Caliche Formation and Features

Öz

Caliche is a general term that describes a secondary carbonate accumulation in unconsolidated sediments, sedimentary rocks and soils under semi-arid and arid climate conditions. Caliches are composed dominantly of small calcite crystals in micrite (< 4 m) and microsparite (5-15 m) size. Small amount of diagenetic minerals such as sepiolite, palygorskite, magnesium calcite and dolomite etc. are associated with calcium carbonate (low Mg-calcite) occurrences. Caliche appears in a variety offorms such as chalky powdery, nodular, tubular, laminated crust, hardpan (indurated crust). In caliche, macroscopic rhizolithic structures and microscopic alfa and beta fabric constituents are common. Two main hypotheses which explain the origin of caliche. These are; (a) downward movement of dissolved CaCO3 (per descensum; pedogenetic); and (b) capillary risefrom groundwater (per ascensum; groundwater) models. During caliche formation, calcium is provided from varied sources.

Anahtar Kelimeler

• Caliche
• calcium carbonate
• diagenetic mineral
• per descensum (pedogenetic) model
• capillary rise (groundwater) model

Kaliş Oluşumu ve Özellikleri

Öz

Kaliş genel bir terim olup, kurak ve yan kurak iklim koşullarında gevşek çökeller, tortul kayaçlar ve topraklar içindeki ikincil kalsiyum karbonat (CaCO3) yığışımlarını tanımlamaktadır. Kalişler mikrit (<4 m) ve mikrosprarit (5-15 m) boyutundaki küçük kalsit kristallerinden oluşmakta ve küçük miktarlardaki diyajenetik mineral oluşundan (sepiyolit, paligorskit, magnezyum kalsit, dolomit gibi) kalsiyum karbonat oluşumlarına (düşük Mg-kalsit) eşlik etmektedir. Kalişler; kireç tozu, yumru, tüp, laminalı kabuk ve sert kabuk gibi farklı oluşum şekillerine sahiptir. Kalişlerde makroskopik kök yapılan ve mikroskopik alfa ve beta dokusal özellikleri yaygın olarak bulunmaktadır. Kalişlerin oluşumu üzerine başlıca iki hipotez önerilmiştir. Bunlar; (a) sızma modeli (per descensum; pedojenik model); çözünmüş CaCO3`ün sızan sulardan çökelimini tanımlamakta ve (b) yeraltı suyunun kapiler yükselim (per ascensum; yeraltısuyu modeli) modelidir. Kaliş oluşumunda kalsiyum değişik kaynaklardan sağlanır.

Anahtar Kelimeler

• Kaliş
• kalsiyum karbonat
• diyajenetik mineral
• sızma (pedojenik) modeli
• kapiler yükselim
• (yeraltısuyu) modeli

Kaynakça

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