کاربرد ویژگی‌های نوری بلور کلسیت در شناسایی نانوفسیل‌های آهکی و اسپیکول‌های دیدمنیدها در سه برش چینه‌شناسی در بلوک لوت

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین‌شناسی، دانشکده علوم، دانشگاه بیرجند، بیرجند، ایران

2 گروه زمین شناسی، دانشکده علوم،‌ دانشگاه پیام نور،‌ تهران، ایران

چکیده

نانوپلانکتون­های آهکی از فراوانترین جاندار‌های پلانکتونی تک‌سلولی کلسیتی بر روی کره زمین هستند. این گروه شامل
کوکولیت­هایی از بلورهای کلسیتی هستند. آن‌ها از مهم­ترین گروه‌های میکروفسیلی در بررسی­های زیست‌چینه‌نگاری، دیرینه‌بوم‌شناسی و پی­جویی­های نفتی هستند و شناسایی دقیق و صحیح‌ آن­ها از اهمیت ویژه‌ای برخوردار است. از طرفی، برخی از انواع اسپیکول­های  دیدمنیدها (Didemnid ascidian spicules) شبیه به نانوفسیل‌ها هستند و تفکیک آن‌ها از هم ضروری و برای تعیین سن درست نهشته‌ها و سازندها لازم است. از این رو، استفاده از ویژگی­های نوری بلور کلسیت که با میکروسکوپ پلاریزان و تیغه کمکی ژیپس مشخص می‌شود، می‌تواند منجر به تفکیک ریزساختارها و آرایش واحدهای فرعی نانوفسیل‌ها و در پی آن تفکیک واحدهای فرعی نانوفسیل‌ها از گروه نام برده شود. در این پژوهش، بر پایه ویژگی­های نوری بلور کلسیت، تعدادی از گونه‌های نانوفسیلی و نیز تعدادی از اسپیکول­های دیدمنید­ها بررسی و شناسایی شد.       

کلیدواژه‌ها


عنوان مقاله [English]

Use of calcite crystal optical properties in the identification of calcareous nannofossils and Didemnid Ascidian Spicules in three stratigraphic sections in the Lut block

نویسندگان [English]

  • Jalili 1
  • Notghi Moghaddam 2
1
2
چکیده [English]

Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Calcareous nanoplankton are one of the most abundant calcite unicellular planktonic organisms on the Earth. This group include coccoliths which are formed from calcite crystals. They are one of the most important microfossil groups in biostratigraphic, paleontologyl and oil exploration studies, and their accurate and correct identification is of great importance. Some species belonging to Didemnid Ascidian Spicules resemble nannofossils and their separation from the nannofossils is essential and is necessary for correct age determination of the deposit. For this reason, the use of the optical properties of calcite crystal of coccoliths, that determined by polarizing microscop and the gypsumplate, can lead to the separation of microstructures and the arrangement of nannofossils subunits and can lead to the separation of nannofossils subunits from the mention group. In this study, with using of optical properties of calcite crystal, a number of nannofossil species and number of Didemnid Ascidian spicules investigated and identified.

کلیدواژه‌ها [English]

  • Crystallography
  • calcite crystal
  • gypsumplate
  • calcareous nannofossils
  • Lut block
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