Murphy Paper
What is the main driver for Murphy's flat slab subduction model?
what is the plume?
What is a foreland basin?
“…elongate trough or moat that forms on continental crust between an orogenic belt and adjacent craton” (Ver Straeten, 2010)
What model, out of the four presented, does Bradley agree with most?
Who are McKerrow and Ziegler
What timing does Bradley vs Murphy propose for the collision between Laurentia and Avalonia?
Siluro-Devonian vs. Ordo-Silurian
What is K-bentonite?
A clay rock formed through the chemical alteration of tephra
Name one observation Murphy tries to explain with his model
1. Onset of diachronism throughout the Devonian
2. 400-380Ma magmatic arc gap in Maritime Canada that was abruptly terminated.
3. intrusion of oceanic lithosphere
4. Regional high-T, low-P metamorphism
5. Gold deposits
6. Rapid Devonian exhumation
What are the Foreland Basin's distinct depozones?
foredeep, back-bulge, wedge-top, and forebulge
Who are the main players in Bradley's model? (oceans included)
Laurentia, Avalonia, Meguma, Iapetus Ocean, Rheic Ocean
What modern analogy/type of subduction does Bradley use vs Murphy?
Molucca Sea Vs. Andean-type/Laramide
What is Tephra?
Any particles thrown in the air during a volcanic eruption
What terrane had already been accreted on Avalonia before the Acadian orogeny?
What is the Meguma Terrane?
What did the Acadian Orogeny produce?
“… a mountain chain that extended from Newfoundland to Alabama” (Ver Straeten, 2010)
Before colliding, the two volcanic arcs were separated by an ocean basin filled with these types of deep-water, gravity-driven sediment deposits, which later became highly deformed.
Turbidites
What massive microcontinental landmass connects Bradley’s model of colliding island arcs, Murphy’s flat-slab subduction history, and Straeten’s foreland basin studies?
Avalonia
What is an Oligomictic Conglomerate?
A Conglomerate made of Quartz
What is the name of the basin that formed after the decapitation of the overridden plume?
What is the Maritime Basin?
To prove the basin shifted back and forth instead of moving in a smooth line, Ver Straeten tracks what ancient volcanic ash layers to use as the exact timestamps across hundreds of miles.
What are K-bentonites?
What previous tectonic event does Bradley note that the volcanic arc built along the Laurentian side of the Merrimack Trough was constructed on?
The Taconic Orogeny
What type of tectonic basin environment is proposed for the primary regional subsidence trends in Ver Straeten vs Bradley?
The foreland basin vs. the outboard mountain belt
Name the four main zones in a foreland basin
wedge top, foredeep, forebulge, back bulge basin
What metal deposits were observed that Murphy explained with his flat slab/plume model?
Gold and siderophile
Even though the entire Acadian Orogeny lasted a total of 40 million years, a rock core drilled directly into an ancient forebulge zone will be missing huge chunks of this time. What is this known as?
What is an unconformity?
The post-orogenic strike slip is a manifestation of what?
Continental escape
Mentioned by Bradley as a product of partial crustal melting and highlighted by Ver Straeten as a key volcanic feature, what specific rock formation is referred to?
Traveler Rhyolite
what is typically the geometry of back bulge basin deposits?
thin and tabular