Early-Middle Ordovician Seascapescale aggregation pattern of sponge-rich reefs across the Laurentia paleocontinent

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Kröger , B & Penny , A 2020 , ' Early-Middle Ordovician Seascapescale aggregation pattern of sponge-rich reefs across the Laurentia paleocontinent ' , Palaios , vol. 35 , no. 12 , pp. 524-542 . https://doi.org/10.2110/palo.2020.039

Title: Early-Middle Ordovician Seascapescale aggregation pattern of sponge-rich reefs across the Laurentia paleocontinent
Author: Kröger, Björn; Penny, Amelia
Contributor organization: Staff Services
Natural Sciences Unit
Finnish Museum of Natural History
Date: 2020-12-28
Language: eng
Number of pages: 19
Belongs to series: Palaios
ISSN: 0883-1351
DOI: https://doi.org/10.2110/palo.2020.039
URI: http://hdl.handle.net/10138/326095
Abstract: During the late Cambrian–Early Ordovician interval the predominant non-microbial reef builders were sponges or sponge-like metazoans. The lithological and faunal composition of Cambro-Ordovician sponge-dominated reefs have previously been analyzed and reviewed. Here we take the relationship between reef aggregation pattern at reef to seascape scale into account, and look for changes during the Early–Middle Ordovician interval, in which metazoans became dominant reef builders. In a comparison of sponge-rich reefs from eight sites of the Laurentia paleocontinent three different seascape level reef growth patterns can be distinguished: (1) mosaic mode of reef growth, where reefs form a complex spatial mosaic dependent on hard substrate; (2) episodic mode, where patch reefs grew exclusively in distinct unconformity bounded horizons within non-reefal lithological units that have a much larger thickness; and (3) belt-and-bank mode, where reefs and reef complexes grew vertically and laterally as dispersed patches largely independent from truncation surfaces. The distinct modes of growth likely represent specific reef forming paleocommunities, because they differ in content and abundance of skeletal metazoan framebuilders, bioturbation intensity of non-skeletal reef sediment matrix, and in association of reef growth with underlying hard substrate. We suggest, based on a review of Laurentian reef occurrences, that the mosaic mode dominated in Early Ordovician strata and that the dominance shifted toward the belt and bank mode from Middle Ordovician strata onward.
Subject: 1171 Geosciences
ST-GEORGE GROUP
TABLE HEAD GROUPS
WESTERN NEWFOUNDLAND
CARBONATE SEDIMENTATION
BIOTURBATION
BIOSTRATIGRAPHY
CONSTRUCTION
PALEOECOLOGY
STRATIGRAPHY
COMMUNITIES
Peer reviewed: Yes
Rights: unspecified
Usage restriction: openAccess
Self-archived version: acceptedVersion


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