علامات النيم

علامات النيم المتكونة بفعل الرياح
Wave/symmetrical ripple, نومگون، منغوليا
مقطع في asymmetric climbing ripples, seen in the Zanskar Gorge, لدخ، شمال غرب الهيمالايا الهندية. Ripples climb when sediment fluxes in the flow are very high.

علامات النيم إنگليزية: Ripple marks وهي عبارة عن تموجات صغيرة على سطح الطبقة العلوية للأرض وتنشأ بفعل الرياح أو التيارات الشاطئية أو الأمواج. ويلاحظ أن تموجات الرياح والتيارات البحرية تتشابه في عدم تماثل شكلها على سطح الرمال. ويمكن من خلال اتجاه ميل هذه العلامات تحديد اتجاه الريح أو التيارات البحرية التي شكلتها. أما علامات النيم الناتجة من فعل الأمواج فغالبا ما تكون متماثلة الشكل وتتميز بقممها الحادة التي تبين أعلى الطبقة وقيعانها المنحنية أو المقوسة.

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تعريف التموج عبر الصفيحة والتموجات غير المتماثلة

Ripple marks in Cretaceous Dakota Formation, east side of Dinosaur Ridge. قضيب مقياس الرسم على الدفتر طوله 10 سم.
الأنواع[1]
مستقيم

Windrippel b76 b.jpg

Straight ripples generate cross-laminae that all dip in the same direction, and lay in the same plane. These forms of ripples are constructed by unidirectional flow of the current.

موجي

Rippelbildungen am Strand von Spiekeroog.JPG

Sinuous ripples generate cross-laminae that are curvy. They show a pattern of curving up and down as shown in picture. Sinuous ripples produce trough cross lamination. All laminae formed under this type of ripple dip at an angle to the flow as well as downstream. These are also formed by unidirectional flow of current.

متسلسل

Ebbe.jpg

Catenary ripples generate cross-laminae that are curvy but have a unidirectional swoop. They show a pattern similar to what a repeated "W" would look like. Like the sinuous ripples, this form of ripple is created by unidirectional flow with the dip at an angle to the flow as well as downstream.

Linguoid / Lunate

Oszillationsrippel.JPG

Linguoid ripples have lee slope surfaces that are curved generating a laminae similar to caternary and sinuous ripples. Linguoid ripples generate an angle to the flow as well as downstream. Linguoid ripples have a random shape rather than a "W" shape, as described in the catenary description. Lunate ripples, meaning crescent shaped ripples, are exactly like linguoid ripples except that the stoss sides are curved rather than the lee slope. All other features are the same.

المقاس (المقياس)[2]
المقاس الوصف
صغيرة جداً Very small cross-lamination means that the ripple height is roughly one centimeter. It is lenticular, wavy and flaser lamination.
سغيرة Small cross-bedding are ripples set at a height less than ten centimeters, while the thickness is only a few milimeters. Some ripples that may fit this category are wind ripples, wave ripples, and current ripples.
Medium Medium cross-lamination are ripples with a height greater than ten centimeters, and less than one meter in thickness. Some ripples that may fit this category would be current-formed sandwaves, and storm-generated hummocky cross stratification.
Large Large cross-bedding are ripples with a height greater than one meter, and a thickness equivalent to one meter or greater. Some ripples that may fit this category would be high energy river-bed bars, sand waves, epsilon cross-bedding and Gilbert-type cross-bedding.


الموجة التي شكلت علامات النيم

Ripple marks formed by aeolian processes

تعاريف

Crest and trough


انظر أيضا

المصادر

  • Easterbrook, Don J. Surface processes and landforms. Upper Saddle River, N.J: Prentice Hall, 1999. Print. ISBN 0-13-860958-6 pp. 479-480.
  • Greeley, Ronald, and James D. Iversen. Wind as a Geological Process On Earth, Mars, Venus and Titan (Cambridge Planetary Science Old). New York: Cambridge UP, 1987. ISBN 0-521-35962-7 pp. 153-154
  • Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997. ISBN 0-314-09577-2 pp. 114-15, 352.
  1. ^ Nichols, Gary. (2009)Sedimentary and Stratigraphy
  2. ^ Stow A.V., Dorrik. (2009) Sedimentary Rocks in the Field: A Color Guide

وصلات خارجية