Microbial boundstone dominated carbonate slope (Upper Carboniferous, N Spain): Microfacies, lithofacies distribution and stratal geometry

Abstract

KEYWORDS:STEEPCARBONATI~;SLOPI; !VIICROBIALP, OLiNI)STONI-. blI(71{()I".,\CIIzS-f.it{()MIblTI~Y ,c, PAIN LII>Ptr.R('AllIT, ONIH{I4()t.;S SumnlaryThe Carboniferous, particularly during the Serpukhovian and Bashkirian time. was a period of scarce shallow-water calcimicrobial-microbialite rccf growth. Organic frameworks developed on high-rising platforms are, however, recorded in the Precaspian Basin subsulface, Kazakhstan, Russia, Japan and Spain and rcpresenl uncommon occurrences within the general trend of low accumulation rates and scarcity of shallow-water reefs. Sierra del Cuera (Cantabrian Mountains, N Spain) is a well-exposed high-rising carbonate platform of Lale Carboniferous (Bashkirian-Mosc(~vian) agc with a microbial boundstone-dominated slope dipping from 2(F up to 45 ~ Kilometer-scale conlJrlunus exposures allow the detailed documentation of slope eeomctry and lithefacies spatial distribution. This study aims to clcvclop a depositional model of steep-margined l.ate Palc(~zoic platforms built by microbial carbonates and lo contribulc to the understanding of the controlling factors on lithefacies characteristics, stacking patterns, accumulation rates and evohltion of the depositional architecture of systems, which differ from light-dependent coralgal platform margins.From the platform break to depths of nearly 300 m. the slope is dominated by massive cement-rich boundstone, which accumulated through the biologically induced precipitation of micrite. Boundslonc facies (type A) with peloidalcarbonate thud, fenestellid and fisluliporid bryozoans, sponge-like molds and primary cavities I'illed by radiaxial fibrous cement occurs all over the slot)e but dominates the deeper settings. Typc B b(~undstone consists ofglobose centimeter-scale laminated accretionary structures, which commonly host bolryddal cement in growth cavities. The laminae nucleate around fenestcl lid bryozoans, sponges, Retialcis and (;trade,ella-like filaments. Type B boundstone typically occurs at depths between 20-150 m to locally more than 300 rn and forms the bulk of the Bashkirian prograding slope. The uppermost slope boundstone (type C: bctwcei~ 0 and 20-100 in depth) includcs peMdal micritc, radiaxial fibrous ccmem. brx.ozoans, sp~mgc mohis. Dr,~eg.ella, Renalui.s. G i r t ' c e l i a . ()rtc~tlello. calcareous algae and calcitorncllid foramini Icrs. From depths of 80-200 m to 450 m. 1-30 m thick Ictlses ofcrinddal packstcme, spiculitic wackesionc, and bryozoan biocmnentstone with rcd-siaincd micrite matrix arc episodically inlcrcalaled with boundsttme and bieccias. These layers incrca.,,c in number Irom the uppermost Bashkirian to the Moscovian in parallel with thcchangc [ rolll {;| rapidly prograding t~ an aggrading architecture. The red-stained strata share comparable Iealures with Lower (2arbonilErous decper-watcr mud-mound Facies and were deposited durin.~ rclative rises of sea Icx.cl and pauses in boundstone production. Rapid relative sea-level rises might have been a.,,sociatcd v,.it h changes in oceanograpllic conditions not ...

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

“…Three carbonate-platform flanks, the Pennsylvanian Sierra del Cuera and Las Llacerias sections Immenhauser et al, 2002;Della Porta et al, 2003;Bahamonde et al, 2004Bahamonde et al, , 2007Van der Kooij et al, 2007, 2009 and the Guadalupian Capitan Reef (Wood et al, 1994(Wood et al, , 1996Tinker, 1998;Kerans & Tinker, 1999;Melim & Scholle, 1999;Rahnis & Kirkland, 1999;Figs 1 and 2) are used as reference for this study. The flanks of these platforms have high-rising, steep slopes with upper domains dominated by microbial-algal boundstones.…”

“…The margin is built by a clinoformal succession, which is predominantly progradational during the Bashkirian and predominantly aggradational during the Moscovian (Fig. 2; Bahamonde et al, 1997;Della Porta et al, 2003). The sigmoid to concave slope is up to 850 m high and has a gradual and gentle platform break in the Bashkirian strata and a relatively sharp platform break in the Moscovian strata reaching maximum slope angles of 42° (Table 1; Fig.…”

“…The sigmoid to concave slope is up to 850 m high and has a gradual and gentle platform break in the Bashkirian strata and a relatively sharp platform break in the Moscovian strata reaching maximum slope angles of 42° (Table 1; Fig. 2;Della Porta et al, 2003. The margin and upper slope extend from the outermost platform to platform break to a palaeobathymetry of ca 400 m. Dominant microbial boundstones are interbedded with grainstones composed of predominantly platform-top-derived material and red-stained, cement-rich limestone intervals (Table 1; Della Porta et al, 2003;Van der Kooij et al, 2007).…”

“…2;Della Porta et al, 2003. The margin and upper slope extend from the outermost platform to platform break to a palaeobathymetry of ca 400 m. Dominant microbial boundstones are interbedded with grainstones composed of predominantly platform-top-derived material and red-stained, cement-rich limestone intervals (Table 1; Della Porta et al, 2003;Van der Kooij et al, 2007).…”

“…Several studies of Recent case settings, such as the continental shelf off the south-eastern coast of the USA (Macintyre & Milliman, 1971), the bottom of the Red Sea (Gevirtz & Friedman, 1966) and the tops and flanks of guyots (Marlowe, 1971), described early marine cements precipitated in hundreds of metres of water. Other work dealt with fossil slope settings such as the Pennsylvanian carbonate slope of the Sierra del Cuera in north-western Spain (Bahamonde et al, 1997Kenter et al, 2002;Immenhauser et al, 2002Immenhauser et al, , 2003Della Porta et al, 2003, the Permian Capitan Reef in Texas and New Mexico (Rahnis & Kirkland, 1999;Weidlich & Fagerstrom, 1999) or the Triassic isolated platforms in the Dolomites of northern Italy (Harris, 1994;Keim & Schlager, 1999;Seeling et al, 2005). The controlling mechanisms of marine carbonate cementation in these intermediate and deeper carbonate slope settings, however, are rarely discussed (Wilber & Neumann, 1993;Paull et al, 2000;Noé et al, 2005).…”