The 36-18 Ma Central Nevada ignimbrite field and calderas, Great Basin, USA: Multicyclic super-eruptions

In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S. In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S. In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S. In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S. In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S. In the central sector of the southern Great Basin ignimbrite province, 11 partly exposed, mostly overlapping source calderas and one concealed source comprise the 36-18 Ma Central Nevada caldera complex. Calderas have diameters as much as 50 km, to possibly 80 km. Intracaldera tuff and intercalated wall-collapse breccia are at least 2000 m thick. Surrounding outflow ignimbrites consist of 17 regional cooling units (>200 km(3)) that have been correlated over two or more mountain ranges on the basis of stratigraphic position, paleomagnetic direction, chemical and modal composition, and 40Ar/39Ar age. Many additional smaller cooling units have been recognized. Possibly as many as eight of the ignimbrites resulted from super-eruptions of 1000 km(3) to as much as 4800 km(3). This Central Nevada ignimbrite field is presently exposed over an area of similar to 65,000 km(2) in south-central Nevada and had a volume of 25,000 km(3) corrected for post-volcanic crustal extension. Six of the largest eruptions broadcast ash flows over an extension-corrected area of greater than 16,000 km(2) and as much as 160 km from their caldera sources. Individual sections of outflow tuff include as many as 14 ignimbrite cooling units; aggregate thicknesses locally reach a kilometer, and stacks a few hundred meters thick are common. Sequences are almost everywhere conformable and lack substantial intervening erosional debris and angular discordances that would testify to synvolcanic crustal extension. Beds of fallout ash a few meters thick associated with the largest eruption have been recognized in the mid-continent of the U.S.