首页
登录
职称英语
Perhaps one of the most dramatic and important changes that took place i
Perhaps one of the most dramatic and important changes that took place i
游客
2025-02-09
12
管理
问题
Perhaps one of the most dramatic and important changes that took place in the
Mesozoic era occurred late in that era, among the small organisms that populate the
uppermost, sunlit portion of the oceans--the plankton. The term "plankton" is a broad
one, designating all of the small plants and animals that float about or weakly propel
(5) themselves through the sea. In the late stages of the Mesozoic era. during the Cretaceous
period, there was a great expansion of plankton that precipitated skeletons or shells
composed of two types of mineral: silica and calcium carbonate. This development
radically changed the types of sediments that accumulated on the seafloor, because,
while the organic parts of the plankton decayed after the organisms died, their mineralized
(10)skeletons often survived and sank to the bottom. For the first time in the Earth’s long
history, very large quantities of silica skeletons, which would eventually harden into rock,
began to pile up in parts of the deep sea. Thick deposits of calcareous ooze made up of
the tiny remains of the calcium carbonate-secreting plankton also accumulated as never
before. The famous white chalk cliffs of Dover, in the southeast of England, are just one
(15)example of the huge quantities of such material that amassed during the Cretaceous
period; there are many more. Just why the calcareous plankton were so prolific during
the latter part of the Cretaceous period is not fully understood. Such massive amounts
of chalky sediments have never since been deposited over a comparable period of time.
The high biological productivity of the Cretaceous oceans also led to ideal conditions
(20)for oil accumulation. Oil is formed when organic material trapped in sediments is slowly
buried and subjected to increased temperatures and pressures, transforming it into
petroleum. Sediments rich in organic material accumulated along the margins of the
Tethys Seaway, the tropical east-west ocean that formed when Earth’s single landmass
(known as Pangaea) split apart during the Mesozoic era. Many of today’s important oil
(25)fields are found in those sediments--in Russia, the Middle East, the Gulf of Mexico, and
in the states of Texas and Louisiana in the United States.
选项
A、How sediments were built up in oceans during the Cretaceous period
B、How petroleum was formed in the Mesozoic era
C、The impact of changes in oceanic animal and plant life in the Mesozoic era
D、The differences between plankton found in the present era and Cretaceous plankton
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3949494.html
相关试题推荐
ByfarthemostimportantUnitedStatesexportproductintheeighteenth
[originaltext]Today,I’dliketotalkaboutsomeofthechangeslandcanun
[originaltext]Today,I’dliketotalkaboutsomeofthechangeslandcanun
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
"PhysicalandChemicalPropertiesandChanges"→Sugar,water
随机试题
Theworldneedslegalguidelinesforburyinggreenhousegasestohelpthesti
以下各项中,不能作为项目成本预算工具或技术的是()A.参数估算 B.资金限制平
公路桥涵工程使用的石料制品主要有()。A.片石 B.细料石 C.粗料石
某公司想运用沪深300股票指数期货合约来对冲价值1000万元的股票组合,假设股指
胰岛素原比胰岛素()A.多一段14肽B.多两个二硫键C.多一段C肽D.少一段C
变电站运行人员绝缘监督工作的任务是什么?
A.0.0058 B.0.0116 C.25 D.20
( )是短时记忆存储的重要条件A.机械复述 B.精细复述 C.联想 D.
上市公司信息披露事务管理制度应当经公司股东大会审议通过,报注册地证监局和证券交易
为获取交易佣金或其他利益,诱导客户进行不必要的证券买卖属于经纪业务的管理风险。
最新回复
(
0
)