Central Atlantic magmatic province

The Central Atlantic magmatic province (CAMP) is the Earth's largest continental large igneous province (LIP). It covers an area of roughly 11 million km² and is made mostly of basalt. This basalt formed before Pangea broke up during the Mesozoic Era, near the end of the Triassic and the beginning of the Jurassic periods.

When Pangea split apart, it created the Atlantic Ocean. But the huge amount of volcanic activity left behind many basaltic dikes, sills, and lavas spread over a wide area around the central North Atlantic Ocean. You can find these deposits in northwest Africa, southwest Europe, northeast South America, and southeast North America.

The volcanic eruptions that formed CAMP happened about 201 million years ago and had four separate cycles. Each cycle lasted no more than 100 years and happened over about 600,000 years. The amount of lava from these eruptions is between two and six million cubic kilometres, making it one of the largest eruptions in Earth's history. This huge event is linked to the Triassic–Jurassic extinction event.

Formation of Pangea

See also: Pangea

Pangea was the last big landmass made up of all the continents joined together. It formed after the earlier landmass called Rodinia split apart. New oceans like the Iapetus Ocean and the Rheic Oceans appeared, but later started to close because of movements deep in the Earth.

Over time, pieces of land called terranes moved toward the edges of a continent named Laurentia. These pieces came from places we now call Africa (Gondwana) and eventually bumped into North and South America (Laurentia). This slow joining happened over millions of years and helped set the stage for big volcanic eruptions that created a lot of basalt rock.

Breakup of Pangea and lead-up to CAMP volcanism

By about 300 million years ago, a huge landmass called Pangea was fully formed. Mountains like the Appalachian Mountains were growing during this time.

Around 252 million years ago, the breakup of Pangea began. This led to one of Earth's largest eruptions called the Siberian Traps. It released a massive amount of lava. Scientists are still not sure what caused this eruption.

After the Siberian Traps, around 247 million years ago, valleys started to form where the land was pulling apart. These valleys filled with sediment and lakes. By 230 million years ago, more valleys formed. Later, magma used these weak spots to reach the surface.

Between about 227 and 202 million years ago, deeper valleys were established. Large pockets of magma were also forming underneath.

Connected magma flows

Scientists discovered that large areas of dark rock, called basalt, found in many places were actually connected. In 1988, they realized these rocks formed together in one big event. Later, in 1999, they found similar rocks in the Amazon River area of Brazil also belonged to this group. These rocks are found on four continents: Africa, Europe, North America, and South America. They formed when the Atlantic Ocean began to open up as the huge landmass called Pangea split apart.

Main article: flood basalt

Main articles: province

Eruptions

See also: Culpeper Basin

The Central Atlantic magmatic province experienced a repeating pattern of events in its rift valleys. First, there would be a period of sediment building up inside these valleys. Then, a very fast burst of volcanic eruptions would happen, lasting less than 100 years. After that, another short period of sediment would form before another quick burst of eruptions. This cycle repeated many times.

One example is the Culpeper Basin. Layers of sediment called the Midland Formation sit right on top of the first wave of volcanic rock, known as the Mount Zion Church Basalt. Between these bursts of eruptions, there was enough time—about 40,000 years—for lakes and new ecosystems to develop. Later, another big burst of volcanic rock, the Hickory Grove Basalt, occurred in a similar quick burst. After this, a longer period of sediment formed, called the Turkey Run Formation, lasting about 550,000 years. Finally, the youngest burst of volcanic rock, the Sander Basalt, also happened in quick bursts.

Connection with the Triassic-Jurassic boundary and the associated mass extinction event

In 2013, scientists learned more about how the Central Atlantic magmatic province was linked to a big change in life on Earth. This change happened near the end of the Triassic period and the start of the Jurassic period. Before this, it was hard to tell exactly when the volcanoes erupted and when many plants and animals died out.

New studies showed that the huge volcanic eruptions happened around the same time as many large groups of plants and animals disappeared. These eruptions and the changes in the air happened in steps over a long time. This helped dinosaurs become the main animals on land. Scientists studied places in Morocco and North American basins to understand these changes better. They looked at fossils, pollen, and spores to see what happened to life during this time.

Geographical extent

The Central Atlantic magmatic province stretches across what was once the supercontinent Pangea. It runs from central Brazil northeastward about 5,000 kilometres across western Africa, Iberia, and northwestern France. It also extends westward for 2,500 kilometres through eastern and southern North America. This area covers roughly 11 million square kilometres, making it one of the largest known continental large igneous province areas.

Most rocks in this province are made of a type called tholeiitic composition, with basalt flows found in many places. There are also large groups of diabase sheets, small lopoliths, and dikes spread throughout the area. This activity happened as Pangea began to break apart during the Late Triassic to Early Jurassic periods. Scientists study this huge area and its brief period of activity to learn about processes deep within the Earth that could create such events.

Morocco

In Morocco, the African part of this province has very thick layers of basalt lava, more than 300 metres thick. The most studied area is the Central High Atlas, where the best-preserved basalt layers are found. Studies show four different types of basalt layers there: Lower, Intermediate, Upper, and Recurrent basalts.

The Lower and Intermediate layers are made of basaltic andesites, while the Upper and Recurrent layers are mostly basalt. From the Lower to the Recurrent layers, scientists notice:

• a slower rate of eruption (the Lower and Intermediate layers make up over 80% of the lava we see today);
• changes in the texture of the rocks;
• a gradual decrease in certain elements in the basalts, which might be linked to changes deep within the Earth.

Isotopic analyses

Scientists used ⁴⁰Ar/³⁹Ar analysis on plagioclase to find the ages of these rocks. They found that the Lower to Upper layers all have about the same age (around 199.5 million years ago), showing that this was a short but intense event. The Recurrent layers are slightly younger (about 197 million years ago) and represent a later event. There is also a layer of sediment about 80 metres thick between the Upper and Recurrent layers.

Magnetostratigraphy

Studies of magnetic directions in the rocks from Morocco divided the events into five groups, each with fewer lava flows than the one before. This suggests there were five short bursts of magma and eruption events. Each burst might have lasted about the same length of time. Magnetic data also show an age of about 198–200 million years ago, close to the time when the Triassic period ended and the Jurassic began. This helps scientists figure out if this event happened before or after that major change in Earth's history.

Magnetostratigraphy

In the Newark Basin, scientists found a change in magnetic direction just below the oldest lava flows, which matches a big change in plant fossils that marks the end of the Triassic. In Morocco, two changes in magnetic direction were found in lava layers. Scientists have suggested different ways these might match up with what was found in North America. Some think the end of the Triassic happened above the lower reverse polarity level in Morocco, meaning North American lava flows happened after this boundary. Others suggest these changes might be from the earliest Jurassic period and could match with changes found in France.

Palynological analyses

The end of the Triassic is not officially marked by a single rock layer, but scientists often look for the last appearance of certain ancient plant spores to find this boundary. In North America, this big change in plant fossils happens below the oldest lava flows. The same pattern is seen in other places in North America. In Morocco, layers just below the oldest lava flows contain plant spores from the Triassic period. However, some scientists think these layers might be mixed up or missing parts, so they may not tell the whole story.

Geochemical analyses

In North America, lava flows can be grouped into three types based on their chemistry: older flows with high titanium, middle flows with low titanium, and younger flows with high titanium and iron. Studies of titanium, magnesium, and silicon content show some links between the older North American flows and the Lower Unit in Morocco. This supports the idea that the Moroccan basalts happened after the end of the Triassic, meaning they likely did not cause the big extinction event at that time.

According to Whiteside et al. (2007), geochemical analyses based upon titanium, magnesium and silicon contents show a certain correlation between the lower North American lava flows and the Lower Unit of the Moroccan CAMP, thus reinforcing the conclusion that the Moroccan basalts postdate the Tr-J boundary. Therefore, according to these data, CAMP basalts should not be included among the direct causes of the Tr-J mass extinction.