The Mesozoic Era, covering an interval of Earth history from about 230 million to 65 mil lion years ago, comprises three geologic time periods: Trias sic, Jurassic, and Cretaceous. The term, meaning "middle life," was introduced in 1841 by the English geologist John Phillips. In most places the rock layers deposited during the three eras are separated from f rom one another by unconformities, breaks in the sequence of deposition deposition of the geologic record.
Paleogeography Paleogeogr aphy and Tectonics
The Mesozoic was a time of transition in the history of life and in the evolution of the Earth. By the close of the Paleozoic Era, geosynclines were confined to the Tethys Seas (modern Mediterranean Sea and Middle East) and circum-Pacif ic region, the others having undergone the final phases of mountain-building orogenies that transformed them into ranges. According to the theory of plate tectonics, the supercontinent of Pangaea, cr eated by the merging of the ancestral continents during the Paleozoic Era, was slowly torn apart during the Mesozoic. In the Jurassic, shallow seas spread northward out of the Tethys and southward from the Arctic onto western Europe. This also happened in North America, where an Arctic sea spread over the present-day Rocky Mountains south to Utah; the area adjacent to the Gulf of Mexico and Atlantic coastal plain was also inundated. These seas retreated by the end of the Jurassic but returned in the Early Cretaceous to roughly their former extent: one reached from the Gulf of Mexico to the Arctic, another covered much of western Europe, and a broad channel spread across the Sahara, joining the Gulf of Guinea and the Tethys. At the close of the Cretaceous Period the seas retreated from the continents. Deformation of the Earth's crust, mi nor during the Triassic, intensified in the Jurassic and reached a peak in the Cretaceous, during which time our present Alpine-Himalayan chain, Rocky Mountains, and Andes began forming. Carbonates are the major sedimentary rock of the Mesozoic in the Tethyan belt; outside this region, detrital rocks predominate. Desert deposits and red bed facies are characteristic of the Triassic, as is chalk of the Cretaceous.
Mesozoikum Era, meliputi selang sejarah Bumi dari 230 juta sampai 65 juta tahun yang lalu, terdiri dari tiga geologi periode waktu: Trias, Jura, J ura, dan Kapur. Istilah, yang berarti "hidup tengah," diperkenalkan pada tahun 1841 oleh ahli geologi Inggris John Phillips. Di kebanyakan tempat lapisan batuan diendapkan selama tiga era dipisahkan satu sama lain oleh ketidakselarasan, istirahat di urutan pengendapan catatan geologi.
Paleogeografi dan Tektonik Mesozoikum adalah waktu transisi dalam sejarah kehidupan dan dalam evolusi Bumi. Dengan penutupan Era Paleozoic, teori geosinklin yang terbatas pada Seas Tethys (yang modern Laut Mediterania dan Timur Tengah) dan sirkum-Pasifik, yang lain telah menjalani tahap akhir orogenies gunung-bangunan yang mengubah mereka menjadi rentang. Menurut teori lempeng tektonik, superbenua Pangaea, yang diciptakan oleh penggabungan dari benua leluhur selama Era Paleozoic, perlahan terkoyak selama Mesozoikum. Dalam Jurassic, laut dangkal menyebar ke utara keluar dari Tethys dan selatan dari Kutub Utara ke Eropa Barat. Hal ini juga terjadi di Amerika Utara, di mana penyebaran laut Arktik selama masa kini Rocky Mountains selatan ke Utah; daerah yang berdekatan dengan Teluk Meksiko dan dataran pantai Atlantik juga terendam. laut ini mundur pada akhir Jurassic namun kembali di Kapur Awal kira-kira mantan sejauh mereka: satu dicapai dari Teluk Meksiko ke Kutub Utara, yang lain menutupi sebagian besar Eropa Barat, dan saluran penyebaran yang luas di seluruh Sahara, bergabung dengan Teluk Guinea dan Tethys. Pada penutupan Periode Cretaceous laut mundur dari benua. Deformasi kerak bumi, kecil selama Tri as, intensif di Jurassic dan mencapai puncaknya di Cretaceous, selama waktu kita sekarang AlpineHimalaya rantai, Rocky Mountains, dan Andes mulai membentuk. Karbonat adalah batuan sedimen utama dari Mesozoikum di sabuk Tethyan; luar daerah ini, batu detrital mendominasi. Desert deposito dan facies tidur merah merupakan ciri khas dari Trias, seperti kapur dari Kapur. http://www.scholastic.com/teachers/article/mesozoic-era
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the … Adapted from: C.R. Scotese, The The University of Texas at Arlington
Triassic Period, in geologic time, the first period of the Mesozoic Era. It began 252 million
years ago, at the close of the Permian Period, and ended 201 million years ago, when it was succeeded by the Jurassic Period.
The Triassic Period marked the beginning of major changes that were to take place throughout the Mesozoic Era, particularly in the distribution of continents, the evolution of life, and the geographic distribution of living things. At the beginning of the Triassic, virtually all the major landmasses of the world were collected into the supercontinent of Pangea. Terrestrial climates were predominately warm and dry (though seasonal monsoons occurred over large areas), and the Earth’s crust was relatively quiescent. At the end of the Triassic, however, plate tectonic activity picked up, and a period of continental rifting began. On the margins of the continents, shallow seas, which had dwindled in area at the end of the Permian, became more extensive; as sea levels gradually rose, the waters of continental shelves were colonized for the first time by large marine reptiles and reef-building corals of modern aspect. The Triassic followed on the heels of the largest mass extinction in the history of the Earth. This event occurred at the end of the Permian, when 85 to 95 percent of marine invertebrate
species and 70 percent of terrestrial vertebrate genera died out. During the recovery of life in the Triassic Period, the relative importance of land animals grew. Reptilesincreased in diversity and number, and the first dinosaurs appeared, heralding the great radiation that
Another episode of mass extinction occurred at the end of the Triassic. Though this event was less devastating than its counterpart at the end of the Permian, it did result in drastic reductions of some living populations — particularly of the ammonoids, primitive mollusks that have served as important index fossils for assigning relative ages to various strata in the Triassic System of rocks. The name Trias (later modified to Triassic) was first proposed in 1834 by the German paleontologist Friedrich August von Alberti for a sequence of rock strata in central Germany that lay above Permian rocks and below Jurassic rocks. (The name Trias referred to the division of these strata into three units: the Bunter [or Buntsandstein], Muschelkalk , and Keuper .) Alberti’s rock sequence, which became known as the “Germanic facies,” had many drawbacks as a standard for assigning relative ages to Triassic rocks from other regions of the world, and s o for much of the 19th and 20th centuries Triassic stages were based mainly on type sections from the “Alpine facies” in Austria, Switzerland, and northern Italy. Since the mid-20th century more complete sequences have been discovered in North America, and these now serve as the standard for Triassic time in general. Meanwhile, studies of seafloor spreading and plate tectonics have yielded important new information on the paleogeography and paleoclimatology of the Triassic, allowing for a better understanding of the evolution and extinction of life -forms and of the paleoecology and paleobiogeography of the period. In addition, paleontologists continue to be occupied with defining the lower and upper boundaries of the Triassic S ystem on a worldwide basis and with understanding the reasons for the mass extinctions that took place at those boundaries.
Periode Triassic, dalam waktu geologi, periode pertama dari Era Mesozoic. Ini dimulai 252 juta tahun yang lalu, pada penutupan Periode Permian, dan berakhir 201 juta tahun yang lalu, ketika digantikan oleh Periode Jurassic. Periode Trias menandai awal dari perubahan besar yang terjadi di seluruh Era Mesozoikum, khususnya dalam distribusi benua, evolusi kehidupan, dan dist ribusi geografis dari makhluk hidup. Pada awal Trias, hampir semua daratan utama dunia dikumpulkan ke dalam
superbenua Pangea. iklim terestrial yang didominasi hangat dan kering (meskipun musim hujan musiman terjadi di daerah yang luas), dan kerak bumi relatif diam. Pada akhir Triassic, namun, piring aktivitas tektonik dijemput, dan periode rifting benua mulai. Di pinggiran benua, laut dangkal, yang telah menyusut di daerah pada akhir Permian, menjadi lebih luas; sebagai permukaan air laut secara bertahap naik, perairan landas kontinen dijajah untuk pertama kalinya oleh reptil laut besar dan karang pembentuk terumbu aspek modern. Trias diikuti pada tumit dari kepunahan massal terbesar dalam sejarah Bumi. Peristiwa ini terjadi pada akhir periode Permian, ketika 85 hingga 95 persen spesies invertebrata laut dan 70 persen dari hewan bertulang belakang genera mati. Selama pemulihan kehidupan di periode Triassic, kepentingan relatif dari hewan darat tumbuh. Reptilesincreased dalam keragaman dan nomor, dan dinosaurus pertama muncul, menggembar-gemborkan radiasi besar yang akan mencirikan kelompok ini selama periode Jurassic dan Cretaceous. Akhirnya, akhir Triassic melihat penampilan pertama mamalia-kecil, bulu-bantalan, shrewlike hewan yang berasal dari reptil.
episode lain dari kepunahan massal terjadi pada akhir Triassic. Meskipun acara ini kurang menghancurkan dari rekan di akhir Permian, hal itu mengakibatkan penurunan drastis dari beberapa populasi-terutama hidup dari ammonoids, moluska primitif yang telah menjabat sebagai fosil indeks penting untuk menetapkan usia relatif terhadap berbagai strata di Trias Sistem batuan. Nama Trias (kemudian dimodifikasi untuk Trias) pertama kali diusulkan pada tahun 1834 oleh ahli paleontologi Jerman Friedrich August von Alberti untuk urutan lapisan batuan di Jerman Tengah yang terletak di atas batu Permian dan di bawah batu J urassic. (Nama Trias disebut pembagian strata ini ke dalam tiga unit. Yang Bunter [atau Buntsandstein], Muschelkalk, dan Keuper) Alberti urutan batuan, yang kemudian dikenal sebagai "facies Jerman," memiliki banyak kekurangan sebagai standar untuk menetapkan usia relatif Trias batu dari daerah lain di dunia, dan untuk sebagian besar abad 19 dan 20 Trias tahap didasarkan terutama pada jenis bagian dari "Alpine f acies" di Austria, Swiss, dan Italia utara. Sejak pertengahan abad ke-20 urutan yang lebih lengkap telah ditemukan di Amerika Utara, dan ini sekarang berfungsi sebagai standar untuk waktu Trias pada umumnya. Sementara itu, studi dasar laut menyebar dan lempeng tektonik telah menghasilkan informasi baru yang penting pada paleogeography dan paleoklimatologi dari Trias, memungkinkan untuk lebih
memahami evolusi dan kepunahan bentuk kehidupan dan dari paleoecology dan paleobiogeography periode. Selain itu, ahli paleontologi terus sibuk dengan mendefinisikan batas-batas bawah dan atas dari Sistem Trias pada dasar di seluruh dunia dan dengan memahami alasan untuk kepunahan massal yang berlangsung di batas-batas. https://www.britannica.com/science/Triassic-Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the … Adapted from: C.R. Scotese, The University of Texas at Arlington
Jurassic Period, second of three periods of the Mesozoic Era, extending from 201.3 million
to 145 million years ago. It immediately followed the Triassic Period (252.2 million to 201.3 million years ago) and was succeeded by the Cretaceous Period (145 million to 66 million years ago). The Morrison Formation of the United States and the Solnhofen
Limestone of Germany, both famous for their exceptionally well-preserved fossils, are geologic features that were formed during Jurassic times.
The Jurassic was a time of significant global change in continental configurations, oceanographic patterns, and biological systems. During this period the supercontinent Pangea split apart, allowing for the eventual development of what are now the central Atlantic Ocean and the Gulf of Mexico. Heightened plate tectonic movement led to significant volcanic activity, mountain-building events, and attachment of islands onto continents. Shallow seaways covered many continents, and marine and marginal marine sediments were deposited, preserving a diverse set of fossils. Rock strata laid down during the Jurassic Period have yielded gold, coal, petroleum, and other natural re sources.
During the Early Jurassic, animals and plants living both on land and in the seas recovered from one of the largest mass extinctions in Earthhistory. Many groups of vertebrate and invertebrate organisms important in the modern world made their first appearance during the Jurassic. Life was especially diverse in the oceans — thriving reef ecosystems, shallowwater invertebrate communities, and large swimming predators, including reptiles and squidlike animals. On land, dinosaurs and flying pterosaurs dominated the ecosystems, and birds made their first appearance. Early mammals also were present, though they were still fairly insignificant. Insect populations were diverse, and plants were dominated by the gymnosperms, or “naked-seed” plants.
The Jurassic Period was named early in the 19th century, by the French geologist and mineralogist Alexandre Brongniart, for the Jura Mountains between France and Switzerland. Much of the initial work by geologists in trying to correlate rocks and develop a relative geologic time scale was conducted on Jurassic strata in western Europe.
THE JURASSIC ENVIRONMENT
Paleogeography
Although the breakup of the supercontinent Pangea had already started in the Triassic Period, the continents were still very close together at the beginning of Jurassic time. The landmasses were grouped into a northern region — Laurasia — consisting of North America and Eurasia,
and a southern region — Gondwana — consisting of South America, Africa, India, Antarctica, and Australia. These two regions were separated by Tethys, a tropical east-west seaway. During the Jurassic, spreading centres and oceanic rifts formed between North America and Eurasia, between North America and Gondwana, and between the various segments of Gondwana itself. In the steadily opening, though still restricted, ocean basins, there was a continuous accumulation of thick flood basalts and a subsequent deposition of sediments. Some of these deposits, such as salt deposits in the Gulf of Mexico and oil-bearing shales of the North Sea, are economically important today. In addition to ocean basin spreading, continental rifting initiated during the Jurassic, eventually separating Africa and South America from Antarctica, India, and Madagascar. The numerous microplates and blocks making up the complex Caribbean region today can be traced to this time inter val. To accommodate the production of new seafloor along the proto-Atlantic Ocean, significant subduction zones (where seafloor is destroyed) were active along virtually all the continental margins around Pangea as well as in southern Tibet, southeastern Europe, and other areas. All along the west coast of North, Central, and South America, plate tectonic activity in the subduction zones brought on the initial formation of north-south mountain ranges such as the Rocky Mountains and the Andes. Along western North America, several terranes (islands or microcontinents riding on a moving plate) were brought east on oceanic crust and collided with the continent, including parts of a microcontinent that collided into the Alaskan and Siberian regions in the northern Pacific. These collisions added to the growth of the North American continent and its mountain chains. One mountain-building event, known as the Nevadan orogeny, resulted in the emplacement of massive igneous and metamorphic rocks from Alaska to Baja California. Granites formed in the Sierra Nevadas during this time can be seen today in Yosemite National Park , California. BRITANNICA STORIES In the Early Jurassic the western interior of North America was covered by a vast sand sea, or erg — one of the largest deposits of dune sands in the geologic record. These deposits (including the Navajo Sandstone) are prominent in a number of places today, including Zion National Park , Utah. In Middle and early Late Jurassic times, the western regions of North America were covered by shallow seaways that a dvanced and retreated repeatedly, leaving successive accumulations of marine sandstones, limestones, and shales. By Late Jurassic time the seaway had retreated, and strata bearing dinosaur fossils were deposited in river
floodplains and stream channel environments, such as those recorded in t he Morrison Formation, Montana.
Cross-bedded sandstone cliffs in Zion National Park, Utah, U.S. Peter L. Kresan
Records of sea level changes can be found on every continent. However, because of the significant tectonic activity occurring around the world, it is not clear which of these local changes can be correlated to global sea level change. Because there is no evidence of major glaciations in the Jurassic, any global sea level change must have been due to thermal expansion of seawater or plate tectonic activity (such as major activity at seafloor ridges). Some geologists have proposed that average sea levels increase d from Early to Late Jurassic time.
Paleoclimate
Jurassic climates can be reconstructed from the analyses of fossil and sediment distribution and from geochemical analyses. Fossils of warm-adapted plants are found up to 60° N and 60° S paleolatitude, suggesting an expanded tropical zone. In higher paleolatitudes, ferns and other frost-sensitive plants indicate that there was a less severe temperature difference between the Equator and the poles than exists today. Despite this decreased temperature gradient, there was a marked difference in marine invertebrates from northern higher
latitudes — the boreal realm — and the tropical Tethyan realm. Decreased latitudinal temperature gradients probably led to decreased zonal winds.
Large salt deposits dating from the Jurassic represent areas of high aridity, while extensive coal deposits suggest areas of high precipitation. It has been suggested that an arid belt existed on the western side of Pangea, while more-humid conditions existed in the east. These conditions may have been caused by large landmasses affecting wind and precipitation in a manner similar to that of modern continents.
Analyses of oxygen isotopes in marine fossils suggest that Jurass ic global temperatures were generally quite warm. Geochemical evidence suggests that surface waters in the low latitudes were about 20 °C (68 °F), while deep waters were about 17 °C (63 °F). Coolest temperatures existed during the Middle Jurassic and warmest temperatures in the Late Jurassic. A drop in temperatures occurred at the Jurassic-Cretaceous boundary.
It has been suggested that increased volcanic and seafloor-spreading activity during the Jurassic released large amounts of carbon dioxide — a greenhouse gas — and led to higher global temperatures. Warm temperatures and decreased latitudinal gradients also may be related to the Tethys Sea, which distributed warm, tropical waters around the world. Ocean circulation was probably fairly sluggish because of the warm temper atures, lack of ocean density gradients, and decreased winds. As stated above, there is no evidence of glaciation or polar ice caps in the Jurassic. This may have been caused by the lack of a continental landmass in a polar position or by generally warm conditions; however, because of the complex relationships between temperature, geographic configurations, and glaciations, it is difficult to state a definite cause and effect.
Periode Jurassic, kedua dari tiga periode dari Era Mesozoic, memperluas 201.300.000145.000.000 tahun yang lalu. Segera diikuti periode Triassic (252.200.000-201.300.000 tahun yang lalu) dan digantikan oleh Periode Cretaceous (145.000.000-66.000.000 tahun yang lalu). Morrison Pembentukan Amerika Serikat dan Solnhofen Limestone dari Jerman, keduanya terkenal karena fosil mereka sangat terawat baik, adalah fitur geologi yang terbentuk pada masa Jurassic.
Jurassic adalah masa perubahan yang signifikan global dalam konfigurasi benua, pola oseanografi, dan sistem biologi. Selama periode ini superbenua Pangea terpecah, yang memungkinkan untuk pengembangan akhirnya apa yang sekarang Samudera Atlantik pusat dan Teluk Meksiko. Semakin tingginya lempeng gerakan tektonik menyebabkan aktivitas signifikan vulkanik, peristiwa pembentukan gunung, dan lampiran pulau ke benua. seaways dangkal ditutupi banyak benua, dan laut dan marginal sedimen laut diendapkan, melestarikan beragam rangkaian fosil. Batu strata meletakkan selama Periode Jurassic telah menghasilkan emas, batubara, minyak bumi, dan sumber daya alam lainnya.
Selama Awal Jurassic, hewan dan tumbuhan yang hidup baik di darat dan di laut pulih dari salah satu kepunahan massal terbesar di Earthhistory. Banyak kelompok vertebrata dan invertebrata organisme penting dalam dunia modern membuat penampilan pertama mereka selama Jurassic. Hidup terutama beragam di ekosistem lautan-berkembang karang, masyarakat invertebrata air dangkal, dan predator renang besar, termasuk reptil dan hewan squidlike. Di darat, dinosaurus dan terbang pterosaurus mendominasi ekosistem, dan burung membuat penampilan pertama mereka. Awal mamalia juga hadir, meskipun mereka masih cukup signifikan. populasi serangga yang beragam, dan tanaman didominasi oleh gymnosperma, atau "telanjang-benih" tanaman.
Periode Jurassic bernama awal abad ke-19, oleh ahli geologi Perancis dan mineralogi Alexandre Brongniart, untuk Jura Mountainsbetween Perancis dan Swiss. Sebagian besar pekerjaan awal oleh ahli geologi dalam mencoba untuk mengkorelasikan batu dan mengembangkan geologi skala waktu relatif dilakukan pada strata Jurassic di Eropa Barat.
THE JURASSIC LINGKUNGAN
paleogeography Meskipun pecahnya Pangea superbenua sudah mulai di periode Triassic, benua masih sangat dekat bersama-sama di awal waktu Jurassic. The daratan dikelompokkan menjadi utara
wilayah-Laurasia-yang terdiri dari Amerika Utara dan Eurasia, dan selatan wilayahGondwana-yang terdiri dari Amerika Selatan, Afrika, India, Antartika, dan Australia. Kedua daerah dipisahkan oleh Tethys, tropis timur-barat Seaway. Selama Jurassi c, pusat penyebaran dan perpecahan samudera terbentuk antara Amerika Utara dan Eurasia, antara Amerika Utara dan Gondwana, dan antara berbagai segmen Gondwana sendiri. Dalam cekungan laut terus membuka, meskipun masih terbatas,, ada akumulasi terus menerus dari basal banjir tebal dan deposisi berikutnya sedimen. Beberapa deposito tersebut, seperti deposito garam di Teluk Meksiko dan serpih bantalan minyak di Laut Utara, secara ekonomi penting hari ini. Selain cekungan laut menyebar, benua rifting dimulai pada Jurassic, akhirnya memisahkan Afrika dan Amerika Selatan dari Antartika, India, dan Madagaskar. Banyak microplates dan blok yang membentuk kawasan Karibia yang kompleks saat dapat ditelusuri ke interval waktu ini. Untuk mengakomodasi produksi dasar laut baru di sepanjang proto-Samudra Atlantik, zona subduksi yang signifikan (di mana dasar laut hancur) yang aktif sepanjang hampir semua tepi benua sekitar Pangea serta di Tibet selatan, tenggara Eropa, dan daerah lain. Sepanjang pantai barat Amerika Utara, Tengah, dan Amerika Selatan, piring aktivitas tektonik di zona subduksi membawa pada pembentukan awal pegunungan utara-selatan seperti Pegunungan Rocky dan Andes. Seiring barat Amerika Utara, beberapa terranes (pulau at au microcontinents naik di atas piring yang bergerak) dibawa timur pada kerak samudera dan bertabrakan dengan benua, termasuk bagian dari mikrokontinen yang bertabrakan ke daerah Alaska dan Siberia di Pasifik utara. tabrakan ini ditambahkan ke pertumbuhan benua Amerika Utara dan rantai gunung tersebut. Salah satu acara pembentukan gunung, yang dikenal sebagai orogeny Nevadan, mengakibatkan emplacement batuan beku dan metamorf besar dari Alaska ke Baja California. Granit terbentuk di Sierra Nevadas selama ini dapat dilihat hari ini di Taman Nasional Yosemite, California. CERITA Britannica Di awal Jurassic interior barat Amerika Utara ditutupi oleh lautan pasir yang luas, atau ergsalah satu deposit terbesar dari pasir dune dalam catatan geologi. Deposito tersebut (termas uk Navajo Sandstone) yang menonjol di sejumlah tempat saat ini, termasuk Zion National Park, Utah. Di Tengah dan awal Akhir kali Jurassic, wila yah barat Amerika Utara ditutupi oleh jalur laut dangkal yang maju dan mundur berulang kali, meninggalkan akumulasi berturut batupasir laut, batugamping, dan serpih. Pada saat Jura Akhir seaway telah mundur, dan
bantalan strata fosil dinosaurus yang disimpan di dataran banjir sungai dan aliran lingkungan channel, seperti yang tercatat dalam Formasi Morrison, Montana. •
Cross-bedded tebing batu pasir di Zion National Park, Utah, AS Peter L. Kresan
Catatan perubahan permukaan laut dapat ditemukan di setiap benua. Namun, karena aktivitas tektonik signifikan yang terjadi di seluruh dunia, tidak jelas mana yang perubahan lokal dapat dikorelasikan dengan perubahan permukaan laut global. Karena tidak ada bukti glasiasi utama dalam Jurassic, setiap perubahan permukaan laut global harus telah karena ekspansi termal air laut atau piring aktivitas tektonik (seperti aktivitas utama di pegunungan dasar laut). Beberapa ahli geologi telah mengusulkan bahwa permukaan laut rata-rat a meningkat dari awal ke waktu Jurassic Akhir. paleoklimatik iklim Jurassic dapat direkonstruksi dari analisis fosil dan distribusi sedimen dan dari analisis geokimia. Fosil tumbuhan hangat-disesuaikan ditemukan hingga 60 ° N dan 60 ° S paleolatitude, menunjukkan zona tropis diperluas. Dalam paleolatitudes lebih tinggi, pakis dan tanaman frost-sensitif lainnya menunjukkan bahwa ada perbedaan suhu kurang parah antara Khatulistiwa dan kutub dari yang ada saat ini. Meskipun ini menurun gradien suhu, ada perbedaan yang jelas dalam invertebrata laut dari utara lintang-tinggi boreal ranah-dan Tethyan ranah tropis. Penurunan gradien suhu lintang mungkin menyebabkan angin zonal menurun.
endapan garam besar berasal dari Jurassic tersebut merupakan daerah kekeringan yang tinggi, sedangkan deposito batubara luas menyarankan daerah curah hujan tinggi. Ia telah mengemukakan bahwa sabuk gersang ada di sisi barat Pangea, sementara kondisi yang lebih
lembab ada di timur. Kondisi ini mungkin disebabkan oleh daratan besar yang mempengaruhi angin dan curah hujan dengan cara yang sama dengan yang benua modern. Analisis isotop oksigen dalam fosil laut menunjukkan bahwa suhu global Jurassic umumnya cukup hangat. bukti geokimia menunjukkan bahwa permukaan air di lintang rendah sekitar 20 ° C (68 ° F), sedangkan perairan dalam sekitar 17 ° C (63 ° F). suhu paling keren ada selama suhu Jurassic Tengah dan terpanas di Jurassic Akhir. Penurunan suhu terjadi pada batas Jurassic-Cretaceous. Ia telah mengemukakan bahwa peningkatan aktivitas vulkanik dan dasar laut menyebar selama Jurassic merilis sejumlah besar gas karbon-dioksida dan-rumah kaca menyebabkan suhu global yang lebih tinggi. suhu hangat dan penurunan gradien lintang juga mungkin terkait dengan Laut Tethys, yang didistribusikan hangat, perairan tropis di seluruh dunia. sirkulasi laut mungkin cukup lesu karena suhu hangat, kurangnya gradien kepadatan laut, dan penurunan angin. Sebagaimana dinyatakan di atas, tidak ada bukti dari glaciation atau es kutub di Jurassic. Ini mungkin disebabkan oleh kurangnya daratan benua dalam posisi kutub atau dengan kondisi umumnya hangat; Namun, karena hubungan yang kompleks antara temperatur, konfigurasi geografis, dan glasiasi, sulit untuk menyatakan penyebab pasti dan efek. https://www.britannica.com/science/Jurassic-Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the … Adapted from C.R. Scotese, The University of Texas at Arlington
Cretaceous Period, in geologic time, the last of the three periods of the Mesozoic Era. The
Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and was succeeded by the Paleogene Period (the first of the two periods into which the Tertiary Period was divided). The Cretaceous is the longest period of the Phanerozoic Eon. Spanning 79 million years, it represents more time than has el apsed since the extinction of the dinosaurs, which occurred at the end of the period. The name Cretaceous is derived from creta, Latin for “chalk ,” and was first proposed by J.B.J. Omalius d’Halloy in 1822. D’Halloy had been commissioned to make a geologic map of France, and part of his task was to decide upon the geologic units to be represented by it. One of his units, the Terrain Crétacé, included chalks and underlying sands. Chalk is a soft, fine-grained type of limestone composed predominantly of the armourlike plates of coccolithophores, tiny floating algae that flourished during the Late Cretaceous. Most
Cretaceous rocks are not chalks, but most chalks were deposited during the Cretaceous. Many of these rocks provide clear and easil y accessed details of the period because they have not been deformed or eroded and are relatively close to the surface — as can be seen in the white cliffs bordering the Strait of Dover between France and England.
The Cretaceous Period began with Earth’s land assembled essentially into two continents, Laurasia in the north and Gondwana in the south. These were almost completely separated by the equatorial Tethys seaway, and the various segments of Laurasia and Gondwana had already started to rift apart. North America had just begun pulling away from Eurasia during the Jurassic, and South America had started to split off from Africa, from which India, Australia, and Antarctica were also separating. When the Cretaceous Period ended, most of the present-day continents were separated from each other by expanses of water such as the North and South Atlantic Ocean. At the end of the period, India was adrift in the Indian Ocean, and Australia was still connected to Antarctica. SIMILAR TOPICS The climate was generally warmer and more humid than today, probably because of very active volcanism associated with unusually high rates of seafloor spreading. The polar regions were free of continental ice sheets, their land instead covered by forest. Dinosaurs roamed Antarctica, even with its long winter night. The lengthy Cretaceous Period constitutes a major portion of the interval bet ween ancient life-forms and those that dominate Earth today. Dinosaurs were the dominant group of land animals, especially “duck - billed” dinosaurs (hadrosaurs), such as Shantungosaurus, and horned forms, such as Triceratops. Giant marine reptiles such as ichthyosaurs, mosasaurs, and plesiosaurs were common in the seas, and flying reptiles ( pterosaurs) dominated the sky. Flowering plants (angiosperms) arose close to the beginning of the Cretaceous and became more abundant as the period progressed. The Late Cretaceous was a ti me of great productivity in the world’s oceans, as borne out by the deposition of thick beds of chalk in western Europe, eastern Russia, southern Scandinavia, the Gulf Coast of North America, and western Australia. The Cretaceous ended with one of the greatest mass extinctions in the history of Earth, exterminating the dinosaurs, marine and flying reptiles, and many marine invertebrates. THE CRETACEOUS ENVIRONMENT Paleogeography
The position of Earth’s landmasses changed significantly during the Cretaceous Period — not unexpected, given its long duration. At the onset of the period there existed two supercontinents, Gondwana in the south and Laurasia in the north. South America, Africa (including the adjoining pieces of what are now the Arabian Peninsula and the Middle East), Antarctica, Australia, India, Madagascar , and several smaller landmasses were joined in Gondwana in the south, while North America, Greenland, and Eurasia (including Southeast Asia) formed Laurasia. Africa had split from South America, the last land connection being between Brazil and Nigeria. As a result, the South Atlantic Ocean joined with the widening North Atlantic. In the region of the Indian Ocean, Africa and Madagascar separated from India, Australia, and Antarctica in Late Jurassic to Early Cretaceous times. Once separated from Australia and Antarctica, India began its journey northward, which culminated in a later collision with Asia during the Cenozoic Era. Madagascar broke away from Africa during the Late Cretaceous, and Greenland separated from North America. Australia was still joined to Antarctica. These were barely attached at the junction of what a re now North and South America.
Sea level was higher during most of the Cretaceous than at any other time in Earth history, and it was a major factor influencing the paleogeography of the period. In general, world oceans were about 100 to 200 metres (330 to 660 feet) higher in the Early Cretaceous and roughly 200 to 250 metres (660 to 820 feet) higher in the Late Cretaceous than at present. The high Cretaceous sea level is thought to have been primarily the result of water in the ocean basins being displaced by the enlargement of midoceanic ridges.
As a result of higher sea levels during the Late Cretaceous, marine waters inundated the continents, creating relatively shallow epicontinental seas in North America, South America, Europe, Russia, Africa, and Australia. In addition, all continents shrank somewhat as their margins flooded. At its maximum, land covered only about 18 percent of the Earth’s surface, compared with approximately 28 percent today. At times, Arctic wat ers were connected to the Tethys seaway through the middle of North America and the central portion of Russia. On several occasions during the Cretaceous, marine animals living in the South Atlantic had a seaway for migration to Tethys via what is presently Nigeria, Niger, Chad, and Libya. Most of western Europe, eastern Australia, parts of Africa, South America, India, Madagascar, Borneo, and other areas that are now land were entirely covered by marine waters for some interval of Cretaceous time.
Detailed study indicates 5 to 15 different episodes of rises and falls in sea level. The patterns of changes for the stable areas throughout history are quite si milar, although several differences are notable. During most of the Earl y Cretaceous, parts of Arctic Canada, Russia, and western Australia were underwater, but most of the other areas were not. During the middle Cretaceous, east-central Australia experienced major inundations called transgressions. In the Late Cretaceous, most continental l andmasses were transgressed but not always at the same time. One explanation for the lack of a synchronous record is the concept of geoidal eustacy, in which, it is suggested, as the Earth’s continents move about, the oceans bulge at some places to compensate. Eustacy would result in sea level being different from ocean basin to ocean basin.
Water circulation and mixing were not as great as they are today, because most of the oceans (e.g., the developing North Atlantic) were constricted, and the temperature differences between the poles and the Equator were minimal. Thus, the oceans experienced frequent periods of anoxic (oxygenless) conditions in the bottom waters that reveal themselves today as black shales. Sometimes, particularly during the mid-Cretaceous, conditions extended to epicontinental seas, as attested by deposits of black shales in the western interior of North America. The Cretaceous world had three distinct geographic subdivisions: the northern boreal, the southern boreal, and the Tethyan region. The Tethyan region separated the two boreal regions and is recognized by the presence of fossilized reef-forming rudist bivalves, corals, larger foraminiferans, and certain ammonites that inhabited only the warmer Tethyan waters. Early in the Cretaceous, North and South America separated suffici ently for the marine connection between the Tethys Seaand the Pacific to deepen substantially. The Tethys-toPacific marine connection allowed for a strong westward-f lowing current, which is inferred from faunal patterns. For example, as the Cretaceous progressed, the similarity between rudist bivalves of the Caribbean and western Europe decreased, while some Caribbean forms have been found on Pacific seamounts, in Southeast Asia, and possibly in the Balkans.
The remnants of the northern boreal realm in North America, Europe, Russia, and Japan have been extensively studied. It is known, for instance, that sediments in the southwestern
Netherlands indicate several changes of temperature during the Late Cretaceous. These temperature swings imply that the boundary between the northern boreal areas and the Tethys region was not constant with time. Russian workers recognize six paleobiogeographic zones: boreal, which in this context is equivalent to Arctic; European; Mediterranean, including the central Asian province; Pacific; and two paleofloristic zonations of land. Southern boreal areas and the rocks representing the southern Tethys margin lack this level of detail.
Magnetically, the Cretaceous was quiet relative to the subsequent Paleogene Period. In fact, magnetic reversals are not noted for a period of some 42 million years, from the early Aptian to the late Santonian ages. The lengths of Earth’s months ( see synodic period) have changed regularly for at least the past 600 million years because of tidal friction and other forces that slow the Earth’s rotation. The rate of change in the synodic month was minimal for most of the Cretaceous but has accelerated since. The reasons for these two anomalies are not well understood.
Kapur Periode, dalam waktu geologi, yang terakhir dari tiga periode dari Era Mesozoic . Kapur mulai 145,0 juta tahun yang lalu dan berakhir 66 juta tahun yang lalu; itu diikuti Periode Jurassic dan digantikan oleh Periode Paleogen (yang pertama dari dua periode di mana Periode Tersier dibagi). Kapur adalah periode terpanjang dari Eon Fanerozoikum. Spanning 79 juta tahun, itu merupakan waktu lebih telah berlalu sejak kepunahan dinosaurus, yang terjadi pada akhir periode. Nama Kapur berasal dari creta, Latin untuk "kapur," dan pertama kali diusulkan oleh J.B.J. Omalius d'Halloy di 1822. D'Halloy telah ditugaskan untuk membuat peta geologi dari Perancis, dan bagian dari tugasnya adalah untuk memutus unit geologi untuk diwakili oleh itu. Salah satu unit nya, yang Crétacé Medan, termasuk kapur dan pasir yang mendasari. Kapur adalah, jenis halus lembut batu kapur terdiri terutama dari piring armourlike dari coccolithophores, kecil ganggang mengambang yang berkembang selama Late Cretaceous. Kebanyakan batuan kapur yang tidak kapur, tetapi sebagian kapur diendapkan selama Kapur. Banyak dari batu-batu ini memberikan rincian yang jelas dan mudah diakses dari periode karena mereka belum cacat atau terkikis dan relatif dekat dengan permukaan-seperti dapat dilihat di tebing putih berbatasan dengan Selat Dover antara Perancis dan Inggris.
Periode Cretaceous dimulai dengan tanah bumi dirakit dasarnya menjadi dua benua, Laurasia di utara dan Gondwana di selatan. Tersebut hampir sepenuhnya dipisahkan oleh Tethys seaway khatulistiwa, dan berbagai segmen Laurasia dan Gondwana sudah mulai Rift terpisah. Amerika Utara baru saja dimulai menarik diri dari Eurasia selama Jurassic, dan Amerika Selatan telah mulai memisahkan diri dari Afrika, yang India, Australia, dan Antartika juga memisahkan. Ketika Periode Cretaceous berakhir, sebagian besar benua ma sa kini yang terpisah satu sama lain oleh hamparan air seperti Utara dan Samudra Atlantik Selatan. Pada akhir periode, India terpaut di Samudera Hindia, dan Australia masih ter hubung ke Antartika. TOPIK SERUPA iklim umumnya lebih hangat dan lebih lembab dari hari ini, mungkin karena vulkanisme sangat aktif dikaitkan dengan tingkat yang sangat tinggi dari dasar laut menyebar. Daerah kutub bebas dari lapisan es benua, tanah mereka bukan ditutupi oleh hutan. Dinosaurus menjelajahi Antartika, bahkan dengan malam musim dingin yang panjang. Periode Cretaceous panjang merupakan bagian utama dari interval antara-bentuk kehidupan kuno dan orang-orang yang mendominasi bumi saat ini. Dinosaurus adalah kelompok dominan hewan darat, terutama "bebek" dinosaurus (hadrosauria), seperti Shantungosaurus, dan bentuk-bentuk bertanduk, seperti Triceratops. reptil laut raksasa seperti ichthyosaurus, mosasaurus, dan plesiosaurus yang umum di laut, dan reptil terbang (Pterosaurus) mendominasi langit. Tanaman berbunga (angiosperma) muncul dekat dengan awal Cretaceous dan menjadi lebih berlimpah sebagai periode berlangsung. Kapur Akhir adalah waktu produktivitas yang besar di lautan dunia, seperti yang ditanggung oleh pengendapan tidur tebal kapur di Eropa barat, timur Rusia, Skandinavia selatan, Gulf Coast Amerika Utara, dan Australia Barat. Kapur berakhir dengan salah satu kepunahan massal t erbesar dalam sejarah Bumi, membasmi dinosaurus, laut dan reptil terbang, dan banyak invertebrata laut. Kapur LINGKUNGAN paleogeography Posisi daratan bumi berubah secara signifikan selama Cretaceous Period-tidak terduga, mengingat durasi panjang. Pada awal periode sana ada dua Superbenua, Gondwana di selatan dan Laurasia di utara. Amerika Selatan, Afrika (t ermasuk potongan sebelah apa sekarang Semenanjung Arab dan Timur Tengah), Antartika, Australia, India, Madagaskar, dan beberapa daratan yang lebih kecil bergabung di Gondwana di selatan, sementara Amerika
Utara, Greenland, dan Eurasia (termasuk Asia Tenggara) dibentuk Laurasia. Afrika telah berpisah dari Amerika Selatan, koneksi tanah terakhir menjadi antara Brasil dan Nigeria. Akibatnya, Samudra Atlantik Selatan bergabung dengan pelebaran Atlantik Utara. Di wilayah Samudra Hindia, Afrika dan Madagascarseparated dari India, Australia, dan Antartika di Jura Akhir untuk kali Kapur Awal. Setelah dipisahkan dari Australia dan Antartika, India memulai perjalanan ke utara, yang memuncak dalam tabrakan kemudian dengan Asia selama Era Kenozoikum. Madagascar memisahkan diri dari Afrika selama Late Cret aceous, dan Greenland terpisah dari Amerika Utara. Australia masih bergabung ke Antartika. Ini nyaris tidak terpasang di persimpangan apa yang sekarang Amerika Utara dan Selatan.
permukaan laut lebih tinggi selama sebagian besar Cretaceous dari pada waktu lainnya dalam sejarah Bumi, dan itu adalah faktor utama yang mempengaruhi paleogeography periode. Secara umum, lautan dunia sekitar 100 sampai 200 meter (330-660 kaki) lebih tinggi di Kapur Awal dan kira-kira 200-250 meter (660-820 kaki) lebih tinggi pada Kapur Akhir daripada sekarang. Permukaan laut Kapur tinggi diduga telah terutama hasil dari air di cekungan laut yang terlantar akibat pembesaran pegunungan midoceanic.
Sebagai hasil dari permukaan air laut lebih tinggi selama Late Cretaceous, perairan laut terendam benua, menciptakan laut epicontinental relatif dangkal di Amerika Utara, Amerika Selatan, Eropa, Rusia, Afrika, dan Australia. Selain itu, semua benua menyusut agak sebagai margin mereka kebanjiran. Pada maksimum, lahan yang tertutup hanya sekitar 18 persen dari permukaan bumi, dibandingkan dengan sekitar 28 persen hari ini. Pada kali, perairan Arktik yang terhubung ke seaway Tethys melalui tengah-tengah Amerika Utara dan bagian tengah Rusia. Pada beberapa kesempatan selama Cretaceous, hewan laut yang hidup di Atlantik Selatan memiliki seaway untuk migrasi ke Tethys melalui apa yang saat ini Nigeria, Niger, Chad, dan Libya. Sebagian besar Eropa Barat, Australia timur, bagian dari Afrika, Amerika Selatan, India, Madagaskar, Kalimantan, dan daerah lainnya yang sekarang tanah seluruhnya tertutup oleh air laut untuk beberapa interval waktu Cretaceous.
studi rinci menunjukkan 5 sampai 15 episode yang berbeda naik dan turun di permukaan laut. Pola perubahan untuk daerah yang stabil sepanjang sejarah cukup mirip, meskipun beberapa
perbedaan yang terkenal. Selama sebagian besar Kapur Awal, bagian dari Arktik Kanada, Rusia, dan Australia Barat yang di bawah air, teta pi sebagian besar daerah lain tidak. Selama Kapur tengah, Australia timur-tengah mengalami genangan besar yang disebut pelanggaran. Dalam Kapur Akhir, yang paling daratan benua yang melanggar tetapi tidak selalu pada waktu yang sama. Satu penjelasan untuk kurangnya catatan sinkron adalah konsep eustacy geoidal, di mana, disarankan, sebagai benua bumi bergerak, lautan tonjolan di beberapa tempat untuk mengkompensasi. Eustacy akan mengakibatkan permukaan laut menjadi berbeda dari cekungan laut ke cekungan laut. sirkulasi air dan pencampuran yang tidak sama besar seperti sekarang, karena sebagian besar lautan (misalnya, mengembangkan Atlantik Utara) yang terbatas, dan perbedaan suhu antara kutub dan Equatorwere minimal. Dengan demikian, lautan mengalami periode sering anoxic (mengandung oksigen) kondisi di dasar perairan yang mengungkapkan diri mereka hari ini sebagai serpih hitam. Kadang-kadang, terutama selama pertengahan Cretaceous, kondisi diperluas ke epicontinental laut, seperti yang dibuktikan oleh deposito serpih hitam di pedalaman barat Amerika Utara. Dunia Kapur memiliki tiga berbeda subdivisi geografis: boreal utara, boreal selatan, dan wilayah Tethyan. Wilayah Tethyan memisahkan dua wilayah boreal dan diakui oleh kehadiran fosil bivalvia pembentuk karang rudist, karang, foraminiferans lebih besar, dan Amon tertentu yang hanya dihuni perairan Tethyan hangat. Di awal Cretaceous, Amerika Utara dan Selatan dipisahkan cukup untuk sambungan laut antara Tethys Seaand Pasifik untuk memperdalam substansial. Tethys-to-Pacific koneksi kelautan diperbolehkan untuk kuat ke arah barat-mengalir saat ini, yang disimpulkan dari pola fauna. Misalnya, sebagai Cretaceous berkembang, kesamaan antara bivalvia rudist dari Eropa Karibia dan barat menurun, sementara beberapa bentuk Karibia telah ditemukan di gunung laut Pasifik, di Asia Tenggara, dan mungkin di Balkan.
Sisa-sisa dari dunia boreal utara di Amerika Utara, Eropa, Rusia, dan Jepang telah dipelajari secara ekstensif. Hal ini diketahui, misalnya, bahwa sedimen di barat daya Belanda menunjukkan beberapa perubahan suhu selama Late Cretaceous. perubahan suhu ini menyiratkan bahwa batas antara wilayah utara bumi utara dan wila yah Tethys itu tidak konstan dengan waktu. pekerja Rusia mengakui e nam zona paleobiogeographic: boreal, yang dalam konteks ini adalah setara dengan Arctic; Eropa; Mediterania, termasuk provinsi Asia
tengah; Pasifik; dan dua zonasi paleofloristic tanah. daerah boreal selatan dan batu-batu yang mewakili margin Tethys selatan kekurangan tingkat detail. Magnetis, Kapur tenang relatif Periode Paleogen berikutnya. Bahkan, pembalikan magnet tidak dicatat untuk jangka waktu sekitar 42 juta tahun, dari Aptian awal untuk usia Santonian akhir. Panjang dari bulan Bumi (lihat periode synodic) telah berubah secara te ratur untuk setidaknya 600 juta tahun terakhir karena gesekan pasang surut dan kekuatan lain yang memperlambat rotasi bumi. Tingkat perubahan di bulan synodic sangat minim untuk sebagian besar Kapur tetapi telah dipercepat sejak. Alasan untuk dua anomali ini tidak dipahami dengan baik. https://www.britannica.com/science/Cretaceous-Period
