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140-628: Before Spanish colonization in the 1770s, the San Juan Creek watershed was inhabited by the Acjachemen or Juañeno Native Americans. The Juañeno were named by Spanish missionaries who built Mission San Juan Capistrano on the banks of a stream they named San Juan Creek. The watershed was used mainly for agriculture and ranching until the 1950s when residential suburban development began on a large scale. Since then, development has continued to encroach on floodplains of local streams. Flooding in

280-560: A drop structure that channels the creek beneath Interstate 5 . In response, the Department of Fish and Game lobbied Caltrans to build a fish ladder at the structure, but it has not yet been implemented, due to concerns about structural stability of the I-5 bridge and the presence of a nearby natural gas pipeline. Before the 18th century, the San Juan Creek watershed was mostly Acjachemen territory, which extended from Aliso Creek in

420-400: A (usually small) angle. Sometimes multiple sets of layers with different orientations exist in the same rock, a structure called cross-bedding . Cross-bedding is characteristic of deposition by a flowing medium (wind or water). The opposite of cross-bedding is parallel lamination, where all sedimentary layering is parallel. Differences in laminations are generally caused by cyclic changes in

560-512: A 100-year flood in the watershed would only affect a roughly 0.5 mi (0.80 km) wide area for the lower reaches of San Juan Creek inside San Juan Capistrano, while for Arroyo Trabuco, only a 0.2 mi (0.32 km) wide area would be affected, mainly due to considerable entrenchment of the river bed. However, the U.S. Army Corps of Engineers considers many levees in the San Juan Capistrano area to be inadequate for handling

700-412: A 30-foot (9.1 m) cascade immediately downstream of a Metrolink bridge, and a concrete drop structure at the terminus of a culvert that crosses underneath Interstate 5 . There are also seven drop structures on Oso Creek, mostly built of riprap. There are no such specifically constructed structures on San Juan Creek itself. This is a list of major crossings of San Juan Creek, proceeding upstream of

840-516: A Spanish soldier and one "neophyte," a recently baptized Native and Spanish translator, a "crowd of painted and well-armed [Acjachemen] Indians, some of whom put arrows to their bowstrings as though they intended to kill the Spanish intruders" surrounded Serra's group. The "neophyte" informed the Acjachemen that attacking would only result in further violence from the Spanish military. As a result,

980-412: A depth of 200 feet (61 m) in the lower elevations to almost none in the high elevations. Groundwater in this basin at the San Juan Capistrano reach is considered of high quality. Although San Juan Creek contains water for most of the year, it is highly seasonal, with strong flows during the wettest months of January through March, and shrinking to a trickle during the other months. In poor rain years,

1120-424: A diagenetic structure common in carbonate rocks is a stylolite . Stylolites are irregular planes where material was dissolved into the pore fluids in the rock. This can result in the precipitation of a certain chemical species producing colouring and staining of the rock, or the formation of concretions . Concretions are roughly concentric bodies with a different composition from the host rock. Their formation can be

1260-419: A dietary preference for birds and small mammals like rabbits. They crafted animal bones into weapons, tools, and jewelry. Acjachemen villages were primarily concentrated along the lower San Juan Creek. In 1775, Spanish colonists erected a cross on an Acjachemen religious site before retreating to San Diego due to a revolt at Mission San Diego . They returned one year later to begin constructing and converting

1400-458: A drought decimated the local cattle ranching industry), consumed native grasses and left hillsides exposed and prone to erosion. The origin of the name of Arroyo Trabuco (Spanish: "Blunderbuss Creek", literally) stems from the Gaspar de Portolà expedition of 1769, during which a soldier lost a blunderbuss ("trabuco"), and the name became associated with the creek after that point. The origin of

1540-509: A little way, formed in pools in some large patches of tules." On the return journey to San Diego , the party used the campsite again, on January 20. In 1776, Father Junípero Serra founded Mission San Juan Capistrano on a site close to the creek (possibly near the Cañada Gobernadora confluence), and the creek was named after the mission. The first site was abandoned due to lack of water, although some historical accounts suggest

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1680-459: A major barrier to migrating fish and other riverine organisms, and thus isolates aquatic environments in upper Arroyo Trabuco from the rest of the San Juan watershed. In 1996, severe floods caused by heavy rainstorms in the San Juan watershed caused San Juan Creek to overflow, destroying long sections of the concrete river banks near their confluence. The damage was attributed to severe erosion at

1820-463: A particular sedimentary environment. Examples of bed forms include dunes and ripple marks . Sole markings, such as tool marks and flute casts, are grooves eroded on a surface that are preserved by renewed sedimentation. These are often elongated structures and can be used to establish the direction of the flow during deposition. Ripple marks also form in flowing water. There can be symmetric or asymmetric. Asymmetric ripples form in environments where

1960-708: A physical barrier for streams flowing off the Santa Ana Mountains. Climate change during the Ice Ages periodically made Southern California much wetter, most recently during the Wisconsinian Glaciation (70,000 to 10,000 years ago), when the area was home to a temperate rainforest climate that would receive rainfall in excess of 80 inches (2,000 mm) per year. The increase in water flow in San Juan Creek allowed it to maintain its course as an antecedent stream , rather than being diverted to

2100-465: A red colour does not necessarily mean the rock formed in a continental environment or arid climate. The presence of organic material can colour a rock black or grey. Organic material is formed from dead organisms, mostly plants. Normally, such material eventually decays by oxidation or bacterial activity. Under anoxic circumstances, however, organic material cannot decay and leaves a dark sediment, rich in organic material. This can, for example, occur at

2240-489: A rock is usually expressed with the Wentworth scale, though alternative scales are sometimes used. The grain size can be expressed as a diameter or a volume, and is always an average value, since a rock is composed of clasts with different sizes. The statistical distribution of grain sizes is different for different rock types and is described in a property called the sorting of the rock. When all clasts are more or less of

2380-465: A sediment after its initial deposition. This includes compaction and lithification of the sediments. Early stages of diagenesis, described as eogenesis , take place at shallow depths (a few tens of meters) and is characterized by bioturbation and mineralogical changes in the sediments, with only slight compaction. The red hematite that gives red bed sandstones their color is likely formed during eogenesis. Some biochemical processes, like

2520-431: A sedimentary rock may have been present in the original sediments or may formed by precipitation during diagenesis. In the second case, a mineral precipitate may have grown over an older generation of cement. A complex diagenetic history can be established by optical mineralogy , using a petrographic microscope . Carbonate rocks predominantly consist of carbonate minerals such as calcite, aragonite or dolomite . Both

2660-516: A small-scale property of a rock, but determines many of its large-scale properties, such as the density , porosity or permeability . The 3D orientation of the clasts is called the fabric of the rock. The size and form of clasts can be used to determine the velocity and direction of current in the sedimentary environment that moved the clasts from their origin; fine, calcareous mud only settles in quiet water while gravel and larger clasts are moved only by rapidly moving water. The grain size of

2800-952: A term for a fissile mudrock (regardless of grain size) although some older literature uses the term "shale" as a synonym for mudrock. Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue. Examples include: Chemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate . Common chemical sedimentary rocks include oolitic limestone and rocks composed of evaporite minerals, such as halite (rock salt), sylvite , baryte and gypsum . This fourth miscellaneous category includes volcanic tuff and volcanic breccias formed by deposition and later cementation of lava fragments erupted by volcanoes, and impact breccias formed after impact events . Alternatively, sedimentary rocks can be subdivided into compositional groups based on their mineralogy: Sedimentary rocks are formed when sediment

2940-417: A texture, only the average size of the crystals and the fabric are necessary. Most sedimentary rocks contain either quartz ( siliciclastic rocks) or calcite ( carbonate rocks ). In contrast to igneous and metamorphic rocks, a sedimentary rock usually contains very few different major minerals. However, the origin of the minerals in a sedimentary rock is often more complex than in an igneous rock. Minerals in

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3080-425: A valuable indicator of the biological and ecological environment that existed after the sediment was deposited. On the other hand, the burrowing activity of organisms can destroy other (primary) structures in the sediment, making a reconstruction more difficult. Secondary structures can also form by diagenesis or the formation of a soil ( pedogenesis ) when a sediment is exposed above the water level. An example of

3220-503: Is deposited out of air, ice, wind, gravity, or water flows carrying the particles in suspension . This sediment is often formed when weathering and erosion break down a rock into loose material in a source area. The material is then transported from the source area to the deposition area. The type of sediment transported depends on the geology of the hinterland (the source area of the sediment). However, some sedimentary rocks, such as evaporites , are composed of material that form at

3360-449: Is Mediterranean, with hot, dry summers and cool, wet winters. Almost all the precipitation occurs between October and April; the average rainfall is 12 to 16 inches (300 to 410 mm), although mountain areas often receive higher amounts. San Juan Creek receives extra runoff from agriculture, urban areas, and other human sources, resulting in unnatural dry season flows that carry trash, heavy metals , oils, pesticides and fertilizer into

3500-421: Is a structure where beds with a smaller grain size occur on top of beds with larger grains. This structure forms when fast flowing water stops flowing. Larger, heavier clasts in suspension settle first, then smaller clasts. Although graded bedding can form in many different environments, it is a characteristic of turbidity currents . The surface of a particular bed, called the bedform , can also be indicative of

3640-409: Is called bedding . Single beds can be a couple of centimetres to several meters thick. Finer, less pronounced layers are called laminae, and the structure a lamina forms in a rock is called lamination . Laminae are usually less than a few centimetres thick. Though bedding and lamination are often originally horizontal in nature, this is not always the case. In some environments, beds are deposited at

3780-549: Is closely related to the Luiseño language still spoken by the neighboring Payómkawichum ( Luiseño ) people. Spanish colonists called the Acjachemen Juaneños , following their conversion to Christianity at Mission San Juan Capistrano in the late 18th century. Today, many contemporary members of organizations for Acjachemen descendants prefer the term Acjachemen as their autonym, or name for themselves. The name

3920-540: Is crossed by a complex network of seismic fault zones, with streams tending to form canyons along fault traces. The Cristianitos fault (Cristianitos) runs northeast-southwest along Oso Creek , passing offshore 7 miles (11 km) south of the mouth of San Juan Creek. The Mission Viejo fault zone parallels the Cristianitos but ends much farther south, in San Diego County . The first recorded earthquake in

4060-569: Is currently proposing a new 5,000-acre-foot (6,200,000 m) reservoir in Verdugo Canyon, another tributary of San Juan Creek, to collect and store reclaimed water. The lower 3.5 miles (5.6 km) of San Juan Creek are channelized between levees , from a point immediately upstream of the Interstate 5 bridge to Doheny Beach. Arroyo Trabuco is only channelized for several hundred yards above its confluence with San Juan Creek. Oso Creek

4200-502: Is derived from the village of Acjacheme , which was less than 60 yards from the site where Mission San Juan Capistrano was built in 1776. Alternate spellings include Acachme or Acagchemem. Acjachemen creation and origins stories represent their history in Southern California as beginning in the beginning of time. Archaeologists argue there has been an Acjachemen presence in the region for at least 10,000 years. In

4340-406: Is found along the banks of free-flowing streams with a measurable flow for at least several months out of the year. These include most of San Juan Creek, upper Arroyo Trabuco, Cañada Gobernadora, Bell Canyon, and other headwater streams, as well as scattered patches along Oso and El Horno creeks. Forests are present at high elevations, and also occur in close proximity to waterways. Coastal sage scrub

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4480-406: Is found on south-facing hillsides, while chaparral is found on higher-elevation hillsides and mesas. There are also a number of rare plant communities along rock outcroppings and vernal pools . However, introduced plant species, such as giant reed, castor bean , and tobacco tree , are rapidly spreading along streams. Giant reed has taken over huge areas of wetlands, swamps and riparian zones along

4620-429: Is higher when the sedimentation rate is high (so that a carcass is quickly buried), in anoxic environments (where little bacterial activity occurs) or when the organism had a particularly hard skeleton. Larger, well-preserved fossils are relatively rare. Fossils can be both the direct remains or imprints of organisms and their skeletons. Most commonly preserved are the harder parts of organisms such as bones, shells, and

4760-491: Is mirrored by the broad categories of rudites , arenites , and lutites , respectively, in older literature. The subdivision of these three broad categories is based on differences in clast shape (conglomerates and breccias), composition (sandstones), or grain size or texture (mudrocks). Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel. Sandstone classification schemes vary widely, but most geologists have adopted

4900-595: Is no longer used for water storage, its roughly 3-to-4-foot (0.91 to 1.22 m) drop still poses a problem for migrating steelhead. There are a few water diversion weirs that exist on San Juan tributary streams to divert water for irrigation, ranching and limited municipal uses, but due to limited flows and polluted water, the usefulness of these structures are limited. A number of drop structures (small dams used to control water velocity and erosion) exist on tributaries of San Juan Creek. On Arroyo Trabuco, there are eight drop structures, mostly built of riprap. The largest are

5040-401: Is reduced. Sediments are typically saturated with groundwater or seawater when originally deposited, and as pore space is reduced, much of these connate fluids are expelled. In addition to this physical compaction, chemical compaction may take place via pressure solution . Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of

5180-401: Is the most heavily modified, flowing in an artificial channel for almost its entire length. Bell Creek and other eastern tributaries have retained their natural characteristics. The USACE describes the San Juan and Arroyo Trabuco levees as providing a "fairly high level of protection currently", though flooding in 1996 and 2005 caused significant damage. As a result, failure scenarios of levees in

5320-493: Is the most stable, followed by feldspar , micas , and finally other less stable minerals that are only present when little weathering has occurred. The amount of weathering depends mainly on the distance to the source area, the local climate and the time it took for the sediment to be transported to the point where it is deposited. In most sedimentary rocks, mica, feldspar and less stable minerals have been weathered to clay minerals like kaolinite , illite or smectite . Among

5460-462: Is underlain by thick alluvial deposits and is still used for farming and grazing. It is joined by Bell Canyon from the right, and Verdugo Canyon Creek from the left. Trampas Canyon enters from the left and Cañada Gobernadora and Cañada Chiquita enter from the right. The creek flows through residential Rancho Mission Viejo , crosses under Interstate 5 , and enters a concrete flood control channel , turning south and receiving El Horno Creek on

5600-463: The history of life . The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology . Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences , such as pedology , geomorphology , geochemistry and structural geology . Sedimentary rocks can be subdivided into four groups based on

5740-682: The organic material of a dead organism undergoes chemical reactions in which volatiles such as water and carbon dioxide are expulsed. The fossil, in the end, consists of a thin layer of pure carbon or its mineralized form, graphite . This form of fossilisation is called carbonisation . It is particularly important for plant fossils. The same process is responsible for the formation of fossil fuels like lignite or coal. Structures in sedimentary rocks can be divided into primary structures (formed during deposition) and secondary structures (formed after deposition). Unlike textures, structures are always large-scale features that can easily be studied in

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5880-505: The "Playanos" (who lived along the coast) and the "Serranos" (who inhabited the mountains, some three to four leagues from the Mission). The religious beliefs of the two groups as related to creation differed quite profoundly. The Playanos held that an all-powerful and unseen being called "Nocuma" brought about the earth and the sea, together with all of the trees, plants, and animals of sky, land, and water contained therein. The Serranos, on

6020-417: The "claims of Indians who had acquired land in the 1841 formation" of the San Juan pueblo, "were similarly ignored, despite evidence that the [American] land commission had data substantiating these Juaneños' titles." By 1860, Acjachemen were recorded in the census "with Spanish first names and no surnames; the occupations of 38 percent of their household heads went unrecorded; and they owned only 1 percent of

6160-408: The "latter part of the nineteenth century individuals and families often moved back and forth between these villages and San Juan for work, residence, family events, and festivals." American occupation resulted in increasing power and wealth for European immigrants and Anglo-Americans to own land and property by the 1860s, "in sharp contrast to the pattern among Californios, Mexicans, and Indians." In

6300-473: The 100-year flood, and that such a flood would cause $ 149 million of property damage. The San Juan Creek watershed covers 133.9 square miles (347 km) in south Orange County and a very small portion of Riverside County. The Santa Ana Mountains occupy most of the north, east and south parts watershed, while the San Joaquin Hills border the watershed on the southwest. Along with San Juan Creek,

6440-665: The 1850s alone, the California Indian population declined by 80 percent. Any land rights Native people had under Mexican rule were completely erased under American occupation, as stated in Article 11 of the treaty: "A great part of the territories which, by the present treaty, are to be comprehended for the future within the limits of the United States, is now occupied by savage tribes." As the United States government declared its right to police and control Native people,

6580-636: The 1990s, the Acjachemen Nation divided into three different governments, all claiming their identity as the Juaneño Band of Mission Indians, Acjachemen Nation. These unrecognized organizations include: The Juaneño Band of Mission Indians, Acjachemen Nation (84A), based in San Juan Capistrano elects a tribal council, assisted by tribal elders. They have about 1,800 members. In 1993, an Assembly Joint Resolution No. 48

6720-401: The 20th and 21st centuries has caused considerable property damage in the San Juan watershed. The San Juan watershed is home to sixteen major native plant communities and hundreds of animal species. However, the watershed is projected to be 48 percent urbanized by 2050. In addition, urban runoff has changed flow patterns in San Juan Creek and introduced pollutants to the river system. Although

6860-474: The 30-foot (9.1 m) Ortega Falls are located along the headwaters of the creek. The creek then flows generally southwest through a canyon, receiving Hot Springs Creek and Cold Springs Creek from the right, and Lucas Canyon Creek from the left. At Caspers Wilderness Park, the San Juan Canyon opens up into a fairly wide valley in the foothills of the Santa Ana Mountains. This reach of San Juan Creek

7000-507: The 500-square-mile (1,300 km) San Juan Hydrologic Unit, which includes the coastal watersheds of Aliso Creek , Salt Creek , Prima Deshecha Cañada , Segunda Deshecha Cañada , and San Mateo Creek , which share a similar range of elevations and climate. Elevation in the Hydrologic Unit ranges from sea level to 5,700 feet (1,700 m) at Santiago Peak (the headwater of Holy Jim Creek, a tributary of Arroyo Trabuco). The climate

7140-400: The Acjachemen "desisted, aware of the serious threat that military retaliation represented." While, before 1783, those who had been converted, known as "Juaneños, both children and adults, represented a relatively small percentage of the Acjachemen population, all that changed between 1790 and 1812, when the vast majority of remaining non-converts were baptized." Spanish colonists referred to

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7280-469: The Acjachemen as Juaneño. The Acjachemen were designated as Juaneños by Spanish priests through the baptismal process performed at Mission San Juan Capistrano, named after St. Juan Capistrano in Spain . Many other local tribes were named similarly (Kizh (pronounced keech ) – Gabrieleño; named after Mission San Gabriel ). During the late 18th century, the mission economy extended over the entire territory of

7420-782: The Acjachemen people and is seen often in art and tribal seals. The Acjachemen language is related to the Luiseño language spoken by the nearby Luiseño tribe located to the interior. Considered to speak a dialect of Luiseño, the Juaneño were part of the Cupan subgroup of the Uto-Aztecan languages . Northern Uto-Aztecan (NUA) is divided into four branches; Numic, Tubatrlabalic, Takic, and Hopic. Takin includes seven languages; Kitanemuk, Serrano (including Vanyume), Gabrielino (including Fernandeńo), Luiseño (including Acjachemen), Cahuilla, Cupeño, and Tataviam. Their language became extinct by

7560-403: The Acjachemen population. The majority of early converts were often children, who may have been brought by their parents in an attempt to "make alliances with missionaries, who not only possessed new knowledge and goods but also presented the threat of force." Spanish military presence ensured the continuation of the mission system. In 1776, as Junípero Serra approached Acjachemen territory with

7700-430: The Acjachemen were now "free," they were "increasingly vulnerable to being forced to work on public projects" if it was determined that they had "'reverted' to a state of dependence on wild fruits or neglected planting crops and herding" or otherwise failed to continue practicing Spanish-imposed methods of animal husbandry and horticulture . Because of a lack of formal recognition, "most of the former Acagchemem territory

7840-603: The Acjachemen. Acjachemen villages still had "access to specific hunting, collecting, and fishing areas" and "within these collectively owned areas villagers also possessed private property." However, the Indigenous land tenure system was first paralleled and then undermined by the mission system and colonization. The Spanish transformed the countryside into grazing lands for livestock and horticulture. Between 1790 and 1804, "mission herds increased in size from 8,034 head to 26,814 head." As European disease also began to decimate

7980-766: The Adelia Sandoval, Jerry Nieblas and other Acjachemen members celebrated the opening of Putuidem Village , a 1.5-acre park (0.61 ha) in San Juan Capistrano, part of their original lands, which commemorates their history. On July 10, 2021, one of the Acjachemen Nation 84A group elected a new tribal council of Heidi Lee Lucero, Chairwoman; Dr. Richard Rodman, Vice Chairman; Ricky Hernandez, Treasurer; Georgia "Chena" Edmundson, Secretary; Sabrina Banda, Member-At-Large; and Ruth "Cookie" Stoffel, Member-At-Large. Acjachemen villages and significant sites in Southern California (a partial list): Sedimentary rock Sedimentary rocks are types of rock that are formed by

8120-586: The Californios." The formation of the San Juan pueblo granted Californios and Acjachemen families solars , or lots for houses, and suertes , or plots of land in which to plant crops. Following the American occupation of California in 1846 and the Treaty of Guadalupe Hidalgo in 1848, "Indian peoples throughout California were drawn into the 'cycles of conquest' that had been initiated by the Spanish." During

8260-501: The Dott scheme, which uses the relative abundance of quartz, feldspar, and lithic framework grains and the abundance of a muddy matrix between the larger grains. Six sandstone names are possible using the descriptors for grain composition (quartz-, feldspathic-, and lithic-) and the amount of matrix (wacke or arenite). For example, a quartz arenite would be composed of mostly (>90%) quartz grains and have little or no clayey matrix between

8400-555: The Metz-San Emigdio, Sorrento-Mocho, Myford, Alo-Bosanko, Cieneba-Anaheim-Soper, and Friant-Cieneba-Exchequer associations, in order from low to high elevations. Steep hills in the San Juan watershed are prone to collapse during heavy rainfall or seismic activity. Over the past 1.2 million years the uplift of the San Joaquin Hills , a small coastal mountain range generally following the Pacific coast of Orange County, created

8540-581: The Puhú village site. However, while Acjachemen "claimed and were granted villages," there was "rarely" any legal title issued, meaning that the land was "never formally ceded" to them following emancipation, which they protested as others encroached upon their traditional territory. While rancho grants issued by the Mexican government on the lands of the San Juan mission "were made in the early 1840s, Indians' rights to their village lands went unrecognized." Although

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8680-571: The San Juan watershed have been extensively studied. To protect against future flooding, work has begun on a new west-bank levee replacement to be finished in 2013. A few check dams exist on small upper tributaries of San Juan Creek, mostly inside the Cleveland National Forest . A larger gabion -type dam is located on the middle part of San Juan Creek near the Cañada Gobernadora. Although the dam has silted in and

8820-639: The San Juan watershed, most sensitive species have been pushed back to the foothills, mountains, and agricultural/ranching areas of the watershed. In 1987, just five bird species were confirmed in the watershed, while for fish , benthic invertebrates , and certain insects there were no confirmed observations, in part due to insufficient site coverage. Historic accounts suggest that San Juan Creek provided habitat for steelhead trout ( Oncorhynchus mykiss irideus ) in many historic accounts. However, pollution and competition from introduced sport fishes such as bluegill and striped bass have extirpated steelhead in

8960-457: The Santa Ana and San Juan Capistrano townships, most Californios lost their ranchos in the 1860s. By 1870, European immigrants and Anglo-Americans now owned 87 percent of the land value and 86 percent of the assets. Native people went from owning 1 percent of the land value and assets, as recorded in the 1860 census, to 0 percent in 1870. Anglo-Americans became the majority of the population by

9100-477: The Spanish Portolá expedition , passed this way on its way north, camping at San Juan Creek on July 23, 1769. Franciscan missionary Juan Crespi noted in his diary: "...we came to a very pleasant green valley, full of willows, alders, live oaks, and other trees not known to us. It has a large arroyo, which at the point where we crossed it carried a good stream of fresh and good water, which, after running

9240-474: The accumulation or deposition of mineral or organic particles at Earth's surface , followed by cementation . Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment , and may be composed of geological detritus (minerals) or biological detritus (organic matter). The geological detritus originated from weathering and erosion of existing rocks, or from

9380-470: The activity of bacteria , can affect minerals in a rock and are therefore seen as part of diagenesis. Deeper burial is accompanied by mesogenesis , during which most of the compaction and lithification takes place. Compaction takes place as the sediments come under increasing overburden (lithostatic) pressure from overlying sediments. Sediment grains move into more compact arrangements, grains of ductile minerals (such as mica ) are deformed, and pore space

9520-425: The area partially destroyed Mission San Juan Capistrano in 1812 (which had been built only six years before), killing forty people in the adobe chapel when it collapsed. Other major quakes occurred in 1862, 1933 and 1938. Soils in the San Juan watershed are mostly sedimentary rock and are highly erosive, resulting in large alluvial deposits along floodplains. Soil types in the San Juan watershed can be divided into

9660-431: The base which caused the concrete to lose support and crumble. A nearby residential community was threatened, but the floods receded before the levee collapsed and no serious harm was done. The failed sections were repaired with grouted riprap. In early 2005, even more severe flooding impacted the San Juan watershed, with an all-time highest flow of 33,650 cubic feet per second (953 m/s) recorded on January 11. Although

9800-485: The bay, it is trapped for extended periods of time. At Doheny State Beach, 850,000 annual visitors are exposed to potential health risks from high bacteria levels in the water. During floods in the 1990s, an almost sheer 30-foot (9.1 m) waterfall appeared on Arroyo Trabuco in northern San Juan Capistrano, threatening the foundations of a railroad bridge. The drop required quick reinforcement with grouted riprap . With an average gradient of 29 percent it has become

9940-399: The bottom of deep seas and lakes. There is little water mixing in such environments; as a result, oxygen from surface water is not brought down, and the deposited sediment is normally a fine dark clay. Dark rocks, rich in organic material, are therefore often shales. The size , form and orientation of clasts (the original pieces of rock) in a sediment is called its texture . The texture is

10080-504: The cement and the clasts (including fossils and ooids ) of a carbonate sedimentary rock usually consist of carbonate minerals. The mineralogy of a clastic rock is determined by the material supplied by the source area, the manner of its transport to the place of deposition and the stability of that particular mineral. The resistance of rock-forming minerals to weathering is expressed by the Goldich dissolution series . In this series, quartz

10220-421: The cement to produce secondary porosity . At sufficiently high temperature and pressure, the realm of diagenesis makes way for metamorphism , the process that forms metamorphic rock . The color of a sedimentary rock is often mostly determined by iron , an element with two major oxides: iron(II) oxide and iron(III) oxide . Iron(II) oxide (FeO) only forms under low oxygen ( anoxic ) circumstances and gives

10360-717: The city of San Juan Capistrano, the largest flood of record occurred on January 11, 2005 with an estimated discharge of 33,650 cubic feet per second (953 m/s). According to the California State Water Resources Control Board (1977) the San Juan Creek Groundwater Basin has a total volume of roughly 900,000 acre-feet (1.1 × 10 m). Natural groundwater recharge in the San Juan basin is estimated at 160,000 acre-feet (200,000,000 m) per year. This amount has been reduced due to extensive urbanization of

10500-639: The continents of the Earth's crust is extensive (73% of the Earth's current land surface), but sedimentary rock is estimated to be only 8% of the volume of the crust. Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks . Sedimentary rocks are deposited in layers as strata , forming a structure called bedding . Sedimentary rocks are often deposited in large structures called sedimentary basins . Sedimentary rocks have also been found on Mars . The study of sedimentary rocks and rock strata provides information about

10640-556: The council of elders ( puuplem ), which was made up of lineage heads and ceremonial specialists in their own right. This body decided upon matters of the community, which were then carried out by the Nota and his underlings. While the placement of residential huts in a village was not regulated, the ceremonial enclosure ( vanquesh ) and the chief's home were most often centrally located. The Acjachemen relied upon harvesting and processing acorns, grasses, seeds, and bay shellfish. They had

10780-824: The creek and its tributaries, although in recent years the county has taken steps toward eradicating it from San Juan Creek and other nearby streams. Historically, the San Juan watershed supported up to 12 invertebrate species, 5 fish species, 12 amphibian species, 35 reptile species, 143 bird species, and 42 mammal species, which benefited from the diverse vegetation communities present. Some streams and ponds host federally listed endangered/threatened species such as tidewater goby , fairy shrimp , and California red-legged frog . Federally listed bird species include least Bell's vireo , California gnatcatcher , California least tern , and southwestern willow flycatcher . Other listed species include Pacific pocket mouse and Quino checkerspot butterfly . As urbanization continues to increase in

10920-436: The creek and its tributaries, creating a dry season "nuisance flow". Historically, only San Juan Creek and Arroyo Trabuco were known to contain water for most or all of the year. Oso Creek was formerly a seasonal stream, but it now has a permanent flow due to urban runoff. Runoff has caused Doheny Beach to rank in the ten most polluted beaches of California. The Upper Oso Reservoir and Lake Mission Viejo , both on Oso Creek, are

11060-609: The creek once had a perennial flow. The mission was moved to a second site in present-day San Juan Capistrano, where it still stands. The Spanish referred to the Acjachemem as the Juañeno . The Spanish made the first recorded anthropogenic changes to hydrology in the San Juan watershed, which included excavating irrigation channels, diverting water from streams, and channelizing and changing course of streams. Grazing animals introduced by Europeans, mainly cattle (and later sheep, after

11200-506: The creek. Bacteria levels in San Juan Creek exceed state standards by 93 percent. The loss of riparian habitat along the lower 2.7 miles (4.3 km) of San Juan Creek and much of Trabuco and Oso Creeks due to channelization has also reduced steelhead habitat. However, in 2003 the California Department of Fish and Game reported three sightings of steelhead in a large stream pool along Trabuco Creek , immediately downstream of

11340-549: The creek. The heaviest source of pollution is Oso Creek. Michael Hazzard, a Southern California environmentalist, said after diving into Upper Oso Creek Reservoir: "I spent three days diving to retrieve an outboard motor and my skin broke out in hives and boils and my gallbladder suffered and I later had six operations over a 2 1 ⁄ 2 -year period." San Juan Creek was originally rich in riparian zones and other types habitat in both its upper and lower watershed, with wetlands totaling over 300 acres (1.2 km) historically in

11480-572: The current is in one direction, such as rivers. The longer flank of such ripples is on the upstream side of the current. Symmetric wave ripples occur in environments where currents reverse directions, such as tidal flats. Mudcracks are a bed form caused by the dehydration of sediment that occasionally comes above the water surface. Such structures are commonly found at tidal flats or point bars along rivers. Secondary sedimentary structures are those which formed after deposition. Such structures form by chemical, physical and biological processes within

11620-663: The dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions: gravel (>2 mm diameter), sand (1/16 to 2 mm diameter), and mud (<1/16 mm diameter). Mud is further divided into silt (1/16 to 1/256 mm diameter) and clay (<1/256 mm diameter). The classification of clastic sedimentary rocks parallels this scheme; conglomerates and breccias are made mostly of gravel, sandstones are made mostly of sand , and mudrocks are made mostly of mud. This tripartite subdivision

11760-468: The early 20th century. People are working at reviving it, with several members learning it. Their studies are based on the research and records of Anastacia Majel and John P. Harrington , who recorded the language in 1933. (The tape recordings resurfaced around 1995.) Several organizations today identify as representing Acjachemen descendants. None of them are federally recognized , and California has no process for creating state-recognized tribes . In

11900-407: The east or west. The U.S. Geological Survey (USGS) measured the discharge of San Juan Creek in the city of San Juan Capistrano for two periods, from 1928 to 1969 and from 1969 to 1985. Stream flows for the earlier period are considerably different from the later period due to increased volumes of urban runoff. For 1928–1969, the average discharge was 14.3 cubic feet per second (0.40 m/s), and

12040-479: The era preceding colonization by Spain, the Acjachemen resided in permanent, well-defined villages and seasonal camps. Village populations ranged from between 35 and 300 residents, consisting of a single lineage in the smaller villages, and of a dominant clan joined with other families in the larger settlements. Each clan had its own resource territory and was politically independent; ties to other villages were maintained through economic, religious, and social networks in

12180-489: The field. Sedimentary structures can indicate something about the sedimentary environment or can serve to tell which side originally faced up where tectonics have tilted or overturned sedimentary layers. Sedimentary rocks are laid down in layers called beds or strata . A bed is defined as a layer of rock that has a uniform lithology and texture. Beds form by the deposition of layers of sediment on top of each other. The sequence of beds that characterizes sedimentary rocks

12320-411: The first Mexican governor of Alta California , issued a "Proclamation of Emancipation" (or " Prevenciónes de Emancipacion ") on July 25, 1826, which freed Native people from San Diego Mission , Santa Barbara , and Monterey . When news of this spread to other missions, it inspired widespread resistance to work and even open revolt. At San Juan, "the missionary stated that if the 956 neophytes residing at

12460-600: The floods did not exceed the San Juan Creek channel capacity of 58,800 cubic feet per second (1,670 m/s), the west levee of the channel inside San Juan Capistrano nearly failed. Also in 2005, pumps were installed on Tick and Dove Creeks (tributaries of Bell Canyon) to remove urban runoff from 1,100-acre (450 ha) of residential areas in eastern Rancho Santa Margarita. The pumps remove excess flow and divert it to storage basins for later use as reclaimed irrigation water. Between 2009 and 2013, extensive levee repairs were conducted along lower San Juan Creek. Construction closed

12600-404: The flow calms and the particles settle out of suspension . Most authors presently use the term "mudrock" to refer to all rocks composed dominantly of mud. Mudrocks can be divided into siltstones, composed dominantly of silt-sized particles; mudstones with subequal mixture of silt- and clay-sized particles; and claystones, composed mostly of clay-sized particles. Most authors use " shale " as

12740-404: The four of the seven mandatory criteria. Despite the lack of federal recognition, in 2008 the Acjachemen community was successful in protecting a sacred site from being desecrated by a toll road. They also reached a legal agreement agreement with CSULB to protect the land of Puvungna , where the university is partially situated. The university made several promises to maintain the integrity of

12880-485: The grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. The increased pressure and temperature stimulate further chemical reactions, such as the reactions by which organic material becomes lignite or coal. Lithification follows closely on compaction, as increased temperatures at depth hasten the precipitation of cement that binds the grains together. Pressure solution contributes to this process of cementation , as

13020-510: The grains, a lithic wacke would have abundant lithic grains and abundant muddy matrix, etc. Although the Dott classification scheme is widely used by sedimentologists, common names like greywacke , arkose , and quartz sandstone are still widely used by non-specialists and in popular literature. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles. These relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as

13160-587: The host rock. For example, a shell consisting of calcite can dissolve while a cement of silica then fills the cavity. In the same way, precipitating minerals can fill cavities formerly occupied by blood vessels , vascular tissue or other soft tissues. This preserves the form of the organism but changes the chemical composition, a process called permineralization . The most common minerals involved in permineralization are various forms of amorphous silica ( chalcedony , flint , chert ), carbonates (especially calcite), and pyrite . At high pressure and temperature,

13300-429: The immediate region. The elite class (composed chiefly of families, lineage heads, and other ceremonial specialists), a middle class (established and successful families), and people of disconnected or wandering families and captives of war comprised the three hierarchical social classes. Native leadership consisted of the Nota, or clan chief, who conducted community rites and regulated ceremonial life in conjunction with

13440-455: The land and 0.6 percent of the assets (including cattle, household items, and silver or gold)." It was recorded that 30 percent of all households were headed by women "who still lived in San Juan on the plots of land that had been distributed in 1841" under Mexican rule. It was reported that "shortly after the census was taken, the entire population began to leave the area for villages to the southeast of San Juan." A smallpox epidemic in 1862 took

13580-488: The land. In the 21st century, the tribe filed a land claim, seeking to regain the territory of the former Marine Corps Air Station El Toro . This had been held by them as an Indian Rancheria until the 1930s. At that time, the US government bought the land for use as a defense facility. In May 2013, the 84A group of the Acjachemen Nation voted to elect the first all-female Acjachemen tribal council in its history. In 2021,

13720-487: The largest impoundments in the watershed, holding about 7,500 acre-feet (9,300,000 m) combined. While Lake Mission Viejo was built solely for recreation, the 115-acre (0.47 km) Upper Oso Reservoir collects Oso Creek water and diverts it for irrigation use. The reservoir is occasionally used by air tankers to combat wildfires in the Cleveland National Forest. The Santa Margarita Water District

13860-435: The lithologies dehydrates. Clay can be easily compressed as a result of dehydration, while sand retains the same volume and becomes relatively less dense. On the other hand, when the pore fluid pressure in a sand layer surpasses a critical point, the sand can break through overlying clay layers and flow through, forming discordant bodies of sedimentary rock called sedimentary dykes . The same process can form mud volcanoes on

14000-418: The lives of 129 Acjachemen people in one month alone of a population now "of only some 227 Indians." The remaining Acjachemen established themselves among the Luiseño , who they "shared linguistic and cultural similarities, family ties, and colonial histories." Even after their relocation to various Luiseño villages, "San Juan remained an important town for Acjachemen and other Indians connected to it" so that by

14140-410: The lower reaches, before urban development began in the 1950s. Only 0.3 percent of those wetlands remain. Recent efforts of stream conservation have been in the planning stage including habitat conservation plan work. There are sixteen prominent vegetation zones in the San Juan watershed, which include riparian vegetation, montane woodlands , coastal sage scrub and chaparral . Riparian vegetation

14280-486: The lower watershed which results in more water running off to the Pacific Ocean. However, water from irrigation run-off and other human activities is responsible for recharging an additional 37,500 acre-feet (46,300,000 m) per year. The Christianitos and Mission Viejo fault zones split the watershed into distinct "Upper" and "Lower" groundwater basins. The groundwater mostly lies in alluvium , which ranges from

14420-511: The main stem of San Juan Creek does not have any major water diversions or dams, some of its tributaries, including Trabuco and Oso Creeks, have been channelized or otherwise heavily modified by urbanization . San Juan Creek begins high in the Santa Ana Mountains southwest of Lake Elsinore , at the head of the steep and narrow San Juan Canyon , at roughly 1,678 feet (511 m) in elevation where Morrell Canyon Creek , draining

14560-404: The mid-1870s, and the towns in which they resided "were characterized by a marked lack of ethnic diversity." In the 1890s, a permanent elementary school was constructed in San Juan. However, until 1920, for education beyond sixth grade, "students had to relocate to Santa Ana – an impossibility for the vast majority of Californio and Acjachemen families." Gerónimo Boscana, a Franciscan scholar who

14700-427: The middle of the San Juan Creek watershed in the 1950s transformed the area into a bedroom community for Los Angeles and permanently erased many remaining grassland, meadow and riparian zones. The percent of urbanized land increased from 3 percent in 1964 to 18 percent in 1988. In the 1990s, the watershed was 32 percent urbanized. With continuing development in east San Juan Capistrano and Rancho Mission Viejo,

14840-450: The mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. This further reduces porosity and makes the rock more compact and competent . Unroofing of buried sedimentary rock is accompanied by telogenesis , the third and final stage of diagenesis. As erosion reduces the depth of burial, renewed exposure to meteoric water produces additional changes to the sedimentary rock, such as leaching of some of

14980-431: The mission compound. Missionaries attempted to prevent "Indigenous forms of knowledge, authority, and power" from passing on to younger generations by placing recently baptized Indian children in monjerios "away from their parents from the age of seven or so until their marriage." Native children and adults were punished for disobeying Spanish priests through confinement and lashings. The logic behind these harsh practices

15120-596: The mission in 1827 were 'kindly begged to go to work,' they would respond by saying simply that they were 'free.'" Following the Mexican secularization act of 1833 , "neophyte alcades requested that the community be granted the land surrounding the mission, which the Acjachemen had irrigated and were now using to support themselves." Terrestrial and marine fauna refuse, food storage vessels, specialized craft goods, ritual artifacts culturally associated with elite clan lineages, and interregional trade connections were found at

15260-757: The mouth. Download coordinates as: Acjachemen The Acjachemen ( / ɑː ˈ x ɑː tʃ ə m ə m / ) are an Indigenous people of California . Published maps often identify their ancestral lands as extending from the beach to the mountains, south from what is now known as Aliso Creek in Orange County to the Las Pulgas Canyon in the northwestern part of San Diego County . However, sources also show that Acjachemen people shared sites with other Indigenous nations as far north as Puvunga in contemporary Long Beach. The Acjachemen language does not have any fluent speakers. It

15400-424: The name of Oso Creek (Spanish: "Bear Creek") is not known. Many of the creeks in the watershed have names of Spanish origin, which were most likely named by the Spanish conquistadors a long time before the area was annexed by the United States. Before urban development, the damage caused by overgrazing during the Spanish period was still considered capable of recovery. However, the completion of Interstate 5 through

15540-453: The north to San Mateo Creek in the south, a distance of roughly 35 miles (56 km). Most of the population lived along the two major streams in the area, San Juan and San Mateo Creeks, as well as Arroyo Trabuco. The Acjachemen lived in villages along San Juan Creek, including villages on the main stem of San Juan Creek, the largest being Putiidhem , which was the mother village of the people, as well as Sajavit and Piwiva , while Huumai

15680-448: The other hand, believed in two separate but related existences: the "existence above" and the "existence below". These states of being were "altogether explicable and indefinite" (like brother and sister), and it was the fruits of the union of these two entities that created "...the rocks and sands of the earth; then trees, shrubbery, herbs and grass; then animals...". The "Starman" drawn by artist Jean Goodwin has become an iconic image with

15820-530: The peak flow was 22,400 cubic feet per second (630 m/s) on February 25, 1969. During the 1969–1985 period, the average flow was 26.1 cubic feet per second (0.74 m/s), and a peak flow of 14,700 cubic feet per second (420 m/s) was recorded on March 4, 1978. After 1985, the USGS stopped measuring discharge but continues to monitor water level in real-time at the La Novia Street bridge. According to

15960-438: The place of deposition. The nature of a sedimentary rock, therefore, not only depends on the sediment supply, but also on the sedimentary depositional environment in which it formed. As sediments accumulate in a depositional environment, older sediments are buried by younger sediments, and they undergo diagenesis. Diagenesis includes all the chemical, physical, and biological changes, exclusive of surface weathering, undergone by

16100-404: The popular San Juan Creek bikeway for two years, inciting protests from many area residents who are frequent users of the path. Although the San Juan Creek watershed is less heavily developed than other coastal Orange County watersheds, extensive works have been constructed to control floods, reduce erosion, and provide reclaimed water for irrigation. A growing amount of urban runoff flows into

16240-627: The processes responsible for their formation: clastic sedimentary rocks, biochemical (biogenic) sedimentary rocks, chemical sedimentary rocks, and a fourth category for "other" sedimentary rocks formed by impacts, volcanism , and other minor processes. Clastic sedimentary rocks are composed of rock fragments ( clasts ) that have been cemented together. The clasts are commonly individual grains of quartz , feldspar , clay minerals , or mica . However, any type of mineral may be present. Clasts may also be lithic fragments composed of more than one mineral. Clastic sedimentary rocks are subdivided according to

16380-400: The projected growth by 2050 is 50 percent. In the late 1960s, Dana Point Harbor was constructed adjacent to the mouth of San Juan Creek. The breakwater prevented the occurrence of a large surf break phenomenon, colloquially known as " Killer Dana ", in the bay. When Killer Dana disappeared, water circulation in the bay decreased. As polluted runoff from San Juan Creek continues to flow into

16520-480: The result of localized precipitation due to small differences in composition or porosity of the host rock, such as around fossils, inside burrows or around plant roots. In carbonate rocks such as limestone or chalk , chert or flint concretions are common, while terrestrial sandstones sometimes contain iron concretions. Calcite concretions in clay containing angular cavities or cracks are called septarian concretions . After deposition, physical processes can deform

16660-448: The right. It receives its largest tributary, Arroyo Trabuco , from the right, then flows south toward the Pacific Ocean. The creek forms a fresh water lagoon at the northern end of Doheny State Beach , which overflows into Capistrano Bay during periods of high flow. All direct tributaries of San Juan Creek, from mouth to source, are listed. The list also includes streams that join major tributaries. The San Juan Creek watershed

16800-454: The rock a grey or greenish colour. Iron(III) oxide (Fe 2 O 3 ) in a richer oxygen environment is often found in the form of the mineral hematite and gives the rock a reddish to brownish colour. In arid continental climates rocks are in direct contact with the atmosphere, and oxidation is an important process, giving the rock a red or orange colour. Thick sequences of red sedimentary rocks formed in arid climates are called red beds . However,

16940-588: The rural population, the dominion and power of the Spanish missions over the Acjachemen further increased." By 1812, the mission was at the peak of its growth: "3,340 persons had been baptized at the mission, and 1,361 Acjachemen resided in the mission compound." After 1812, the rate of Acjachemen who died surpassed the amount of those who were baptized. By 1834, the Acjachemen population had declined to about 800. The Acjachemen resisted assimilation by practicing their cultural and religious ceremonies, performing sacred dances and healing rituals both in villages and within

17080-469: The same size, the rock is called 'well-sorted', and when there is a large spread in grain size, the rock is called 'poorly sorted'. The form of the clasts can reflect the origin of the rock. For example, coquina , a rock composed of clasts of broken shells, can only form in energetic water. The form of a clast can be described by using four parameters: Chemical sedimentary rocks have a non-clastic texture, consisting entirely of crystals. To describe such

17220-433: The sediment supply, caused, for example, by seasonal changes in rainfall, temperature or biochemical activity. Laminae that represent seasonal changes (similar to tree rings ) are called varves . Any sedimentary rock composed of millimeter or finer scale layers can be named with the general term laminite . When sedimentary rocks have no lamination at all, their structural character is called massive bedding. Graded bedding

17360-402: The sediment, producing a third class of secondary structures. Density contrasts between different sedimentary layers, such as between sand and clay, can result in flame structures or load casts , formed by inverted diapirism . While the clastic bed is still fluid, diapirism can cause a denser upper layer to sink into a lower layer. Sometimes, density contrasts occur or are enhanced when one of

17500-443: The sediment. They can be indicators of circumstances after deposition. Some can be used as way up criteria . Organic materials in a sediment can leave more traces than just fossils. Preserved tracks and burrows are examples of trace fossils (also called ichnofossils). Such traces are relatively rare. Most trace fossils are burrows of molluscs or arthropods . This burrowing is called bioturbation by sedimentologists. It can be

17640-535: The solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement , which are called agents of denudation . Biological detritus was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies ( marine snow ). Sedimentation may also occur as dissolved minerals precipitate from water solution . The sedimentary rock cover of

17780-414: The stream can often dry up completely in its lower reaches. The total natural ( unimpaired ) surface outflow from the San Juan basin into the Pacific is estimated at 5,200 acre-feet (6,400,000 m) per year. Agricultural and urban runoff significantly increased the average outflow, to 7,800 acre-feet (9,600,000 m) as of 1993. The maximum annual outflow is 9,000 acre-feet (11,000,000 m). Although

17920-453: The subsurface that is useful for civil engineering , for example in the construction of roads , houses , tunnels , canals or other structures. Sedimentary rocks are also important sources of natural resources including coal , fossil fuels , drinking water and ores . The study of the sequence of sedimentary rock strata is the main source for an understanding of the Earth's history , including palaeogeography , paleoclimatology and

18060-527: The three major types of rock, fossils are most commonly found in sedimentary rock. Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants. Often these fossils may only be visible under magnification . Dead organisms in nature are usually quickly removed by scavengers , bacteria , rotting and erosion, but under exceptional circumstances, these natural processes are unable to take place, leading to fossilisation. The chance of fossilisation

18200-509: The two largest tributaries – Trabuco and Bell Creeks – both originate in the Santa Ana Mountains. Although more than half of the watershed is undeveloped land, it also includes parts of the cities of Dana Point , Laguna Hills , Laguna Niguel , Mission Viejo , Rancho Santa Margarita , San Clemente , San Juan Capistrano , and the unincorporated communities of Trabuco Canyon (near Rancho Santa Margarita) and Rancho Mission Viejo (east of San Juan). There are four main alluvial river valleys in

18340-435: The use of local surface water and groundwater is increasing, local groundwater levels have not been affected significantly by human use, due to the relatively high natural recharge rate. Due to the lower amount of urbanization in the San Juan watershed as compared with other watersheds in the county, the 100-year flood inundation risk is also significantly lower than in other parts of Orange County. It has been calculated that

18480-463: The watershed (part of suburban Rancho Santa Margarita ). The Oso Creek valley is narrower, running south through Mission Viejo and Laguna Hills, and is mostly urbanized. The Bell Creek valley is the least urbanized of the four, being mostly located in the Cleveland National Forest, Starr Ranch Preserve and Caspers Wilderness Park. There are 19 other major tributaries in the watershed. The California Department of Water Resources includes San Juan Creek in

18620-400: The watershed. The San Juan Creek valley occupies the south portion of the watershed; the heavily urbanized lower (southwest) portion is located in the cities of San Juan Capistrano and Dana Point, while the largely rural (northeast) portion extends well into the foothills of the Santa Ana Mountains. The Arroyo Trabuco valley forms a large alluvial plain called "Plano Trabuco" in the north part of

18760-539: The western Elsinore Mountains and southernmost Santa Ana Mountains, has its confluence with Bear Canyon Creek . From there, it flows steeply down a rocky gorge over rapids and waterfalls. San Juan Canyon forms the mountain pass for California State Route 74 (the Ortega Highway ), which connects San Juan Capistrano to Lake Elsinore and the Inland Empire. San Juan Falls, a 15-foot (4.6 m) cascade, and

18900-404: The woody tissue of plants. Soft tissue has a much smaller chance of being fossilized, and the preservation of soft tissue of animals older than 40 million years is very rare. Imprints of organisms made while they were still alive are called trace fossils , examples of which are burrows , footprints , etc. As a part of a sedimentary rock, fossils undergo the same diagenetic processes as does

19040-467: Was "integral to Catholic belief and practice." Gerónimo Boscana , a missionary at San Juan between 1812 and 1822, admitted that, despite harsh treatment, attempts to convert Native people to Christian beliefs and traditions were largely unsuccessful: "All the missionaries in California, declares Boscana, would agree that the true believer was the rare exception." Governor José María de Echeandía ,

19180-589: Was filed in the state of California, which "memorialized the President and Congress of the United States to declare the Juaneno Band of Mission Indians, Acjachemem Nation, to be the aboriginal tribe of Orange County." The Juaneno Band of Mission Indians, Acjachemen Nation 84A petitioned for federal recognition in 1999. On November 26, 2007, the Bureau of Indian Affairs declined the petition due to not meeting

19320-539: Was incorporated into Californio ranchos by 1841, when San Juan Mission was formed into a pueblo." The formation of the San Juan pueblo was a direct result of the actions of San Diego settlers, who petitioned the government to gain access to the lands of the mission territory. Before the formation of the pueblo, the "one-hundred or so Acjachemen living there" were asked if they favored or opposed this change: seventy voted in favor, while thirty, mostly older, Acjachemen opposed, "possibly because they did not want to live among

19460-452: Was located on the tributary Cañada Gobernadora . The Acjachemen diet usually consisted of fruits, acorns, grains, and some meat, while they practiced little agriculture. Shell middens indicate that they also harvested shellfish from the coast. Native peoples in this area are not known to have built permanent structures in this area or significantly influenced the natural environment. The first European land exploration of Alta California ,

19600-416: Was stationed at San Juan Capistrano for more than a decade beginning in 1812, compiled the first, comprehensive study of Acjachemen religious practices. Religious knowledge was secret, and the prevalent religion, called Chinigchinich , placed village chiefs in the position of religious leaders, an arrangement that gave the chiefs broad power over their people. Boscana divided the Acjachemen into two classes:

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