Transgressive Oversized Radial Ooid Facies in the Late Jurassic Adriatic Platform Interior: Low-Energy Precipitates from Highly Supersaturated Hypersaline Waters

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Transgressive oversized radial ooid facies in the Late Jurassic Adriatic Platform interior: Low-energy precipitates from highly supersaturated hypersaline waters

Antun Husinec† Croatian Geological Survey, Sachsova 2, HR-10000 Zagreb, Croatia J. Fred Read† Department of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, Virginia 24061, USA

ABSTRACT Keywords: radial ooids, low energy, plat- (Fig. 1). This huge Mesozoic, Bahamas-like form-interior parasequences, Late Jurassic, platform is characterized by a 6-km-thick pile of Dark-gray oolitic units characterized by Adriatic Platform. predominantly shallow-water carbonate depos- oversized ooids with primary radial cal- its, punctuated by periods of subaerial exposure, cite fabrics occur in the interior of the Late INTRODUCTION paleokarst and bauxites, and by several pelagic Jurassic Late Tithonian, Adriatic Platform, a (incipient drowning) episodes (e.g., Velić et al., large Mesozoic, Tethyan isolated platform in Distinctive oolite units on the Late Jurassic 2002; Jelaska, 2003; Vlahović et al., 2005). The Croatia. They differ from open-marine, plat- (Tithonian) Adriatic Platform, Croatia (Tišljar, Lastovo Island section is ~25 km inboard from form-margin ooid grainstones in their dark 1985), are characterized by oversized ooids the platform margin (Grandić et al., 1999) and color, cerebroid outlines, broken and recoated with radial primary calcite fabrics. Many have grains, abundant inclusions, highly restricted cerebroid outlines, are broken and recoated, and biota, and lack of cross-stratifi cation. They are poorly sorted. The oolite units have super- have been interpreted as being of vadose ori- imposed vadose fabrics, lack marine biotas, and 10°E AUSTRIA 20°E gin (“vadoids”) at tops of upward-shallowing do not have high-energy sedimentary structures. A HUNGARY parasequences. However, detailed sections They also have been reported from the Italian 45°N CROATIA 45°N show that most oolitic units occur at bases of and French Jurassic (Simone, 1974; Adams and ADRIATIC ?? PLATFORM precessional parasequences, overlying ero- MacKenzie, 1998). ? sional surfaces on fenestral carbonates. The These oolitic units lack the characteristic fea- Adriatic??????? Sea? oolitic units are similar to quiet-water ooids tures of high-energy marine oolites. They have N ITALY that form today in low-energy settings. They been considered to be vadose caps on regressive developed in an arid climate during initial carbonate cycles resulting from upward shallow- transgression of supratidal fl ats, along lowing, culminating in emergence. The ooids were energy shores seaward of tidal fl ats, and along termed “vadoids” by Tišljar (1985). However, 10°E 20°E the margins of restricted lagoons and inter- detailed measured sections show that many of 17°E tidal ponds. Superimposed fenestral fabrics, these distinctive oolitic units occur in the bases B PELJEŠAC meniscus micrite cements, and grain break- of parasequences in the oolite-rich sections. The 43°N ˘ age occurred as they aggraded to high-tide evidence suggests that they developed along Blato KORCULA level and were subjected to wetting and dry- low-energy shorelines and in intertidal ponds ing, thermal expansion and contraction, and and lagoons established on previously emergent Adriatic Sea Study area wind transport. They migrated landward with hypersaline fl ats during transgressions driven transgression, forming extensive sheets, and by precessional forcing. We suggest that their were overlain by subtidal lagoonal facies that geologic distribution refl ects the juxtaposition 42°45Ń LSLLSL 42°45Ń LASTOVO shallow up into fenestral carbonates. These of calcite seas, high supersaturation states, arid 0 5 10 20 km N distinctive facies may have been overlooked climate, and presence of fl at-topped platforms in 16°30É 17°E in the geological record, or their geological a greenhouse world. distribution requires juxtaposition of calcite Figure 1. (A) Map of south-central Europe seas, high-calcite supersaturation states, arid SETTING showing location of Adriatic Platform (mod- climate, and presence of fl at-topped carbon- ifi ed from Grandić et al., 1999; Velić et al., ate platforms in a greenhouse world. The Jurassic (Tithonian) oolitic carbonates are 2002). Rectangle shows area enlarged in B. well exposed on Lastovo Island in southern Cro- (B) Location of the studied section on Las- †E-mails: [email protected]; [email protected]. atia, on the southern part of the Adriatic Platform tovo Island (LSL).

GSA Bulletin; May/June 2006; v. 118; no. 5/6; p. 550–556; doi: 10.1130/B25864.1; 5 ﬁ gures.

550 For permission to copy, contact [email protected] © 2006 Geological Society of America LATE JURASSIC LOW-ENERGY RADIAL CALCITE OOIDS exposes an undisturbed ~750-m-thick succes- basal transgressive oolite, skeletal mudstone- ing of ooids, even though aragonitic mollusk and sion of Upper Jurassic–Tithonian shallow-water wackestone (rare), skeletal-intraclastic pack- algal fragments that form nuclei of ooids and carbonate sediments of the platform interior, stone-grainstone, regressive oolite (less com- aragonitic grains in enclosing beds were leached the upper part of which is oolitic. The intense mon), and unfossiliferous mudstone capped by and fi lled by sparry calcite. This is compatible dolomitization further inboard makes it diffi - fenestral grainy and muddy carbonate. with the calcite seas of the Late Jurassic–Creta- cult to determine how far into the platform the Parasequences are grouped into parasequence ceous (Wilkinson et al., 1985), in which calcite oolitic facies extends. The Tithonian limestones sets commonly 8–14 m thick. Sets consist of precipitation was promoted because of oceanic are underlain by Upper Kimmeridgian–Lower several parasequences. Lower parts of some sets Mg/Ca ratios below two (Stanley and Hardie, Tithonian shallow subtidal and peritidal (fenes- commonly contain thin units of the deeper sub- 1998). The Mg/Ca ratio of the oceans, and hence tral) limestones with the dasycladacean alga tidal facies and thick oolitic carbonates; upper aragonite versus calcite seas, largely refl ects pro- Clypeina jurassica (Korolija et al., 1977; Sokaˇc parts of sets commonly contain peritidal fenes- cesses controlled by spreading rates and global et al., 1984). They are overlain by earliest Cre- tral carbonates. mid-ocean-ridge volumes. taceous (Berriasian) peritidal limestones with The oolitic units (Fig. 4) occur as 0.1–1.5-m-, paleosols (Husinec, 2002; Fig. 2). and rarely, 4-m-thick, massive beds of grain- Evidence against Open-Marine Origin for The oolitic carbonates described here from stone and packstone. The oolitic units range Oolite Units Croatia resemble similar facies that occur in from light-gray beds of fi ne- to medium-sand- Italy and as far west as France (Simone, 1974; size, commonly superfi cial ooids, to darker, Modern high-energy oolitic sands on isolated Adams and MacKenzie 1998). brown-to-gray, large coarse-sand-size to gran- platforms commonly are located within a few ule-sized (1–3 mm) units. They also contain kilometers, and rarely up to 15 km, from the mar- DESCRIPTION AND OCCURRENCE OF whole and fragmented-and-recoated radial gin (Harris and Kowalik, 1994). The oolitic units OOLITIC FACIES ooids (Fig. 4A–D; “vadoids” of Tišljar, 1985), in the studied section, located 25 km inboard or bimodal mixtures of fi ne and coarse ooids; from the platform margin, show few features The typical distribution of these oolitic units other grains include grapestone-like aggregates typical of high-energy marine ooid sands. They is shown in Figures 2 and 3. Oolitic facies pre- of ooids bound by marine cement and thin generally lack marine burrow structures, ripple dominate in the topmost 160 m of the Upper oolitic coatings (Fig. 4F–G), minor peloids, cross-lamination, herringbone cross-stratifi ca- Tithonian of the study area (Fig. 2), although and a restricted biota of gastropods and dasy- tion, or foreset bedding associated with migra- individual oolite beds occur a few tens of meters cladacean algae. The ooids commonly have cer- tion of submarine dunes. In addition, they have both below and above this interval. They are ebroid outlines (Fig. 4E) with well-developed superimposed vadose diagenetic fabrics (fenes- interbedded with relatively restricted marine radial structure (Figs. 4A and 4D–E), and lesser- tral fabrics, crystal silts, and meniscus cements) facies and fenestral carbonates. They commonly developed concentric laminae of micritized car- and contain numerous broken and recoated ooids occur in parasequences (Fig. 3) that consist of bonate (Fig. 4F). The cortex contains numerous (which are rare in radial oolitic units of high- dark micron-sized inclusions of possible organic energy, open-marine subtidal origin). They also material(?). Coatings show little evidence of have very restricted biotas, which include the abrasion of radial crystal terminations (Fig. 4E) dasycladacean algae (Campbelliella) and small nor is there much rounding of broken ooids gastropods, both of which groups are common in Peritidal (Fig. 4D). Some units have superimposed fenes- hypersaline settings today (Logan et al., 1974). parasequences tral fabric, and many ooids typically are bound The coarser oolitic units are dark gray (probably CRET. EARLY with paleosols together by meniscus cements of micritic car- due to incorporation of numerous dark organic Berriasian bonate (Figs. 4B–C) and later, fi ne- to coarse- inclusions in the ooid cortex). In contrast, most Ooid based grained, equant calcite cement. Broken and modern and many ancient marine oolites are parasequences recoated ooids become common near the tops of light cream, refl ecting intense wave and current some oolitic units (Tišljar, 1985). Hardgrounds energy that results in oxidation of any organics. that are planar at the outcrop scale are irregular Thus, the evidence indicates these oolitic units Peritidal at the microscopic scale and contain incipient are not typical, high-energy oolitic sand bodies parasequences meniscus cement (Fig. 4H). Although aragonite (cf. Ball, 1967; Bathurst, 1973; Harris, 1984). fossils in the oolitic carbonates are leached and 500 fi lled with fi ne- to coarse-grained equant calcite Transgressive versus Regressive Setting of

Tithonian cement, ooids are not leached. Vadose Ooids

LATE JURASSIC LATE Subtidal ORIGIN OF THE UPPER JURASSIC Parasequences containing the oolitic units parasequences ABERRANT OOLITE UNITS are likely to be precessional cycles, given their 2.5 m average thicknesses and the 15 cm/k.y. Mineralogy accumulation rate for the Tithonian (Husinec and Read, 2005). The parasequence sets of 12 m L. In contrast to modern, as well as Early and or so, composed of 4–6 cycles, may be short-

Kimm. 0 m Middle Jurassic radial ooids, which commonly term eccentricity cycles. The well-developed Figure 2. Generalized stratigraphic column are aragonitic (Halley, 1977; Loreau and Purser, tidal-ﬂ at caps and the associated shallow-water showing stratigraphic location of Upper 1973; Tišljar, 1983), the Late Jurassic ooids in facies strongly suggest global greenhouse con- Tithonian oolitic limestones within platform this paper are composed of primary calcite. This ditions and low-amplitude sea-level changes (cf. interior succession. is indicated by the lack of any evidence of leach- Read, 1998; Husinec and Read, 2005).

Geological Society of America Bulletin, May/June 2006 551 HUSINEC and READ

Figure 3. (A) Uppermost Tithonian section AB Sedimentary from Lastovo Island (section LSL; Fig. 1) 800 structures Facies 5th order paraseq. showing facies stacking, parasequences, 4th order sets and parasequence sets. Upward-deepening units are shown by upward-narrowing triangle; upward-shallowing units are shown by upward-widening triangle. (B) Details of portion of measured section showing location of oolitic units within parasequences. (C) Idealized succession of facies within an Upper Tithonian parasequence. M—lime mudstone, W—wackestone, P—packstone, G—grainstone, F—ﬂ oatstone, R—rudstone.

Tišljar (1985) interpreted the oolitic facies to be a result of vadose diagenesis following shallowing from subtidal lagoonal carbonates up 750 into subtidal–lower intertidal microbial fenestral carbonates. With further emergence, the sediments were partly eroded, and “vadoids” were formed in the vadose and subaerial zone. Tišljar (1985) suggested that broken and recoated vadoids were carried in from the neighboring vadose zone. Thus, the oolitic units were interpreted to be vadose caps to shallowing-upward 10m cycles (Tišljar, 1985). We agree that some of the oolitic units are regressive, especially those in upper parts of parasequences, beneath tidal-fl at laminites. Some of these regressive oolite units may have 5 developed along low-energy shores in front of prograding tidal fl ats, or in intertidal-supratidal ponds (cf. Loreau and Purser, 1973). However, oolitic units at bases of parasequences overlie 700 fenestral carbonates (commonly with erosional 0 contacts), and are transgressive deposits. It MG/RW/F P would be diffi cult to develop these extensive C Flooding surface oolitic units by simple shallowing upward, LAMINATED culminating in deposition of oolite in vadose CARBONATE supratidal settings (Fig. 5). The erosional sur- RESTRICTED LIME M GRAIN TYPES faces capping the fenestral carbonates beneath P/G the oolitic units were supratidal surfaces that W/P peloid intraclast developed during regression, and thus renewed ONCOID- superficial ooid marine ooid deposition would require transgres- SKELETAL large ooid M/W/F UPWARD-SHALLOWING sion and refl ooding of fl ats, discounting eolian PARASEQUENCE (5TH ORDER) PARASEQUENCE (?)hydrozoan OOID fragment deposits (Fig. 5). Thus, rather than capping G/P LAMINATED dasycladacean algae upward-shallowing parasequences, many of the CARBONATE (Campbelliella) oolite units in the bases of parasequences likely are transgressive. Such a transgressive setting FACIES fenestral carbonates and also would have provided accommodation for microbial laminites (tidal flat) the thicker oolite units of 1–4 m to develop. This radial ooid G/R 650 is not to imply that all Late Jurassic ooids else- (hypersaline shallow subtidal/ intertidal shoals and ponds where on the platform were formed in this way. skeletal-peloid-intraclast M/W/P/G (subtidal lagoon) Low-Energy versus Marginal-Marine Origin SEDIMENTARY STRUCTURES fenestrae (laminoid) Marine, high-energy radial ooids are well fenestrae (irregular and tubular) MWPG sorted, spherical, and have a cortex composed of

552 Geological Society of America Bulletin, May/June 2006 LATE JURASSIC LOW-ENERGY RADIAL CALCITE OOIDS

A B

C D

E F

G H

Figure 4. Thin-section photomicrographs of typical Upper Jurassic (Tithonian) ooid grainstone composed of large, whole and fragmented- and-recoated radial ooids, Lastovo Island, Croatia. Bar scale is 1 mm. (A) Typical ooid grainstone facies. (B) Large fenestral pore (f) developed within ooid grainstone. Meniscus cements shown by arrows. (C) Ooids bound together by micritic meniscus cements (arrows). (D) Broken radial ooids showing little or no abrasion, coated with radial envelopes. (E) Ooid (center) characterized by cerebroid outlines with well-developed radial structure, and lesser-developed concentric laminae of micritized carbonate. (F and G) Small clusters of whole and fragmented ooids forming grapestone-like aggregates coated with radial calcite laminae. (H) Hardground and contact of skeletal (Campbelliella) wackestone and ooid grainstone.

Geological Society of America Bulletin, May/June 2006 553 HUSINEC and READ concentric laminae with radial fabric alternating lag time with concentric “micritized” laminae, resulting sea level erosional from periods of abrasion and micritization alter- surface nating with periods of ooid accretion (Strasser, 5 1986; Davies and Martin, 1976). Thus, high- energy marine ooids are quite distinct from the Tithonian ooids described here. 0 Small radial ooids form on low-energy sand fl ats along the seaward fringes of the sabkhas in the Arabian Gulf, whereas larger radial ooids (m) Elevation form along the margins of restricted hypersaline lagoons, ponds, and minor depressions 02040 behind beach spits. These larger ooids are up to Time (k.y.) 1–3 mm, in contrast to most marine ooids, and are subjected only to small waves and moder- Figure 5. One-dimensional model illustrating how transgressive oolite parasequences may ate energy, due to protection by adjacent spits form under low-amplitude precessionally driven sea-level oscillations. Following emergence and barriers (Loreau and Purser, 1973). The of tidal-fl at laminites, transgression initiated renewed fl ooding of the tidal-fl at surface and large size of the ooids is favored by a low pro- ooid formation in hypersaline low-energy marginal-marine settings in tidal vadose zone. duction rate of nuclei (Sumner and Grotzinger, Subsequent deepening occurred following cessation of ooid deposition. Oolitic units became 1993), as might be expected in restricted hyper- buried beneath prograding shallow-marine sediments. Less common, regressive oolites (not saline lagoon and pond settings during gradual shown) would develop in front of, and be buried by, prograding tidal-fl at facies transgression, because there is little produc- tion of skeletal fragments, fecal pellets, and eroded grains that would provide nuclei. Large ooids also would be favored by high growth precipitation would have commenced almost Origin of the Vadose Fabrics rates (Sumner and Grotzinger, 1993), which immediately along the shore of shallow ponds would occur in hypersaline ponds and restricted and restricted lagoons (Fig. 5). Oolitic envi- How can we reconcile this transgressive set- lagoons being replenished by tidal waters in an ronments fringing the supratidal fl ats and bor- ting for the bulk of the oolite units and their evaporative semi-arid setting. dering intertidal ponds and restricted lagoons association with vadose features? Radial cal- We propose that, rather than being purely would have migrated laterally as well as land- cite ooids that formed on wave- and tide-swept vadose in origin (Tišljar, 1985), the radial ooids ward with transgression to form sheet-like ooid open-marine subtidal shoals in calcite seas were formed in low-energy subaqueous settings units. As transgression continued and waters rarely show broken ooids. This suggests that it (Strasser, 1986). The Tithonian ooids are strik- became less supersaturated, the tidal-supratidal is not the radial fabric that is the main control of ingly similar to modern radial ooids that are ponds would have coalesced and merged with breakage of ooids. Broken ooids are abundant forming in low-energy settings in lakes (Eard- the regional lagoonal setting, in which pellet- in carbonate eolianites (Hunter, 1993), which ley, 1938; Halley, 1977; Popp and Wilkinson, intraclast-skeletal packstone-grainstone would suggests that expansion and contraction due to 1983), and low-energy marginal-marine settings have formed on shallow subtidal sand fl ats. heating and cooling in the subaerial environ- in the Middle East (Loreau and Purser, 1973; This deepening into shallow subtidal depths ment (Tišljar, 1985) and grain-to-grain contact Friedman et al., 1973) and Texas (Rusnak, 1960; would have been facilitated by a lag between during eolian transport likely causes the break- Freeman, 1962). In the Upper Jurassic deposits, the oolitic units and the overlying subtidal age of the ooids. Thus, the broken ooids imply quiet-water depositional environments are sup- nonoolitic facies (Fig. 5). that either the ooids accreted to supratidal lev- ported by lack of abrasion of broken ooids, and Why do the transgressive oolite units of the els along pond shores, or that the ponds peri- cerebroid outlines of many ooids. The poor sort- Jurassic differ markedly from the transgres- odically dried out. Periodic refl ooding of these ing suggests an absence of high-velocity cur- sive relict, oolitic units that fl oor large interior ponds and lagoons would have allowed recoat- rents. Primary calcite radial ooids do not always portions of the Bahama Platform (Winland ing of the fragmented ooids. Eolian transport of form in quiet water, but many do (Strasser, 1986; and Matthews, 1974)? The Bahamian units some of the ooids is evidenced by their wide- Popp and Wilkinson, 1983). are now dominantly grapestone, formed by spread dispersion on the platform, where they Transgressive oolite formation on the Juras- micritization, aggregation due to organic and occur as isolated grains in almost every facies, sic platform would have occurred when shal- inorganic binding, and cementation of concen- including low-energy mudstones (cf. Eardley, low hypersaline, intertidal to very shallow sub- trically laminated aragonite ooids. Much of 1938; Abegg et al., 2001). tidal, low-energy, oolitic ponds and lagoons the original ooid structure has been destroyed The Jurassic oolitic units lack the classic were established as the fl ats were inundated. It in the Bahamian examples, because they were hypersaline vadose tepees and aragonite and is noteworthy that the thicker vadose pisolite not covered by later, shallower water deposits, high-Mg calcite supratidal crusts of pendant complexes of the Permian of West Texas are which would have protected them from fab- radial and micritic cement, such as those form- postulated to have formed within transgres- ric-destructive marine diagenetic processes at ing in the Arabian Gulf and the seepage face sive parts of sequences (Tinker, 1998). On the the sediment-water interface. We suggest that in Lake McLeod (Scholle and Kinsman, 1974; Jurassic platform, organics produced by cyano- the Jurassic ooids were protected from marine Handford et al., 1984). Nor do they show the bacteria in the ponds may have been incorpo- micritization by rapid burial, promoted by well-developed teepees and vadose pisolites rated in the ooids to form the dark coloration. the high long-term accumulation rates (up to of concentrically laminated cryptocrystalline Once the fl ats started to be fl ooded, oolite 15 cm/k.y.). carbonate, as in the Permian of West Texas

554 Geological Society of America Bulletin, May/June 2006 LATE JURASSIC LOW-ENERGY RADIAL CALCITE OOIDS

(Esteban and Pray, 1977). The Tithonian parase- by high calcite supersaturation of the platform Implications for Picking Parasequences quence tops also do not show evidence of cali- waters and global ocean in the Late Jurassic, che (calcrete) formation, which would develop due to relatively low Mg/Ca ratios of the ocean If we are correct, the transgressive rather than with long-term exposure (cf. Read, 1974). (Wilkinson and Given, 1986; Stanley and Har- regressive position of many of the oolitic units The relative scarcity of such vadose crusts die, 1998; Kiessling et al., 2003). Wilkinson et has implications for picking parasequences. In and fabrics in the Tithonian, and the deposi- al. (1985) showed that the Late Jurassic had the many platform-margin settings, the oolitic units tional setting of modern radial, oversized ooids highest abundance of oolite since the Carbon- overlie lower-energy, fi ner-grained subtidal suggest that the Tithonian examples formed in iferous. Overall, the Jurassic–Early Cretaceous muddy facies, and thus cap upward-coarsening low-energy, very shallow subtidal to intertidal, was considered a time of mild cyanobacterial parasequences (Harris, 1984). However, in more subaqueous settings that were periodically sub- calcifi cation by Riding (1992), compared to interior locations of platforms, as in this paper, jected to vadose processes. The shallow ponds the intense calcifi cation of the Triassic, and the oolitic units commonly form transgressive and restricted lagoons containing the Tithonian the extremely mild cyanobacterial calcifi cation coarse-grained bases of parasequences that fi ne ooids might have periodically dried out, allow- of the Late Cretaceous–Cenozoic. However, up into laminated and fenestral muddy carbon- ing tidal-vadose fenestral fabrics and meniscus microbial calcifi cation and microbial oncoids ate caps. Such grainy transgressive units occur cements to develop. Periodic drying of restricted in subtidal facies reached their peak in the Late in the interior of the Cambrian-Ordovician plat- lagoons and intertidal ponds could have been Jurassic and are extremely rare today, sug- form margin, U.S. Appalachians, where grainy, due to strong seasonal, offshore winds that sup- gesting that oceans had high carbonate super- locally oolitic facies form bases of upward-fi n- pressed tidal infl ow for days or weeks, as occurs saturation in the Late Jurassic (Kiessling et al., ing parasequences (Demicco 1985; Koerschner in Shark Bay (cf. Logan et al., 1974). Lower- 2003). Precipitation perhaps was restricted to and Read, 1989) and in some of the Tithonian- ing of saline groundwater tables also could calcite even under high supersaturation by the Berriasian cycles described from the French Jura have been due to periodic climate change and low Mg/Ca content of the oceans (Stanley and Mountains by Strasser (1994). Farther inboard increased aridity. Additionally, rapid upbuilding Hardie, 1998). on broad platforms, such grainy facies are rarely of the oolite surface to supratidal levels due to If these oolitic units required just an arid cli- developed, and parasequences are dominated by localized high sedimentation rate would have mate, high calcite supersaturation, and peritidal muddy facies from base to top. placed the oolitic units within the tidal-vadose settings to develop, why aren’t they more abun- zone, resulting in the vadose overprint. This dant in the Phanerozoic geologic record? Have CONCLUSIONS would have subjected the ooids to weathering these types of ooid facies been overlooked in the processes, breakage, and eolian transport. It also Phanerozoic, or are they relatively rare? Large Oversized, whole, broken and recoated radial is possible that each transgression driven by pre- deposits of giant ooids occur in several areas in ooids that form distinctive units in the Tithonian cessional forcing was not a single uniform rise, the Neoproterozoic (Sumner and Grotzinger, (Late Jurassic) of the Adriatic Platform, Croa- but might have been interrupted by higher-fre- 1993; Grotzinger and James, 2000). Low nucle- tia, were formerly interpreted as having formed quency sub-Milankovich sea-level fl uctuations, ation rate and low fl ux of nuclei, high supersatu- in the vadose zone at tops of regressive parase- such as those proposed for the Middle Triassic ration, increased storminess due to prevalence of quences. Based on their striking resemblance to Latemar (Zühlke et al., 2003) and the Holo- ramps rather than rimmed margins, and possibly modern low-energy lake and marginal-marine cene (Bond and Lotti, 1995). This would have stormier climates have been invoked for these pond ooids, and their common position at bases resulted in periodic emergence and vadose dia- giant ooids. The Jurassic oolitic facies described of parasequences, we reinterpret these as hav- genesis of the accumulating oolitic units. in this paper appear to be distinct from the Neo- ing formed dominantly during initial inundation proterozoic giant ooids, and low nucleation rate of supratidal fl ats, along the shores of shallow Climatic and Saturation State Controls and low fl ux of ooids, coupled with postulated hypersaline ponds and restricted lagoons of the high supersaturation, appear to be common to platform interior. Their abundance in the Titho- The Late Jurassic throughout western Tethys both. However, the postulated relatively low- nian of Tethys may be due to an arid greenhouse was characterized by a relatively dry climate, energy setting of the Tithonian examples differs climate and associated small precessional sea- which is marked by the extensive evaporites of from the Neoproterozoic cases. If these distinc- level oscillations, the high calcite saturation the Middle East (Murris, 1980). This dry cli- tive facies that typify the Tithonian examples in state of the waters, and the fl at-topped, platform- mate likely was a key element in developing this paper have not been overlooked, then their interior morphology. Some oolitic carbonates at these distinctive oolitic facies, which extend scarcity might be due to a special combination bases of parasequences within platform interiors as far west as France (Adams and MacKenzie, of circumstances, including the fl at-topped iso- elsewhere may have formed in a similar manner, 1998). The low rainfall allowed the develop- lated platform setting, low-energy, greenhouse especially on fl at-topped platforms in arid set- ment of hypersaline ponds that must have been conditions, and arid settings that promote cal- tings under greenhouse conditions. highly supersaturated with respect to calcite but cite supersaturation as platform waters become in which low Mg/Ca ratios prevented aragonite hypersaline (but below the salinities required ACKNOWLEDGMENTS precipitation (Stanley and Hardie, 1998). The for widespread calcium sulfate precipitation), This paper represents part of a postdoctoral research lack of widespread evaporites on the Adriatic with low Mg/Ca ratios of the oceans at the time project (grant no. 68428172) sponsored by the Ful- Platform (Veseli, 1999) suggests that the climate precluding aragonite precipitation. The geo- bright Program, U.S. State Department. We thank was not suffi ciently arid or that the platform was logic community might examine stratigraphic I. Vlahović, T. Grgasović, L. Fuˇcek, and D. Palenik, not suffi ciently restricted to promote widespread sections within carbonate platform interiors for who assisted in section logging during the work on deposition of gypsum or anhydrite. similar massive, non-cross-bedded oolitic facies the Geologic Map of Croatia (scale 1:50,000), sponsored by the Ministry of Science, Education and The widespread deposition of calcite ooids at bases of parasequences for oversized and Sport of Croatia. J.F. Read was supported by National in the Adriatic Platform interior in the Late broken radial ooids to determine if this facies is Science Foundation grant EAR-0341753. We thank Jurassic may have been strongly infl uenced indeed rare, or has just been overlooked. D. McNeill, M. Harris, and D. Sumner for their help

Geological Society of America Bulletin, May/June 2006 555 HUSINEC and READ

in revising the manuscript. We also thank J. Tišljar for Hunter, R.E., 1993, An eolian facies in the Ste. Genevieve Mesozoici dell’area Appennino-dinarica e delle Baha- comments on an early draft. Limestone of southern Indiana, in Keith, B., and Zup- mas meridionali: Bolletino della Societa Geologica pann, C., eds., Mississippian oolites and modern ana- Italiana, v. 93, p. 513–545. logs: Association of Petroleum Geologists, Studies in Sokaˇc, B., Tišljar, J., and Velić, I., 1984, Jurassic carbon- REFERENCES CITED Geology, no. 35, p. 31–47. ate sediments of Ivanjica–Konavle Hills, Islands of Husinec, A., 2002, Mesozoic stratigraphy of the island of Mljet, Lastovo and Kopist: Report on lithofacies and Abegg, F.E., Harris, P.M., and Loope, D.B., eds., 2001, Mljet within the geodynamic evolution of the southern sedimentology: Croatian Geological Survey Open-File Modern and ancient carbonate eolianites: Tulsa, Okla- part of the Adriatic carbonate platform [Ph.D. thesis]: Report 140/84, 228 p. [in Croatian]. homa, Society for Sedimentary Geology Special Pub- Zagreb, University of Zagreb, 300 p. [in Croatian with Stanley, S.M., and Hardie, L.A., 1998, Secular oscilla- lication 71, 207 p. English summary]. tions in the carbonate mineralogy of reef-building and Adams, A.E., and MacKenzie, W.S., 1998, A color atlas of Husinec, A., and Read, J.F., 2005, Facies stacking patterns sediment-producing organisms driven by tectonically carbonate sediments and rocks under the microscope: in a Late Jurassic Bahama-type platform interior, Adri- forced shifts in seawater chemistry: Palaeogeography, New York, John Wiley & Sons, 180 p. atic Platform, Croatia (abs.): American Association of Palaeoclimatology, Palaeoecology, v. 144, p. 3–19, Ball, M.M., 1967, Carbonate sand bodies of Florida and the Petroleum Geologists 2005 Annual Convention, v. 14, doi: 10.1016/S0031-0182(98)00109-6. Bahamas: Journal of Sedimentary Petrology, v. 37, p. A65. Strasser, A., 1986, Ooids in the Purbeck (lowermost Creta- p. 556–591. Jelaska, V., 2003, Carbonate platforms of the External Dina- ceous) of the Swiss and French Jura: Sedimentology, Bathurst, R.G.C., 1973, Carbonate sediments and their dia- rides, in Vlahović, I., and Tišljar, J., eds., Evolution of v. 33, p. 711–727. genesis: Amsterdam, Elsevier, 620 p. depositional environments from the Palaeozoic to the Strasser, A., 1994, Milankovitch cyclicity and high-resolu- Bond, G.C., and Lotti, R., 1995, Iceberg discharges into the Quaternary in the Karst Dinarides and the Pannonian tion sequence stratigraphy in lagoonal-peritidal car- North Atlantic on millennial time scales during the last Basin: Zagreb, 22nd International Association of Sedi- bonates (Upper Tithonian–Lower Berriasian, French glaciation: Science, v. 267, p. 1005–1010. mentologists Meeting of Sedimentology, Field-Trip Jura Mountains), in DeBoer, P.L., and Smith, D.G., Davies, P.J., and Martin, K., 1976, Radial aragonite ooids, Guidebook, p. 67–71. eds., Orbital forcing and cyclic sequences: Interna- Lizard Island, Great Barrier Reef, Queensland, Aus- Kiessling, W., Flügel, E., and Golonka, J., 2003, Patterns of tional Association of Sedimentologists Special Publi- tralia: Geology, v. 4, p. 120–122, doi: 10.1130/0091- Phanerozoic carbonate platform sedimentation: Lethaia, cation 19, p. 285–301. 7613(1976)4<120:RAOLIG>2.0.CO;2. v. 36, p. 195–226, doi: 10.1080/00241160310004648. Sumner, D.Y., and Grotzinger, J.P., 1993, Numerical mod- Demicco, R.V., 1985, Platform and off-platform carbonates Koerschner, W.F., and Read, J.F., 1989, Field and modelling eling of ooid size and the problem of Neoproterozoic of the Upper Cambrian of western Maryland: Sedimen- studies of Cambrian carbonate cycles, Virginia Appa- giant ooids: Journal of Sedimentary Petrology, v. 63, tology, v. 32, p. 1–22. lachians: Journal of Sedimentary Petrology, v. 59, p. 974–982. Eardley, A.J., 1938, Sediments of Great Salt Lake, Utah: p. 654–687. Tinker, S.W., 1998, Shelf-to-basin facies distribution and American Association of Petroleum Geologists Bul- Korolija, B., Borović, I., Grimani, I., Marinˇcić, S., Jagaˇcić, T., sequence stratigraphy of a steep-rimmed carbonate letin, v. 10, p. 1305–1411. Magaš, N., and Milovanović, M., 1977, Basic geo- margin: Capitan depositional system, McKittrick Can- Esteban, M., and Pray, L.C., 1977, Origin of the pisolite logic map of Socialist Federative Republic of Yugo- yon, New Mexico and Texas: Journal of Sedimentary facies of the shelf crest, in Upper Guadalupian facies slavia: Geology of Lastovo, Korˇcula and Palagruža Research, v. 68, p. 1146–1174. Permian Reef complex, Guadalupe Mountains, New sheets: Belgrade, Institute of Geology Zagreb, scale Tišljar, J., 1983, Coated grains facies in the Lower Cretaceous Mexico and West Texas: Field Conference Guide- 1:100,000, 53 p. of the Outer Dinarides (Yugoslavia), in Peryt, T., ed., book, Permian Basin Section, Society of Economic Logan, B.W., Read, J.F., Hagan, G.M., Hoffman, P., Brown, Coated grains: New York, Springer-Verlag, p. 566–576. Pa leontologists and Mineralogists Publication, v. 77-16, R.G., Woods, P.J., and Gebelein, C.D., eds., 1974, Tišljar, J., 1985, Structural type and depositional environ- p. 479–483. Evolution and diagenesis of Quaternary carbonate ments of Jurassic coated grain limestones in the south- Freeman, T., 1962, Quiet water oolites from Laguna Madre, sequences, Shark Bay, Western Australia: Tulsa, Okla- ern Adriatic region: Krš Jugoslavije, v. 11, p. 71–99. Texas: Journal of Sedimentary Petrology, v. 32, homa, American Association of Petroleum Geologists Velić, I., Vlahović, I., and Matiˇcec, D., 2002, Depositional p. 475–483. Memoir 22, 358 p. sequences and palaeogeography of the Adriatic Car- Friedman, G.M., Amiel, A.J., Braun, M., and Miller, D.S., Loreau, J.P., and Purser, B.H., 1973, Distribution and ultra- bonate Platform: Memorie della Società Geologica 1973, Generation of carbonate particles and lami- structure of Holocene ooids in the Persian Gulf, in Italiana, v. 57, p. 141–151. nates in algal mats—Examples from sea-marginal Purser, B.H., ed., The Persian Gulf: Holocene carbon- Veseli, V., 1999, Carbonate facies of the late Mesozoic and hypersaline pool, Gulf of Aqaba, Red Sea: American ate sedimentation and diagenesis in a shallow epiconti- Paleogene in offshore wells from northern Adriatic Sea Association of Petroleum Geologists Bulletin, v. 57, nental sea: New York, Springer-Verlag, p. 279–328. [Ph.D. thesis]: Zagreb, University of Zagreb, 306 p. [in p. 541–557. Murris, R.J., 1980, Middle East: Stratigraphic evolution and Croatian with English summary]. Grandić, S., Boromisa-Balaš, E., Šušterˇcić, M., and Kolbah, oil habitat: American Association of Petroleum Geolo- Vlahović, I., Velić, I., Tišljar, J., and Matiˇcec, D., 2005, Evo- S., 1999, Hydrocarbon possibilities in the eastern Adri- gists Bulletin, v. 64, p. 597–618. lution of the Adriatic Carbonate Platform: Palaeogeog- atic slope zone of Croatian off-shore area: Nafta, v. 50, Popp, B.N., and Wilkinson, B.H., 1983, Holocene lacustrine raphy, main events and depositional dynamics: Palaeo- p. 51–73. ooids from Pyramid Lake, Nevada, in Peryt, T., ed., geography, Palaeoclimatology, Palaeoecology, v. 220, Grotzinger, J.P., and James, N.P., 2000, Precambrian carbon- Coated grains: New York, Springer-Verlag, p. 142–153. p. 333–360, doi: 10.1016/j.palaeo.2005.01.011. ates: Evolution of understanding, in Grotzinger, J.P., Read, J.F., 1974, Calcrete deposits and Quaternary sediments, Wilkinson, B.H., and Given, R.K., 1986, Secular variation and James, N.P., eds., Carbonate sedimentation and Edel province, Shark Bay, Western Australia, in Logan, in the composition of abiotic marine carbonates: Con- diagenesis in the evolving Precambrian world: Soci- B.W., Read, J.F., Hagan, G.M., Hoffman, P., Brown, straints on atmospheric carbon dioxide contents and ety for Sedimentary Geology Special Publication 67, R.G., Woods, P.J., and Gebelein, C.D., eds., Evolution oceanic Mg/Ca ratios during the Phanerozoic: The p. 3–20. and diagenesis of Quaternary carbonate sequences, Journal of Geology, v. 94, p. 321–333. Halley, R.B., 1977, Ooid fabric and fracture in the Great Salt Shark Bay, Western Australia: American Association of Wilkinson, B.H., Owen, R.M., and Caroll, A.R., 1985, Lake and the geologic record: Journal of Sedimentary Petroleum Geologists Memoir 22, p. 250–282. Submarine hydrothermal weathering, global eustasy, Petrology, v. 47, p. 1099–1120. Read, J.F., 1998, Phanerozoic carbonate ramps from green- and carbonate polymorphism in Phanerozoic marine Handford, C.R., Kendall, A.C., Prezbindowski, D.R., Dun- house, transitional and ice-house worlds: Clues from oolites: Journal of Sedimentary Petrology, v. 55, ham, J.B., and Logan, B.W., 1984, Salina-margin tepees, fi eld and modelling studies, in Wright, V.P., and Bur- p. 109–119. pisoliths, and aragonite cements, Lake MacLeod, West- chette, T.P., eds., Carbonate ramps: Geological Society Winland, H.D., and Matthews, R.K., 1974, Origin and sig- ern Australia: Their signifi cance in interpreting ancient [London] Special Publication 149, p. 107–135. nifi cance of grapestone, Bahama Islands: Journal of analogs: Geology, v. 12, p. 523–527, doi: 10.1130/0091- Riding, R., 1992, Temporal variation in calcifi cation in Sedimentary Petrology, v. 44, p. 921–927. 7613(1984)12<523:STPAAC>2.0.CO;2. marine cyanobacteria: Journal of the Geological Soci- Zühlke, R., Bechstadt, T., and Mundil, R., 2003, Sub- Harris, P.M., 1984, Cores from a modern carbonate sand ety of London, v. 149, p. 979–989. Milankovitch and Milankovitch forcing on a model body; the Joulters ooid shoal, Great Bahama Bank, in Rusnak, G.A., 1960, Some observations of recent oolites: Mesozoic carbonate platform—The Latemar (Middle Harris, P.M., ed., Carbonate sands—A Core Workshop: Journal of Sedimentary Petrology, v. 30, p. 471–480. Triassic, Italy): Terra Nova, v. 15, p. 69–80, doi: San Antonio, Society of Economic Paleontologists and Scholle, P.A., and Kinsman, D.J.J., 1974, Aragonitic and 10.1046/j.1365-3121.2003.00366.x. Mineralogists Core Workshop 5, p. 429–464. high-Mg calcite caliche from the Persian Gulf—A Harris, P.M., and Kowalik, W.S., eds., 1994, Satellite images modern analog for the Permian of Texas and New MANUSCRIPT RECEIVED BY THE SOCIETY 28 JUNE 2005 of carbonate depositional settings: Examples of reser- Mexico: Journal of Sedimentary Petrology, v. 44, REVISED MANUSCRIPT RECEIVED 23 JANUARY 2006 voir- and exploration-scale geologic facies variation: p. 904–916. MANUSCRIPT ACCEPTED 1 FEBRUARY 2006 American Association of Petroleum Geologists Meth- Simone, L., 1974, Genesi e signifi cato ambientale degli ods in Exploration Series, v. 11, 147 p. ooidi a struttura fi broso-raggiata di alcuni depositi Printed in the USA

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