The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, the longest period of the Phanerozoic Eon; the Cretaceous Period is abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas; these oceans and seas were populated with now-extinct marine reptiles and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared; the Cretaceous ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.
The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk, found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta; the Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use; as with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is defined, being placed at an iridium-rich layer found worldwide, believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico.
This layer has been dated at 66.043 Ma. A 140 Ma age for the Jurassic-Cretaceous boundary instead of the accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. From youngest to oldest, the subdivisions of the Cretaceous period are: Late Cretaceous Maastrichtian – Campanian – Santonian – Coniacian – Turonian – Cenomanian – Early Cretaceous Albian – Aptian – Barremian – Hauterivian – Valanginian – Berriasian – The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms; the Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type, formed under warm, shallow marine circumstances.
Due to the high sea level, there was extensive space for such sedimentation. Because of the young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide. Chalk is a rock type characteristic for the Cretaceous, it consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast; the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not consolidated and the Chalk Group still consists of loose sediments in many places; the group has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is a marine system consisting of competent limestone beds or incompetent marls.
Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean. Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval; these shales are an important source rock for oil and gas, for example in the subsurface of the North Sea. During th
Atascosa County, Texas
Atascosa County is a county located in the U. S. state of Texas. As of the 2010 census, the population was 44,911, its county seat is Jourdanton. The county is named for the Atascosa River. Atascosa County is part of TX Metropolitan Statistical Area. According to the U. S. Census Bureau, the county has a total area of 1,221 square miles, of which 1,220 square miles is land and 1.9 square miles is water. Interstate 35 Interstate 37 U. S. Highway 281 Alt. US 281 State Highway 16 State Highway 85 State Highway 97 Bexar County Wilson County Karnes County Live Oak County McMullen County La Salle County Frio County Medina County As of the 2010 United States Census, there were 44,911 people residing in the county. 84.9% were White, 0.8% Black or African American, 0.8% Native American, 0.3% Asian, 0.1% Pacific Islander, 10.9% of some other race and 2.3% of two or more races. 61.9% were Hispanic or Latino. As of the census of 2000, there were 38,628 people, 12,816 households, 10,022 families residing in the county.
The population density was 31 people per square mile. There were 14,883 housing units at an average density of 12 per square mile; the racial makeup of the county was 73.23% White, 0.60% Black or African American, 0.80% Native American, 0.31% Asian, 0.06% Pacific Islander, 21.53% from other races, 3.47% from two or more races. 58.56% of the population were Hispanic or Latino of any race. There were 12,816 households out of which 41.70% had children under the age of 18 living with them, 60.30% were married couples living together, 13.00% had a female householder with no husband present, 21.80% were non-families. 18.90% of all households were made up of individuals and 8.70% had someone living alone, 65 years of age or older. The average household size was 2.99 and the average family size was 3.41. In the county, the population was spread out with 31.70% under the age of 18, 8.90% from 18 to 24, 27.60% from 25 to 44, 21.00% from 45 to 64, 10.80% who were 65 years of age or older. The median age was 32 years.
For every 100 females, there were 96.60 males. For every 100 females age 18 and over, there were 94.20 males. The median income for a household in the county was $33,081, the median income for a family was $37,705. Males had a median income of $27,702 versus $18,810 for females; the per capita income for the county was $14,276. About 16.10% of families and 20.20% of the population were below the poverty line, including 25.60% of those under age 18 and 21.70% of those age 65 or over. The following school districts serve Atascosa County: Charlotte Independent School District Jourdanton Independent School District Karnes City Independent School District Lytle Independent School District Pleasanton Independent School District Poteet Independent School District Somerset Independent School District Charlotte Jourdanton Lytle Pleasanton Poteet Christine Leming National Register of Historic Places listings in Atascosa County, Texas Recorded Texas Historic Landmarks in Atascosa County Atascosa County Government Atascosa County, Texas from the Handbook of Texas Online Atascosa County from the Texas Almanac Atascosa County from the TXGenWeb Project "Atascosa County Profile" from the Texas Association of Counties
The Texas Revolution was a rebellion of colonists from the United States and Tejanos in putting up armed resistance to the centralist government of Mexico. While the uprising was part of a larger one that included other provinces opposed to the regime of President Antonio López de Santa Anna, the Mexican government believed the United States had instigated the Texas insurrection with the goal of annexation; the Mexican Congress passed the Tornel Decree, declaring that any foreigners fighting against Mexican troops "will be deemed pirates and dealt with as such, being citizens of no nation presently at war with the Republic and fighting under no recognized flag." Only the province of Texas succeeded in breaking with Mexico, establishing the Republic of Texas, being annexed by the United States. The revolution began in October 1835, after a decade of political and cultural clashes between the Mexican government and the large population of American settlers in Texas; the Mexican government had become centralized and the rights of its citizens had become curtailed regarding immigration from the United States.
Colonists and Tejanos disagreed on whether the ultimate goal was independence or a return to the Mexican Constitution of 1824. While delegates at the Consultation debated the war's motives, Texians and a flood of volunteers from the United States defeated the small garrisons of Mexican soldiers by mid-December 1835; the Consultation declined to declare independence and installed an interim government, whose infighting led to political paralysis and a dearth of effective governance in Texas. An ill-conceived proposal to invade Matamoros siphoned much-needed volunteers and provisions from the fledgling Texian Army. In March 1836, a second political convention declared independence and appointed leadership for the new Republic of Texas. Determined to avenge Mexico's honor, Santa Anna vowed to retake Texas, his Army of Operations entered Texas in mid-February 1836 and found the Texians unprepared. Mexican General José de Urrea led a contingent of troops on the Goliad Campaign up the Texas coast, defeating all Texian troops in his path and executing most of those who surrendered.
Santa Anna led a larger force to San Antonio de Béxar, where his troops defeated the Texian garrison in the Battle of the Alamo, killing all of the defenders. A newly created Texian army under the command of Sam Houston was on the move, while terrified civilians fled with the army, in a melee known as the Runaway Scrape. On March 31, Houston paused his men at Groce's Landing on the Brazos River, for the next two weeks, the Texians received rigorous military training. Becoming complacent and underestimating the strength of his foes, Santa Anna further subdivided his troops. On April 21, Houston's army staged a surprise assault on Santa Anna and his vanguard force at the Battle of San Jacinto; the Mexican troops were routed, vengeful Texians executed many who tried to surrender. Santa Anna was taken hostage. Mexico refused to recognize the Republic of Texas, intermittent conflicts between the two countries continued into the 1840s; the annexation of Texas as the 28th state of the United States, in 1845, led directly to the Mexican–American War.
After a failed attempt by France to colonize Texas in the late 17th century, Spain developed a plan to settle the region. On its southern edge, along the Medina and Nueces Rivers, Spanish Texas was bordered by the province of Coahuila. On the east, Texas bordered Louisiana. Following the Louisiana Purchase of 1803, the United States claimed the land west of the Sabine River, all the way to the Rio Grande. From 1812 to 1813 anti-Spanish republicans and U. S. filibusters rebelled against the Spanish Empire in what is known today as the Gutiérrez–Magee Expedition during the Mexican War of Independence. They won battles in the beginning and captured many Texas cities from the Spanish that led to a declaration of independence of the state of Texas as part of the Mexican Republic on April 17, 1813; the new Texas government and army met their doom in the Battle of Medina in August 1813, 20 miles south of San Antonio, where 1,300 of the 1,400 rebel army were killed in battle or executed shortly afterwards by royalist soldiers.
It was the deadliest single battle in Texas history. 300 republican government officials in San Antonio were captured and executed by the Spanish royalists shortly after the battle. What is significant is a Spanish royalist lieutenant named Antonio López de Santa Anna fought in this battle and followed his superiors' orders to take no prisoners. Another interesting note is two founding fathers of the Republic of Texas and future signers of the Texas Declaration of Independence in 1836, José Antonio Navarro and José Francisco Ruiz, took part in the Gutiérrez–Magee Expedition. Although the United States renounced that claim as part of the Transcontinental Treaty with Spain in 1819, many Americans continued to believe that Texas should belong to their nation, over the next decade the United States made several offers to purchase the region. Following the Mexican War of Independence, Texas became part of Mexico. Under the Constitution of 1824, which defined the country as a federal republic, the provinces of Texas and Coahuila were combined to become the state Coahuila y Tejas.
Texas was granted only a single seat in the state legislature, which met in Saltillo, hundreds of miles away. After months of grumbling by Tejanos outraged at the loss of their political autonomy, state officials agreed to make Tex
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain amount of rock strata that have a comparable lithology, facies or other similar properties. Formations are not defined by the thickness of their rock strata; the concept of formally defined layers or strata is central to the geologic discipline of stratigraphy. Groups of strata are divided into formations; the definition and recognition of formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata. Formations were at first described as the essential geologic time markers, based on their relative ages and the law of superposition; the divisions of the geological time scale were described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries. The lithology of a rock is a description of its visible physical characteristics. Modern geology prefers to use lithology, that it an examination of the visible features of the component rocks, to identify discrete formations.
Geologic formations are divided into the broad categories of: sedimentary rock layers. Intrusive igneous rocks are not considered to be formations; the contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region. Formations must be able to be delineated at the scale of geologic mapping practiced in the region. Geologic formations are named after the geographic area in which they were first described. Formations cannot be defined by any criteria other than primary lithology, it is useful to define biostratigraphic units on paleontological criteria, chronostratigraphic units on the age of the rocks, chemostratigraphic units on geochemical criteria. The term "formation" is used informally to refer to a specific grouping of rocks, such as those encountered within a certain depth range in an oil well "Formation" is used informally to describe the odd shapes that rocks acquire through erosional or depositional processes; such a formation is abandoned.
Some well-known cave formations include stalagmites. Geochronology – Science of determining the age of rocks and fossils List of rock formations – Links to Wikipedia articles about notable rock outcrops List of Chinese geological formations List of fossil sites – A table of worldwide localities notable for the presence of fossils
Uvalde County, Texas
Uvalde County is a county located in the U. S. state of Texas. As of the 2010 census, its population was 26,405, its county seat is Uvalde. The county was created in 1850 and organized in 1856, it is named for the Spanish governor of Coahuila. Uvalde County was founded by Reading Wood Black who founded the city of Uvalde, Texas. Uvalde County comprises TX Micropolitan Statistical Area. Artifacts establish human habitation dating back to 7000 B. C. Evidence of a permanent Indian village on the Leona River at a place south of the Fort Inge site is indicated in the written accounts of Fernando del Bosque's exploration in 1675. Comanche, Tonkawa and Lipan Apache continued hunting and raiding settlers into the 19th Century. On January 9, 1790, Juan de Ugalde, governor of Coahuila and commandant of the Provincias Internas, led 600 men to a decisive victory over the Apaches near the site of modern Utopia at a place known as Arroyo de la Soledad. In honor of his victory, the canyon area was thereafter called Cañon de Ugalde.
French botanist Jean-Louis Berlandier visited the area in the late 1820s. James Bowie guided a group of silver prospectors into the area of north central Uvalde County in the 1830s. A trail used by General Adrián Woll's Mexican Army on its way to attack San Antonio in 1842 crossed the territory of Uvalde County and became the main highway to San Antonio. Fort Inge was established in 1849 to repress Indian depredations on the international border with Mexico, was served by the Overland Southern Mail. One of the first settlers to the environs was William Washington Arnett, who arrived in the winter of 1852; the Canyon de Ugalde Land Company, formed by land speculators in San Antonio in 1837, began purchasing headright grants in Uvalde County in the late 1830s. Reading Wood Black, who with a partner, Nathan L. Stratton, purchased an undivided league and labor on the Leona River in 1853 at the future site of Uvalde. May 2, 1855, Black hired San Antonio lithographer Wilhelm Carl August Thielepape, laid out Encina, the town known as Uvalde.
Waresville settlement by Capt. William Ware in the upper Sabinal Canyon and Patterson Settlement by George W. Patterson, John Leakey, A. B. Dillard on the Sabinal River coincided with Reading Black's development of the Leona River at Encina. In November 1855, Reading Wood Black lobbied the Texas legislature to organize Uvalde County. On May 12, the county was formally organized. On June 14, Encina was named county seat; the second floor of the courthouse was made into a school, six school districts were organized for the county in 1858. The San Antonio-El Paso Mail route was extended along the county's main road with a stop at Fort Inge in 1857. Conflict between Mexicans and Anglos during and after the Mexican War continued in Uvalde County, with the reported lynching of eleven Mexicans near the Nueces River in 1855. Laws passed in 1857 prohibited Mexicans from traveling through the county. Residents of Uvalde County voted 76–16 against secession from the Union; the abandonment of Fort Inge after secession was followed by renewed Indian attacks.
Many men in Uvalde County fought for the Confederacy, while some Unionists fled to Mexico to avoid persecution. Uvalde County endured three decades of unrelenting lawlessness after the Civil War. Violence and Confederate-Union conflicts among citizens were so pervasive that armed guards were employed to assist the county tax assessor and collector, the county had no sheriff for nearly two years; the years following the Civil War were marked by conflicts between Confederates and Unionists returning to live in Uvalde County. Smugglers and horse rustlers, numerous other desperadoes saturated the area, including notorious cattle rustler, J. King Fisher, appointed Uvalde sheriff in 1881. Willis Newton of The Newton Gang robbed his first train near Uvalde. Jess and Joe Newton retired to Uvalde; the Uvalde Umpire began publication in 1878 and the Hesparian in 1879. The Galveston and San Antonio Railway was built through the county, passing through Sabinal and Uvalde City, in 1881. William M. Landrum introduced Angora goats to the area in the 1880s.
By the turn of the century goats outnumbered cattle. Pat Garrett lived in the county 1891–1900By 1905 the Southern Pacific had established railheads in Uvalde and Sabinal; the local bee industry developed a product. Garner State Park built by the Civilian Conservation Corps and opened in 1941. Garner Army Air Field the same year; the National Fish Hatchery, completed in 1937, produced a million catfish, largemouth bass and sunfish in the 1970s. $45 million was generated by farming in Uvalde County in 1974. In January 1989 Uvalde County withdrew from the Edwards Underground Water District. In 1990 Uvalde County had a population of 23,340, with 60 percent identified as Hispanic. From the Mexican Revolution in 1910, immigrant labor force cleared large tracts of land and digging ditches, as irrigation spread throughout the county; the Uvalde and Northern Railway to Camp Wood, the Asphalt Beltway Railway in 1921, the expansion of the asphalt mines in far southwestern Uvalde County at Blewett and Dabney were completed with the help of Mexican labor.
By 1960 Mexican Americans made up one half of Uvalde County's 16,015 population. Seasonal migrant workers continued to move to Uvalde and Sabinal during the 1960s.. The Alien Land Laws of 1891, 1892 and 1921 prohibited ownership of Texas land by non-citizen residents; the laws were repealed in 1965 by the Fifty-ninth Texas Legislature. These and other discriminatory deed restrictions had limited Tejanos in the purchase of town lots in the county. Efforts to gain civil rights for
Frio County, Texas
Frio County is a county located in the U. S. state of Texas. As of the 2010 census, its population was 17,217; the county seat is Pearsall. The county was created in 1858 and organized in 1871. Frio is named for the Frio River, whose name is Spanish for "cold". According to the U. S. Census Bureau, the county has a total area of 1,134 square miles, of which 1,134 square miles is land and 0.8 square miles is covered by water. Interstate 35 U. S. Highway 57 State Highway 85 State Highway 173 Medina County Atascosa County La Salle County Dimmit County Zavala County As of the census of 2000, 16,252 people, 4,743 households, 3,642 families resided in the county; the population density was 14 people per square mile. The 5,660 housing units averaged 5 per square mile; the racial makeup of the county was 71.86% White, 4.87% Black or African American, 0.58% Native American, 0.41% Asian, 0.02% Pacific Islander, 19.76% from other races, 2.50% from two or more races. About 73.76% of the population was Hispanic or Latino of any race.
Of the 4,743 households, 40.70% had children under the age of 18 living with them, 55.20% were married couples living together, 16.00% had a female householder with no husband present, 23.20% were not families. About 20.60% of all households was made up of individuals and 9.30% had someone living alone, 65 years of age or older. The average household size was 2.98 and the average family size was 3.44. In the county, the population was distributed as 28.70% under the age of 18, 11.20% from 18 to 24, 30.80% from 25 to 44, 18.70% from 45 to 64, 10.60% who were 65 years of age or older. The median age was 31 years. For every 100 females, there were 121.40 males. For every 100 females age 18 and over, there were 130.20 males. The median income for a household in the county was $24,504, for a family was $26,578. Males had a median income of $23,810 versus $16,498 for females; the per capita income for the county was $16,069. About 24.50% of families and 29.00% of the population were below the poverty line, including 36.20% of those under age 18 and 30.40% of those age 65 or over.
Dilley Pearsall Bigfoot Hilltop Moore North Pearsall Derby Frio Town National Register of Historic Places listings in Frio County, Texas Recorded Texas Historic Landmarks in Frio County Winter Garden Region Frio County Government Frio County from the Handbook of Texas Online Historic Frio County materials, hosted by the Portal to Texas History. Frio County Profile from the Texas Association of Counties
Hydraulic fracturing is a well stimulation technique in which rock is fractured by a pressurized liquid. The process involves the high-pressure injection of'fracking fluid' into a wellbore to create cracks in the deep-rock formations through which natural gas and brine will flow more freely; when the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants hold the fractures open. Hydraulic fracturing began as an experiment in 1947, the first commercially successful application followed in 1950; as of 2012, 2.5 million "frac jobs" had been performed worldwide on gas wells. S; such treatment is necessary to achieve adequate flow rates in shale gas, tight gas, tight oil, coal seam gas wells. Some hydraulic fractures can form in certain veins or dikes. Hydraulic fracturing is controversial in many countries, its proponents advocate the economic benefits of more extensively accessible hydrocarbons, as well as replacing coal with gas, cleaner and emits less carbon dioxide.
Opponents argue that these are outweighed by the potential environmental impacts, which include risks of ground and surface water contamination and noise pollution, the triggering of earthquakes, along with the consequential hazards to public health and the environment. Methane leakage is a problem directly associated with hydraulic fracturing, as a Environmental Defense Fund report in the US highlights, where the leakage rate in Pennsylvania during extensive testing and analysis was found to be 10%, or over five times the reported figures; this leakage rate is considered representative of the hydraulic fracturing industry in the US generally. The EDF have announced a satellite mission to further locate and measure methane emissions. Increases in seismic activity following hydraulic fracturing along dormant or unknown faults are sometimes caused by the deep-injection disposal of hydraulic fracturing flowback, produced formation brine. For these reasons, hydraulic fracturing is under international scrutiny, restricted in some countries, banned altogether in others.
The European Union is drafting regulations that would permit the controlled application of hydraulic fracturing. Fracturing rocks at great depth becomes suppressed by pressure due to the weight of the overlying rock strata and the cementation of the formation; this suppression process is significant in "tensile" fractures which require the walls of the fracture to move against this pressure. Fracturing occurs; the minimum principal stress exceeds the tensile strength of the material. Fractures formed in this way are oriented in a plane perpendicular to the minimum principal stress, for this reason, hydraulic fractures in well bores can be used to determine the orientation of stresses. In natural examples, such as dikes or vein-filled fractures, the orientations can be used to infer past states of stress. Most mineral vein systems are a result of repeated natural fracturing during periods of high pore fluid pressure; the impact of high pore fluid pressure on the formation process of mineral vein systems is evident in "crack-seal" veins, where the vein material is part of a series of discrete fracturing events, extra vein material is deposited on each occasion.
One example of long-term repeated natural fracturing is in the effects of seismic activity. Stress levels rise and fall episodically, earthquakes can cause large volumes of connate water to be expelled from fluid-filled fractures; this process is referred to as "seismic pumping". Minor intrusions in the upper part of the crust, such as dikes, propagate in the form of fluid-filled cracks. In such cases, the fluid is magma. In sedimentary rocks with a significant water content, fluid at fracture tip will be steam. Fracturing as a method to stimulate shallow, hard rock oil wells dates back to the 1860s. Dynamite or nitroglycerin detonations were used to increase oil and natural gas production from petroleum bearing formations. On 25 April 1865, US Civil War veteran Col. Edward A. L. Roberts received a patent for an "exploding torpedo", it was employed in Pennsylvania, New York and West Virginia using liquid and later, solidified nitroglycerin. Still the same method was applied to water and gas wells.
Stimulation of wells with acid, instead of explosive fluids, was introduced in the 1930s. Due to acid etching, fractures would not close resulting in further productivity increase. Harold Hamm, Aubrey McClendon, Tom Ward and George P. Mitchell are each considered to have pioneered hydraulic fracturing innovations toward practical applications; the relationship between well performance and treatment pressures was studied by Floyd Farris of Stanolind Oil and Gas Corporation. This study was the basis of the first hydraulic fracturing experiment, conducted in 1947 at the Hugoton gas field in Grant County of southwestern Kansas by Stanolind. For the well treatment, 1,000 US gallons of gelled gasoline and sand from the Arkansas River was injected into the gas-producing limestone formation at 2,400 feet; the experiment was not successful as deliverability of the well did not change appreciably. The process was further described by J. B. Clark of Stanol