Question 1

How do you say Oxfordian?

Accepted Answer

Oxfordian is pronounced ox-FORD-ee-un, with the stress on the second syllable, FORD. Break it down like this: OX, then FORD, then EE, then UN. It sounds almost exactly like the city Oxford with '-ian' tacked on the end. Once you hear it a couple of times it becomes very easy to remember.

Question 2

What does Oxfordian mean?

Accepted Answer

Oxfordian is a geological term that means 'belonging to the age of Oxford,' named after the city of Oxford in England. French geologist Alcide d'Orbigny coined the name in 1850 because distinctive limestone rocks from this period of Jurassic time were well exposed in the English countryside around Oxford. The '-ian' ending is a Latin suffix that geologists attach to place names to create the names of time periods. So Oxfordian literally means 'of or relating to Oxford,' in this context referring to a specific slice of geological time.

Question 3

When was the Oxfordian age?

Accepted Answer

The Oxfordian age lasted from approximately 163.5 million years ago to 157.3 million years ago, making it about 6.2 million years long. It is part of the Late Jurassic epoch, sitting between the Callovian age before it and the Kimmeridgian age after it. To put that in perspective, the Oxfordian ended roughly 92 million years before the mass extinction that wiped out the non-bird dinosaurs. It was a time when giant sauropod dinosaurs like Brachiosaurus and fearsome predators like Allosaurus roamed the Earth.

Question 4

What dinosaurs lived during the Oxfordian?

Accepted Answer

Some of the most iconic dinosaurs in history lived during the Oxfordian age. Brachiosaurus, Diplodocus, Apatosaurus, and many other giant long-necked sauropods roamed what is now the western United States. Stegosaurus, with its famous back plates and tail spikes, also lived during this time. The fierce predator Allosaurus was the top land hunter of the Oxfordian world, capable of taking down prey much larger than itself. Many of these species are known from fossils found in the Morrison Formation, which began forming during the Oxfordian stage.

Question 5

Is the Oxfordian a period or a stage?

Accepted Answer

Technically, the Oxfordian is a stage, which is a subdivision of a geological period. The Jurassic is the period, and it is divided into three epochs: Early, Middle, and Late Jurassic. The Oxfordian is a stage within the Late Jurassic epoch. Geologists use the word 'stage' for these smaller time divisions, which are generally defined by changes in the types of fossils found in marine rocks, especially ammonites. In everyday conversation people sometimes call it an 'age' as well, which means exactly the same thing as a stage but refers to time rather than rock.

Question 6

What was the climate like during the Oxfordian?

Accepted Answer

The Oxfordian climate was warm and humid across most of the planet, much warmer than today. There were no polar ice caps, and sea levels were significantly higher than they are now, flooding large parts of Europe with shallow tropical seas. Average global temperatures may have been 5 to 10 degrees Celsius higher than modern temperatures. These warm conditions supported lush vegetation on land and highly productive reef ecosystems in the shallow seas, which is why Oxfordian rocks are so rich in fossils of corals, sponges, and marine invertebrates.

Question 7

Why is the Oxfordian named after Oxford England?

Accepted Answer

French scientist Alcide d'Orbigny chose Oxford because the limestone rocks in and around Oxfordshire, England, were some of the best-studied Jurassic marine deposits in Europe at the time he was creating his geological classification system in 1850. The distinctive oolitic limestone and clay beds around Oxford and the Cotswolds contain excellent fossils of Jurassic ammonites and other marine creatures. It was standard practice for d'Orbigny to name geological stages after the places where their defining rock types were most clearly seen, which is why so many stage names reference European locations.

Question 8

What sea covered Europe during the Oxfordian?

Accepted Answer

During the Oxfordian, a warm shallow sea connected to the ancient Tethys Ocean spread across much of what is now central and western Europe. This epicontinental sea covered large parts of present-day England, France, Germany, Poland, and Switzerland, turning the landscape into a scattered archipelago of islands surrounded by tropical reef-filled waters. The warm carbonate-rich conditions of this Tethys-linked sea were perfect for coral and sponge reef growth, and the thick limestone deposits it left behind are now exposed in places like the Jura Mountains and the English Cotswolds.

Question 9

Did Stegosaurus really live during the Oxfordian?

Accepted Answer

Yes, Stegosaurus lived during the Late Jurassic, including the Oxfordian age, and its fossils are found in rocks from the Morrison Formation in the American West, which began depositing during this time. Stegosaurus shared its ecosystem with giant sauropods like Diplodocus and Brachiosaurus as well as the predator Allosaurus. Fossils of Stegosaurus relatives have also been found in Portugal and other parts of Europe, which during the Oxfordian had land connections to North America, explaining how similar animals could live on both continents.

Question 10

What is the Morrison Formation and does it come from the Oxfordian?

Accepted Answer

The Morrison Formation is one of the most famous fossil-bearing rock sequences in the world, stretching across the western United States through states like Colorado, Utah, Wyoming, and Montana. It began forming during the Oxfordian age around 156 million years ago and continued into the Kimmeridgian and Tithonian stages. The Morrison has produced fossils of Allosaurus, Diplodocus, Brachiosaurus, Stegosaurus, Camarasaurus, and dozens of other dinosaurs. It was deposited by a vast river and floodplain system that covered the area during the Late Jurassic.

Question 11

How do geologists know where one geological stage ends and another begins?

Accepted Answer

Geologists use index fossils, especially ammonites, to define the boundaries between geological stages like the Oxfordian. Ammonites evolved rapidly and spread widely through the world's oceans, so different species appear and disappear at very specific points in geological time. When geologists see a particular set of ammonite species replace an earlier set in the rock record, they know they have crossed a stage boundary. The International Commission on Stratigraphy uses these fossil assemblages to formally define each boundary, and there is usually a single reference location in the world called a GSSP, or Global Boundary Stratotype Section and Point, where the boundary is officially recognized.

Question 12

What came before and after the Oxfordian?

Accepted Answer

The Oxfordian followed the Callovian age, which lasted from approximately 166.1 to 163.5 million years ago and was also part of the Middle to Late Jurassic transition. After the Oxfordian came the Kimmeridgian age, lasting from about 157.3 to 152.1 million years ago. All three stages are part of the Late Jurassic epoch, which itself ended around 145 million years ago with the beginning of the Cretaceous period. Each stage is defined by characteristic ammonite fossil assemblages found in marine sedimentary rocks across Europe and the rest of the world.

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