Geology of Aruba: Difference between revisions
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The island of Aruba formed within the past 145 million years, beginning in the [[Cretaceous]], as part of the [[Lesser Antilles island arc]]. The island is built on a thick sequence of volcanic rock, but also has carbonate sediment deposits because it was submerged for parts of its existence. |
The island of Aruba formed within the past 145 million years, beginning in the [[Cretaceous]], as part of the [[Lesser Antilles island arc]]. The island is built on a thick sequence of volcanic rock, but also has carbonate sediment deposits because it was submerged for parts of its existence.<ref>{{cite article |author=Jackson & Robinson |year=1994|title=Caribbean Geology: An Introduction|publisher=University of West Indies|p=251-255}}</ref> |
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==Stratigraphy & Geologic History== |
==Stratigraphy & Geologic History== |
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The three kilometer thick [[Aruba Lava Formation]] is the oldest unit on the island, from the [[Cretaceous]], which is intruded by a [[tonalite]] [[pluton]]. Older geologic research referred to this unit as the Diabase-Schist-Tuff Formation. Although mainly [[basalt]], it also includes volcaniclastic [[conglomerate]], [[dolerite]], [[chert]] and chert [[limestone]]. Small sedimentary inclusions preserve [[ammonite]] fossils, suggesting it formed during the [[Turonian]], while [[rubidium-strontium dating]] gives an age of 85 to 70 million years ago. Remnant [[pillow lava]] an sheet-flows record ancient eruptions, flowing down to and often cooling very quickly in seawater. The intrusion of the pluton caused contact metamorphism in some of the surrounding basalt and left behind [[epidote]], [[hornblende]], [[albite]] and [[uralite]] in the rocks. Geochemists have found that the major and trace element chemistry of the rocks is almost the same as in Curaçao. |
The three kilometer thick [[Aruba Lava Formation]] is the oldest unit on the island, from the [[Cretaceous]], which is intruded by a [[tonalite]] [[pluton]]. Older geologic research referred to this unit as the Diabase-Schist-Tuff Formation. Although mainly [[basalt]], it also includes volcaniclastic [[conglomerate]], [[dolerite]], [[chert]] and chert [[limestone]]. Small sedimentary inclusions preserve [[ammonite]] fossils, suggesting it formed during the [[Turonian]], while [[rubidium-strontium dating]] gives an age of 85 to 70 million years ago. Remnant [[pillow lava]] an sheet-flows record ancient eruptions, flowing down to and often cooling very quickly in seawater. The intrusion of the pluton caused contact metamorphism in some of the surrounding basalt and left behind [[epidote]], [[hornblende]], [[albite]] and [[uralite]] in the rocks. Geochemists have found that the major and trace element chemistry of the rocks is almost the same as in Curaçao. |
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The [[hornblende]] tonalite batholith is a major part of Aruba's geology. The "roof" of the formation is made out of the oldest intrusive material, [[norite]] and [[gabbro]]. The norite shifts from [[hypersthene]] to [[augite]] while the gabbro has abundant [[augite]], [[hornblende]] and [[quartz |
The [[hornblende]] tonalite batholith is a major part of Aruba's geology. The "roof" of the formation is made out of the oldest intrusive material, [[norite]] and [[gabbro]]. The norite shifts from [[hypersthene]] to [[augite]] while the gabbro has abundant [[augite]], [[hornblende]] and [[quartz]]. The tonalite is mainly [[plagioclase]], interstitial quartz and [[potassium feldspar]] as well as dark minerals like hornblende, [[biotite]], [[clinopyroxene]] and [[magnetite]]. There are also small occurrences of [[trondhjemite]]. {{sfn|Jackson & Robinson|1994|p=251-253}} |
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==Cenozoic (66 million years ago-present)== |
==Cenozoic (66 million years ago-present)== |
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A small outcrop of [[Eocene]] and [[Oligocene]] limestone occurs at Butucu Ranch in east-central Aruba, without quartz, but containing fossils from the time period such as algae and [[foraminifera]]. Named for exposures on Curaçao, the Seroe Domi Formation is on the southwestern side of Aruba and includes a series of detrital limestone and conglomerates. |
A small outcrop of [[Eocene]] and [[Oligocene]] limestone occurs at Butucu Ranch in east-central Aruba, without quartz, but containing fossils from the time period such as algae and [[foraminifera]]. Named for exposures on Curaçao, the Seroe Domi Formation is on the southwestern side of Aruba and includes a series of detrital limestone and conglomerates. |
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| ⚫ | In 1942, two French friars using divining rods instructed a team to drill the Oranjestad borehole down 302 meters, which revealed the Orenjastad sands and clays from the [[Pliocene]] and [[Late Miocene]], as well as a hypersaline artesian well.{{sfn|Jackson & Robinson|1994|p=254-255}} Five limestone terraces formed during the past 2.5 million years of the [[Quaternary]]. |
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| ⚫ | In 1942, two French friars using divining rods instructed a team to drill the Oranjestad borehole down 302 meters, which revealed the Orenjastad sands and clays from the [[Pliocene]] and [[Late Miocene]], as well as a hypersaline artesian well.{{sfn|Jackson & Robinson|1994|p=254-255}} Five limestone terraces formed during the past 2.5 million years of the [[Quaternary]].<ref>{{cite article |author=Alexander, C. |year=1961|title=THE MARINE TERRACES OF ARUBA, BONAIRE, AND CURAÇAO, NETHERLANDS ANTILLES|publisher=Annals of the Association of American Geographers|url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1467-8306.1961.tb00370.x}}</ref> |
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==References== |
==References== |
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Revision as of 18:34, 4 June 2018
The island of Aruba formed within the past 145 million years, beginning in the Cretaceous, as part of the Lesser Antilles island arc. The island is built on a thick sequence of volcanic rock, but also has carbonate sediment deposits because it was submerged for parts of its existence.[1]
Stratigraphy & Geologic History
The three kilometer thick Aruba Lava Formation is the oldest unit on the island, from the Cretaceous, which is intruded by a tonalite pluton. Older geologic research referred to this unit as the Diabase-Schist-Tuff Formation. Although mainly basalt, it also includes volcaniclastic conglomerate, dolerite, chert and chert limestone. Small sedimentary inclusions preserve ammonite fossils, suggesting it formed during the Turonian, while rubidium-strontium dating gives an age of 85 to 70 million years ago. Remnant pillow lava an sheet-flows record ancient eruptions, flowing down to and often cooling very quickly in seawater. The intrusion of the pluton caused contact metamorphism in some of the surrounding basalt and left behind epidote, hornblende, albite and uralite in the rocks. Geochemists have found that the major and trace element chemistry of the rocks is almost the same as in Curaçao.
The hornblende tonalite batholith is a major part of Aruba's geology. The "roof" of the formation is made out of the oldest intrusive material, norite and gabbro. The norite shifts from hypersthene to augite while the gabbro has abundant augite, hornblende and quartz. The tonalite is mainly plagioclase, interstitial quartz and potassium feldspar as well as dark minerals like hornblende, biotite, clinopyroxene and magnetite. There are also small occurrences of trondhjemite. [2]
Cenozoic (66 million years ago-present)
A small outcrop of Eocene and Oligocene limestone occurs at Butucu Ranch in east-central Aruba, without quartz, but containing fossils from the time period such as algae and foraminifera. Named for exposures on Curaçao, the Seroe Domi Formation is on the southwestern side of Aruba and includes a series of detrital limestone and conglomerates.
In 1942, two French friars using divining rods instructed a team to drill the Oranjestad borehole down 302 meters, which revealed the Orenjastad sands and clays from the Pliocene and Late Miocene, as well as a hypersaline artesian well.[3] Five limestone terraces formed during the past 2.5 million years of the Quaternary.[4]
References
- ^ Template:Cite article
- ^ Jackson & Robinson 1994, p. 251-253.
- ^ Jackson & Robinson 1994, p. 254-255.
- ^ Template:Cite article