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Pedogenetic calcretes in early syn-rift alluvial systems (Upper Jurassic, west Cameros Basin), northern Spain

Sara Sacristan-Horcajada, Maria Eugenia Arribas and Ramon Mas
Pedogenetic calcretes in early syn-rift alluvial systems (Upper Jurassic, west Cameros Basin), northern Spain
Journal of Sedimentary Research (March 2016) 86 (3): 268-286


Exceptional pedogenetic calcretes occur in the earliest syn-rift sedimentary record (Tithonian) of the west Cameros Basin. These calcretes show different types of pedogenetic facies (nodular, massive, laminar, and brecciated-pisolithic) and microfabrics: brecciated intraclasts, carbonate nodules, coated clasts and grains, etched quartz grains, rhizocretions, pedotubules and fragmented alveolar-septal structures. In addition, calcrete fragments have been observed in the conglomerate and sandy channelized deposits that form the alluvial systems, indicating the reworking of previous calcrete deposits. Calcrete facies appear organized in several sequences developed over different architectural elements in three different types of alluvial systems. The type of calcrete sequence is different depending on the architectural arrangement of each alluvial-fan system. Laminar (L (MN)-S) and brecciated-pisolithic (BP (L)-S) calcrete sequences are predominant in the alluvial sedimentary record of poorly channelized alluvial systems. These calcretes are thick, morphologically complex, and laterally continuous, due to the formation of long-term stable subaerial surfaces favored by the intermittent behavior of the alluvial systems. Massive-nodular (M (N)-S) and laminar (L (MN)-S) sequences are predominant in highly channelized alluvial systems and develop only locally in interchannel or floodplain areas where sedimentation stops temporally. Calcrete sequences in the distributive fluvial fan systems can be considered as poorly developed, being massive-nodular (M (N)-S) and nodular (N-S). After analyzing the location of these calcrete sequences in the studied record and their genesis and environmental significance, their variations can be related to different autocyclic factors such as sedimentation rate, channel network organization, texture of the host sediment, and water-table influence. Also three main allocyclic factors such as climate, tectonics, and drainage area controlled the carbonate sedimentation and therefore the development of the calcretes.

ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 86
Serial Issue: 3
Title: Pedogenetic calcretes in early syn-rift alluvial systems (Upper Jurassic, west Cameros Basin), northern Spain
Affiliation: Universidad Complutense de Madrid, Departamento de Estratigrafia, Madrid, Spain
Pages: 268-286
Published: 201603
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 65
Accession Number: 2016-083558
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
N42°17'60" - N42°17'60", E14°24'00" - E14°24'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201640
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