The history of geomorphology in low latitudes

2020 ◽  
pp. 3-11
Author(s):  
I. Douglas ◽  
T. Spencer
Keyword(s):  
Low Latitudes ◽  
History Of

Welcome to the C4 World

2000 ◽  
Vol 6 ◽  
pp. 273-286 ◽  
Author(s):  
Thure E. Cerling ◽  
James R. Ehleringer
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Warm Season ◽  
The Other ◽  
Cool Season ◽  
Carbon Compound ◽  
Low Latitudes ◽  
The World ◽  
History Of ◽  
Recent Origin

There are two principal mechanisms of photosynthesis amongst the plants of the world. One produces a 3-carbon compound as the primary photosynthate and is called C3 photosynthesis. The other produces a 4-carbon compound as its primary photosynthate and is called C4 photosynthesis. This latter method is of rather recent origin, and its inception had important consequences for the flora and fauna of the world. The C4 plants make up a significant portion of global net primary productivity, especially in low latitudes. C4 plants are predominantly warm-season grasses, while C3 plants include most dicotyledons and cool-season monocotyledons. In this review we answer the questions about how C4 photosynthesis differs from C3 photosynthesis, where C4 plants are found, and review the paleoecological history of C4 photosynthesis.

The Mesozoic scleractinian genus Adelocoenia (Stylinidae) and its Jurassic species

2020 ◽  
Vol 20 (19) ◽  
pp. 367-406
Author(s):  
Bernard Lathuilière ◽  
Rosemarie C. Baron-Szabo ◽  
Sylvain Charbonnier ◽  
Jean-Michel Pacaud
Keyword(s):  
Geographical Distribution ◽  
Middle Jurassic ◽  
Type Species ◽  
Late Jurassic ◽  
Single Specimen ◽  
Low Latitudes ◽  
Distributional Patterns ◽  
Taxonomic History ◽  
Combined Features ◽  
History Of

The genus Adelocoenia ORBIGNY, 1849, is revised and a neotype is designated for its type species Astrea castellum MICHELIN, 1844. For various reasons that lie in the taxonomic history of scleractinian corals, it has become a difficult task to reliably assign Mesozoic corals having the combined features of plocoid corallite integration and the absence of a columella. Therefore, many such genera are in need of revision, one of which is Adelocoenia. In addition to the revision of the type species, Jurassic species grouped within Adelocoenia are revised using type material when it was possible. Many new synonymies are proposed based mainly on characters such as symmetry and dimensions of skeletal features. Another consequence is that most species previously grouped with Pseudocoenia ORBIGNY are transferred to Adelocoenia. Furthermore, we present a clarified view of the paleogeographical and stratigraphical distributional patterns of the genus Adelocoenia, according to which Adelocoenia had its first appearance during the Early Jurassic, represented by a single specimen known from the Sinemurian of France. Subsequently, this genus had a significant increase in both distribution and diversity during the Middle Jurassic. The pinnacle of its success followed in the Late Jurassic during which Adelocoenia had its greatest morphological disparity and taxonomical diversity, and its largest geographical distribution. The genus survived in the Cretaceous record. Throughout its history, Adelocoenia predominantly occurred in inner platform environments that were located in low latitudes.

Paleomagnetic constraints on the tectonic history of the Foreland Belt, southern Canadian Cordillera: preliminary results

1997 ◽  
Vol 34 (3) ◽  
pp. 260-270 ◽  
Author(s):  
R. J. Enkin ◽  
P. M. Wheadon ◽  
J. Baker ◽  
K. G. Osadetz
Keyword(s):  
Canadian Cordillera ◽  
Thrust Sheet ◽  
Western Front ◽  
Tectonic History ◽  
Sequence Of Events ◽  
Folded Structure ◽  
Low Latitudes ◽  
Magnetic Period ◽  
Normal Polarity ◽  
History Of

In the southern Canadian Cordillera, the paleomagnetic memory of Paleozoic carbonate strata in the Front Ranges and Inner Foothills of the Foreland thrust and fold belt retains no record of their known deposition at low latitudes. Instead, each folded structure exhibits a similar, but asynchronous, sequence of events including an eastwardly progressing, predeformational chemical remagnetization during the Cordilleran orogeny. The remagnetization of a "western Front Ranges" structure occurs during a period of normal polarity before 130 Ma. The paleomagnetic pole requires that the subsequent deformation of the western Front Ranges is Jurassic or younger. The remagnetization of a Front Ranges structure in the Lewis thrust sheet occurs during a period of normal polarity after 130 Ma but before deformation which, from other evidence, occurred around 75 Ma. The predeformational remagnetization of an "Inner Foothills" structure occurs during a reversed magnetic period that we interpret to be after 75 Ma. An Early Cretaceous sill in the Lewis thrust sheet was remagnetized during a reverse-polarity chron prior to the end of Lewis thrust deformation, when about 70% of the present dip of the sill was acquired. Remagnetization consistently predates deformation, whereas it occurs later at more easterly localities. There are also similarities in character and style of the remagnetizations among localities. When coupled with the eastward progression of the deformation, our observations suggest that an important and pervasive, but hitherto unrecognized and unappreciated, orogenic chemical process affected Paleozoic carbonate strata in the van of the deforming Cordilleran tectonic wedge.

scholarly journals Characteristic study of double substorm onsets in response to IMF variations

2018 ◽  
Author(s):  
Ching-Chang Cheng ◽  
Christopher T. Russell ◽  
Ian R. Mann ◽  
Eric Donovan ◽  
Wolfgang Baumjohann
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Time History ◽  
Spectral Features ◽  
Onset Timing ◽  
Low Latitudes ◽  
History Of ◽  
Substorm Onsets ◽  
Two Stages

Abstract. A study of the characteristics of double substorm onsets in response to variations of the interplanetary magnetic field (IMF) is undertaken with magnetotail and ground observations by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission on 18 March 2009 and 3 April 2009 (Kp ~ 0), and on 16 February 2008 and 24 February 2010 (Kp ~ 2–3). During the time of interest, THEMIS probes at −8RE > XGSM > −20RE and 5RE > YGSM > −5RE observed earth-bound flow bursts accompanied by magnetic dipolarizations varying in two stages. The keograms and all sky images close to their footprints showed two consecutive auroral breakups of which the first appeared at lower latitudes than the second. The ground-based magnetometers sensed magnetic bays and perturbations resulting from the formation of substorm current wedge. Two consecutive pulsations in the Pi2-Ps6 band period occurred simultaneously from high to low and very low latitudes. They appeared in the same cycle of growth and then decline in Kyoto-AL. The onset timing of ground pulsations mapped to the solar wind observation just in front of Earth’s magnetopause shows their occurrence under an IMF variation cycle of north-to-south and then north. Their dynamic spectrums have the spectral features of double substorm onsets triggered by northward IMF turning. Hence in response to IMF variations, double substorm onsets can be characterized with two-stage magnetic dipolarizations in the magnetotail, two auroral breakups of which the first occurring at lower latitudes than the second, and two consecutive Pi2-Ps6 band pulsations.

A hidden cradle of plant evolution in Permian tropical lowlands

Science ◽  
2018 ◽  
Vol 362 (6421) ◽  
pp. 1414-1416 ◽  
Author(s):  
Patrick Blomenkemper ◽  
Hans Kerp ◽  
Abdalla Abu Hamad ◽  
William A. DiMichele ◽  
Benjamin Bomfleur
Keyword(s):  
Plant Evolution ◽  
Deep Roots ◽  
Evolutionary Origins ◽  
Evolutionary Innovation ◽  
Plant Fossil ◽  
Plant Groups ◽  
Low Latitudes ◽  
Marine Realm ◽  
History Of ◽  
Tropical Lowlands

The latitudinal biodiversity gradient today has deep roots in the evolutionary history of Earth’s biota over geologic time. In the marine realm, earliest fossil occurrences at low latitudes reveal a tropical cradle for many animal groups. However, the terrestrial fossil record—especially from drier environments that are thought to drive evolutionary innovation—is sparse. We present mixed plant-fossil assemblages from Permian equatorial lowlands in present-day Jordan that harbor precocious records of three major seed-plant lineages that all became dominant during the Mesozoic, including the oldest representative of any living conifer family. These finds offer a glimpse of the early evolutionary origins of modern plant groups in disturbance-prone tropical habitats that are usually hidden from observation.

scholarly journals On the consistency of HNO<sub>3</sub> and NO<sub>2</sub> in the Aleutian High region from the Nimbus 7 LIMS Version 6 data set

2018 ◽  
Vol 11 (6) ◽  
pp. 3611-3626
Author(s):  
Ellis Remsberg ◽  
Murali Natarajan ◽  
V. Lynn Harvey
Keyword(s):  
Climate Models ◽  
Polar Vortex ◽  
Zonal Distribution ◽  
Data Set ◽  
Model Calculations ◽  
The North ◽  
Low Latitudes ◽  
History Of ◽  
Sulfuric Acid Aerosols ◽  
Short Time

Abstract. This study uses photochemical calculations along kinematic trajectories in conjunction with Limb Infrared Monitor of the Stratosphere (LIMS) observations to examine the changes in HNO3 and NO2 near 30 hPa in the region of the Aleutian High (AH) during the minor warming event of January 1979. An earlier analysis of Version 5 (V5) LIMS data indicated increases in HNO3 without a corresponding decrease in NO2 in that region and a quasi-wave 2 signature in the zonal distribution of HNO3, unlike the wave 1 signal in ozone and other tracers. Version 6 (V6) LIMS also shows an increase of HNO3 in that region, but NO2 is smaller than from V5. The focus here is to convey that V6 HNO3 and NO2 are of good quality, as shown by a re-examination of their mutual changes in the AH region. Photochemical model calculations initialized with LIMS V6 data show increases of about 2 ppbv in HNO3 over 10 days along trajectories terminating in the AH region on 28 January. Those increases are mainly a result of the nighttime heterogeneous conversion of N2O5 on background stratospheric sulfuric acid aerosols. Changes in the composition of the air parcels depend on the extent of exposure to sunlight and, hence, on the dynamically controlled history of the trajectories. Trajectories that begin in low latitudes and traverse to across the North Pole in a short time lead to the low HNO3 in the region separating the anticyclone from the polar vortex, both of which contain higher HNO3. These findings help to explain the observed seasonal evolution and areal extent of both species. V6 HNO3 and NO2 are suitable, within their errors, for the validation of stratospheric chemistry–climate models.

Effects of Holocene Climatic Change on some Tropical Geomorphic Processes

1976 ◽  
Vol 6 (4) ◽  
pp. 529-556 ◽  
Author(s):  
Rhodes W. Fairbridge
Keyword(s):  
Coral Reefs ◽  
Ice Age ◽  
Tropical Regions ◽  
Climatic Oscillations ◽  
Climatic Control ◽  
Low Latitudes ◽  
History Of ◽  
Climatic Transition ◽  
Geomorphic Processes

Man's interference with the landscape process places him in the role of a “paraglacial” agent: He tends to duplicate ice-age stresses such as deforestation, accelerated erosion, and climate alteration. Against a background climatic control dictated by the Milankovich mechanisms, the 10,000-year history of the Holocene has seen very large secondary modulations that must be better understood so that they may be distinguished from anthropogenic effects. If they are exogenetically controlled, as it seems, then they are probably predictable from astronomic data. Four geomorphic type areas are selected for demonstrating Holocene changes in tropical regions, because they have been somewhat neglected within the framework of Quaternary science and because they include some of the most fragile and easily disrupted environments: lakes, semiarid desert margins, coastlines, and coral reefs. In a nutshell, the tropical Holocene has seen three major changes: (a) the evolution from the hyperaridity of the last pleniglacial stage to the “postglacial pluvial”; (b) the “climatic optimum,” which was highly diachronous and strongly retarded as it shifted from low latitudes to high; (c) the postoptimum “deterioration” that has involved desiccation of lakes, readvances of the deserts, fall of sea level, and truncation of coral reefs. While this deterioration is predictable in terms of an interglacial-glacial climatic transition, strong natural climatic oscillations, not yet well understood, together with man's activities, make the future a cause for concern.

scholarly journals On the consistency of HNO<sub>3</sub> and NO<sub>2</sub> in the Aleutian High reigon from the Nimbus 7 LIMS version 6 dataset

2018 ◽  
Author(s):  
Ellis Remsberg ◽  
Murali Natarajan ◽  
V. Lynn Harvey
Keyword(s):  
Climate Models ◽  
Polar Vortex ◽  
Zonal Distribution ◽  
Model Calculations ◽  
Stratospheric Chemistry ◽  
Low Latitudes ◽  
History Of ◽  
Sulfuric Acid Aerosols ◽  
Short Time ◽  
Time Lead

Abstract. This study uses photochemical calculations along kinematic trajectories in conjunction with Limb Infrared Monitor of the Stratosphere (LIMS) observations to examine the changes in HNO3 and NO2 near 30 hPa in the region of the Aleutian High (AH) during the minor warming event of January 1979. An earlier analysis of Version 5 (V5) LIMS data indicated increases in HNO3 without a corresponding decrease in NO2 in that region and a wave-2 signature in the zonal distribution of HNO3, unlike the wave-1 signal in ozone and other tracers. Version 6 (V6) LIMS also shows an increase of HNO3 in that region, but NO2 is smaller than from V5. The focus here is to convey that both V6 HNO3 and NO2 are of better quality than from V5, as shown here by a re-examination of their mutual changes in the AH region. Photochemical model calculations initialized with LIMS V6 data show increases of about 2 ppbv in HNO3 over 10 days along trajectories terminating in the AH region on 28 January. Those increases are mainly a result of the nighttime heterogeneous conversion of N2O5 on background stratospheric sulfuric acid aerosols. Changes in the composition of the air parcels depend on the extent of exposure to sunlight and, hence, on the dynamically controlled history of the trajectories. Trajectories that begin in low latitudes and traverse to across the Pole in a short time lead to the low HNO3 in the region separating the anticyclone from the polar vortex, both of which contain higher HNO3. These findings help to explain the observed seasonal evolution and areal extent of both species. V6 HNO3 and NO2 are suitable, within their errors, for the validation of stratospheric chemistry/climate models.

scholarly journals Using archaeogenomic and computational approaches to unravel the history of local adaptation in crops

2015 ◽  
Vol 370 (1660) ◽  
pp. 20130377 ◽  
Author(s):  
Robin G. Allaby ◽  
Rafal Gutaker ◽  
Andrew C. Clarke ◽  
Neil Pearson ◽  
Roselyn Ware ◽  
...  
Keyword(s):  
Local Adaptation ◽  
Computational Models ◽  
Evolutionary Process ◽  
Human Environment ◽  
Complex Process ◽  
Low Latitudes ◽  
History Of ◽  
Dna Capture ◽  
Genome Level ◽  
Methylation Patterns

Our understanding of the evolution of domestication has changed radically in the past 10 years, from a relatively simplistic rapid origin scenario to a protracted complex process in which plants adapted to the human environment. The adaptation of plants continued as the human environment changed with the expansion of agriculture from its centres of origin. Using archaeogenomics and computational models, we can observe genome evolution directly and understand how plants adapted to the human environment and the regional conditions to which agriculture expanded. We have applied various archaeogenomics approaches as exemplars to study local adaptation of barley to drought resistance at Qasr Ibrim, Egypt. We show the utility of DNA capture, ancient RNA, methylation patterns and DNA from charred remains of archaeobotanical samples from low latitudes where preservation conditions restrict ancient DNA research to within a Holocene timescale. The genomic level of analyses that is now possible, and the complexity of the evolutionary process of local adaptation means that plant studies are set to move to the genome level, and account for the interaction of genes under selection in systems-level approaches. This way we can understand how plants adapted during the expansion of agriculture across many latitudes with rapidity.

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