| San Diego Formation | |
|---|---|
| Stratigraphic range: Pliocene | |
| Type | Geologic formation |
| Lithology | |
| Primary | Conglomerate |
| Other | Sandstone |
| Location | |
| Region | San Diego County, California, Baja California |
| Country | United States, Mexico |
| Type section | |
| Named for | San Diego, California |
The San Diego Formation is a geological formation in southwestern San Diego County, California, United States, and northwestern Baja California, Mexico.
It is a coastal transitional marine and non-marine pebble and cobble conglomerate deposit and marine sandstone rock with marine fossils, from a former bay, deposited during the Middle Pliocene to Late Pliocene ages (2–3 million years ago), of the Pliocene period during the Cenozoic Era.
This formation is found from the south side of Mount Soledad in San Diego County to Rosarito Beach in northern Baja California, including Tijuana, Mexico, and the southwestern corner of San Diego County from San Ysidro to Pacific Beach.
San Diego Formation deposits were formed in a large, open, crescent-shaped bay similar in size to Monterey Bay that existed on the coast in Pliocene times. [1] [2]
The formation contains the San Diego Formation Basin, a large aquifer under Imperial Beach, Chula Vista, National City, and southern portions of the city of San Diego. The San Diego Formation Basin is a confined shallow aquifer. It has a basin ground surface area of 79,724 acres (32,263 ha) and an estimated groundwater storage capacity of 960,000 acre-feet. The depth to groundwater is about 100 feet (30 m). [3] The groundwater in the San Diego Formation is brackish, and its quality is considered to be fair to poor. [3] Due to its proximity to the ocean, the risk of seawater intrusion is a primary concern regarding water quality. To avoid intrusion, the Sweetwater Authority constantly monitors the basin water levels, which have remained stable since the 1980s. A factor that contributes to limit the groundwater pumping is the importation of Colorado River water. However, to reduce demands for imported water, desalination plants have been installed. The Richard A. Reynolds Groundwater Desalination Facility, in Chula Vista, was completed in 1999 and holds a production capacity of 4 million gallons of drinking water per day. [3] The Claude "Bud" Lewis Carlsbad Desalination Plant in Carlsbad, California, was completed in 2015 and produces 50 million gallons of water per day. [4] In this way, these plants contribute to reducing vulnerability and secure water supply, especially during drought periods. The use of groundwater contributes to a regional effort to reduce demands for imported water. [5]
Besides those of clams and other mollusks, quite a few bird fossils (which are generally rare) have been found in this geological formation. Among them is a possible ancestor of Cassin's auklet (Ptychoramphus aleuticus) and the loons Gavia concinna and G. howardae. The former was quite likely a close relative or even ancestor of the large black-headed [6] loons; the latter was perhaps a small relative of the large grey-headed [7] loons. [8] [9]
| Mysticetes reported from the San Diego Formation | ||||
|---|---|---|---|---|
| Genus | Species | Stratigraphic position | Notes | Images |
B. davidsonii [10] | An extinct rorqual belonging to Balaenoptera. | |||
"Balaenoptera" | "B." portisi | Formerly assigned to Balaenoptera, probably a member of Cetotheriophanes . | ||
H. morrowi | A cetotheriid. | |||
N. miocaena | A stem-balaenopteroid, previously considered to be a relative of humpback whale. | |||
| Odontocetes reported from the San Diego Formation | ||||
|---|---|---|---|---|
| Genus | Species | Stratigraphic position | Notes | Images |
P. sternbergi [11] | A close relative of the baiji. | |||
S. ceruttii | A porpoise with a lower jaw extended few inches beyond the upper jaw (similar to a halfbeak). [12] | |||
| Pinnipeds reported from the San Diego Formation | ||||
|---|---|---|---|---|
| Genus | Species | Stratigraphic position | Notes | Images |
C. gilmorei [13] | A relative of the northern fur seal. | |||
D. seftoni [14] | A walrus. | |||
V. chulavistensis [14] | A walrus. | |||
| Sirenians reported from the San Diego Formation | ||||
|---|---|---|---|---|
| Genus | Species | Stratigraphic position | Notes | Images |
H. cuestae | A close relative of the Steller's sea cow. | |||
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater and fresh water together, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root brak. Certain human activities can produce brackish water, in particular civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming. Brackish water is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it can be damaging to the environment.
Loons or divers are a group of aquatic birds found in much of North America and northern Eurasia. All living species of loons are members of the genus Gavia, family Gaviidae and order Gaviiformes.
Balaenoptera is a genus of rorquals containing eight extant species. Balaenoptera comprises all but two of the extant species in its family ; the genus is currently polyphyletic, with the two aforementioned species being phylogenetically nested within it.
Fossil water, fossil groundwater, or paleowater is an ancient body of water that has been contained in some undisturbed space, typically groundwater in an aquifer, for millennia. Other types of fossil water can include subglacial lakes, such as Antarctica's Lake Vostok. UNESCO defines fossil groundwater as "water that infiltrated usually millennia ago and often under climatic conditions different from the present, and that has been stored underground since that time."
The Delaware Basin is a geologic depositional and structural basin in West Texas and southern New Mexico, famous for holding large oil fields and for a fossilized reef exposed at the surface. Guadalupe Mountains National Park and Carlsbad Caverns National Park protect part of the basin. It is part of the larger Permian Basin, itself contained within the Mid-Continent oil province.
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
The Kattendijk Formation is a five million years old marine geological formation north of Antwerp, Belgium. including the north-western parts of the Campine region. The area was named by De Heuter and Laga in 1976. The sands range from medium fine to coarse and contain a large proportion of shell grit.
Protororqualus is a genus of extinct rorqual from the late Pliocene of Mount Pulgnasco, Italy.
Plesiocetus is a genus of extinct rorquals found worldwide. It has had a chequered taxonomic history, having served as a wastebasket genus for a handful of mysticete species.
The Capistrano Formation is a geologic formation in coastal southern Orange County, California. It preserves fossils dating back to the late Miocene to early Pliocene, with the Oso Member representing a near-shore environment. Fifty-nine species and varieties of foraminifera are recognized from the Capistrano Formation alongside a diverse array of marine mammals including up to five species of walrus.
The Tulare Formation is a Pliocene to Holocene epoch geologic formation in the central and southern San Joaquin Valley of central California.
Borrego Valley Groundwater Basin, located in the very southern region of California, is one of the driest basins in the state. With climate change predicted to have strong effects into foreseeable future, the region is viewed with a skepticism in the sustainable use of water at current rates of consumption. Both natural and man-made geographic divisions within this basin allow for a closer inspection of the various management techniques implemented throughout the years, and provide a basis for what may be pursued for an uncertain future.
Balaenoptera siberi is an extinct species of baleen whale from the Late Miocene, described by Pilleri and Pilleri in 1989, based on fossils found in the Pisco Formation of the Pisco Basin in southwestern Peru.
The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.
The geology of Arizona began to form in the Precambrian. Igneous and metamorphic crystalline basement rock may have been much older, but was overwritten during the Yavapai and Mazatzal orogenies in the Proterozoic. The Grenville orogeny to the east caused Arizona to fill with sediments, shedding into a shallow sea. Limestone formed in the sea was metamorphosed by mafic intrusions. The Great Unconformity is a famous gap in the stratigraphic record, as Arizona experienced 900 million years of terrestrial conditions, except in isolated basins. The region oscillated between terrestrial and shallow ocean conditions during the Paleozoic as multi-cellular life became common and three major orogenies to the east shed sediments before North America became part of the supercontinent Pangaea. The breakup of Pangaea was accompanied by the subduction of the Farallon Plate, which drove volcanism during the Nevadan orogeny and the Sevier orogeny in the Mesozoic, which covered much of Arizona in volcanic debris and sediments. The Mid-Tertiary ignimbrite flare-up created smaller mountain ranges with extensive ash and lava in the Cenozoic, followed by the sinking of the Farallon slab in the mantle throughout the past 14 million years, which has created the Basin and Range Province. Arizona has extensive mineralization in veins, due to hydrothermal fluids and is notable for copper-gold porphyry, lead, zinc, rare minerals formed from copper enrichment and evaporites among other resources.
The geology of Saudi Arabia includes Precambrian igneous and metamorphic basement rocks, exposed across much of the country. Thick sedimentary sequences from the Phanerozoic dominate much of the country's surface and host oil.
The Santa Fe Group is a group of geologic formations in New Mexico and Colorado. It contains fossils characteristic of the Oligocene through Pleistocene epochs. The group consists of basin-filling sedimentary and volcanic rocks of the Rio Grande rift, and contains important regional aquifers.
Gavia howardae is an extinct species of loon from the Piacenzian age from United States. Fossils of this bird were initially found in 1947 by Clifford Kennell in the San Diego Formation, California and were given a name in 1953 by Pierce Brodkorb. These first specimens consisted of humeri bones, which Brodkorb indicated based on the distal end of the humerus were a smaller species of the genus Gavia, with a possible relationship with the pacific loon. More specimens were collected from the same deposits covering the entirety of the wing, some more complete than others. Chandler (1990) described and published these new materials and found G. howardae to be related to the red-throated loon instead. Additional material has been recovered from the Yorktown Formation, North Carolina where in addition more wing bones, there were also remains of the leg and shoulder regions. Based on the overall size of the remains, G. howardae was on average smaller than the red-throated loon, and one of the smallest species of Neogene loons from North America.
Gavia brodkorbi is an extinct species of loon from the Clarendonian age from United States. The holotype and only known specimen is a complete left ulna that was collected from the Monterey Formation in Laguna Niguel, California by Marion J. Bohreer in 1969. The ulna is shorter but more stouter in comparison to the red-throated loon and pacific loon. The area of attachment of the ligaments is different from the extant species, as it is shorter and less oval. Hildegarde Howard would described the bird in 1978 on a paper discussing the Late Miocene seabird fauna of Orange County named the species after Pierce Brodkorb for his contribution for the field of paleornithology including his review of Pliocene loons.
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