استفاده از ترمولومینسانس قرمز در سن‌یابی رسوبات بادی (loess)

نوع مقاله : پژوهشی

نویسنده

مؤسسة ژئوفیزیک دانشگاه تهران، صندوق پستی 6466- 14155

چکیده

رسوبات بادی (loess) در آسیای مرکزی، چین، اروپا و امریکا اهمیت زیادی در مطالعة آب و هوای گذشتة کرة زمین دارند. سن‌یابی به روش لومینسانس، تاکنون در تحقیقات مربوط به سن‌یابی رسوبات بادی، نقش مهمی داشته است. اما همچنان نیاز به گسترش روش‌های لومینسانس برای تعیین سن رسوبات بادی است.
تابش آبی- فرابنفش ترکیبات چند ماده معدنی و فلدسپارها از نشت سیگنال رنج می‌برند. در حالی که تابش آبی- فرابنفش لومینسانس کوارتز در ماکزیمم  Gy500 اشباع می‌شود، تابش قرمز لومینسانس گرمایی (RTL) دارای ظرفیتKGY50 بوده و لذا توانایی سن‌یابی آتشفشانی تا 2 میلیون سال را دارد.
این مقاله امکان سن‌یابی رسوبات بادی با استفاده از SAR-RTL ناشی از کوارتز را به این طریق بررسی کرده است:‌ الف)، وجود ترمولومینسانس قرمز در رسوبات بادی مشاهده شد. ب)، ترمولومینسانس قرمز ناشی از این رسوبات زیر نور خورشید مؤلفه نوری خود را از دست داد. پ)، SAR-RTL توانست دز مشخص را در آزمایشگاه بازیابی کند. ت)، به‌کمک  SAR-RTLمی‌توان دز معادل دز طبیعی را تا حدود Gy 1000 به‌دست آورد. این اطلاعات نشان می‌دهد که RTL کوارتز می‌تواند ناحیة سنی روش‌های لومینسانس را در اندازه‌گیری سن رسوبات بادی افزایش دهد.

کلیدواژه‌ها


عنوان مقاله [English]

Dating loess by red thermoluminescence of quartz■

نویسنده [English]

  • Morteza Fattahi
Institute of Geophysics, University of Tehran, P.O. Box 14155-6466, Tehran, Iran / OUCE, University of Oxford, Mansfield Road, OX1 3TB
چکیده [English]

The loess deposits in central Asia, China, Europe and the USA provide records of past climate, which permits the study of paleoclimatology. Although luminescence dating has had an important role in dating loess, significant challenges still remain.
UV-blue emission from polymineral and feldspar suffer from anomalous fading. UV-blue emission from quartz saturates at c. <500 Gy. Fattahi (2001) reported the ability of red thermoluminescence for dating volcanic quartz to c.1.3 Ma.
This paper investigates the possibility of applying single aliquot regeneration red thermoluminescence (SAR RTL) protocol for dating loess and demonstrating that:
1-  It is possible to detect red thermoluminescence from loess.
2-  Red thermoluminescence from loess is bleachable.
3-  SAR RTL is able to recover a known laboratory dose.
4-  Equivalent doses around 1000 Gy are accessible.
This information suggests that SAR RTL is a powerful protocol for dating loess which can extend the time range of luminescence dating of unburnt Aeolian sediments.

کلیدواژه‌ها [English]

  • red thermoluminescence (RTL)
  • loess
  • Dating
  • Single aliquot RTL (SAR RTL)
  • Quartz
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