Post by Admin on Mar 2, 2022 11:19:23 GMT -7
Steens Mountain, Upper Great Basin, Eastern Oregon. About 50-miles long and 5,000 feet above the desert floor, Steens Mountain is the largest single fault-block mountain in North America.
www.oregongeology.org/pubs/og/OBv38n04.pdf
State of Oregon Department of Geology and Mineral Industries 1069 State Office BI dg. Portland Oregon 97201
STEENS MOUNTAIN, OREGON - Ernest H. Lund* and Elton Bentley**
Rock Sequence
The bedrock exposed in Steens Mountain is mostly flow lava, but bedded pyroclastics and intrusive bodies are also exposed in the east scarp of the High Steens. The scarp provides the thickest exposed section in the southeastern part of the State, and rocks as old as Oligocene (Walker and Repenning, 1965) crop out at the base. Fuller (1931) made a comprehensive study of the rocks of Steens Mountain, and the more recent work by Walker and Repenning has led to modifications of Fuller’s interpretation of the volcanic sequence. The following descriptions of the rock units are drawn principally from these two works. For detailed lithologic descriptions, the reader is referred to Fuller and for mapped distributions to Walker and Repenning.
AIvord Creek beds
Fuller applied the name Alvord Creek beds to light-colored tuffs that crop out at a number of places in the lower thousand feet of the scarp (Figure 3) between Cottonwood and Toughey Creeks, a distance of more than 5 miles. The unit consists of stratified acidic tuffs. The color is predominantly white, but brownish and greenish varieties of altered tuff are common. North of Alvord Creek, two thick andesite flows are interlayered with the sediment, and north of Uttle Alvord Creek the beds are intruded by a 200-foot-thick basalt sill. A rhyolite intrusion in the form of a laccolith has up-arched the sedimentary beds and sill and has altered them locally.
Although the Alvord Creek beds appear to be at the base of the Miocene rock sequence in the east scarp of Steens Mountain, there is disagreement on the age and distribution of the unit. A study of plant fossiIs in the Alvord Creek beds by Chaney (in Fuller, 1931, p. 51) led him to conclude that the unit was equivalent to the late Miocene Mascall Formation in the John Day Valley. Axelrod (1944, p. 225) assigned an early Pliocene age to the beds on the basis of composition of the fossil flora and its geographic and. climatic implications. Possibly, rock units of similar lithology occurring in Pliocene structural terraces as well as beneath Miocene volcanic rocks are being mapped as Alvord Creek beds by different workers. The fossil flora includes species of fir, spruce, pine, juniper, maple, aspen, cottonwood, willow, beech, Oregon grape, service berry, mountain mahogany, Christmas berry , cherry, rose, mountain ash, sumac, madrona, chaparral, and pondweed. Axelrod concluded that this flora denotes a region of moderate topographic diversity with an annual rainfall of 20 to 30 inches and temperatures ranging from below freezing in winter to high in summer and that these conditions are intermediate between the moister and milder climate of the Miocene and the drier and colder climate of the region today.
Pike Creek Volcanic Series
Fuller gave the name Pike Creek Volcanic Series to a thick series of acidic flows and stratified tuffs that are best exposed in Pike Creek Canyon (Figure 5). The aggregate thickness totals more than 1,500 feet. The lower 1,000 feet of the series consists of two tuff members interlayered with two rhyolite flows, each unit 200 to 300 feet thick. The lowermost tuff unit is intruded by five basalt sills ranging from a few inches to 15 feet in thickness. A 40-foot layer of tuff overlies the uppermost rhyolite, and this is in turn followed by two biotite-dacite flows, the lower of which is about 200 feet thick and the upper ranging from 200 feet to 500 feet. Walker (Walker and Repenning, 1965) renamed this series the Pike Creek Formation, to which he assigns an age of Oligocene and Miocene.
Steens Mountain Andesitic Series
This series consists of an andesite flow up to 200 feet or more in thickness at the base and capped by a stratified tuff unit up to 20 feet thick, a unit called the "great flow" with a maximum thickness of about 900 feet, and a series of alternating thin layers of andesite breccias and platy flow- andesite with a maximum aggregate thickness of more than 600 feet. Pyroclastic deposits marking sites of small volcanic cones are related to the upper andesite series.
The "great flow" is a prominent unit in the Alvord Creek locality, where it is about 900 feet thick. Joint columns measure as much as 5 feet across and rise 300 feet above the talus. The unit thins to about 500 feet in the valley of Cottonwood Creek, a mile to the north. Fuller did not identify the unit with certainty north of there, though he reports that similar rock with exposed thickness of about 400 feet crops out at Mann Creek, about 7 miles north of Cottonwood Creek. South of Alvord Creek the flow is exposed only in scattered outcrops.
Steens Mountain Basalt
The Steens Mountain Basalt (name shortened to Steens Basalt) (Figure 2), a series of thin flood or plateau basalt, constitutes the bulk of the mountain and extends into Pueblo Mountain to the south and to Abert Rim to the west. It makes up the upper 3,000 feet of the east scarp and is the rock exposed along the glacial valleys on the back slope of the mountain. Except where covered locally by a younger ash flow, it is the bedrock over most of the western slope.
The maximum original thickness of the Steens Basalt is not known, for much of it has been removed from the High Steens by glacial erosion, and it is only on the east scarp of this part of Steens Mountain that the base is exposed. Wilkerson (1958) measured 3,280 feet of section on the west rim of Wild Horse Canyon but believed the formation was much thicker. Individual flow with range of less than a foot to more than 70 feet in thickness, are of totally crystalline rock, predominantly a fairly basic olivine basalt. Textures of rock in the series range from fine grained, in which a few or no individual grains can be discerned, to porphyritic, in which plagioclase plates are as much as 4 centimeters long. In some porphyritic varieties the plagioclase crystals are clustered in a radiating or stellate arrangement. Many of the flows are diklytaxitic, a term proposed by Fuller (1931, p. 116) for a porous texture in which plagioclase laths are in a netlike arrangement with empty space in between. Numerous dikes (Figure 2) , believed to be feeders, cut the flow.
Based on potassium-argon ages determined by Evernden and co-workers (1964, p. 164, 190) the formation is assigned the age of middle and late Miocene. Ages of 14.5 m.y. and 14.7 m.y. were obtained from a unit high in the series on Steens Mountain, and an age of 14.6 m.y. was obtained from sediments interbedded with steens basalt on Beatys Butte west of Catlow Valley.
Ash-flow tuff (Danforth Formation)
Numerous small isolated patches of Pliocene welded tuff are scattered over Smith Flat, and an extensive sheet veneers the Steen Basalt on the lower slopes of the High Steens and the Northern Steens. The rock consists of glass shards, crystal fragments, and fragments of pumice and other rock all welded together. In places where the rock is only lightly welded, it is soft and erodes easily. Where welding is intense, the rock is compact and has a glassy or porcelaneous appearance.
From it’s patchy distribution all over Smith Flat and other parts of the mountain, it appears that welded tuff was originally widespread and likely formed a veneer over all the Steens Basalt on thewest slope of the mountain but was later eroded from most of the High Steens by glacial ice and running water. The distribution of welded tuff around the Harney Basin and over Steens Mountain suggests that it was emplaced before the onset of fault blocking. Potassium argon ages average 9.2 m.y. (Green, 1973, p. 3). This would place the beginning of the Steen s uplift at about 9 to 10 million years ago. Movement likely continues into the Pleistocene, but the mountain had acquired most of it’s height before glaciation.
www.visitoregon.com/steens-mountain-oregon/
Deep in the southeast section of Oregon, a lone mountain sits. The mountain is locked in an arid country, far from any urban developments. A road leads to it; a pathway little-traveled except by scientists looking for answers to an ancient mystery, or those seeking solace from the travails of urban life in a natural place, built by forces beyond our control. The mountain was once known as a sacred place by Native Americans who lived on its slopes. Later, the area became known as Steen’s Mountain, named after the Army Cavalry Major, who defeated and removed the Native American population from the mountain during the Snake Indian Wars. Today, in recognition that no man can own such a place, the name dropped the ownership apostrophe and became Steens Mountain. Another mystery stacked on top of so many others.
The Legend
I first heard the creation story that labeled Steens Mountain as the birthplace of the world from a fellow student in college during the 1960s. Anthony, a son of the Paiute tribe, told me of the mighty Wolf who brought his minions across the star trail to the void at the center of the world. The wolf tasked his followers to find a way to the surface. The route was blocked by water. Many tried but failed to swim through. Finally, the mightiest of Wolf’s followers volunteered to find a way. After ages of exploration through waterfilled caves, the follower found the surface and returned to lead the others. At night they emerged from a cave, which Wolf named Malheur Cave in celebration of their success. That night the world quivered, and they looked up in the morning to see a majestic mountain that reached for the star trail high in the sky. They did not name the mountain; it was too powerful to be limited to a name.
Wolf called the followers to him. He asked them to explore the land and decide where they wished to dwell. After a while, they returned to Wolf and proclaimed where and how they would live. The most powerful, the follower who found the way into the world, was granted the body and life of the Sage Hen so she could sail the sky, walk the soil, and dig into the ground. Another was labeled an Otter while another was a Mountain Goat and a fourth a Coyote. More of the minions became other creatures that explored the mountain and lived there in separate places. Wolf gave them a name—the nuwudu—the Animal People. Wolf charged them with a great responsibility. They were to guard the mountain until the nuwu—the new people—arrived. Then, they were to hide the cave and guide the nuwu to a life of respect and appreciation for what was created for them.
Wolf left through the cave and was never seen again. The nuwudu stayed, each in their home. The nuwu appeared many ages later, crawling through Malheur Cave. They were dirty, uneducated, and stood on two legs. The nuwudu hid Malheur Cave and taught the nuwu the way of the world, sacrificing themselves for the new people. The nuwudu are still there, waiting, watching, and guiding the faithful until Malheur Cave opens again, and the nuwu and nuwudu can return to the old home by the star path with the knowledge and the spirit for which they sacrificed much.
It was Anthony’s oral recitation from the Northern Paiute lore that excited me about Steens Mountain. I visited it soon afterward. I was not prepared to hike the terrain. Still, I saw enough to understand that Steens Mountain is a place of contradictions. The mountain is a massive bulge against a star-filled sky. The land is arid yet filled with flora and fauna on the western side. The eastern side is the opposite in every way. A few mesquites and scrub plants endure the parched conditions on the east side of the mountain, but below the feet of the mountain, everything is desert, pancaked earth, cracked under the punishing sun. The only thing alive there are the dancing dust-devils locked in a series of magnificent minuets.
(Image)
Steens Mountain“Steens Mountain” by BLM Oregon & Washington is licensed under CC BY 2.0
The Science
When I returned home, I began searching for information on Steens Mountain. There was not much to be found as even scientists were not curious about the formation. At that time, the idea of tectonic migration was not yet recognized, and the construction of such heights was considered one of the unsolvable mysteries of the world.
With the events of the 1960s in front of me, I took my attention away from Steens Mountain to what seemed to be more important things. Civil Rights, fear of “The Bomb,” and the Vietnam War took center stage in my life, just as they did for nearly every other citizen of the country. Anthony’s story simmered in my mind. I married, began a family, and took on responsibilities in life and at work that demanded my attention. Still, something was missing, something that the fast world of urban life could never satisfy, that ever-present quality of human curiosity that makes us question the meaning of our existence.
Others questioned established ideas. Geologists found the mystery of tectonic movement and began searching for further evidence, which led them directly to Steens Mountain. After years of study, they discovered that Steens Mountain is the result of fault-block action where the crust stretches until a fissure forms from which the mantle oozes upward, forming a block. In the most extensive fault-block actions, the crack opens several times, creating block after block, forcing the already solidified material upward. At Steens Mountain, multiple events occurred four million years ago, some of them creating layers of basalt a hundred feet thick or more.
When the Earth cooled, glacial action carved great gashes into the mountain that ran from east to west. These glaciers failed to cut through the east side of the mountain, leaving a continuous 52-mile peak that still exists today. The length of the peak running from north to south builds its own climate. The mountain summit of 9,733 feet effectively blocks weather from traveling eastward, creating a dry area called the Alvord Desert—the driest region in Oregon with only four inches of rain per year. While the wester slopes of the mountain receives ample moisture for vegetation growth, the east side is parched, creating a contrasting ecology where different species exist in a relatively small area. From Steens summit on a clear day, you can seen Mount Hood, Mount Jefferson, Mount Batchelor, and the Sisters Mountains.
The temperatures, though always cool due to the elevation, around Steens Mountain vary widely throughout the year, as this table shows.
Weather - You will have to go to the site to see the rest. www.visitoregon.com/steens-mountain-oregon/
www.oregongeology.org/pubs/og/OBv38n04.pdf
State of Oregon Department of Geology and Mineral Industries 1069 State Office BI dg. Portland Oregon 97201
STEENS MOUNTAIN, OREGON - Ernest H. Lund* and Elton Bentley**
Rock Sequence
The bedrock exposed in Steens Mountain is mostly flow lava, but bedded pyroclastics and intrusive bodies are also exposed in the east scarp of the High Steens. The scarp provides the thickest exposed section in the southeastern part of the State, and rocks as old as Oligocene (Walker and Repenning, 1965) crop out at the base. Fuller (1931) made a comprehensive study of the rocks of Steens Mountain, and the more recent work by Walker and Repenning has led to modifications of Fuller’s interpretation of the volcanic sequence. The following descriptions of the rock units are drawn principally from these two works. For detailed lithologic descriptions, the reader is referred to Fuller and for mapped distributions to Walker and Repenning.
AIvord Creek beds
Fuller applied the name Alvord Creek beds to light-colored tuffs that crop out at a number of places in the lower thousand feet of the scarp (Figure 3) between Cottonwood and Toughey Creeks, a distance of more than 5 miles. The unit consists of stratified acidic tuffs. The color is predominantly white, but brownish and greenish varieties of altered tuff are common. North of Alvord Creek, two thick andesite flows are interlayered with the sediment, and north of Uttle Alvord Creek the beds are intruded by a 200-foot-thick basalt sill. A rhyolite intrusion in the form of a laccolith has up-arched the sedimentary beds and sill and has altered them locally.
Although the Alvord Creek beds appear to be at the base of the Miocene rock sequence in the east scarp of Steens Mountain, there is disagreement on the age and distribution of the unit. A study of plant fossiIs in the Alvord Creek beds by Chaney (in Fuller, 1931, p. 51) led him to conclude that the unit was equivalent to the late Miocene Mascall Formation in the John Day Valley. Axelrod (1944, p. 225) assigned an early Pliocene age to the beds on the basis of composition of the fossil flora and its geographic and. climatic implications. Possibly, rock units of similar lithology occurring in Pliocene structural terraces as well as beneath Miocene volcanic rocks are being mapped as Alvord Creek beds by different workers. The fossil flora includes species of fir, spruce, pine, juniper, maple, aspen, cottonwood, willow, beech, Oregon grape, service berry, mountain mahogany, Christmas berry , cherry, rose, mountain ash, sumac, madrona, chaparral, and pondweed. Axelrod concluded that this flora denotes a region of moderate topographic diversity with an annual rainfall of 20 to 30 inches and temperatures ranging from below freezing in winter to high in summer and that these conditions are intermediate between the moister and milder climate of the Miocene and the drier and colder climate of the region today.
Pike Creek Volcanic Series
Fuller gave the name Pike Creek Volcanic Series to a thick series of acidic flows and stratified tuffs that are best exposed in Pike Creek Canyon (Figure 5). The aggregate thickness totals more than 1,500 feet. The lower 1,000 feet of the series consists of two tuff members interlayered with two rhyolite flows, each unit 200 to 300 feet thick. The lowermost tuff unit is intruded by five basalt sills ranging from a few inches to 15 feet in thickness. A 40-foot layer of tuff overlies the uppermost rhyolite, and this is in turn followed by two biotite-dacite flows, the lower of which is about 200 feet thick and the upper ranging from 200 feet to 500 feet. Walker (Walker and Repenning, 1965) renamed this series the Pike Creek Formation, to which he assigns an age of Oligocene and Miocene.
Steens Mountain Andesitic Series
This series consists of an andesite flow up to 200 feet or more in thickness at the base and capped by a stratified tuff unit up to 20 feet thick, a unit called the "great flow" with a maximum thickness of about 900 feet, and a series of alternating thin layers of andesite breccias and platy flow- andesite with a maximum aggregate thickness of more than 600 feet. Pyroclastic deposits marking sites of small volcanic cones are related to the upper andesite series.
The "great flow" is a prominent unit in the Alvord Creek locality, where it is about 900 feet thick. Joint columns measure as much as 5 feet across and rise 300 feet above the talus. The unit thins to about 500 feet in the valley of Cottonwood Creek, a mile to the north. Fuller did not identify the unit with certainty north of there, though he reports that similar rock with exposed thickness of about 400 feet crops out at Mann Creek, about 7 miles north of Cottonwood Creek. South of Alvord Creek the flow is exposed only in scattered outcrops.
Steens Mountain Basalt
The Steens Mountain Basalt (name shortened to Steens Basalt) (Figure 2), a series of thin flood or plateau basalt, constitutes the bulk of the mountain and extends into Pueblo Mountain to the south and to Abert Rim to the west. It makes up the upper 3,000 feet of the east scarp and is the rock exposed along the glacial valleys on the back slope of the mountain. Except where covered locally by a younger ash flow, it is the bedrock over most of the western slope.
The maximum original thickness of the Steens Basalt is not known, for much of it has been removed from the High Steens by glacial erosion, and it is only on the east scarp of this part of Steens Mountain that the base is exposed. Wilkerson (1958) measured 3,280 feet of section on the west rim of Wild Horse Canyon but believed the formation was much thicker. Individual flow with range of less than a foot to more than 70 feet in thickness, are of totally crystalline rock, predominantly a fairly basic olivine basalt. Textures of rock in the series range from fine grained, in which a few or no individual grains can be discerned, to porphyritic, in which plagioclase plates are as much as 4 centimeters long. In some porphyritic varieties the plagioclase crystals are clustered in a radiating or stellate arrangement. Many of the flows are diklytaxitic, a term proposed by Fuller (1931, p. 116) for a porous texture in which plagioclase laths are in a netlike arrangement with empty space in between. Numerous dikes (Figure 2) , believed to be feeders, cut the flow.
Based on potassium-argon ages determined by Evernden and co-workers (1964, p. 164, 190) the formation is assigned the age of middle and late Miocene. Ages of 14.5 m.y. and 14.7 m.y. were obtained from a unit high in the series on Steens Mountain, and an age of 14.6 m.y. was obtained from sediments interbedded with steens basalt on Beatys Butte west of Catlow Valley.
Ash-flow tuff (Danforth Formation)
Numerous small isolated patches of Pliocene welded tuff are scattered over Smith Flat, and an extensive sheet veneers the Steen Basalt on the lower slopes of the High Steens and the Northern Steens. The rock consists of glass shards, crystal fragments, and fragments of pumice and other rock all welded together. In places where the rock is only lightly welded, it is soft and erodes easily. Where welding is intense, the rock is compact and has a glassy or porcelaneous appearance.
From it’s patchy distribution all over Smith Flat and other parts of the mountain, it appears that welded tuff was originally widespread and likely formed a veneer over all the Steens Basalt on thewest slope of the mountain but was later eroded from most of the High Steens by glacial ice and running water. The distribution of welded tuff around the Harney Basin and over Steens Mountain suggests that it was emplaced before the onset of fault blocking. Potassium argon ages average 9.2 m.y. (Green, 1973, p. 3). This would place the beginning of the Steen s uplift at about 9 to 10 million years ago. Movement likely continues into the Pleistocene, but the mountain had acquired most of it’s height before glaciation.
www.visitoregon.com/steens-mountain-oregon/
Steens Mountain: Oregon’s Mysterious Secret
Deep in the southeast section of Oregon, a lone mountain sits. The mountain is locked in an arid country, far from any urban developments. A road leads to it; a pathway little-traveled except by scientists looking for answers to an ancient mystery, or those seeking solace from the travails of urban life in a natural place, built by forces beyond our control. The mountain was once known as a sacred place by Native Americans who lived on its slopes. Later, the area became known as Steen’s Mountain, named after the Army Cavalry Major, who defeated and removed the Native American population from the mountain during the Snake Indian Wars. Today, in recognition that no man can own such a place, the name dropped the ownership apostrophe and became Steens Mountain. Another mystery stacked on top of so many others.
The Legend
I first heard the creation story that labeled Steens Mountain as the birthplace of the world from a fellow student in college during the 1960s. Anthony, a son of the Paiute tribe, told me of the mighty Wolf who brought his minions across the star trail to the void at the center of the world. The wolf tasked his followers to find a way to the surface. The route was blocked by water. Many tried but failed to swim through. Finally, the mightiest of Wolf’s followers volunteered to find a way. After ages of exploration through waterfilled caves, the follower found the surface and returned to lead the others. At night they emerged from a cave, which Wolf named Malheur Cave in celebration of their success. That night the world quivered, and they looked up in the morning to see a majestic mountain that reached for the star trail high in the sky. They did not name the mountain; it was too powerful to be limited to a name.
Wolf called the followers to him. He asked them to explore the land and decide where they wished to dwell. After a while, they returned to Wolf and proclaimed where and how they would live. The most powerful, the follower who found the way into the world, was granted the body and life of the Sage Hen so she could sail the sky, walk the soil, and dig into the ground. Another was labeled an Otter while another was a Mountain Goat and a fourth a Coyote. More of the minions became other creatures that explored the mountain and lived there in separate places. Wolf gave them a name—the nuwudu—the Animal People. Wolf charged them with a great responsibility. They were to guard the mountain until the nuwu—the new people—arrived. Then, they were to hide the cave and guide the nuwu to a life of respect and appreciation for what was created for them.
Wolf left through the cave and was never seen again. The nuwudu stayed, each in their home. The nuwu appeared many ages later, crawling through Malheur Cave. They were dirty, uneducated, and stood on two legs. The nuwudu hid Malheur Cave and taught the nuwu the way of the world, sacrificing themselves for the new people. The nuwudu are still there, waiting, watching, and guiding the faithful until Malheur Cave opens again, and the nuwu and nuwudu can return to the old home by the star path with the knowledge and the spirit for which they sacrificed much.
It was Anthony’s oral recitation from the Northern Paiute lore that excited me about Steens Mountain. I visited it soon afterward. I was not prepared to hike the terrain. Still, I saw enough to understand that Steens Mountain is a place of contradictions. The mountain is a massive bulge against a star-filled sky. The land is arid yet filled with flora and fauna on the western side. The eastern side is the opposite in every way. A few mesquites and scrub plants endure the parched conditions on the east side of the mountain, but below the feet of the mountain, everything is desert, pancaked earth, cracked under the punishing sun. The only thing alive there are the dancing dust-devils locked in a series of magnificent minuets.
(Image)
Steens Mountain“Steens Mountain” by BLM Oregon & Washington is licensed under CC BY 2.0
The Science
When I returned home, I began searching for information on Steens Mountain. There was not much to be found as even scientists were not curious about the formation. At that time, the idea of tectonic migration was not yet recognized, and the construction of such heights was considered one of the unsolvable mysteries of the world.
With the events of the 1960s in front of me, I took my attention away from Steens Mountain to what seemed to be more important things. Civil Rights, fear of “The Bomb,” and the Vietnam War took center stage in my life, just as they did for nearly every other citizen of the country. Anthony’s story simmered in my mind. I married, began a family, and took on responsibilities in life and at work that demanded my attention. Still, something was missing, something that the fast world of urban life could never satisfy, that ever-present quality of human curiosity that makes us question the meaning of our existence.
Others questioned established ideas. Geologists found the mystery of tectonic movement and began searching for further evidence, which led them directly to Steens Mountain. After years of study, they discovered that Steens Mountain is the result of fault-block action where the crust stretches until a fissure forms from which the mantle oozes upward, forming a block. In the most extensive fault-block actions, the crack opens several times, creating block after block, forcing the already solidified material upward. At Steens Mountain, multiple events occurred four million years ago, some of them creating layers of basalt a hundred feet thick or more.
When the Earth cooled, glacial action carved great gashes into the mountain that ran from east to west. These glaciers failed to cut through the east side of the mountain, leaving a continuous 52-mile peak that still exists today. The length of the peak running from north to south builds its own climate. The mountain summit of 9,733 feet effectively blocks weather from traveling eastward, creating a dry area called the Alvord Desert—the driest region in Oregon with only four inches of rain per year. While the wester slopes of the mountain receives ample moisture for vegetation growth, the east side is parched, creating a contrasting ecology where different species exist in a relatively small area. From Steens summit on a clear day, you can seen Mount Hood, Mount Jefferson, Mount Batchelor, and the Sisters Mountains.
The temperatures, though always cool due to the elevation, around Steens Mountain vary widely throughout the year, as this table shows.
Weather - You will have to go to the site to see the rest. www.visitoregon.com/steens-mountain-oregon/