Ordovician sea-level change and rapid change in crustal … · 2012. 11. 15. · nisms and distinguish Ordovician glaciation-related sea-level changes and events of rapid crustal

www.elsevier.com/locate/rgg

Ordovician sea-level change and rapid change in crustal subsidence ratesin East Siberia and Baltoscandia

E.V. Artyushkov a, Yu.I. Tesakov b, P.A. Chekhovich c, *

a United Institute of the Physics of the Earth, Russian Academy of Sciences, 10 ul. B. Gruzinskaya, Moscow, 123810, Russiab Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia

c Moscow State University, Vorob’evy Gory, Moscow, 119899, Russia

Received 7 May 2007; accepted 16 November 2007

Abstract

Sea-level change has been commonly interpreted to be of eustatic origin, and many eustatic events were hypothesized for the Phanerozoic,including several 1–3 Myr long cycles in the Ordovician with magnitudes up to 100 or 200 m. However, sea-level change modeling usingstratigraphic data from Northern Estonia, which was an area of slow shallow-marine (<10 m) deposition through most of the Ordovician,indicates fluctuations of no more than 20 m. In the Late Ordovician the sea level fell only twice for ∼100 m within 1 Myr during theGondwanian glaciation. Although the sea level remained relatively stable, there were frequent 100–200 m changes of sea depths we inferredwith reference to the time spans of stratigraphic units and intervals between tectonic events estimated reliably against stable durations of EastSiberian chronozones (biochrons) of the Ordovician. In the absence of eustatic events, the sea-depth changes most likely resulted from rapidcrustal uplift and subsidence. According to correlated well-documented Ordovician sections from East Siberia, the rate of crustal subsidencechanged rapidly in different periods and in different places of the area, thus being of a regional scale. The controversy between the sea-levelstability and the regional-scale variations in sea depths controlled by rates of crustal uplift and subsidence can be resolved assuming a modelof variable eclogitization rates in the lower crust caused by lithospheric stress change. Our inferences undermine the traditional petroleumprediction approach implying formation of depositional traps due to rapid eustatic sea-level change.

Keywords: Ordovician; epeiric basins; sea level; eustatic fluctuations; tectonics; eclogitization; geochronology; East Siberia; Estonia

Introduction

Geological, paleontological, and seismic stratigraphic dataindicate notable time-dependent depth variations of epeiricseas (e.g., Hallam, 1992; Haq et al., 1987; Hardenbol et al,1998) which are inferred from benthic assemblages and facieschange as records of shoreline advance and retreat (e.g., Brettet al., 1993; Haq et al., 1987). Special attention is commonlygiven to third-order sea-level fluctuations with magnitudesfrom 20 to 100–200 m and durations of 1 to 3 Myr becauseof their implications for petroleum geology (Posamentier andAllen, 2000) and for regional or global correlations (Cooperand Nowlan, 1999; Koren’, 2000). Third-order cycles are mostoften interpreted as eustatic events (e.g., Hallam, 1992; Haqet al, 1987; Hardenbol et al., 1998) or are attributed to tectonicmovements (Badenas et al., 2004; Brandano and Corda, 2002;

Paul and Pluijm, 1999; Pindell and Drake, 1998). Theireustatic origin is sometimes refuted (Miall and Miall, 2001)for the low chronostratigraphic accuracy insufficient for globalcorrelations. Events of a large-scale but short sea-level fall maybe due to glaciations but they are known also in the so-calledgreenhouse periods. Thus, the origin of third-order cycles longremained unclear, the alternative being whether they resultedfrom eustasy or from regional crustal uplift (subsidence).

Artyushkov et al. (2000) disproved eustatic fluctuations ofmore than 20 m for the Cambrian which were suggested, forinstance, in (Miller, 1984; Montanez et al., 1996). LaterArtyushkov and Chekhovich (2002, 2004) and Artyushkov etal. (2003) used data on shallow-marine deposition (at depthsless than 10 m) in the Cambrian Eastern Baltic area (Popovet al., 1989) and Silurian East Siberia (Tesakov et al., 2000)to show that Silurian third-order sea-level change, likewisetaken for eustatic events (Johnson, 1996), never exceeded∼10 m.

Artyushkov and Chekhovich (2004) recognized ∼0.5 Myrlong events of abrupt crustal subsidence acceleration simulta-

Russian Geology and Geophysics 49 (2008) 633–647

* Corresponding author.E-mail address: [email protected] (P.A. Chekhovich)

© 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

1068-7971/$ - see front matter D 2008, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

doi:10.1016/j.rgg.2007.11.015555

neously in geographically dispersed areas of Silurian EastSiberia, which appeared very unusual for a platform, andexplained them by variable rates of metamorphic phasetransition in the lower crust controlled by stress change. Thesea-depth changes in the absence of eustatic events wererecognized proceeding from a relatively stable duration (stra-tigraphic volume) of chronozones (biological zones) in Silu-rian sections of East Siberia which ensured a reliable referencein correlations of regional stratigraphic units and intervalsbetween tectonic events.

In this study we use East Baltic (Männil and Meidla, 1994;Nestor and Einasto, 1997; Pylma, 1982) and East Siberian(Kanygin et al., 1989; Obut, 1982, 1984; Tesakov et al., 2003)data to estimate the maximum possible magnitudes of third-order sea-level fluctuations in the Ordovician. The Ordovicianis a classic period where 100–200 m eustatic events weresuggested as the main cause of sea-depth changes (Fig. 1)(e.g., Dronov et al., 1995; Erdtmann, 1986; Ross and Ross,1995; Webby and Laurie, 1992). They are, for instance, theAcerocare event assumed to mark the Cambrian-Ordovicianboundary (Cooper et al., 2001; Fortey, 1984; Erdtmann, 1986;Koren’, 2000) or a notable sea-level fall at the end of the

Ordovician associated with Gondwanian glaciation (Ghienne,2003; Hambrey, 1985; Monod et al., 2003; Paris et al, 1995).In addition, we re-estimate eustatic fluctuations for someSilurian intervals for which we obtained very low magnitudesbefore (Artyushkov and Chekhovich, 2002, 2004).

The Ordovician third-order cycles are analyzed belowfollowing the method developed in (Artyushkov and Chek-hovich, 2002, 2004; Artyushkov et al., 2007). We discusschanges in crustal subsidence rates and their possible mecha-nisms and distinguish Ordovician glaciation-related sea-levelchanges and events of rapid crustal uplift (subsidence) ondifferent continents. According to the recommendations of theSubcommission on the Ordovician Stratigraphy, reference ismade to the revised British scale (Cooper et al., 2001) and tothe updated subdivision of the Ordovician (Bergström et al.,2006; Chen et al., 2007; Koren’, 2002).

Northern Estonia

Ordovician-Silurian strata exposed in northern Estonia andtapped by numerous drill holes represent the northernmostperiphery of the 1000 km long and up to 600 km wide Baltic

Fig. 1. Ordovician global and regional geological time scales with eustatic curve. Time scale after (Gradstein et al., 2004); global stages after (Bergstrom et al., 2006;Chen et al., 2007); British stages after (Cooper et al., 2001); Baltoscandian regional stages after (Koren’, 2002; Mannil and Meidla, 1994); East Siberian regionalstages (chronozone numbers in parentheses) after (Tesakov et al., 2003); North American groups and eustatic curve modified after (Ross and Ross, 1995).

634 E.V. Artyushkov et al. / Russian Geology and Geophysics 49 (2008) 633–647

sedimentary basin. The basin extends southwestward from theGulf of Finland to the East European Craton margin (Teis-seyre—Tornquist line) and lies upon a Paleoproterozoic(2.5–1.6 Ga) crystalline basement (Gorbatschev and Bog-danova, 1993; Poprawa et al., 1999).

Sedimentation pattern. The Northern Estonian facies zoneof the Baltic basin, about 300 km long and 40–45 km wide(Fig. 2), was a very shallow (<10 m) sea from the LateCambrian to the latest Silurian (Kaljo, 1977; Kaljo and Nestor,1990; Nestor and Einasto, 1997; Pylma, 1982); south of itthere was a deeper sea connected with the Tornquist ocean.The basin accumulated terrigenous sand and clay in the LateCambrian and earliest Ordovician, and carbonates and fineterrigenous sediments from the Arenigian to the latest Silurian.The area has been well documented, with detailed subdivisionof the section provided by abundant fossils (Kaljo and Nestor,1990), and was thus chosen as a standard for stratigraphicscales and facies models. According to paleodepth estimatesreliably constrained by faunas, the earliest Late Cambrian tolatest Silurian deposition was above the fair-weather wavebase (FWB), except few subaerial gaps (Kaljo and Nestor,1990; Nestor and Einasto, 1997; Pylma, 1982). FWB in EarlyPaleozoic shelf basins is usually assumed to be 10–15 m (Brettet al., 1993) but it most likely was within ∼10 m in NorthernEstonia where waves lost energy rapidly on a flat shelf.

The Late Cambrian and the earliest Ordovician (Tremado-cian) in Northern Estonia was the time of slow terrigenous

deposition (Fig. 2) of fine sand and clay in an environmentof very shallow sea depths indicated by abundance of benthicLingula brachiopods (Brett et al., 1993; Boucot, 1975).Burrowed in mud, the animals easily adapted to highlychangeable peritidal conditions with brief freshening, drying,or silting spells. More evidence for shallow-marine conditionsin the Tremadocian comes from widespread algae that werethe source of oil shale (Estonian kukersite).

Deposition from Arenigian to Ashgillian was mainly car-bonate, with pronounced meter-scale cyclicity (of fourth andfifth order) of slightly deeper or shallower sea depths at thebeginning and end of each cycle, respectively. This cyclicityis typical of very shallow seas where even minor water levelfluctuations can cause marked changes to sedimentationpatterns (Johnson and Lescinsky, 1986; Wilson, 1980). Theelementary cycles usually contain numerous mud cracks,ripple marks, stromatolite buildups and mats, and oolite layersin the upper part (Einasto, 1989; Pylma, 1982), i.e., the seafloor was close to the water surface and emerged occasionallyduring low tide. Wave-resistant algal buildups and biohermstypical of above-FWB conditions likewise indicate that the seawas very shallow.

The earliest Arenigian to latest Ordovician interval includesmany sedimentation lulls and gaps, mostly shorter than 1 Myr,which, however, were submarine and left no breaks inbiostratigraphy (Einasto, 1989; Pylma, 1982). The NorthernEstonian sections lack signatures of subaerial gaps (obviously

Fig. 2. Eastern Baltica in Ordovician and Silurian. Sedimentation curves after (Kaljo, 1977; Kaljo et al., 1990; Nestor et al., 2001). Inset shows Ordovician faciespattern, after (Nestor and Einasto, 1997): 1 — land, 2 — shallow sea with depths less than 10 m, 3 — areas where seafloor was below FWB (∼10 m).

E.V. Artyushkov et al. / Russian Geology and Geophysics 49 (2008) 633–647 635

nonmarine basal conglomerates coming from distant sources,or channel incisions, or karstic surfaces); pebble materialfound at different levels is always of local (intraformation)origin. Subaerial deposition was apparently restricted to theTremadocian-Arenigian boundary, and the Hirnantian (latestLate Ordovician).

We use the sedimentation data from Northern Estonia(Fig. 2) to estimate the maximum possible magnitudes ofeustatic fluctuations, with reference to the GTS 2004 timescale (Gradstein et al., 2004) updated according to the recentSOS report (Chen et al., 2007). First we assume that a eustaticevent with the magnitude b has a distinct regression phase(Fig. 3, a)*. Then, the absence of regression means that the

b sea-level fall was less than the sea depth hw0 ; the latter being

under 10 m, b for events of this kind was correspondingly(see Appendix)

b ≤ 10 m (1)

This condition holds throughout the Ordovician, except forthe earliest Arenigian and the Hirnantian. Now we considereustatic fluctuations of the form (Fig. 3, b)

ζeu = −b sin2(πτ), (2)

where b is the fluctuation magnitude and τ = t/T is thedimensionless time. At the beginning and end of an event withthe duration T, τ = 0 and τ = 1, respectively. We assume thatthe crust subsides at a constant rate υ = a/T, where a is thesubsidence in one cycle, and the mean rate of carbonatesedimentation υsd at shallow sea depths (≤10 m) is propor-

tional to the depth h:

υsd = a(h/hw0 )/T. (3)

In the absence of eustatic events h = hw0 and υsd = a/T, i.e.,

sedimentation keeps up with subsidence. A eustatic event ofform (2) changes the sea depth as (Artyushkov and Chek-hovich, 2002)

h = hw0 − {πb/[4π2 + (a/hw

0 )2]}×

[(a/hw0 ) sin2πτ − 2π cos2πτ + 2π exp [−(a/hw

0 )τ]} (4)

if the sea floor never emerges. The latter condition means thatsea depth (4) remains finite and nonzero (h < 0). Therefore,we find the maximum eustatic fluctuation magnitude b = bmax

for the case of submerged crust surface, at hw0 = 10 m and the

a = υ/T ratio known from subsidence curves (Fig. 2), withregard to sediment compaction. The subsidence rate υsd

changed with time (Fig. 2), but remained approximatelyconstant for T = 0–5 Myr in bmax(T) intervals (Fig. 4). Eustaticfluctuations of form (2), with periods T = 1–3 Myr charac-teristic of most third-order cycles, did not exceed 13 m in the488–468.9 and 456–449.3 Ma intervals, when crustal subsi-dence was very slow at 0.5 to 3.7 m/Myr (Fig. 2), and wereno more than 20 m at 449.3–446 and 460–456 Ma whensubsidence accelerated to 12–13 m/Myr. These bmax valuesare far less than the 100–200 m eustatic fluctuations predictedfor the Silurian before the Hirnantian glaciation.

Hirnantian sea-level fall. In the Ashgillian, the shallowNorthern Estonian shelf (Fig. 2) slowly advanced to the southtoward the Southern Estonian deeper part of the Baltic basin(Harris et al, 2004; Kaljo et al., 2001; Nestor and Einasto,1997). The faunal assemblages and carbonate-clay sedimentsrecord sea depths of no more than ∼100–120 m, i.e., belowthe storm wave base (SWB) (∼50 m) but within the open shelf

Fig. 3. Eustatic fluctuations with sharp regressions (a) and harmonic fluctuations (b).

* h is the sea depth, hw0 is the initial sea depth, ∆hw is the eustatic sea-depth change, ∆hw

1 is the eustatic sea-depth change under local isostasy, b is the eustaticfluctuation magnitude, bmax is the maximum possible eustatic fluctuation magnitude, υ is the crustal subsidence rate, υ0 is the average crustal subsidence rate,υ1 is the variable component of the crustal subsidence rate, υsd is the sedimentation rate, ζeu is the eustatic fluctuation, t is the time, T is the eustatic period,τ = t/T is the dimensionless time, a is the crustal subsidence for a eustatic cycle, hchz is the chronozone thickness, tchz is the chronozone duration, (hchz)av is theaverage chronozone thickness, ∆hchz is the deviation of the chronozone thickness from the average, δ is rms deviation of the chronozone thickness from theaverage (percent), Te is the effective elastic thickness of lithosphere, Te

0 is the average effective elastic thickness of lithosphere, ∆Te is the deviation of the effectiveelastic thickness of lithosphere from the average, x is the horizontal coordinate, z is the vertical coordinate, L is the width of anomaly in the effective elasticthickness of lithosphere, ξ is the deviation of lithosphere from isostasy, si0 is the magnitude of the deviation of lithosphere from isostasy, ∆Σ is the change ofadditional horizontal force applied to the lithosphere, ∆l is the shoreline advance (retreat), ϕ is the mean sea-floor slope, ρm is the mantle density, ρsd is thesediment density, ρw is the water density, g is the acceleration due to gravity, RP is the ridge push, c is the porosity, d is the depth at which porosity decreases bya factor of e.


(Kaljo et al., 2001; Nestor and Einasto, 1997; Pylma, 1982).Both areas emerged in the earliest Hirnantian, which causeda brief erosional gap (Fig. 5, a), but soon returned to theenvironments of a very shallow sea in Northern Estonia (A

..rina

Formation in Fig. 5, a) and a 50 to 100–120 m deep openshelf in Southern Estonia (Bernati Member).

The Gondwanian continents experienced glaciation in theHirnantian, with a large ice sheet subject to repeated waxing-waning cycles (e.g., Brenchley et al., 2006; Ghienne, 2003;Hambrey, 1985) accompanied by sea-level fall and rise events,respectively. The sea-level changes in the northern Baltic basin

have exactly this pattern and can be thus attributed to theearliest Hirnantian glaciation (Fig. 5, b). The regression inSouthern Estonia, where the sea depths were from ∼50 to100–120 m, indicates a sea-level fall of at least ∼100 m, oreven more (exact estimates, however, are impossible becausethe true elevation of the area during the regression isunknown).

Very shallow marine deposition persisted till the MiddleHirnantian in Northern Estonia while the area of SouthernEstonia remained an open shelf. Northern Estonia emerged inthe second half of the Hirnantian (Fig. 5, a) and becameexposed to karst formation and secondary dolomitization.The Middle Hirnantian Edole member in Southern Estonia(Fig. 5, a) bears signature of brief regression spells (mudcracks), redeposited ooids, and voluminous terrigenous quartzmaterial (Kaljo et al., 2001) which is evidence of shoaling anddeposition in a very shallow sea. The peritidal environmentpredominated in Southern Estonia in the second half of theHirnantian (Saldus Formation in Fig. 5, a) before the openshelf conditions resumed in the earliest Silurian, synchro-nously with return to shallow-marine deposition in NorthernEstonia (Kaljo, 1977). These sedimentation patterns are con-sistent with a sea-level fall in the Middle-Late Hirnantian.

As we mentioned, the Baltic basin lies upon Paleoprotero-zoic lithosphere, which has an effective elastic thickness ofmore than 70 km (Watts, 2001). Flexure of such a lithosphericlayer under surface loading can span a distance of >200 km.The relatively deep basin part of Southern Estonia was nowider than 200–300 km (Fig. 2), i.e., its half-width (100–150 km) was less than the characteristic width of lithosphericflexure. That is why no isostatic uplift was required tocompensate the regression (emergence), and the sea-depthdecrease was approximately equal to the sea-level fall. Thesea depth in Southern Estonia was more than ∼50 m but lessthan 100–120 m in the first half of the Hirnantian, and becameas shallow as <10 m in the second half. Thus, the sea-levelfall was most likely between ∼40 and ∼100 m, or it may havebeen greater due to ice waxing in the second half of theHirnantian as there were two short subaerial gaps (Fig. 5, a).

Silurian. Shallow-marine carbonate deposition in SilurianNorthern Estonia (Fig. 2) was never interrupted by subaerialgaps (Kaljo, 1977). Crustal subsidence over a great part of the

Fig. 4. Maximum magnitudes (bmax) of harmonic eustatic events inferred fordifferent intervals of Ordovician and Silurian.

Fig. 5. a — Upper Ordovician stratigraphy of Estonia, modified after (Kaljo et al., 2001); b — eustatic events inferred from lithological and stratigraphic data. Verticalhatching shows sedimentation gaps.


area in the 426–420 and 440–431 Ma intervals was at quitea low rate of 3.4 and 4.5 m/Myr, respectively. The correspond-ing maximum magnitudes of eustatic fluctuations of form (2)(Fig. 4) were no larger than bmax = 13 m for T = 3 Myr. Thisinference is in line with the absence of large eustatic eventsin the Silurian hypothesized for East Siberia (Artyushkov andChekhovich, 2002, 2004).

East Siberia

Deposition in northwestern East Siberia. The Ordoviciansection at sites 1–4 (Fig. 6) reaches a thickness of 1300 m(Fig. 7). From the latest Cambrian to the earliest MiddleCaradocian it was carbonate sedimentation (Tesakov et al.,2003), with biota and stacking patterns similar to those inNorthern Estonia. Widespread variegated clastic and finelimestones, primary dolomites, often gypsum-bearing, anddolomite marls (domerites) typical of shallow peritidal envi-ronments indicate deposition without subaerial gaps, on a flatshallow upper shelf and in restricted lagoons at sea depths lessthan 10 m. Dolomites and domerites often bear mud cracksproduced by brief drying in the peritidal zone. The sea depthsof ≤10 m can be also inferred from buildups and mats ofbiohermal stromatolites and oolitic and ooidal limestones, andrather poorly diverse (brachiopods, trilobites, and gastropods)and suppressed faunas. The sea grew deeper in the earliestCaradocian but the younger shelf deposits were eroded duringa Late Ordovician uplift and left Lower Silurian sediments tolie immediately upon the Upper Caradocian strata.

The Tremadocian-Arenigian transition in sections 1–4 andin the stratotype section along the Kulyumbe River (Sokolov,1982) is continuous, which indicates the absence of anyeustatic event. Therefore, the subaerial gap between theTremadocian and the Arenigian in Northern Estonia may beattributed to a small crustal uplift soon followed by subsi-dence. The transition from the Cambrian to the Ordovicianlikewise appears continuous in shallow-marine facies exposedin the Kulyumbe section, and this casts doubt on the eustaticevent assumed commonly to mark the Cambrian-Ordovicianboundary (Cooper et al., 2001; Erdtmann, 1986; Finney andEthington, 2000; Fortey, 1984).

Duration of Ordovician chronozones and their timescale implications. The Ordovician section of East Siberiawas divided into 52 regional stratigraphic units (cycles orchronozones) corresponding to biochrons (biological zones)proceeding from abundant faunal evidence (global and re-gional species) and from correlation of sedimentation patterns(Tesakov et al., 2003). Shallow-marine sediments of first 30zones are found at sites 1–4 (Fig. 6). Ordovician carbonateswere quite strongly compacted under the overlying sedimen-tary strata and flood basalts, and in this study we assume acompaction by a factor of 1.18 (see Appendix). With thisassumption, the initial thicknesses of first 30 zones (hchz) asshown in Fig. 8 are used to estimate their duration (tchz) andcrustal subsidence rates (υ) by comparing their variations indifferent sections.

There are several intervals (Fig. 8) of quite small relativehchz changes. Let the deviation of zone thickness from theaverage (gray bands in Fig. 8) be ∆hchz = hchz − (hchz)av. Atshallow sea depths, hchz = υtchz. The subsidence rate υdepends on tectonic regime in each specific area, and the zoneduration tchz is constrained by fauna changes on global andregional (over East Siberia) scales. The parameters υ and tchzwhich represent two different processes which are independentif the sea depths remain within ∼10 m. Therefore, the changesin both subsidence rate (υ) and zone duration (tchz) were minorat the intervals of relatively stable zone thicknesses∆hchz/(hchz)av (Fig. 9).

The average zone thickness in an interval of n zones is(hchz)av = Σi(hchz)i/n. The ratio (δ, %) of the rms deviation of

zone thickness Σi {[(hchz)i − (hchz)av]2/n}1/2 to the averagethickness (hchz)av is shown in Fig. 9 for each interval as

δ = Σi {[(hchz)i − (hchz)av]2/n}1/2/(Σi hchz)/n. This ratio is small(δ = 4−10%) in most intervals that include 3 to 16 zones,though it reaches 52% at the Ledyanka site in the short intervalof zones 11–14, where sediments of zones 11 are almostabsent (Fig. 8), possibly because the slow deposition abruptlybecame still slower for a short while.

Fig. 6. Location map of Lower and Middle Ordovician shallow-marine sectionsin East Siberia. 1–4: sites in northwestern East Siberia: Igarka (1), Noril’sk (2),Ledyanka (3), Maimecha (4); 5–9: sites in western Irkutsk amphitheater: Vik-horeva River catchment (5), Ust’-Ilim Roadway (6), Tulun Roadway (7), Nizh-neudinsk area (8), Kova River mouth area (9); 10–14: sites in Lena facies zone:Ust’-Kut area (10), Kirensk area (11), Polovinka Village area (12), Nyuya River(13), Tochilino Village area (14).


The ratio δ does not exceed 10% at the sites where bothzone duration (tchz) and subsidence rate (υ) change insignifi-cantly. For instance, it is low (9%), in the interval of zones11–20 in Igarka and during zones 15–30 in Maimecha, i.e.,with the overlap of two intervals in zones 15–20, the zoneduration did not change much through the 11–30 span.

The zone thicknesses (hchz) change abruptly at all four sitesat points I and II, between zones 3 and 4 and 10 and 11(Fig. 8). We estimate the hchz change as a total thickness ratioof two following zones (hchz)2 to two preceding zones(hchz)1 – (hchz)2/(hchz)1 (Table 1), assuming that the zonethickness and duration change by the same factor, thesubsidence rate being constant. This is a reasonable assump-tion because the zone thickness is controlled either bysubsidence rate (υ) at invariable zone duration (tchz) or by tchzat constant υ; the two parameters do not correlate, and theirsynchronous changes which would cancel in the product(υtchz = hchz) are very unlikely. The thickness ratios differstrongly at points I and II (Table 1). Judging by their scatter,it was the subsidence rate that changed rather than the zoneduration, and the change magnitudes were different at the foursites. Furthermore, υ changed within very short spells nolonger than the zone duration tchz.

Thus, zones 1–30 spanned a total of 25 Myr and remainedof almost invariable duration of about 0.83 Myr on average,which is comparable with the length of the Tremadocian,Floian, and Dapingian stages (Gradstein et al., 2004) corre-sponding to chronozones 10, 8 and 6, respectively, of EastSiberia (Fig. 1). The following 28 zones (25–52) span 24 Myrand have a similar average duration of tchz = 0.86 Myr.

Southern Siberian craton. Sections of very shallowmarine sediments (Kanygin et al., 1989; Sokolov, 1984) areknown from the Irkutsk amphitheater and from the Lena facieszone (sites 5–9 and 10–14 in Fig. 6, respectively). Mostsections comprise Upper Cambrian and Ordovician strata to

the Middle Caradocian (Fig. 10). Cambrian terrigenous depo-sition was in a highly saline lagoon connected in the northwith a shallow sea of normal salinity, and the shallow seafloor emerged frequently in brief events recorded in numerousmud cracks and prints of salt crystals.

Normal marine conditions set in since the earliest Ordovi-cian and persisted as long as the Early Caradocian, withoutsignificant subaerial gaps. In the Tremadocian, the southernSiberian craton was an area of shallow-marine carbonatedeposition (Ust’-Kut Formation) at high-energy waves. Thesignatures of shallow sea depths are abundant stromatolites(stromatolite bioherms, spherolites, and oolites) and typicalbeach heavy minerals in the terrigenous component of sedi-ments, while wave energy shows up in plane to wavy,lenticular, or cross lamination, and rounded mudrocks.

Crustal subsidence in the Tremadocian was at quite a lowmean rate, especially in the Lena zone and in the northernIrkutsk amphitheater (≤20 m/Myr in the Nyuya River area and∼4 m/Myr at the Polovinka Village site). The transition fromterrigenous Cambrian to carbonate Ordovician deposition issmooth in all sections and appears as alternating variegatedterrigenous and carbonate rocks within an interval of severalmeters thick. This rules out any eustatic event at the Cam-brian-Ordovician boundary given the shallow sea depth andslow subsidence.

The Lena zone remained an area of shallow marinesedimentation till the Middle Caradocian, and carbonatedeposition in the Irkutsk amphitheater gradually changed tothat of terrigenous fine and medium sand, silt, and clay sincethe earliest Arenigian. Shallow sea depths in both areas arerecorded in poor diversity and low numbers of benthiccommunities and abundance of mud burrowers, such asinarticulate brachiopods (lingulid, obolus, etc.). The absenceof subaerial gaps at the Tremadocian-Arenigian boundarymeans the absence of marked eustatic events. A subaerial gap

Fig. 7. Curves of Ordovician sedimentation at sites 1–4 in northwestern East Siberia, after (Tesakov et al., 2003). See Fig. 6 for location of sites.


Fig. 8. Thicknesses of Ordovician zones 1–30 at sites 1–4 in East Siberia, after (Tesakov et al., 2003). Gray color shows average chronozone thicknesses over intervalswhere they remained almost invariable. See Fig. 6 for location of sites.


(karstic surfaces and weathering mantle) at the Ilim site of theIrkutsk amphitheater was apparently due to a small crustaluplift.

In the Middle Caradocian crustal subsidence accelerated(Kanygin et al., 1989; Sokolov, 1984), and the sea depthdeepened to below SWB (≥50 m) throughout the area.

Possible magnitude of third-order eustatic fluctuations.We can check whether the absence of large eustatic events inthe Early-Middle Ordovician inferred from Northern Estoniandata is valid for East Siberia. Marine sedimentation innorthwestern East Siberia in the first half of the Ordovicianlikewise was at a depth of ≤10 m, without subaerial gaps, i.e.,the magnitude of sea-level change with a sharp regressivephase did not exceed ∼10 m. The maximum possible magni-tude bmax of form (2) events were estimated using data fromthe Maimecha River sections where crustal subsidence wasthe slowest (Fig. 11). Crustal subsidence in East Siberia wasmuch more rapid than in Northern Estonia, and the corre-sponding bmax for T = 3 Myr are times greater (17–28 m),but are still far below the predicted ∼100−200 m events (Rossand Ross, 1995).

Causes of subsidence rate change in northwesternEast Siberia

The rate of crustal subsidence changes abruptly at pointsI–VI (Fig. 8), becoming faster at I, III and IV and slower atII simultaneously in all areas. Unlike these concordantchanges, υ at point V increases notably at the Igarka andNoril’sk sites but slightly decreases in Ledyanka and Mai-mecha; at VI, subsidence slows down only in Igarka; at II thezone thicknesses are 50 m in the area of Noril’sk and about30 m in Igarka and Ledyanka. The thickness contrasts aremuch above the ≤10 m sea depth and must be due to causesother than deposition deficit relative to the previous subsi-dence. Zone thicknesses differ also in some intervals wherehchz is only weakly variable: zone 8 is 30 m thicker than zone7 in the Igarka section (Fig. 8), and the subsidence rate thuschange within no longer than ∼0.8 Myr. In other intervals, onthe contrary, the difference is minor (zones 1–3 at all sites,zones 4–10, 11–14, and 15–30 in Maimecha, 15–20 and 21–28in Ledyanka, and 11–20, 21–25, 26–28, and 29–30 in Igarka),i.e., subsidence was at approximately same rate.

The total Ordovician crustal subsidence in northwesternEast Siberia was quite large (Figs. 7, 10), more than 1 km in

Fig. 9. Intervals of Early and Middle Ordovician where chronozone thicknesses remained almost invariable.

Table 1Points of abrupt change of chronozone thicknesses (Lower and Middle Ordovician, East Siberia)

Site Points (I–VI), numbers of adjacent zones

I II III IV V VI

3-4 9-10 14-15 20-21 25-26 28-29

1. Igarka 1.5 0.42 1.17 1.4 1.41 0.58

2. Noril’sk 1.24 0.3 1.34 1.4 1.28 0.97

3. Ledyanka 2 0.19 1.56 1.36 0.94 0.8

4. Maimecha 1.94 0.4 1.6 1.14 0.91 1.05

Note. Magnitudes of changes are estimated as total thickness ratio of two following to two preceding zones, at all sites.


the areas of Noril’sk and Igarka. This amount of subsidencein a 1 Ga old cold platform was possible only by densityincrease in the mafic lower crust as a result of metamorphicphase change from gabbro to garnet granulite (Artyushkov,

1993; Artyushkov and Chekhovich, 2004). To check thishypothesis, we first assume, as it is often done (e.g., Burgesset al., 1997), that eclogitization-driven subsidence was at aconstant rate (υ0) but could depart from uniformity wheninterfered with uplift (subsidence) related to other mecha-nisms.

We investigated the deviations from uniform crustal subsi-dence (Fig. 12 for sites 1–4) in Fischer plots (Diecchio andBrodersen, 1994; Fischer, 1964) based on thicknesses ofshallow-marine sediments deposited during zones 1–30 (Ar-tyushkov and Chekhovich, 2004) and found them to be aslarge as 230 m in Noril’sk and 140 m in Igarka. Below wediscuss possible causes of this nonuniformity.

Flexural response of lithosphere to horizontal stresschange. The lithospheric thickness is most often laterallyvariable. Forces applied along a lithospheric plate warp it upor down (Artyushkov, 1974, 1979), and the amount ofdisplacement is controlled by the force magnitude, which is acommonly invoked mechanism of crustal uplift or subsidence(Cloetingh et al., 1985; Nikishin et al., 1996). Let the effectiveelastic thickness of lithosphere Te (Burov and Diament, 1995)

change along the x axis as Te(x) = Te0 + ∆Tesin (πx/: L). Then,

a Σ change in the force ∆Σ applied along the lithospheric platecauses the vertical displacement ζ ≈ ζ0sin(πx/L) (Artyushkovet al., 2000; Artyushkov and Chekhovich, 2004), where

ζ0 = π2∆Σ ∆Te/[2(ρm − ρsd)gL2]. (5)

Here ρm = 3350 kg/m3 is the mantle density, ρsd is the

sediment density, and g = 9.81 m/s2 is the acceleration dueto gravity. If the nonuniformity of crustal subsidence (Fig. 12)is assumed to be due to in-plane force change, synchronousυ increase or decrease at points I–IV indicates, to a largeprobability, that sites 1–4 (Fig. 6) may belong to the samezone of high or low Te. The nonuniformity of subsidence(Fig. 12) increases from east to west, from Maimecha toLedyanka, to reach the maximum in Noril’sk (note thatMaimecha is apparently at the margin and Noril’sk in thecenter of the Te zone). Thus, the distance between the twosites (500 km) roughly corresponds to the half-width of thezone which then has a total width of L ≈ 1000 km. Assume

Fig. 10. Curves of Ordovician sedimentation in southern East Siberia, after (Kanygin et al., 1989; Obut, 1984).

Fig. 11. Maximum magnitudes (bmax) of harmonic eustatic events inferred fordifferent intervals of first half of Ordovician, after (Tesakov et al., 2003).


that the in-plane force change ∆Σ has the same order ofmagnitude as the ridge push (mean pressure of spreading

oceanic ridges on the adjacent plates) RP ≈ 2⋅1012 N/m(Artyushkov, 1979; Harper, 1986). The lateral variations of Teon the old platform of East Siberia hardly exceeded2∆Te ≈ 20−30 km, which corresponds to ∆Te = 10−15 km.

Substituting into (5) the mean density of limestone in the firsthalf of the Ordovician assumed to be ρsd = 2400 kg/m3 and

L ≈ 1000 km gives the disequilibrium

ζ0 ≈ 11−16 m. (6)

This deviation from uniform subsidence is an order ofmagnitude lower than the real values. To provide a ∼ 230 mdeparture from isostasy, ∆Σ should far exceed additional forcesand the forces Σ on platforms, or the variations in lithosphericeffective elastic thickness should be more than the thickness

itself, which is also unlikely. Therefore, the flexural responseto horizontal stress change hardly can have changed the crustalsubsidence rates in Ordovician northwestern East Siberia.

Effective elastic thickness of lithosphere is different onpassive oceanic margins, but, according to recent geodynamicreconstructions (Nokleberg et al., 2004), northwestern EastSiberia was located 500–600 km away from the passivemargin complexes which currently occur in Central Taimyr.With the ∼200−300 km characteristic width of lithosphericflexure, deformation at the passive margin could not cause anysignificant influence on crustal movements.

Variations of dynamic mantle topography. Now wecheck another mechanism that may be responsible for time-dependent variations in crustal subsidence rate on platforms,that is vertical deflection of the asthenospheric top from theequilibrium (the so-called dynamic topography) controlled bymantle flow over subducting oceanic plates (Burgess et al.,1997). In the Ordovician, subduction occurred in the Sayanarea south of the Siberian craton (in the present frame ofreference) (Sengör and Natal’in, 1993) ∼2000 km far fromsites 1–4 (Fig. 6). Deformation caused by changes in theposition, slope, and rate of subduction normally decreasesaway from the collision front, which is northward in the caseof East Siberia. The nonuniformity of subsidence was, how-ever, large and varying strongly in the W-E direction (Figs. 8,12), being thus hardly related to subduction parameters.

Eclogitization in the lower crust. Subsidence in the areasof Noril’sk and Igarka (Fig. 8) was times faster than inMaimecha and Ledyanka. This difference was most likely dueto metamorphic phase change in the lower crust whichmaintained regional crustal subsidence.

The rate of gabbro-to-eclogite transition grows rapidly withtemperature, especially in the presence of even minor amountsof aqueous fluid (Ahrens and Schubert, 1975; Austrheim,1998). Yet, the temperature of cratonic lithosphere with acharacteristic time of thermal relaxation of ∼100 Myr stayedalmost invariable for ∼1 Myr in Ordovician East Siberia andthere was no way of fluid supply (neither dissolution ofhydrous minerals in the lower crust nor arrival of smallfluid-bearing mantle plumes at the lithospheric base whichwould show up as swelling). Thus, there remains one plausiblecontrol of eclogitization rate, that is lithospheric stress able tochange rapidly simultaneously in geographically dispersedareas (Artyushkov and Chekhovich, 2004). Eclogitization canspeed up or slow down by opening or closure of cracksassociated with shear stress change which drive fluids fromone zone to another under lithostatic pressure.

Rapid crustal uplift and subsidence on platforms

Thus, we infer that, except for a brief spell of theGondwanian glaciation, 1–3 Myr sea-level change neverexceeded ∼20 m in the Ordovician, though it was the time oflarge regressions and transgressions in many platform areas.The regression and transgression events at a stable sea levelwere rather caused by rapid crustal uplift and subsidence. Forinstance, the eustatic curve for North America (Fig. 1) includesthree regression events in the Early Ordovician (Tremadocian

Fig. 12. Deviations from uniform crustal subsidence at sites 1–4 in East Siberia.Plots are based on thicknesses of chronozones, after (Tesakov et al., 2003), withduration about 0.8 Myr in all sections. See Fig. 6 for location of sites.


and first half of Arenigian) in which the platform rose over200 m above the sea level. During a regression at theEarly-Middle Ordovician boundary (about the middleArenigian), the platform stood ∼160 m above the sea level,and the high stand, overprinted with rapid ∼100 m uplift andsubsidence events, continued all the Middle Ordovician longand led to erosion of carbonate shelves (Ross et al., 1989). Inthe Late Ordovician, the platform was mostly low relative tothe sea level, and there were several 100–200 m regressions.Many epeiric basins elsewhere are known to dry out in theMiddle Ordovician, namely, in Australia (Goiter, 1992), SouthAnatolia (Dean and Martin, 1992), and Western Argentina(Beresi, 1992). The regressions in those areas might beattributed to a large eustatic sea-level fall, but this interpreta-tion contradicts the existence of shallow-marine facies at theEarly-Middle Ordovician boundary in Northern Estonia andEast Siberia.

Implications for depositional oil and gas traps in epeiric basins

Regression and shelf emergence in 1–3 Myr cycles werequite frequent events in epeiric basins. The regression envi-ronments were favorable for oil and gas traps to form nearthe shoreline due to deposition of porous sands on emergedshelves and in channels (Posamentier and Allen, 2000), sandlenses, which often became capped later by clay, and turbiditesspread along the slope toe. Large depositional traps of thisorigin are known, for instance, in the Achimovka Member inWest Siberia (Borodkin et al., 2003; Brekhuntsov et al., 2003;Vyssotski et al., 2006).

According to geological and seismic-stratigraphic evidence(e.g., Haq et al., 1987), epeiric sea often advanced orbackstepped for distances of more than 100–200 km within∼1 Myr. Thus, prospecting for depositional traps requires theknowledge of shoreline location in respective periods. Largeshoreline displacement has been commonly attributed toeustatic sea-level change. If this is true, a sea-level change of∆hw, at the average seafloor slope ϕ (Fig. 13), would causemigration to the distance

∆l = ∆hw cot ϕ. (7)

The seafloor being flat along the margins of many epeiricbasins, 100–200 m sea-level rise or fall can provide 100–200 km or longer shoreline displacement, for example,∆l = 172 km at ∆hw = 150 m, ϕ = 3′, and cot ϕ = 1146.

Assuming the eustatic sea-level change to be globallyuniform and applying (7) to estimate ∆hw for any basin oneobtains the direction and amount of shoreline migration forany other basin where the slope ϕ is known, which makesprediction for eustatic depositional traps very easy.

Earlier we inferred from East Siberian and Estonian datathat third-order eustatic events in Cambrian and Silurian timenever exceeded a few tens of meters (Artyushkov et al., 2000;Artyushkov and Chekhovich, 2001, 2002), and, as we showin this study, were about the same magnitude also over mostof the Ordovician, except for two brief events of ∼100 m fallin the latest Ordovician.

Thus, there were almost no large third-order eustaticfluctuations in the Early Paleozoic for a time span of 126 Myr,i.e., during a quarter of the Phanerozoic. We chose theOrdovician to profit from the availability of detailed geologi-cal data, but the absence of large eustatic events may beproven in the same way for other Phanerozoic periods. Thisinference has important petroleum prospecting implications asprediction for depositional traps becomes no longer simple.On the contrary, it requires studying the tectonic setting,including sea depth changes, shoreline retreat and advance,and crustal uplift (subsidence) in the sediment provenance,separately for each basin, because the paleo-depths changedasynchronously and for different magnitudes.

Basic results and discussion

The idea of frequent 1–3 Myr long eustatic events withmagnitudes from 20 to 200 m reported in many publications(e.g., Haq et al., 1987; Hardenbol et al., 1998) has becomecommon knowledge or even the basic paradigm (Miall andMiall, 2001). Several such events were suggested also for theOrdovician (Fig. 1) (Ross and Ross, 1995). However, we inferfrom the available geological evidence that, except for the∼100 m sea-level fall associated with the Hirnantian glaciation,third-order sea-level fluctuations remained within a few tensof meters over 42 Myr of the Ordovician. Together with theCambrian (Artyushkov et al., 2000) and the Silurian (Ar-tyushkov and Chekhovich, 2002, 2004), eustatic stabilityspanned 126 Myr (Gradstein et al., 2004), which casts doubton the existence of multiple eustatic events in the Paleozoic(Hallam, 1992), at least in the Early Paleozoic.

Brief glaciations may be expected to have occurred beforethe Hirnantian, by analogy with the Pliocene and Pleistocenecold spells of less than 100 Kyr (Crowley and North, 1991),but they left no signature of erosion or karst surfaces in EastSiberia and Northern Estonia.

We estimated the duration of Ordovician chronozones(biochrons) by comparing their thicknesses in East Siberiansections (Tesakov et al., 2003) from areas that experiencedcrustal subsidence at different rates and obtained an almostinvariable value of ∼0.8 Myr. These estimates, along with thedurations of Silurian zones (Tesakov et al., 2000) of ∼0.5 Myr(Artyushkov and Chekhovich, 2004), allow updating theexisting time scale (Gradstein et al., 2004) due to more exactconstraints on the lengths of stratigraphic units and on theintervals between tectonic events. The same approach may be

Fig. 13. Shoreline advance and retreat (∆l) in an epeiric basin associated with aeustatic event of ∆hw. ϕ is average seafloor slope.


useful to update the chronology of other Phanerozoic periodsas well.

Proceeding from the quasi-periodicity of chronozones, werevealed rapid (in ≤0.8 Myr) changes in crustal subsidencerates varying geographically in magnitude, in the Ordovicianas well as in the Silurian. This is an unexpected discovery forplatforms which are commonly believed to be tectonicallystable. The abrupt subsidence rate changes were most likelyassociated with density variations in the mafic lower crust asa result of metamorphic phase change. In the absence offluid-bearing mantle plumes at the lithospheric base, the rateof metamorphic reactions may be controlled by lithosphericstress change and ensuing redistribution of the fluid catalysts.The same processes possibly occurred also in other sedimen-tary basins but they remain hidden for low resolution ofregional time scales.

Frequent large regression and transgression events knownin many platform Ordovician basins on different continents,given the relatively stable sea level over most of the period,may be related to multiple events of 100–200 m crustal upliftand subsidence. At some stratigraphic levels, these events wereglobally synchronous, namely, a regression at the Early-Mid-dle Ordovician boundary and a transgression at the Middle-Late Ordovician transition. Global-scale synchronicity of theseevents in other Phanerozoic periods inspired the idea of theireustatic origin. This, however, appears doubtful as theirmagnitudes vary geographically, though eustatic change is stillthe mechanism most often invoked to explain regressions andtransgressions.

According to our earlier (Artyushkov et al., 2000; Ar-tyushkov and Chekhovich, 2002, 2004) and present results,basins of shallow-marine deposition with almost stable seadepths existed at the time of regressions and transgressionselsewhere. Therefore, those regressions and transgressionswere driven by crustal uplift or subsidence rather than beingeustatic events. In this respect, there arises another seriousproblem, that of the mechanism responsible for rapid uplift orsubsidence of different magnitudes which acted synchronouslyor almost synchronously in many regions but not everywhere.

Rapid sea depth changes were favorable for the formationof numerous depositional oil and gas traps, with their locationdepending on the shoreline position. Our results, however,undermine the basic idea behind the prospecting strategy forthese traps which turn out to be controlled by regional-scalecrustal uplift and subsidence rather than by eustatic fluctua-tions.

The study was supported by grant 06-05-65197 from theRussian Foundation for Basic Research and was carried outas part of Program ESD-1 of the Earth Science Departmentof the Russian Academy of Sciences.

AppendixEstimating maximum possible magnitudes of eustatic events

Sea-depth changes in sedimentary basins are accompaniedby isostatic crustal motion. The sea-depth change of themagnitude b in a large basin is

∆hw1 = [ρm/(ρm − ρw)]b, (A.1)

where ρm is the mantle density and ρw is the water density.

At ρm = 3350 kg/m3 and ρw = 1030 kg/m3,

b = 0.69∆hw1 . (A.2)

Seafloor located at the depth hw0 below the water surface

emerges by the sea-level fall ∆hw > hw0 . The sea depths in

Northern Estonia remained within ∼10 m all along theOrdovician and the sea floor never emerged, except theTremadocian-Arenigian and Hirnantian regressions. Then,according to (A.2), the magnitude of regression could notexceed ∼7 m.

Northern Estonia lying on the Ordovician basin marginmust have experienced smaller eustasy-related regional loadchange than elsewhere in the large basin, and a eustaticsea-level fall caused a slightly greater ∆hw decrease there.

More rigorous constraints on the ∆hw1 −b relationship are

impossible the configuration of the Ordovician basin and thepattern of the effective elastic thickness of lithosphere (Burovand Diament, 1995) being uncertain. Therefore, we confine

ourselves to the condition b ≤ hw1 , which implies overestimated

b. With hw0 ≈ 10 m, the uncertainty in b estimates will be no

more than a few meters, which is far below the hypotheticalmagnitudes of Ordovician eustatic events (Ross and Ross,1995).

Ordovician sediments in Northern Estonia were compactedunder the overlying Silurian and Devonian strata. The latterwere no more than 300–400 m thick and were eroded later,as follows from the available maps of Paleozoic sedimentthicknesses (Puura et al., 2003) and drilling evidence (Nestoret al., 2001). The change of porosity (c) with depth (z) isusually estimated as (Korvin, 1984):

c(z) = c(0) exp (−z/d), (A.3)

where c(0) is the porosity on the surface and d is thecharacteristic rock depth. These values are often assumed tobe c(0) ≈ 0.4 and d ≈ 4 km for Tremadocian sands (Ershovet al., 1998; Sclater and Christie, 1980) and c(0) ≈ 0.2,d ≈ 2.6 km for limestones deposited since the Arenigian.Compaction at a depth of 0.5–0.6 km is 5–6% in sand and∼4% in limestone, with the average of 5% for the Tremadocianand Arenigian, 4% for the second half of the Llanvirnian tothe first half of the Caradocian, and 3.3% for the higherOrdovician units.

Quite strong compaction of Lower and Middle Paleozoiccarbonates in East Siberia was provided by thick traps, whichwere then denuded. At sites 1–4 the current porosity ofSilurian carbonates is estimated at 5% (Sokolov, 1992), andthe porosity of the underlying Ordovician strata must be lower.Assuming it to be 3 % in the first half of the Ordovician, wearrive at a compaction of 1.2 times at an initial porosityof 20%.


References

Ahrens, T. J., Schubert, G., 1975. Gabbro-eclogite reaction rate and itsgeophysical significance. Rev. Geophys. Space Phys. 13, 383–400.

Artyushkov, E.V., 1974. Can the Earth’s crust be in a state of isostasy?J. Geophys. Res. 79, 741–752.

Artyushkov, E.V., 1979. Geodynamics [in Russian]. Nauka, Moscow.Artyushkov, E.V., 1993. Physical Tectonics [in Russian]. Nauka, Moscow. Artyushkov, E.V., Chekhovich, P.A., 2001. The East Siberian basin in the

Silurian: Evidence for no large-scale sea-level changes. Earth Planet. Sci.Let. 193, 183–196.

Artyushkov, E.V., Chekhovich, P.A., 2002. Silurian deposition in East Siberiaand the absence of large-scale eustatic fluctuations. Geologiya i Geofizika(Russian Geology and Geophysics) 43 (10), 893–915 (839–862).

Artyushkov, E.V., Chekhovich, P.A., 2004. Mechanisms of sea depth changesin Silurian epeiric basins of East Siberia. Geologiya i Geofizika (RussianGeology and Geophysics) 45 (11), 1273–1291 (1219–1236).

Artyushkov, E.V., Chekhovich, P.A., Tarling, D.H., 2003. The origin ofwater-depth changes in past epeiric seas. Doklady Earth Sci. 388 (1), 21.

Artyushkov, E.V., Kanygin, A.V., Tesakov, Yu.I., Chekhovich, P.A., 2007.Sea level in the Ordovician: sharp fluctuations in subsidence rates of theSiberian craton crust. Doklady Earth Sci. 412 (1), 53.

Artyushkov, E.V., Lindström, M., Popov, L.E., 2000. Relative sea-levelchanges in Baltoscandia in the Cambrian and early Ordovician: thepredominance of tectonic factor and the absence of large-scale eustaticfluctuations. Tectonophysics 320, 375–407.

Austrheim, H., 1998. Influence of fluid and deformation on metamorphismof the deep crust and consequences for the geodynamics of collision zones,in: Hacker, B.R., Liou, J.G. (Eds.), When Continents Collide: Geody-namics and Geochemistry of Ultrahigh-Pressure Rocks. Kluwer, Dor-drecht, pp. 297–323.

Badenas, V., Salas, R., Aurell, M., 2004. Three orders of regional sea-levelchanges control facies and stacking patterns of shallow platform carbon-ates in the Maestrat Basin (Tithonian-Berriasian, NE Spain). Intern.J. Earth Sci. 93, 144–162.

Beresi, M. S., 1992. Ordovician cycles and sea level fluctuation in thePrecordillera Terrane, western Argentina, in: Webby, B.D., Laurie, J.R.(Eds), Global perspectives on Ordovician geology. Balkema, Rotterdam,pp. 337– 344.

Bergström, S.M., Finney, S.C., Chen, X., Goldman, D., Leslie, S.A., 2006.Three new Ordovician global stage names. Lethaia 39 (3), 287–288.

Borodkin, V.N., Brekhuntsov, A.M., Nesterov, I.I., Nechepurenko, L.V., 2003.Regional geological models of the Neocomian clinoform complex innorthern West Siberia. Bull. VNIIOENG (Geology, Geophysics, andDevelopment of Oil and Gas Fields) 4–5, 50–61.

Boucot, A.J., 1975. Evolution and Extinction Rate Controls. Elsevier,Amsterdam.

Brandano, M., Corda, L., 2002. Nutrients, sea level and tectonics: constrainsfor the facies architecture of a Miocene carbonate ramp in central Italy.Terra Nova 14 (4), 257–262.

Brekhuntsov, A.M., Taninskaya, N.V., Shimanskii, V.V., Khafizov, S.F.,2003. Lithology and facies criteria of petroleum prediction for theAchimovka Member, East Urengoi zone. Geologiya Nefti i Gaza 3, 2–10.

Brenchley, P.J., Marshall, J.D., Harper, D.A.T., Buttler, S. J., Under-wood, C.J., 2006. A late Ordovician (Hirnantian) karstic surface in asubmarine channel, recording glacioeustatic sea-level changes: Meifod,central Wales. Geol. J. 41, 1–22.

Brett, C.E., Boucot, A. J., Jones, B., 1993. Absolute depths of Silurian benthicassemblages. Lethaia 26, 25–40.

Burgess, P.M., Gurnis, M., Moresi, L.N., 1997. Formation of sequences inthe cratonic interior of North America by interaction between mantle,eustatic, and stratigraphic processes. Geol. Soc. Amer. Bull. 109, 1515–1535.

Burov, E.B., Diament, M., 1995. The effective elastic thickness (Te) of thecontinental lithosphere: What does it really mean? J. Geophys. Res. 100,3095–3927.

Chen, X., Gutierrez-Marco, J.C., Albanesi, G.L. 2007. Subcommission onOrdovician Stratigraphy (SOS) Annual Report for 2005. Ordovician News24, 1–4.

Cloetingh, S., McQueen, H., Lambeck, K., 1985. On a tectonic mechanismfor regional sea level variations. Earth Planet. Sci. Lett. 51, 139–162.

Cooper, A., Nowlan, G.S. (Eds.), 1999. Proposed Global Stratigraphic Sectionand Point for Base of the Ordovician System. International Working Groupon the Cambrian-Ordovician Boundary. Circular March, Calgary.

Cooper. R.A., Nowlan. G.S., Williams, S.H., 2001. Global stratotype and pointfor base of the Ordovician System. Episodes 24 (1), 19–28.

Crowley, T.J., North, G.R., 1991. Paleoclimatology. Oxford Univ. Press, NewYork

Dean, W.T., Martin, F., 1992. Ordovician biostratigraphic correlation insouthern Turkey, in: Webby, B.D., Laurie, J.R. (Eds), Global Perspectiveson Ordovician Geology. Balkema, Rotterdam.

Diecchio, R.J., Brodersen, B.T., 1994. Recognition of regional (eustatic?) andlocal (tectonic?) relative sea-level events in outcrop and gamma-ray logs,Ordovician, West Virginia, in: Dennison, J.M., Ettensohn, F.R. (Eds.),Tectonic and Eustatic Controls on Sedimentary Cycles: SEPM Conceptsin Sedimentology and Paleontology, pp. 171–180.

Dronov, A.V., Koren, T.N., Popov, L.E., Tolmacheva, T.Ju., Holmer, L.E.,1995. Uppermost Cambrian and Lower Ordovician in northwestern Russia:sequence stratigraphy, sea level changes and bio-events. Ordovicianodyssey, in: Cooper, J.D., Droser, M.L., Finney, S.L. (Eds.), Short Papersfor the 7th Int. Symp. Ordovician System. Pacific Section, SEPM,Fullerton, CA, pp. 319–322.

Einasto, R.E., 1989. A system of gaps in the Northern Baltic Silurian sections,in: Sokolov B.S. (Ed.), Geology and Paleontology [in Russian]. Nauka,Leningrad.

Erdtmann, B.D., 1986. Early Ordovician eustatic cycles and their bearing onpunctuations in early nematophorid (planctic) graptolite evolution, in:Walliser, O.H. (Ed.), Global Bio-Events: Lecture Notes in Earth Sciences8. Springer-Verlag, Berlin-Heidelberg, pp.139–152.

Ershov, A.V., Brunet, M.-F., Nikishin, A.M., Bolotov, S.N., Korotaev, M.V.,Kosova, S.S., 1998. Evolution of the Eastern Fore-Caucasus basin duringthe Cenozoic collision: Burial history and flexural modeling, in: Crasquin-Soleau, S., Barrier, E. (Eds.), Epicratonic Basins of Peritethian Platforms.Peri-Tethys Memoir 4. Mémoires du Musée National d’Histoire Naturelle179, Paris, pp. 111–130.

Finney, S.C., Ethington, R.L., 2000. Global Ordovician series boundaries andglobal event biohorizons, Monitor Range and Roberts Mountains, Nevada.Geol. Soc. Amer. Field Guide Ser. 2, 301–318.

Fischer, A.G., 1964. The Lofer cyclothems of the Alpine Triassic. KansasGeol. Surv. Bull. 169, 107–149.

Fortey, R.A., 1984. Global earlier Ordovician transgressions and regressionsand their biological implications. Aspects of the Ordovician System, in:Bruton, D.L. (Ed.). Palaeontol. Contrib. Univ., Oslo 295, pp. 37–50.

Ghienne, J.-F., 2003. Late Ordovician sedimentary environments, glacialcycles, and post-glacial transgression in the Taoudeni Basin, West Africa.Palaeogeogr., Palaeoclimatol., Palaeoecol. 189, 117–145.

Goiter, J. D., 1992. Ordovician petroleum in Australia in relation to eustasy,in: Webby, B.D., Laurie, J.R. (Eds), Global Perspectives on OrdovicianGeology. Balkema, Rotterdam, pp. 433–443.

Gorbatschev, R, Bogdanova, S., 1993. Frontiers in the Baltic Shield. Prec.Res. 64, 3–21.

Gradstein, F.M., Ogg, J.G., Smith, A.G. (Eds.), 2004. A Geologic Time Scale2004. Cambridge Univ. Press, New York.

Hallam, A., 1992. Phanerozoic Sea Level Changes. Columbia Univ. Press,New York

Hambrey, M.J., 1985. The Late Ordovician–Early Silurian glacial period.Palaeogeogr., Palaeoclimatol., Palaeoecol. 51, 273–289.

Haq, B.U., Hardenbol, J., Vail, P.R., 1987. Chronology of fluctuating sealevels since the Triassic. Science 235, 1156–1167.

Hardenbol, J., Thierry, J., Farley, M.B., Jacquin, T., de Graciansky, P.C., Vail,P.R., 1998. Mesozoic and Cenozoic sequence chronostratigraphic frame-work of European basins, in: Graciansky, P.C., Hardenbol, J., Jacquin, T.,Vail, P.R. (Eds.), Mesozoic and Cenozoic Sequence Stratigraphy ofEuropean Basins. SEPM Spec. Publ. 60, Tusla, pp. 3–13.


Harper, J.F., 1986. Mantle flow and plate motions. Geophys. J. Roy. Astron.Soc 87, 265–284.

Harris, M.T., Schultz, T., Sheehan, P.M., Ainsaar, L., Nolvak, J., Hints, L.,Mannil, P., Rubbel, M., 2004. The Upper Ordovician of Estonia: Facies,Sequences and Basin Evolution, in: Hints, O, Ainsaar, L. (Eds.),WOGOGOB-2004 Conference Materials Tartu Univ. Press, Tartu, pp. 37–38.

Johnson, M. E., Lescinsky, H. L., 1986. Depositional dynamics of cycliccarbonates from the Interlake Group (Lower Silurian) of the WillistonBasin. Palaios 1 (2), 111–21.

Johnson, M.E., 1996. Stable cratonic sequences and a standard for Silurianeustasy. Geol. Soc. Amer. Bull. Spec. Paper 306, 202–211.

Kaljo, D.L. (Ed.), 1977. Baltic Silurian Facies and Faunas [in Russian]. Izd.AN ESSR, Tallin.

Kaljo, D., Hints, L., Martma, T., Nolvak, J., 2001. Carbon isotope stratigraphyin the latest Ordovician of Estonia. Chem. Geol. 175, 49–59.

Kaljo, D., Nestor, H. (Eds.), 1990. Field Meeting Estonia. An ExcursionGuidebook. Tallinn.

Kanygin,. A.V., Moskalenko, T.A., Yadrenkina, A.G., Abaimova, G.P.,Semenova, B.C., Sychev, O.V., Timokhin, A.V., 1989. The Ordovician ofthe Siberian Craton. Fauna and Stratigraphy of the Lena Facies Zone [inRussian]. Nauka, Novosibirsk.

Koren’, T.N. (Ed.), 2000. Using Event-Stratigraphic Levels for PhanerozoicInterregional Correlation in Russia [in Russian]. Izd. VSEGEI, St. Peters-burg.

Koren’, T.N., 2002. Problems of the general Ordovician stratigraphic scale.Regional’naya Geologiya i Metallogeniya 15, 14–25.

Korvin, A., 1984. Shale compaction and statistical physics. Geophys. J. Roy.Astron. Soc. 78, 35–50.

Männil, P R., Meidla T. The Ordovician System of the East European Platform(Estonia, Latvia, Lithuania, Byelorussia, parts of Russia, the Ukraine andMoldova), in: Webby, B.D., Ross, R.J., Zhen, Y.Y. (Eds.), The OrdovicianSystem of the East European Platform and Tuva (Southeastern Russia).Int. Union Geol. Sci. Publ. 28 A, pp. 1–52.

Miall, A.D., Miall, C.E., 2001. Sequence stratigraphy as a scientific enterprise:the evolution and persistence of conflicting paradigms. Earth Sci. Rev.54, 321–348.

Miller, J.F., 1984. Cambrian and earliest Ordovician conodont evolution,biofacies, and provincialism, in: Clark, D.L. (Ed.), Conodont Biofaciesand Provincialism. Geological Society of America, Special Paper 196,pp. 43–68.

Monod, O., Kozlu, H., Ghienne, J.-F., Dean, W. T., Gunay, Y., Le Herisse, A.,Paris, F., Robardet, M., 2003. Late Ordovician glaciation in southernTurkey. Terra Nova 15, 249–257.

Montanez, L.P., Banner, J.L., Osleger, D.A., Borg, L.E., Bosserman, P.J.,1996. Integrated Sr isotope variations and sea-level history of Middle toUpper Cambrian platform carbonates: Implications for the evolution ofCambrian seawater 87Sr/86Sr. Geology 24, 917–920.

Nestor, H., Einasto, R., 1997. Ordovician and Silurian carbonate sedimentationbasin, in: Raukas, A., Teedunme, A. (Eds.), Geology and MineralResources of Estonia. Estonian Acad. Publ., Tallinn, pp. 192–204.

Nestor, H., Einasto, R, Nestor, V., Marss, T., Viira, V., 2001. Description ofthe type section, cyclicity, and correlation of the Riksu Formation(Wenlock, Estonia). Proc. Estonian Acad. Sci. Geol. 50 (3), 149–173.

Nikishin, A.M., Ziegler, P.A., Stephenson, R.A., Cloetingh, S.A.P.L., Fume,A.V., Fokin, P.A., Ershov, A. V., Bolotov, S.N., Korotaev, M.V.,Alekseev, A.S., Gerbachev, V.I., Shipilov, E.V., Lankreijer, A., Bembi-nova, E.Yu., Shalimov, I.V., 1996. Late Precambrian to Triassic historyof the East European Craton: dynamics of sedimentary basin evolution.Tectonophysics 268, 23–63.

Nokleberg, W.J., Badarch, G., Berzin, N.A., Diggles, M.F., Hwang DukHwan, Khanchuk, A.I., Miller, R.J., Naumova, V.V., Obolenskiy, A.A.,Ogasawara Masatsugu, Parfenov, L.M., Prokopiev, A.V., Rodionov, S.M.,Yan Hongquan, 2004. Open-File Report 2004-1252. U.S. Department ofthe Interior, U.S. Geological Survey, http:.pubs.usgs.gov/of/2004/1252.

Obut A.M. (Ed.), 1984. The Ordovician of the Western Irkutsk Amphitheater[in Russian]. Nauka, Moscow.

Paris, F., Elaouad-Debbaj, Z., Jaglin, J.C., Massa, D., Oulebsir, L., 1995.Chitinozoans and Late Ordovician glacial events on Gondwana. Ordovi-cian odyssey, in: Cooper, J.D., Droser, M.L., Finney, S.L. (Eds.), ShortPapers for the 7th Int. Symp. Ordovician System. Pacific Section, SEPM,Fullerton, CA, pp. 171–176.

Paul, D.H., Pluijm, B.A., 1999. Structural sequences and styles of subsidencein the Michigan basin. GSA Bull. 111 (7), 974–991.

Pindell, J.L. Drake, C.L. (Eds.), 1998. Paleogeographic Evolution andNon-glacial Eustasy, Northern South America SEPM Special Publication58, Tulsa.

Popov, L.E., Khazanovich, K.K., Borovko, N.G., Sergeeva, S.P., Sobolev-skaya, R.F., 1989. Reference Sections and Stratigraphy of the Cambrian-Ordovician Phosphate-Bearing Obolovo Strata in the NorthwesternRussian Platform [in Russian]. Nauka, Leningrad.

Poprawa, P., Pliaupa, S., Stephenson, R., Lazauskiena, J., 1999. LateVendian–Early Paleozoic tectonic evolution of the Baltic Basin: regionaltectonic implications from subsidence analysis. Tectonophysics 314,219–239

Posamentier, H.W., Allen, G.P., 2000. Siliciclastic Sequence Stratigraphy –Concepts and Applications. SEPM Concepts in Sedimentology andPaleontology 7, 216.

Puura, V., Flodén, T., Mokrik, R., 2003. The Baltic Sea basin in the geologyof Fennoscandia and Baltic region. Litosfera, Vilnius, 7, 134–137.

Pylma, L., 1982. Comparative Lithology of Ordovician Carbonate Rocks inNorthern and Central Baltic Region [in Russian]. Valgus, Tallin.

Ross, C.A., Ross, J.R.P., 1995. North American Ordovician depositionalsequences and correlations. Ordovician Odyssey, in: Cooper, J.D., Droser,M.L., Finney, S.L. (Eds.), Short Papers for the 7th Int. Symp. OrdovicianSystem. Pacific Section, SEPM, Fullerton, CA, pp. 309–313.

Ross, R. J., James, N. P., Hintze, L. F., Poole, F.G., 1989. Architecture andevolution of a Whiterockian (Early Middle Ordovician) carbonate plat-form, Basin Ranges of western U.S.A., in: Crevello, P.D., Sarg, J.F.,Read, J.F. (Eds.), Controls on Carbonate Platform and Basin Development.Society of Economic Paleontologists and Mineralogists Spec. Publ. 44,pp. 167–185.

Sclater, J.G., Christie, P.A.F., 1980. Continental stretching, an explanation ofthe post mid-Cretaceous subsidence of the Central North Sea basin.J. Geophys. Res. 85, 3711–3739.

Sengör, A.M.C., Natal’in, B.A., Burtman, V.S., 1993. Evolution of the Altaidtectonic collage and Palaeozoic crustal growth in Eurasia. Nature 364,299–307.

Sokolov B.S. (Ed.)., 1982. The Ordovician of the Siberian Craton (ReferenceSection in Kulyumbe River) [in Russian]. Nauka, Moscow.

Sokolov, B.S. (Ed.), 1992. Silurian Sections and Faunas in the NorthernTunguska Basin [in Russian]. Nauka, Novosibirsk.

Tesakov, Yu.I., Kanygin, A.V., Yadrenkina, A.G., Simonov, O.N., Sychev,O.V., Abaimova, G.P., Divina, T.A., Moskalenko, T.A., 2003. TheOrdovician of the Northwestern Siberian Craton [in Russian]. Izd. SORAN, filial “Geo”, Novosibirsk.

Tesakov, Yu.I., Predtechenskii, N.N., Lopushinskaya, T.V., Khromykh, V.G.,Bazarova, L.S, Berir, A.R., Kovalevskaya, E.O., 2000. Stratigraphy ofPetroleum Basins of Siberia. Silurian of the Siberian Platform [in Russian],PH SB RAS, Novosibirsk.

Vyssotski, A. V., Vyssotski, V.N., Nezhdanov, A.A., 2006. Evolution of theWest Siberian Basin. Mar. Petrol. Geol. 23, 93–126.

Watts, A.B., 2001. Isostasy and Flexure of the Lithosphere. CambridgeUniversity Press, Cambridge, Melbourne, New York.

Webby, B.D., Laurie, J.R. (Eds), 1992. Global Perspectives on OrdovicianGeology. Balkema, Rotterdam.

Wilson, J.L. (Ed.), 1975. Carbonate Facies in Geological History. Springer,Berlin.

Editorial responsibility: O.P. Polyansky


Documents

Ordovician sea-level change and rapid change in crustal … · 2012. 11. 15. · nisms and distinguish Ordovician glaciation-related sea-level changes and events of rapid crustal