Calcareous Sands from a Coral Atoll-Should It Be Mined or Not?     

T. K. Mallik 《Marine Georesources & Geotechnology》1999,17(1):27-32

Many lagoons of coral atolls contain huge reserves of very pure calcareous sands in an easily exploitable form that can be used in a number of industries. It is well known that the geomorphic situation in these coral islands is very delicate. With reference to the calcareous sand deposits in the coral atolls of Lakshadweep, a diversity of opinion exists on the aspect of exploitation, though the reserves were proved more than 20 years ago. Elsewhere calcareous sands have been used for several purposes. No raw materials other than coral sands and corals are available in these islands for developmental work such as construction of building and jetties. Several recommendations have been made to keep the system undisturbed to maintain the ecosystem. It is suggested that an attempt should be made to determine an optimum depth of exploitation of these sands without affecting the reef growth and balance of the ecosystem. This will improve the island economy and better quality of life for the islanders. The strategy will help development elsewhere also.  相似文献   

Braarudosphaera -rich sediments in the Turonian of the Bohemian Cretaceous Basin, Czech Republic     

Braarudosphaera 《Cretaceous Research》1999,20(6):773

Braarudosphaera -rich sediments occur in the Turonian (nannofossil zones CC13 and UC9a) epicontinental marine sediments of the Bohemian Cretaceous Basin. This phenomenon is linked to the input of terrigenous material during deceleration of sea-level rise, or stillstand in sea level, which possibly both triggered the Braarudosphaera bigelowii bloom and reduced the diversity of the nannoplankton assemblages. The occurrence of Marthasterites furcatus and Lithastrinus septenarius probably reflects depositional conditions that were suitable for their preservation. Hence, the resultant limitations to their use as local zonal markers in the Bohemian Cretaceous Basin are discussed. The influence of the Tethyan Bioprovince is documented by the coincident first occurrences of L. septenarius and M. furcatus. The presence of the high-latitude species Thiersteinia ecclesiastica indicates penetration of Boreal biota into this depositional area within the Turonian.  相似文献   

西太平洋晚第三纪钙质超微化石及其化石带的划分     

徐钰林 《现代地质》1992,6(3):243-253,T002,T000

本文研究了菲律宾海东、北部“大洋钻探工程”125航次782A相786A二个钻孔晚第三纪的钙质超微化石。根据Okada和Bukry分带。本区自下而上划分为13个带(或亚带)。讨论了渐新世和中新世、中新世和上新世及第三纪和第四纪的界线。本区存在3个沉积间断:晚渐新世与中中新世之间:中中新世与晚中新世之间以及晚中新世与早上新世之间。修正了Cyclicargolithus abiseclus的时限分布,提出了 Cycliargolithus floridanus floridanus和cychcargoluhas flondanus abisectus是Cyclicargolithus floridanus的2个生态亚种。  相似文献