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To date, facies architecture models of submarine channel–levees have largely been derived from seismic data, isolated core data and limited field studies. We report field observations of an Upper Cretaceous submarine channel–levee complex within the Rosario Formation, Baja California, Mexico, which provide high-resolution data of lithofacies and ichnofacies distribution, and levee depositional thickness decay along transects perpendicular to the channel axis. Within the levee, both sandstone thickness and the overall proportion of sandstone decrease according to a power law away from the channel axis. Spatial variation in sedimentary structures away from the channel axis is predictable and provides an important link to the depositional flow regime. In channel-proximal locations, structureless sands, parallel lamination, overturned ripples, and ripple cross-lamination (including climbing ripple cross-lamination) are common; in channel-distal localities starved ripples are abundant. Sandstone bed thickness generally increases up stratigraphy within the levee succession, which is interpreted to indicate increasing turbidity current magnitude and/or contemporaneous channel floor aggradation reducing relative levee relief. However, in the most channel-proximal location sandstone bed thickness decreases with height; combined with evidence from both facies and palaeocurrent analysis this allows the position of the levee crest to be inferred. The thickest beds occur at higher levels with increasing distance from the channel axis, using this evidence we present a model for levee growth and migration of the crest.
Quantitative analysis of ichnofacies distribution reveals that traces typical of the Cruziana and Skolithos ichnofacies are superimposed over the ‘normal’ background Nereites ichnofacies, forming a ‘bioturbation front’ which is indicative of proximity to the channel. By analogy with modern canyons and channels, the association of Cruziana and Skolithos ichnofacies with the channel may be attributed to oxygen and nutrient enrichment and possible turbidity current transport of organisms responsible for these ichnofacies.
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Answer:
The World in Spatial Terms
Where is this happening?
Is the place by a river or on a mountain?
Where are the cities located?
How far are these places from each other?
Places and Regions
Is the location warm or cold?
Which religion do the people practice?
Explanation:
There are six essential elements of geography:
The World in Spatial Terms,
Places and Regions,
Physical Systems,
Human Systems,
Environment and Society,
and The Uses of Geography.
The World in Spatial Terms refers to the absolute and relative location
Places and Regions refer to what makes the place special, as well as its physical and human characteristics.
Answer:
See explanation below:
Explanation:
Transit Photometry is the most widely-used and effective to date, it has been a method that measures the light curve of distant stars for periodic dips in brightness. These are the result of exoplanets passing or transiting in front of the star relative to the observer. It is currently the most effective and sensitive method for detecting extrasolar planets, particularly from an observatory in space. When combined with radial velocity data, a transit can also provide a good estimate of the planet's mass. This method detects distant planets by measuring the minute dimming of a star as an orbiting planet passes between it and the Earth.
The main reason direct detection of exoplanets is difficult is because most planets orbit planets orbit at small angular separations on the sky, this means a direct detection is only possible if the star's light can be suppressed or occulted such that the faint light from the planet can be detected.
Some planets are found via the wobble method, using both methods, combining mass and size, scientists can calculate the planet's density, an important step towards assessing its composition.
