The Wessel Islands of the Northern Territory, off Napier Peninsula from Elcho Island to Wessel Marchinbar Island, are startling because of the way they line up in a thin straightish line, or two thin straightish lines. Or, adding land further SE, four thin straightinst lines.

What’s the geology here? Are these sedimentary (synclines or anticlines), or volcanic (eg. dykes), or other?

Most other long thin island chains around the world are the result of crustal uplift at plate boundaries, or coral action, (or in rarer cases hotspot movement) but none of those can apply to the Wessel Islands.

PS. Possibly Cretaceous?

mollwollfumble said:

The Wessel Islands of the Northern Territory, off Napier Peninsula from Elcho Island to Wessel Marchinbar Island, are startling because of the way they line up in a thin straightish line, or two thin straightish lines. Or, adding land further SE, four thin straightinst lines.

What’s the geology here? Are these sedimentary (synclines or anticlines), or volcanic (eg. dykes), or other?

Most other long thin island chains around the world are the result of crustal uplift at plate boundaries, or coral action, (or in rarer cases hotspot movement) but none of those can apply to the Wessel Islands.

PS. Possibly Cretaceous?

Remnants of the land bridge?

roughbarked said:

mollwollfumble said:

The Wessel Islands of the Northern Territory, off Napier Peninsula from Elcho Island to Wessel Marchinbar Island, are startling because of the way they line up in a thin straightish line, or two thin straightish lines. Or, adding land further SE, four thin straightinst lines.

What’s the geology here? Are these sedimentary (synclines or anticlines), or volcanic (eg. dykes), or other?

Most other long thin island chains around the world are the result of crustal uplift at plate boundaries, or coral action, (or in rarer cases hotspot movement) but none of those can apply to the Wessel Islands.

PS. Possibly Cretaceous?

Remnants of the land bridge?

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

roughbarked said:

roughbarked said:

mollwollfumble said:

The Wessel Islands of the Northern Territory, off Napier Peninsula from Elcho Island to Wessel Marchinbar Island, are startling because of the way they line up in a thin straightish line, or two thin straightish lines. Or, adding land further SE, four thin straightinst lines.

What’s the geology here? Are these sedimentary (synclines or anticlines), or volcanic (eg. dykes), or other?

Most other long thin island chains around the world are the result of crustal uplift at plate boundaries, or coral action, (or in rarer cases hotspot movement) but none of those can apply to the Wessel Islands.

PS. Possibly Cretaceous?

Remnants of the land bridge?

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

There’s more info. here.

https://www.environment.gov.au/system/files/resources/dc614f8f-b053-4388-bfbb-944c9dfded32/files/nmb-geomorphic-report.pdf

Speedy said:

roughbarked said:

roughbarked said:

Remnants of the land bridge?

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

There’s more info. here.

https://www.environment.gov.au/system/files/resources/dc614f8f-b053-4388-bfbb-944c9dfded32/files/nmb-geomorphic-report.pdf

Also:

https://d28rz98at9flks.cloudfront.net/11217/Rec1963_134.pdf

There are some landscape photos of the area on GoogleEarth. Like this one:

party_pants said:

There are some landscape photos of the area on GoogleEarth. Like this one:

Now I need a holiday :)

Geological map and notes and stuff here (old, though). No significant faults, not much other structure:

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

Speedy said:

party_pants said:

There are some landscape photos of the area on GoogleEarth. Like this one:

Now I need a holiday :)

Mind the crocs and sharks and irukandji.

Speedy said:

party_pants said:

There are some landscape photos of the area on GoogleEarth. Like this one:

Now I need a holiday :)

:)

Michael V said:

Geological map and notes and stuff here (old, though). No significant faults, not much other structure:

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

Got it. The main island chain is “upper Proterozoic thin bedded quartz sandstone”
The island chain next to it (Elcho Island) is “undifferentiated sand and residual soil from the Cainozoic”

Upper Proterozoic sandstone as a thin bacd would have to be folded sediments, wouldn’t it?

mollwollfumble said:

Michael V said:

Geological map and notes and stuff here (old, though). No significant faults, not much other structure:

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

Got it. The main island chain is “upper Proterozoic thin bedded quartz sandstone”
The island chain next to it (Elcho Island) is “undifferentiated sand and residual soil from the Cainozoic”

Upper Proterozoic sandstone as a thin bacd would have to be folded sediments, wouldn’t it?

Did you zooom in on the photo? https://portal.geoscience.gov.au/

mollwollfumble said:

Michael V said:

Geological map and notes and stuff here (old, though). No significant faults, not much other structure:

https://geoscience.nt.gov.au/gemis/ntgsjspui/handle/1/81730

Got it. The main island chain is “upper Proterozoic thin bedded quartz sandstone”
The island chain next to it (Elcho Island) is “undifferentiated sand and residual soil from the Cainozoic”

Upper Proterozoic sandstone as a thin bacd would have to be folded sediments, wouldn’t it?

No. Sub-horizontal; no significant folding.