Cenozoic period

Figure 1.146, Stre.ss trajectory map.s of southern Northeast Honshu in the late Cenozoic period, after Tsunakawa and Takeuchi (1986) with a slight addition. oh, . trajectory is drawn by smoothing the inferred stress orientations from the selected dike-swarms with K-Ar dates. Selected major faults with age estimation are also shown for indicating types of stress fields. T Extensional stress field, where ay > a 2>cth , and normal or gravity faulting is preferable. P Compre.ssional, oh > ay, reverse or thrust faulting...

The Silver Bell Mine area consists of dipping units that are composed of dacite porphyry, alaskite and monazite. The rock ages span the Paleozoic, Mesozoic and Cenozoic periods. The Paleozoic wall rocks consist of quartzite, siltstone and altered limestone. The carbonate rocks are exposed along the contact between the host rock and intrusions, and host the... 

Red beds are continental or marine sedimentary rocks with an eye-catching red colour which has been responsible for the interest in them. They are widespread all over the world and belong mainly to the Late Palaeozoic, Early Mesozoic, and Late Cenozoic periods. 

Cenozoic Tertiary 66 Myr Climate Cools. Continents nearing modern positions. Drying trend in middle of period. Radiation of birds, mammals, flowering plants, pollinating insects... 

Fig. 4.3. (A) Composite multispecies benthic foraminiferal Mg/Ca records from three deep-sea sites DSDP Site 573, ODP Site 926, and ODP Site 689. (B) Species-adjusted Mg/Ca data. Error bars represent standard deviations of the means where more than one species was present in a sample. The smoothed curve through the data represents a 15% weighted average. (C) Mg temperature record obtained by applying a Mg calibration to the record in (B). Broken line indicates temperatures calculated from the record assuming an ice-free world. Blue areas indicate periods of substantial ice-sheet growth determined from the S 0 record in conjunction with the Mg temperature. (D) Cenozoic composite benthic foraminiferal S 0 record based on Atlantic cores and normalized to Cibicidoides spp. Vertical dashed line indicates probable existence of ice sheets as estimated by (2). 3w, seawater S 0. (E) Estimated variation in 8 0 composition of seawater, a measure of global ice volume, calculated by substituting Mg temperatures and benthic 8 0 data into the 8 0 paleotemperature equation (Lear et al., 2000).

Figure 16. (a) Ca isotope record from marine carbonates (De La Rocha and DePaolo 2000). The variations are inferred to reflect variations in the isotopic composition of seawater (which is heavier by about 1,4%o). The small excursions of S Ca reflect changes in the global weathering cycle they are recast in (b) in terms of the ratio of the flux of calcium being delivered to the ocean by weathering (Fw) to the flux of Ca being removed from the ocean by carbonate sedimentation (c) Smoothed record of benthic foraminiferal 5 0 for the Cenozoic time period from Zachos et al. (2001). 

Cenozoic is a time of high but variable pCOj. By early Miocene time (ca. 22 Ma) COj levels are comparable to the present (pre-industrial) values. The calculated pCOj for the period from the middle Miocene through the Pliocene comes out lower than the modem value, which does not correspond well with the 5 0 evidence for continued cooling between 15 Ma and the present (Fig. 16c). It may be noteworthy that higher assumed values for 5 correspond to very high levels of atmospheric COj in the early Cenozoic, whereas 5w values in the range -0.5 to -0.6 correspond to the lx to lOx higher COj levels that are typically estimated with other approaches (e.g., Ekart et al. 1999). 

Era A division of geologic time that includes several periods. The Cenozoic Era ranges from the extinction of the dinosaurs about 65 million years ago to the present. 

Cenozoic Era The period of geologic time beginning after the end of the Mesozoic Era 65 million years ago and encompassing the present. Commonly referred to as the age of mammals. 

Mesozoic Era The period of geologic time beginning 245 million years ago and ending 65 million years ago the age of the dinosaurs and cycads, the Mesozoic falls between the Paleozoic and Cenozoic Eras and includes the Triassic, Jurassic, and Cretaceous Periods. 

Pleistocene The first geologic epoch of the Quaternary Period of the Cenozoic Era that ended 10,000 years ago with the retreat of the last glaciers. 

Quaternary Period The most recent geologic period of the Cenozoic Era, the Quaternary began 2 million years ago with the growth of northern hemisphere continental glaciers and the ice age. 

Mass extinctions have been recognized in the fossil record since the middle of the nineteenth century. Levels of mass extinction of species were selected as marker levels in the stratigraphic record because the death of index-fossil species provided a convenient marker to subdivide and correlate strata. The mass-extinction level called the Permian-Triassic boundary is so profound in terms of faunal and floral change that it was early on noted and chosen to represent the transition from Paleozoic to Mesozoic era. The mass-extinction level called the Cretaceous-Tertiary boundary is also quite distinctive in terms of faunal and floral change, and it too was noted early on and chosen to represent the transition from Mesozoic to Cenozoic era. Other less profound, but nevertheless distinctive levels of mass extinction of fossils have been selected to represent marker points in the stratigraphic record at which geological periods, epochs, ages, and other intervals of lesser temporal value are defined. 

The Cenozoic Era (c.65 million years BP to the present) encompasses the Tertiary and the Quaternary Periods. During the Tertiary the Earth s climate began an overall cooling trend of about 12 °C in the past 40 million years. Over the past two and a half million years the climate has varied from cool to warm periods, accompanied by massive expansions and contractions of the polar ice caps. This period of climate fluctuation is termed the Quaternary Period and spans the geologic time scale from the end of the Pliocene Epoch, roughly 1.8-2.6 million years ago, to the present. The Quaternary Period includes the Pleistocene and Holocene Epochs, with the Holocene... 

The basin occupied by Long Island Sound is a product of the period of prolonged erosion of eastern North America that occupied the late Mesozoic and the Cenozoic eras. Because the onshore geological record consists of erosion surfaces, and the products of this erosion are now submerged on the continental shelf, reconstruction of a detailed geological history is not possible. However, the main events are well established. 

Quaternary 1) Time The second and last period in the Cenozoic Era. Normally, it is subdivided into the Holocene (Recent) and Pleistocene Epochs. The short chronology places its beginning at the traditionally defined boundary atroughly 1.78 Ma, while the long chronology places it at the start of the Matuyama Magnetochron at approximately 2.48 Ma. 2) Rocks The sediment and rocks formed during the Quaternary Period. 

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