Texas contains a great variety of geologic settings. The state\'s sedimentary re
ID: 291044 • Letter: T
Question
Texas contains a great variety of geologic settings. The state's sedimentary record has been largely influenced by marine transgression-regression cycles over the past 600 million years, with a lesser but still significant contribution from tectonic activity over the past 30 million years. Texas is approximately divided in two by a series of faults (the Balcones Fault System) that strike southwest to northeast across the state, nearly following the 1-35 highway from Nuevo Laredo to Dallas. South and east of the faults, rocks are mainly Cenozoic sandstones and shales, underlain by salt domes. North and west of the faults, there are a number of plateaus, which define the up-thrown block of the fault system. This enormous fault block is an area of extensive Cretaceous shale and limestone outcrops that formed during a long marine transgression. Nearly in the exact center of the state lies the Llano Uplift (aka- Enchanted Rock), a geologic granitic dome, or batholith, that formed in the Pre-Cambrian. West of the Llano uplift, the surface rocks are late Paleozoic and early Mesozoic marine sediments. In the Trans-Pecos Region, near Big Bend and El Paso, there is another, smaller series of faults associated with extensive volcanic deposits (the only volcanic rocks in Texas...). South of these, in Big Bend National Park, which lies in furthest west Texas along the Mexican border, the Marathon Mountains represent the remnants of an ancient orogeny (mountain-building event), the same event that formed the Ouachitas (in Oklahoma) and the Appalachians (in the Eastern US).Explanation / Answer
1.Locate the following cities on the map and name the Texas geologic provience to the which they belong:
a). Ausitn - Texas also has quarries for granite in an around the Llano uplift, as well as mines, that produce uranium, mercury, silver, and copper.
b) Houstin - Houstin's land surface are unconsolidated clays, shales, and poorly- cemented sands extending to depth of several miles. The regions geology developed from stream deposits that originated in erosion of rocky mountains during the formation of the Gulf coastal plain, in Territary period.
c) Dallas - Texas is approximately divided in two by a series of faults ( the Balcones faults system) that strike southest to notheast across the state.
d) EI Pasco - West of the Llano uplift, the surface of the rocks are Palezoic and early Mesozoic marine sediments. In the Trans Pesco region, near big band and EI Paso, there is another smaller series of faults associated with extensive volcanic deposits.
e) Lubock - Texas cover with shallow seas to the west, with evaporation flats that precipitation many evaporate rocks to the east and north in the High plain region.
2. List the time period when these geologic provience :
a)Pre -Cambrian : The oldest rocks preserved in Texas are formed the Pre- Cambrian, about 1bya (billian years ago). At this time, the Grenvillie orogeny, which occured as part of the collision of the super contient Rodinia, was occuring.
b) Palezoic - In the late Palezoic a plate collision occured along the current location of the Balcones faults system, which raised up the ouachita mountains.
c) Mesozoic - In the early Mesozoic the Gulf of Mexico began to form, as the super- continent pangaca split apart and North America separated from Europe. Because of this, these are few early Mesozoic rocks in Texas.
d) Cenozoic - The western Ineterier seaway regressed (retreated), establishing the current Texas drainage system by leaving behind rivers that drin the higher.
3. a) what is the name and age of the formation containing the oldest rocks found in Texas:
The oldest rocks preserved in Texas are form the Pre-Cambrian about 1 bya (billion year ago).
b) What is the name and age of the formation containing the youngest rocks found in Texas:
In the early Mesozoic the Gulf of Mexico began to form the youngest rocks in Texas.
4.a) what formation underlies the city of Houston:
Houston's land surface are unconsolidated clays, shales and poorly - cemented sands, extending to depth of several milies.
b) how old is this formation:
They are formed late cretaceos about 138 billion years .
7. Austin and Dallas both lie on the rock fromation:
Dallas- south and east of the faults are mainly cenozoic sand stone and shales, underlain by salt domes.
Austin - north and west of faults, there are number of plateaus, which define the up-thrown block of the fault system. A geologic granite dome or batholith. The age of these rocks formation is over the past 30 millian years.
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