Early Diagenesis of Plitvice Lakes Waterfall and Barrier Treavertine Deposits

Abstract

Travertine forms spectacular waterfalls, barriers, and subaqueous finegrained lake-fill accumulations throughout the Plitvice National Park, Croatia, northwestern Yugoslavia. Barrier deposits form dams, behind which, the lakes of the Plitvice complex are situated. Three generations of low-magnesian calcite spar comprise the waterfall and barrier forming travertines. The initial precipitates generally are composed of cloudy, very finely to medium crystalline equant to bladed spar. A later generation is composed of clear, isopachous layers of medium to coarsely crystalline bladed crystals. Additionally, centimeter-thick laminated speleothem-like crusts, composed of clear, bladed to columnar spar, are the common precipitates around micritic accumulations within the older travertine. In comparison, the lake-fill deposits are primarily composed of moderately (recent lake-fill deposits) to well-developed (relict lake-fill deposits) 3-8 ^m calcite rhombohedrons. Petrographie analyses clearly show that cyanobacteria, fungi, and/or other microbial organisms bore into the spar and micritize it. This sparmicritization is pervasive throughout the waterfall and barrier deposits. Bladed spar crystals range from those which are pristine to those whose original bladed morphology can only be interpreted by comparison with laterally adjacent crystals. Individual samples display multiple generations of spar which have undergone various degrees of sparmicritization. Sparmicritization results in a thoroughly micritized accumulation in which evidence of the original spar composition has been completely obliterated.

Geobody architecture, genesis and petrophysical characteristics of the Budakalász travertines, Buda Hills (Hungary)

“…The second micrite fabrics related to micritisation are found as micrite patches in cloudy sparite crystals that laterally occur together with clean sparite crystals. These crystals represent a range in degree of sparmicritization as reported by Chafetz et al (1994). The latter authors relate the patchy micrite to micro-boring activity.…”

“…Postformation processes may cause micritisation (e.g. Kahle, 1977;Chafetz et al, 1994;Guo and Riding, 1994;Nicoll et al, 1999 andJones, 2007) or sparitisation (e.g. Love and Chafetz, 1988;Freytet and Verrecchia, 1999;Golubic et al, 2008 andBrasier et al, 2011).…”

“…This kind of micrite envelopes is typically formed by microboring (or microetching cfr. Pentecost, 2005) of dendritic spars (Kahle, 1977;Chafetz et al, 1994). The second micrite fabrics related to micritisation are found as micrite patches in cloudy sparite crystals that laterally occur together with clean sparite crystals.…”

What do we really know about early diagenesis of non-marine carbonates?

“…A similar process, mediated by the activity of cyano-and other bacteria, fungi and algae can transform spar, columnar or fibrous crystals to micrite or microspar in non-marine settings ( Fig. 5G; Chafetz et al, 1994;Jones, 2010;Capezzuoli et al, 2014). Microorganisms, colonizing the surface during periods of reduced precipitation rates (Takashima and Kano, 2008), or present as endolithic communities in porous laminae of a primary crust, are believed to break apart crystals (Fig.…”

“…5B; Chafetz and Guidry, 2003;Turner and Jones, 2005;Rainey and Jones, 2007;Jones and Renaut, 2008;Arp et al, 2013b); columnar, acicular, gothic arch or bladed crystals forming isopachous calcite (Fig. 5C, D) and fibrous aragonite, void lining cements (Chafetz et al, 1994;Arp et al, 1998;Claes et al, 2015), radial splays (Barth and Chafetz, 2015), anhedral, calcite-micrite banded crusts, mosaic cements and overgrowths (Fig. 5E) (Rainey and Jones, 2007;Jones and Renaut, 2008;Gandin and Capezzuoli, 2014;Claes et al, 2015).…”