depositional environment? |
an area where sediment was deposited under certain conditions in Earth's past |
What is a delta? |
A delta is a triangular landform created where a stream enters a body of water and deposits sediment. |
Other than sand dunes in a desert environment, where else would you expect to find well-rounded and sorted sand deposits? |
beach |
Describe the distribution of sedimentary deposits you would expect to find on a delta. |
Sand in channels, mud on floodpain |
The formation of sedimentary rock requires _____. |
weathering and erosion of pre-existing rocks |
Which is an example of a sedimentary rock composed of solid masses of intergrown crystals? |
rock salt |
You find a sedimentary rock that has all its flat particles aligned in parallel. From this you can infer that _____. |
the particles have been compacted |
Sedimentary rocks that exhibit the intergrowth of crystal masses are generally formed from the products of _____. |
chemical weathering |
Which two minerals are most common in detrital sedimentary rocks? |
clay minerals and quartz |
What is the most abundant chemical sedimentary rock in Earth's crust? |
limestone |
Working in the field, you find a rock that contains rounded fragments that are greater than 2 mm in diameter. What would you call this rock? |
basalt |
The geologic laboratory where you work received a sample for analysis that is composed of calcite that includes many microscopic fossils of marine organisms and reacts with acid. What name would identify this rock? |
chalk |
Which structure is common in sedimentary rock? |
fossils, mudcracks, ripple marks, cross bedding |
What property of detrital sedimentary rocks can be indicative of the energy of sediment transport? |
grainsize |
For a detrital sedimentary rock that contains mudcracks, you could be confident that the environment in which it formed was _____. |
alternately wet and dry |
In your field area you find a quartz sandstone unit with cross-bedding in it that is on the order of 2 m high. In what environment would you deduce this rock formed? |
sand dunes |
In another field area you find a detrital sedimentary rock that contains particles larger than 264 mm that are rounded and surrounded by finer-grained particles. In what environment might you think these sediments were deposited? |
glacial morain |
If all the particles in a detrital sedimentary rock are nearly the same size, it is __________. |
well-rounded |
A smooth grain shaped like a cigar is __________ and shows __________. |
well-rounded; low sphericitity |
wind-blown sand deposits would most likely be __________ and _________ |
very well sorted; well rounded |
which of the following correlate to transport distance? |
grain size and rounding |
A conglomerate is poorly sorted with well-rounded grains. This rock was likely formed in what depositional environment? |
mountain stream |
Name the progression of coal types with increased heat and pressure from burial. |
peat, lignite, bituminous, ahthracite |
Abundant plant material accumulating in a swampy environment with __________ is required for peat to form. |
low oxygen level |
What coal is soft, black in color, and produces soot upon handling? |
bituminous |
How is anthracite produced from bituminous coal? |
metamorphism |
In the United States, the most common type of coal is __________ and the largest producing state is __________. |
sub-bituminous; wyoming |
During the process that forms sedimentary rocks, how does compaction affect sediment? |
it decreases the volume of pore spaces |