potentially hit Earth in the future.

Most, but not all are smaller than the one that hit us 65 million years ago. Fossils found in soil layers of different ages show a record of slow, gradual changes in species, with simple organisms gradually being replaced by more complex organisms, apparently by evolutionary processes driven by natural selection. For example, million years abbreviate My ago, the oceans held only simple organisms like algae, while the land was relatively lifeless.

Fish fossils appear in strata after about My ago; dinosaurs and giant reptiles were on the land by My ago. Mammals were not common until after 65 My ago, and humanlike creatures appeared only in the last 4 My. Fundamentalists are defined as people who believe that the primary way of learning about nature should not be the scientific method, or compilation of evidence tested in different labs in different countries, but rather interpretation of ancient manuscripts, such as the Koran, the Old Testament of the Bible, the New Testament, or other ancient writings.

The scientific method was hammered out mainly in the s, when naturalists of that period agreed that information about nature could best be determined by direct observations of nature, and experiments, which would be published openly, in international literature.

Cretaceous-Tertiary extinction event

Indeed, had it not been for the presence of abundant dinosaur remains in the Ojo Alamo Sandstone, its Paleocene age would probably never have been questioned. Because the last occurrence of dinosaur bone has always been considered by vertebrate paleontologists to mark the end of the Cretaceous Period, various explanations were suggested to explain away the presence of these dinosaur remains in what otherwise appeared to be Paleocene rocks.

For a complete discussion of those explanations, see Fassett et al.

PDF | 40Ar/39Ar dating of drill core samples of a glassy melt rock recovered from from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites across the Cretaceous/Paleogene (K/Pg) boundary, the massive eruptions in.

Was it a comet or asteroid impact? Volcanic eruptions? Climate change? In an attempt to resolve the issue, an international team of scientists have determined the most precise dates yet for the dinosaur extinction 66 million years ago and for the well-known impact that occurred around the same time. The new extinction date is precise to within 11, years.

The revised dates clear up lingering confusion over whether the impact actually occurred before or after the extinction, which was characterized by the almost overnight disappearance from the fossil record of land-based dinosaurs and many ocean creatures. The new date for the impact — 66,, years ago — is the same within error limits as the date of the extinction, said Renne, making the events simultaneous.


You may print out a copy for personal or educational use, and you may link to this site. Illustrations are missing from this Web version of the chapter. Cowen, R.

sediments dating back to the boundary between the Cretaceous and Tertiary periods (called the K-T boundary). This iridium did not have an.

The study, based on high-precision radiometric dating techniques, said the events occurred within 33, years of each other. It is believed to have been formed by a six-mile- 9. Glassy spheres known as tektites, shocked quartz and a layer of iridium-rich dust are still found around the world today. Renne and colleagues reanalyzed both the dinosaur extinction date and the crater formation event and found they occurred within a much tighter window in time than previously known.

The study looked at tektites from Haiti, tied to the asteroid impact site, and volcanic ash from the Hell Creek Formation in Montana, a source of many dinosaur fossils. He says ecosystems already were in a state of deterioration due to a major volcanic eruption in India when the asteroid struck. About 1 million years before the impact, Earth experienced six abrupt shifts in temperature of more than 2 degrees in continental mean annual temperatures, according to research cited by Renne and his co-authors.

The temperature swings include one shift of 6 to 8 degrees that happened about , years before the extinction. Discover Thomson Reuters. Directory of sites. United States.

Cretaceous/Tertiary (K-T) Boundary Impact, Climate Effects

Plants and the K—T Boundary. Its impact on plant life appears to have been of a much lesser magnitude. The authors, both on the staff of the Denver Museum of Nature and Science, have published extensively on fossil plants of Tertiary and Cretaceous age. Nichols has been mainly concerned with the palynology the microfossil record , while Johnson has concentrated on leaf assemblages megafossils of this age span. The Alvarez father-and-son team argued that the cause of the peak occurrence of that element was the result of the impact of an extra-terrestrial body.

Actual radioisotope dating was done a bit later in date of K-Pg is ± MA (millions of years ago), date of the Chicxulub crater is.

This boundary layer is well marked and recognized world-wide and has been long known to mark one of the largest mass extinctions in the fossil record. What has always clearly marked this boundary layer is the fossils above and below. In the younger, Tertiary sediments, there are only tiny, less ornate foraminifera. Other creatures, prominently the ammonites, the fish of the oceans except they are cephalopods like the octopus and the chambered nautilus in the Paleozoic and Mesozoic Eras, some to 65 million years ago, abruptly disappeared.

And of course, the terrible reptiles, the dinosaurs, disappeared from the face of the Earth. Clearly, something happened 65 million years ago to cause a mass extinction. A core sample of rock, taken across the boundary layer but not from Gubbio is shown here:.

The Day the Dinosaurs Died

A few days ago, a follower of mine gave me an interesting read from The Atlantic regarding the dinosaur extinction. Like many of my generation, I was taught in school that dinosaurs died because an asteroid hit the Earth. Yes, I am a proud parent.

ABSOLUTE DATING METHODS: Radiometric dating can be used on a sample to produce an actual age in years. There are many independent techniques.

Maybe the global climate changed, maybe they were killed by disease, volcanoes, or the rise of mammals. It was this event that pushed the dinosaurs over the edge into extinction. A thin dark line found in layers of sediment around the world; evidence that something devastating happened to the planet 65 million years ago. This line is known as the K-T boundary.

What is the K-T boundary? K is actually the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period. So the K-T boundary is the point in between the Cretaceous and Tertiary periods. Geologists have dated this period to about

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