Question: What mountain is often called the southernmost peak of a mountain range formed roughly 480 million years ago?

Context paragraphs:
Geological history of oxygen: Before photosynthesis evolved, Earth's atmosphere had no free oxygen (O).  Photosynthetic prokaryotic organisms that produced O as a waste product lived long before the first build-up of free oxygen in the atmosphere, perhaps as early as 3.5 billion years ago.  The oxygen they produced would have been rapidly removed from the atmosphere by weathering of reducing minerals, most notably iron.  This "mass rusting" led to the deposition of iron oxide on the ocean floor, forming banded iron formations.  Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the Great Oxygenation Event.  This mass oxygenation of the atmosphere resulted in rapid buildup of free oxygen.  At current rates of primary production, today's concentration of oxygen could be produced by photosynthetic organisms in 2,000 years.  In the absence of plants, the rate of oxygen production by photosynthesis was slower in the Precambrian, and the concentrations of O attained were less than 10% of today's and probably fluctuated greatly; oxygen may even have disappeared from the atmosphere again around 1.9 billion years ago.  These fluctuations in oxygen concentration had little direct effect on life, with mass extinctions not observed until the appearance of complex life around the start of the Cambrian period,   million years ago .  The presence of O2 provided life with new opportunities.  Aerobic metabolism is more efficient than anaerobic pathways, and the presence of oxygen undoubtedly created new possibilities for life to explore.  Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume.  The maximum of 35% was reached towards the end of the Carboniferous period (about 300 million years ago), a peak which may have contributed to the large size of insects and amphibians at that time.  Whilst human activities, such as the burning of fossil fuels, affect relative carbon dioxide concentrations, their effect on the much larger concentration of oxygen is less significant.

Evolution of insects: The most recent understanding of the evolution of insects is based on studies of the following branches of science: molecular biology, insect morphology, paleontology, insect taxonomy, evolution, embryology, bioinformatics and scientific computing.  It is estimated that the class of insects originated on Earth about 480 million years ago, in the Ordovician, at about the same time terrestrial plants appeared.  Insects evolved from a group of crustaceans.  The first insects were land bound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so.  The oldest definitive insect fossil, "Rhyniognatha hirsti", is estimated to be  396 .  Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects.  The Pterygotes (winged insects) underwent a major radiation in the Carboniferous (356 to 299 million years ago) while the Endopterygota (insects that go through different life stages with metamorphosis) underwent another major radiation in the Permian (299 to 252 million years ago).

Appalachian Mountains: The Appalachian Mountains ( , French: "les Appalaches" ), often called the Appalachians, are a system of mountains in eastern North America.  The Appalachians first formed roughly 480 million years ago during the Ordovician Period.  It once reached elevations similar to those of the Alps and the Rocky Mountains before naturally occurring erosion.  The Appalachian chain is a barrier to east-west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most roads running east or west.

Sierra de Bequeville: Sierra de Bequeville is a mountain range in Argentina.  It is formed by two ridges, one mostly formed by Ordovician flysch and the other by rocks of uncertain age.  The Eocene Geste Formation, a 500 m thick welded tuff and correlative rocks dated to 16.7 ± 0.1 million years ago, and continental clast strata from 13.21 ± 0.6 million years ago form the rest of the range.

Haian Range: The Coastal Mountain Range, also known as the Hai'an Range (), is a mountain range situated on the eastern coast of the island of Taiwan, and spans the border between Hualien and Taitung Counties.  Coastal Mountain Range is part of the Philippine Mobile Belt which was formed over 400 million years ago by the collision and compression of Philippine Mobile Belt and Eurasian Plate.  The geological structure is composed of soft sediments which have weaker anti-erosion property and are vulnerable to wind.

Pinhoti National Recreation Trail: The Pinhoti Trail is a long-distance trail, 335 mi long, located in the United States within the states of Alabama and Georgia.  The trail's southern terminus is on Flagg Mountain, near Weogufka, Alabama, the southernmost peak in the state that rises over 1000 ft .  (The mountain is often called the southernmost Appalachian peak, though by most geological reckonings, the actual Appalachian range ends somewhat farther north in Alabama.)  The trail's northern terminus is where it joins the Benton MacKaye Trail.

Chaotian (geology): In the geologic record the Chaotian eon or era is unofficially proposed to denote the time preceding the solidification of the Earth's crust and the formation of Earth's moon, it is the earliest era within the eon of Hadean.  It lasted 196 million years, at   million years ago to the beginning of the Zirconian era,   million years ago .  It is named after Chaos, the primeval void in Greek mythology.  The Chaotian sets in with the emergence of Earth at 4.6 billion years ago.  Its upper limit and thus the transition to the Zirconian era is defined by the occurrence of the first conservation capable mineral.  These are zircon, the oldest mineral in the Jack Hills of Narryer Gneiss Terrane in Western Australia (Yilgarn craton) found and were dated 4,404 ± 8 million years ago

McDowell Mountains: The McDowell Mountain Range (Yavapai: Wi:kajasa) is located about twenty miles north-east of downtown Phoenix, Arizona, and may be seen from most places throughout the city.  The range is composed of miocene deposits left nearly five million years ago.  The McDowells share borders with the cities of Fountain Hills, Scottsdale, and Maricopa County.  The city of Scottsdale has made its share of the McDowells a preserve, and has set up a wide trail network in partnership with the McDowell Sonoran Conservancy.  The McDowell Sonoran Conservancy was established in 1991.  The highest peak in the McDowells is East End, at 4,069 ft .  This mountain range also serves as a sacred marker to the Yavapai people.  The boundaries of the range are generally defined by Saddleback Mountain in the South and Granite Mountain as the Northern boundary.  The McDowells also comprise popular landmarks such as Pinnacle Peak and Tom's Thumb.  Although technically a stand-alone, Mt. McDowell (referred to as Red Mountain by Phoenix residents), not to be confused with McDowell Peak, is sometimes listed on maps as a part of the McDowell Mountains.

Cobequid fault: The Cobequid Fault is a fault that is the extension of the Chedabucto Fault.  This fault runs from Truro to Cape Chignecto south of the Cobequid Hills.  Both the Cobequid fault and the Chedabucto Fault form the Minas Fault zone splitting Nova Scotia into the Avalon Zone and the Meguma Zone.  Movement on the Cobequid Fault started before 400 million years ago and end around 40 million years ago.  Between that time around 350 million years violent volcanic eruptions at Spicers Cove north Cape Chignecto Provincial Park and 50 million years after grey sandstone rich in fossil plants were deposited.  At Five Islands Provincial Park there are red rocks formed by the large accumulation of mud, sand and gravel around 210 million years ago.

Geology of the Appalachians: The geology of the Appalachians dates back to more than 480 million years ago.  A look at rocks exposed in today's Appalachian Mountains reveals elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor - strong evidence that these rocks were deformed during plate collision.  The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangaea with the Appalachians and neighboring Little Atlas (now in Morocco) near the center.  These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.

Supporting paragraphs: Pinhoti National Recreation Trail Appalachian Mountains
Answer: Flagg Mountain