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1

High-resolution Campanian-Maastrichtian carbon and oxygen stable isotopes of bulk-rock and skeletal components: palaeoceanographic and palaeoenviron-mental implications for the Boreal shelf sea

Wilmsen M., Niebuhr B.

Acta Geologica Polonica

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2017

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Vol. 67, no. 1

47--74

EN

A high-resolution latest Early Campanian to Early Maastrichtian carbon and oxygen stable isotope record from the northern German Boreal shelf sea based on 537 analyses of co-occurring belemnites, brachiopods, inoceramids, oysters, and bulk rock samples is presented. All samples are precisely related to their stratigraphic, systematic and facies backgrounds and form an integrated, nearly 10-myr-long dataset with considerable palaeoenvironmental and palaeoceanographical implications. Petrographic studies indicate that low-magnesium calcitic coccoliths and calcispheres (i.e., planktic carbonate) predominate the bulk-rock data (marl-limestone rhythmites and chalks), thus representing a sea-surface water signal, and that only minor diagenetic alteration of the carbonate muds took place. Based on TL and CL microscopy, the investigated belemnites are extraordinarily well preserved, which may in part be explained by their early diagenetic surficial silicification (container effect), while the other macroinvertebrate groups are all less well preserved. The (plankton-dominated) δ13C values of the marl-limestone rhythmites and chalks (+1.1 to +2.5‰), recording a surface water signal, compare well with the δ13C data of inoceramids while δ13C brach.values (+1.5 to +3.0‰) are heavier than the bulk rock data. The large variation in the δ13Cbel. (-0.1 to +3.6‰) is attributed to isotopic disequilibrium of the biogenic carbonate formed by the belemnite animal. The bulk rock δ18O values show a remarkable low scatter, supporting petrographic observation of only minor diagenetic stabilisation/cementation, and can be approximated with northern German shelf sea-surface temperatures of ca. 20°C for the Late Campanian (ca. -2‰ δ18O), being slightly cooler during the Early Maastrichtian. The δ18O values of the belemnite rostra are even less variable and quite rich in heavier 18O (-0.7 to +0.6 with a mean of -0.1‰ δ18Obel.) in comparison to bulk rock and other skeletal components. Based on their excellent microstructural preservation and non-luminescence, we conclude that the belemnite rostra are diagenetically unaltered and have preserved the primary δ18O signal of ambient seawater (12±2°C). In the absence of any indication for migration from cooler water masses and evidence for authochtonous populations we assume that the belemnites of the genera Belemnitella and Belemnella lived as nektobenthos near the sea-floor and thus record the temperature of the bottom mixed layer of the seasonally weakly stratified north German shelf sea at water depths of 100 to 150 m; the temperature gradient was thus 12.5–18.75 m/1°C. A conspicuous latest Campanian cooling event is evident in both sea-surface and bottom-water temperatures. The δ18O values of nearly all investigated benthic fossils lie between the isotope values of pristine belemnites and bulk rock, and, therefore, should be used for palaeotemperature reconstructions only with great care.

2

The benthic macrofauna from the Lower Maastrichtian chalk of Kronsmoor (northern Germany, Saturn quarry): taxonomic outline and palaeoecologic implications

Engelke J., Esser K. J. K., Linnert C., Mutterlose J., Wilmsen M.

Acta Geologica Polonica

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2016

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Vol. 66, no. 4

671--694

EN

The benthic macroinvertebrates of the Lower Maastrichtian chalk of Saturn quarry at Kronsmoor (northern Germany)been studied taxonomically based on more than 1,000 specimens. Two successive benthic macrofossil assemblages were recognised: the lower interval in the upper part of the Kronsmoor Formation (Belemnella obtusa Zone) is characterized by low abundances of macroinvertebrates while the upper interval in the uppermost Kronsmoor and lowermost Hemmoor formations (lower to middle Belemnella sumensis Zone) shows a high macroinvertebrate abundance (eight times more than in the B. obtusa Zone) and a conspicuous dominance of brachiopods. The palaeoecological analysis of these two assemblages indicates the presence of eight different guilds, of which epifaunal suspension feeders (fixo-sessile and libero-sessile guilds), comprising approximately half of the trophic nucleus of the lower interval, increased to a dominant 86% in the upper interval, including a considerable proportion of rhynchonelliform brachiopods. It is tempting to relate this shift from the lower to the upper interval to an increase in nutrient supply and/or a shallowing of the depositional environment but further data including geochemical proxies are needed to fully understand the macrofossil distribution patterns in the Lower Maastrichtian of Kronsmoor.

3

Taxonomy and taphonomy of Cenomanian (Upper Cretaceous) nautilids from Annopol, Poland

Machalski M., Wilmsen M.

Acta Geologica Polonica

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2015

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Vol. 65, no. 4

495--506

EN

A nautilid faunule of seven specimens, comprising Eutrephoceras bouchardianum (d’Orbigny, 1840), Cymatoceras deslongchampsianum (d’Orbigny, 1840), and Cymatoceras tourtiae (Schlüter, 1876) is described from a condensed middle Cenomanian interval at Annopol, Poland. C. tourtiae is recorded for the first time in Poland. The studied material consists of reworked phosphatised internal moulds of phragmocones, which may be of early or middle Cenomanian age, given the stratigraphic range of the associated ammonites. The nautilid moulds vary in inferred mode of infilling, and in intensity of abrasion, bioerosion and mineralisation. The sediment entered the phragmocones in two ways: 1) through punctures in the shell, the result of bioerosion or mechanical damage; 2) through siphonal openings by intracameral currents. In contrast to the fossil moulds from the Albian phosphorites of Annopol, which originated via direct precipitation of apatite around and/or inside fossils, the present nautilid moulds seem to have originated through secondary phosphatisation of the initially calcareous moulds. Diversity of taphonomic signatures in nautilid material from the middle Cenomanian interval at Annopol is compatible with the complex, multievent depositional scenario proposed for this level.

4

Upper Albian and Cenomanian (Cretaceous) ammonites from the Debarsu Formation (Yazd Block, Central Iran)

Wilmsen M., Storm M., Fürsich F. T., Majidifard M. R.

Acta Geologica Polonica

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2013

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Vol. 63, no. 4

489--513

EN

New ammonite faunas consisting of 13 taxa provide the first reliable biostratigraphic dating of the Debarsu Formation of the Yazd Block, west-central Iran, indicating several levels in the Upper Albian and Lower Cenomanian, while a foraminiferal assemblage places the top of the Formation in the Middle Turonian. Among the identified ammonite taxa, Acompsoceras renevieri (Sharpe, 1857) is recorded from Iran for the first time. The upper part of the lower Upper Albian is proved by the occurrences of mortoniceratines of the Mortoniceras (M.) inflatum Zone in the lowermost part of the Debarsu Formation. For the upper Upper Albian (traditional Stoliczkaia dispar Zone), the M. (Subschloenbachia) rostratum and M. (S.) perinflatum zones are proved by their index taxa. However, there is no evidence of the terminal Arrhaphoceras (Praeschloenbachia) briacensis Zone. The upper part of the lower Lower Cenomanian Mantelliceras mantelli Zone (M. saxbii Subzone) is proved by M. saxbii and M. cf. mantelli. Below, there is an ammonite-barren interval of ca. 100 m in thickness between M. (S.) perinflatum zonal strata and the M. saxbii Subzone. The upper Lower Cenomanian is documented by the presence of typically M. dixoni zonal ammonites such as Acompsoceras renevieri. Upper Cenomanian and Turonian ammonites have not been found in the upper part of the Debarsu Formation, but micro-biostratigraphic evidence (planktonic foraminifers) from the uppermost part of the formation indicate that the formation ranges into the Turonian. For the development of the major tectonic unconformity at the base of the overlying Haftoman Formation (which yielded Lower Coniacian inoceramids near its base), only 2–3 myr remain, stressing the geodynamic activity of Central Iran during mid-Cretaceous times.

5

Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

Schneider S., Jäger M., Kroh A., Mitterer A., Niebuhr B., Vodrážka R., Wilmsen M., Wood C. J., Zágoršek K.

Acta Geologica Polonica

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2013

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Vol. 63, no. 4

555--610

EN

With approximately 100 species, the invertebrate macrofauna of the Neuburg Kieselerde Member of the Wellheim Formation (Bavaria, southern Germany) is probably the most diverse fossil assemblage of the Danubian Cretaceous Group. Occurring as erosional relicts in post-depositional karst depressions, both the Cretaceous sediments and fossils have been silicified during diagenesis. The Neuburg Kieselerde Member, safely dated as Early Cenomanian to Early Turonian based on inoceramid bivalve biostratigraphy and sequence stratigraphy, preserves a predominantly soft-bottom community, which, however, is biased due to near-complete early diagenetic loss of aragonitic shells. The community is dominated by epifaunal and semi-infaunal bivalves as well as sponges that settled on various (bio-) clasts, and may widely be split into an early bivalve-echinoid assemblage and a succeeding sponge-brachiopod assemblage. In addition to these groups we document ichnofauna, polychaete tubes, nautilids and bryozoans. The fauna provides evidence of a shallow to moderately deep, calm, fully marine environment, which is interpreted as a largescale embayment herein. The fauna of the Neuburg Kieselerde Member is regarded as an important archive of lower Upper Cretaceous sea-life in the surroundings of the Mid-European Island.

6

Late Cenomanian.Turonian (Cretaceous) ammonites from Wadi Qena, central Eastern Desert, Egypt : taxonomy, biostratigraphy and palaeobiogeographic implications

Nagm E., Wilmsen M.

Acta Geologica Polonica

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2012

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Vol. 62, no. 1

63-89

EN

In Egypt, marine Upper Cenomanian.Turonian strata are well exposed in the Eastern Desert. The southernmost outcrops are located in the central part of Wadi Qena, where the lower Upper Cretaceous is represented by the fossiliferous Galala and Umm Omeiyid formations. From these strata, numerous ammonites have been collected bed-by-bed and 13 taxa have been identified, which are systematically described herein. Four of them (Euomphaloceras costatum, Vascoceras globosum globosum, Thomasites gongilensis and Pseudotissotia nigeriensis) are recorded from Egypt for the first time. The ammonite ranges are used for a biostratigraphic zonation of the lower Upper Cretaceous succession in the northern and central part of Wadi Qena: the Upper Cenomanian.Lower Turonian has been subdivided into five biozones (including a new upper Lower Turonian biozone based on the occurrence of Pseudotissotia nigeriensis), and one biozone has been recognized in the Upper Turonian. Palaeobiogeographically, the ammonite assemblage has a Tethyan character. During the Early Turonian, influences of the Vascoceratid Province were predominant with strong affinities to typical Nigerian faunas. This shows the significance of faunal exchange between Egypt and Central and West Africa via the Trans-Saharan Seaway. Compared to contemporaneous ammonoid faunas from the northern part of the Eastern Desert, Boreal influences are much less obvious in Wadi Qena. Thus, the present study greatly enhances the knowledge of the Late Cretaceous palaeobiogeography and biostratigraphy of Egypt and adjacent areas.

7

Facies and integrated stratigraphy of the Upper Turonian (Upper Cretaceous) Grossberg Formation south of Regensburg (Bavaria, southern Germany)

Niebuhr B., Richardt N., Wilmsen M.

Acta Geologica Polonica

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2012

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Vol. 62, no. 4

595-615

EN

The Upper Turonian Grossberg Formation of the Regensburg area (Danubian Cretaceous Group, Bavaria, southern Germany) has a mean thickness of 20-25 m and consists of sandy bioclastic calcarenites and calcareous sandstones which are rich in bryozoans, serpulids and bivalves (oysters, rudists, inoceramids). Eight facies types have been recognized that characterize deposition on a southward dipping homoclinal ramp: the inner ramp sub-environment was characterized by high-energy sandwave deposits (sandy bioclastic rud- and grainstones, bioclastic sandstones) with sheltered inter-shoal areas. In mid-ramp settings, bioturbated, glauconitic, calcareous sand- and siltstones as well as bioturbated, bioclastic wacke- and packstones predominate. The carbonate grain association of the Grossberg Formation describes a temperate bryomol facies with indicators of warm-water influences. An inferred surplus of land-derived nutrients resulted in eutrophic conditions and favoured the heterozoan communities of the Grossberg Ramp. Carbon stable isotope geochemistry cannot significantly contribute to the stratigraphic calibration of the Grossberg Formation due to the depleted and trendless bulk-rock [delta^13]C values, probably resulting from a shallow-water aquafacies with depleted [delta^13]C DIC values and low [delta^13]C values of syndepositional and early diagenetic carbonate phases. However, strongly enriched skeletal calcite [delta^13]C values support a correlation of the Grossberg Formation with the mid-Late Turonian positive Hitch Wood isotope event (Hyphantoceras Event of northern Germany). This interpretation is supported by biostratigraphic data and a range from the Mytiloides striatoconcentricus Zone into the lower My. scupini Zone is indicated by inoceramid bivalves. Both the base and top of the Grossberg Formation are characterized by unconformities. Sequence boundary SB Tu 4 at the base is a major regional erosion surface (erosional truncation of the underlying Kagerhoh Formation in the Regensburg area, fluvial incision at the base of the Seugast Member of the Roding Formation in the Bodenwohr area towards the north and northeast). It is suggested that this unconformity corresponds to a major sea-level drop recognized in many other Cretaceous basins below the Hitch Wood or Hyphantoceras Event. The transgression and highstand of the Grossberg Formation is concomitant to the deposition of the fluvial Seugast Member and the onlap of the marginal-marine. Veldensteiner Sandstein. onto the Frankische Alb. The unconformity at the top of the Grossberg Formation (late Late Turonian SB Tu 5) is indicated by a ferruginous firm-/ hardground and an underlying zone of strongly depleted [delta^13]C values. The abrupt superposition by deeper marine marls of the lower Hellkofen Formation (uppermost Turonian.Lower Coniacian) may be connected with inversion tectonics at the southwestern margin of the Bohemian Massif.

8

Integrated stratigraphy of the Upper Hauterivian to Lower Barremian Agua de la Mula Member of the Agrio Formation, Neuquen Basin, Argentina

Archuby F., Wilmsen M., Leanza H.

Acta Geologica Polonica

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2011

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Vol. 61, no. 1

1-26

EN

The Upper Hauterivian to Lower Barremian Agua de la Mula Member of the Agrio Formation (Neuquen Basin, Argentina) was studied applying an integrated stratigraphic approach and facies analysis. The ammonite biostratigraphy of the member has been improved based on bed-by-bed collecting. The already defined biozones (Spitidiscus riccardii, Crioceratites schlagintweiti, Crioceratites diamantensis and Paraspiticeras groeberi) were recognized, precisely related to the succession, and further refinement was proposed. Sequences of different order are built by stacked starvation/dilution (s/d) sequences, regarded here as sixth-order sequences with only two components that can be unequivocally distinguished: the lower starvation hemisequence and the upper dilution hemisequence. Pro- and retrogradational stacking pattern of s/d sequences define supra-ordinate sequences. The sequence-stratigraphic analysis resulted in the subdivision of the member into four main depositional sequences (dsAM-1 to -4) and several subordinate sequences. Previously published sequence stratigraphic charts of the Neuquen Basin did not relate sedimentary sequences to biozones, and are hence not comparable to the scheme presented here and other charts. Our study shows a good agreement with the sequence-chronostratigraphic scheme of european basins, thus arguing in favour of a predominantly eustatic control on sequence development during the Late Hauterivian to early Barremian. A latest early Barremian age is proposed for the almost ammonite-barren upper part of the Agrio Formation, based on correlations of sequence boundaries.

9

Cenomanian Acanthoceratoidea (Cretaceous Ammonoidea) from the Koppeh Dagh, NE Iran : taxonomy and stratigraphic implications

Mosavinia A., Wilmsen M.

Acta Geologica Polonica

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2011

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Vol. 61, no. 2

175-192

EN

Seven species of the acanthoceratoidean genera Forbesiceras Kossmat, 1897, Mantelliceras Hyatt, 1903, Acanthoceras Neumayr, 1875 and Cunningtoniceras Collignon, 1937 are described and illustrated from the upper (i.e., Cenomanian) part of the Aitamir Formation of the Koppeh Dagh, northeast Iran. The mantelliceratines were collected from Lower Cenomanian silty shales while the rest of the fauna stems from lower Middle Cenomanian glauconitic sandstones in the upper part of the formation. The ammonite association allows recognition of the lower Lower Cenomanian Mantelliceras mantelli and the lower Middle Cenomanian Acanthoceras rhotomagense zones. The upper Lower Cenomanian M. dixoni Zone is not proven by its index but is most likely represented by a unit of fossil-poor shales intercalated between the two above-mentioned zones. The lowermost Middle Cenomanian Cunningtoniceras inerme Zone, however, is potentially at least partly missing due to a major sea-level fall and lowstand in the latest Early to earliest Middle Cenomanian. A preliminary sequence stratigraphic interpretation of the successions suggests the presence of Lower Cenomanian sequence boundaries Sb Ce 1-3. The Aitamir Formation is truncated along a major regional unconformity at the base of the overlying Abderaz Formation (Turonian.Coniacian). The Upper Cenomanian and most likely also (parts of) the Lower Turonian are missing. This major unconformity has a tectonic origin as it deviates from the eustatic sea-level trend which was very high at this time. Furthermore, contemporaneous tectonic unconformities are also known from Central Iran and may have their origins in rotational movements of the Central-East Iranian Microcontinent.

10

Occurrence and significance of Cenomanian belemnites in the lower Danubian Cretaceous Group (Bavaria, southern Germany)

Wilmsen M., Niebuhr B., Chellouche P.

Acta Geologica Polonica

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2010

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Vol. 60, no. 2

231-241

EN

The belemnite records of the lower Danubian Cretaceous Group (DCG, northeastern Bavaria, southern Germany) are compiled, taxonomically described and placed within the new integrated stratigraphic framework of the group. Three specimens from the lower Regensburg Formation (Saal Member) south of Regensburg can be assigned to Neohibolites cf. ultimus (d'Orbigny) and are dated as late Early Cenomanian (Mantelliceras dixoni Zone). Eight specimens represent Praeactinocamax plenus (Blainville) and occur in an event (plenus Event) in the lower Eibrunn Formation (Regensburg area) or basal Regensburg Formation (Roding area in the Bodenwohrer Senke). Biostratigraphy and carbon stable isotopes suggest that the belemnite horizon with P. plenus in the DCG has strictly the same chronostratigraphic position (mid-Late Cenomanian, middle Metoicoceras geslinianum Zone) as elsewhere in Central and NW Europe. The lithostratigraphic units of the lower Danubian Cretaceous Group (i.e., the Regensburg and Ebirunn formations), however, are characterized by a pronounced diachronism based on their time-transgressive (i.e., onlapping) deposition during the Cenomanian.Early Turonian transgression. The distribution of P. plenus around the Mid-European Island can be easily explained by migration around the positive area without the necessity of a marine strait across the Bohemian Massif.

11

Integrated stratigraphy of the upper Lower - lower Middle Cenomanian of northern Germany and southern England

Wilmsen M.

Acta Geologica Polonica

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2007

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Vol. 57, no. 3

263-279

EN

A high-resolution stratigraphic calibration of the upper Lower (upper Mantelliceras dixoni Zone) and lower Middle Cenomanian (Cunningtoniceras inerme Zone and lower Acanthoceras rhotomagense Zone) based on an integrated analysis of macrofossil biostratigraphy, event, cyclo-, stable-isotope and sequence stratigraphy of northern German and southern England key sections is presented. Classic event stratigraphy has a good potential in refining biostratigraphic correlations as most of the classic bioevents are isochronous within the integrated stratigraphy. Many lithological event beds such as marker marls can be incorporated into the cyclo- and sequence stratigraphic framework, explaining their significance in interregional correlation. The best stratigraphic resolution provides the cyclostratigraphy based on the typical Cenomanian marl-limestone couplets and their stacking pattern, inferred to reflect orbital forcing of the Milankovitch frequency band: detailed bed-by-bed correlation of couplets (precession cycle, ca. 20 kyr) allows a stratigraphic calibration within [similar to]10 kyr time slices. Conspicuous marker marl beds embrace bundles of [similar to]five couplets and are related to the short eccentricity (100 kyr) cycle. However, for the upper Lower Cenomanian (dixoni Zone) it appears that the existing couplet scale is incomplete. Sequence stratigraphic analysis demonstrates that the investigated interval comprises the maximum flooding and highstand interval of an Early Cenomanian sequence, capped by a significant late dixoni Zone sequence boundary, followed by uppermost Lower to Middle Cenomanian lowstand and transgressive deposits grading into a Middle Cenomanian maximum flooding zone ("calcimetry break"). Carbon stable-isotope values are stable around 2[per mil] vs. V-PDB within the mid- and late dixoni Zone,related to equilibrium conditions during maximum flooding and highstand conditions of sea-level. The latest Early to earliest Middle Cenomanian sea-level fall and lowstand was accompanied by a negative [delta] [^13]C excursion of ca. 0.4[per mil] in couplets B34-B40 (Lower-Middle Cenomanian boundary isotope Event, LMCE, new name) followed by a rise of 0.4.0.6[per mil] [delta] [^13]C in couplets B41-C2 during the early transgressive systems tract (Middle Cenomanian [delta] [^13]C excursion MCE 1). These observations support the interpretation that the [delta] [^13]C signal is a good proxy for (eustatic) sea-level changes. The LMCE is suggested as a proxy marker for the base of the Middle Cenomanian Substage.

12

The Upper Triassic - Middle Jurassic Shemshak Group of Iran: foreland basin or rift basin?

Fürsich F., Wilmsen M., Seyed-Emami K., Majidifard M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

41-41

EN

The Shemshak Group is a predominantly siliciclastic rock unit occurring over much of the Iran Plate. The group is sandwiched between two unconformities: the lower one resulted from the late Middle Triassic Early Cimmerian Orogeny, which documents the collision of the Iran Plate with Eurasia, the upper one results from the still poorly understood Bajocian Mid-Cimmerian tectonic movements. At the base, the group overlies, with distinct stratigraphic gap documented by karst features and locally extensive bauxite deposits, the platform carbonates of the Shotori and Elikah formations. At the top, the group is overlain by the marls of the Dalichai Formation, part of a widespread carbonate system existing for most of the late Middle-Late Jurassic and locally extending into the Early Cretaceous. The Shemshak Group reaches enormous thicknesses (up to 4000 m) and consists largely of fluvial sediments with common intercalations of coal beds. At the base and at the top, the group is represented by marine sediments which include reef and lagoonal carbonates, deposits of the storm-influenced shelf, deltas, and basinal mudstones. Another characteristic feature are volcanic and volcanoclastic rocks, which are commonly intercalated at or near the base of the group. Conventionally, the Shemshak Formation has been interpreted as the fill of a foreland basin. However, detailed sedimentological and stratigraphic studies over much of the outcrop belt of the group show that such a simple interpretation can no longer be upheld. Instead, the Shemshak Group is thought to reflect the following major tectono-sedimentary settings: during the Late Ladinian - Carnian initial collision of the Iran Plate with Eurasia in northeastern Iran (Koppeh Dagh-Binalud area), the Triassic carbonate platforms of the Iran Plate suffered warping and extensive lateritic weathering. In the Alborz area, a remnant basin of the Palaeotethys persisted, in which basinal sediments were deposited. During the Norian-Raethian, distension of the Iran Plate in connection with the onset of subduction of the Neotethys led to formation of rapidly subsiding marine grabens which were filled with sediments of neighbouring horsts (Nayband Formation). In the Alborz area, the remnant basin of the Palaeotethys became gradually infilled with partly shallow marine and partly fluvial sediments. The major collision between the Iran Plate and Eurasia took place around the Triassic/Jurassic boundary. Concomitant with the rising Cimmerian Mountains, a foreland basin developed, which received a thick conglomeratic fill in the north which southwards graded into a fluvial system with widespread coal swamps. During the Toarcian-Aalenian, this foreland basin changed into a rift basin, which is documented by transgression and a rapid change to basinal deposits, indicative of high rates of subsidence. By the end of the Early Jurassic, the Cimmerian Mountains were more or less eroded. The following Mid-Cimmerian tectonic movements are seen as recording strong distensional tectonics in connection with the opening of the South Caspian Basin in the north.

13

The Kashafrud Basin (NE Iran): a key for understanding the Jurassic geodynamic evolution of the Iran Plate

Wilmsen M., Fürsich F., Taheri J., Brunet M.-F., Seyed-Emami K., Majidifard M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

69-69

EN

The boundary between the Koppeh Dagh and the Binalud Mountains in northeastern Iran corresponds to the suture of the Palaeotethys, an ocean which, in the area of present-day Iran, had been completely subducted below the Turan Plate as part of Eurasia in the north towards the end of the Triassic (Early Cimmerian orogeny). At this boundary between the Turan Plate and the Iran Plate, the latter a part of the so-called Cimmerian Microcontinent Collage, a strongly subsiding, NW-SE-trending basin formed during the Late Bajocian-Bathonian, which became infilled with a thick (>2000 m) pile of fluvial to deep-marine siliciclastic sediments, combined in the so-called Kashafrud Formation. This Kashafrud Basin is a key for understanding the geodynamic history of the Iran Plate during the Middle-Late Jurassic. The Kashafrud Formation overlies, often with angular unconformity and a thick basal conglomerate, Triassic and older rocks. In the area of the southwestern basin margin (Binalud Mountains), coarse-grained fluvial sediments grade into marine sediments (fan deltas, deltas, storm-influenced shelf). Short transport distances and steep relief are indicated by high compositional and textural immaturity. In the northeastern part of the outcrop belt, towards the Koppeh Dagh Mountains, the Kashafrud Formation is marine throughout and rapidly grades into deep-marine, dark shales with turbidite intercalations, indicating a slope to basin plain environment. By the Early Callovian, siliciclastic sedimentation was gradually replaced by carbonates and the Kashfrud Basin was infilled with carbonate platform and slope sediments of the Chaman Bid and Mozduran formations (Callovian - Upper Jurassic). Estimates of subsidence rates indicate very high values of 700 m/my and more during the Late Bajocian-Bathonian, indicative of young continental rift zones, and the Kashafrud Basin is thus interpreted as a rift basin. Integrated facies and stratigraphic analyses indicate that the bulk of the sediments entered the basin from the SW, derived from erosion of the uplifted rift shoulders in the Binalud Mountains. Deeper marine, basinal areas extended to the NE, probably far below the Cretaceous cover of the Koppeh Dagh. A coeval subsidence pulse of similar magnitude, related to the Mid-Cimmerian tectonic movements, also occurred in northern Iran (deep marine marls of the Dalichai Formation in the Alborz Mountains). From a geodynamic viewpoint, the Kashafrud Basin is the southeastern extension of the rapidly subsiding South Caspian Basin (SCB) which, in northern Iran, started to develop already in the Toarcian-Aalenian. In the Bajocian-Bathonian, this basin was enlarged towards the E-SE (opening of the Kashafrud Basin), leading to a renewed separation of the Iran and Turan plates after the Early Cimmerian collision. The reactivation of a former ocean suture for the development of a strongly subsiding basin is rather exceptional (the SCB possibly also reached the spreading stage) and the reasons for its opening are still poorly understood.

14

Stratigraphy and depositional environments of the Upper Bajocian-Bathonian Kashafrud Formation (NE Iran)

Taheri J., Fursich F., Wilmsen M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

105-106

EN

The Upper Bajocian-Bathonian Kashafrud Formation is a thick (>2 km), siliciclastic sedimentary unit, distributed in a NW-SE-trending, 200 km long and 80 km wide outcrop belt in the area between the Koppeh Dagh and the Binalud Mountains (NE Iran). It was deposited in a strongly subsiding rift basin developing between the Iran Plate and Eurasia (Turan Plate) in response to Middle Jurassic crustal extension following the Mid-Cimmerian tectonic movements. The Kashafrud Basin is a southeastern prolongation of the South Caspian Basin, opening along the ocean suture which has been formed by the Late Triassic closure of the Palaeotethys (so-called Early Cimmerian orogeny). The stratigraphy and depositional environments of the Kashafrud Formation are the scope of this integrated analysis. Ten sections of the Kashafrud Formation were logged in detail and sampled for lithology, macro- and trace fossils, and facies analysis. At several localities, ammonites occur near the base of the formation, in every case providing a Late Bajocian age. Within the middle and upper parts of the Kashafrud Formation, ammonites are rare. However, in its uppermost part and at the base of the overlying unit (marls of the Chaman Bid Formation), ammonites of the genus Macrocephalites indicate an Early Callovian age. Thus, the Kashafrud Formation can be mainly assigned to the Upper Bajocian-Bathonian. Commonly, the Kashafrud Formation rests with angular unconformity on rocks affected by the Early Cimmerian orogeny. Based on thicknesses and principal facies development, two NW-SE-striking (basin-axis-parallel) zones can be differentiated, i.e., a more proximal one close to the Binalud Mountains in the SW and a distal one towards the Koppeh Dagh in the NE. Basal conglomerates tend to be thickest and coarsest in the proximal zone, at the southwestern basin margin. Rapid lateral thickness changes indicate a fault-controlled deposition (proximal alluvial fans or rockfalls). Up-section, the conglomerates are replaced by highly immature arcosic sandstones and pebbly sandstones of a short-headed braided river system grading into marine fan delta deposits. Rapid deposition and subsidence are indicated by the lack of significant maturation of the sediments even in settings above the fair-weather wave base. In some sections, basal conglomerates are thin and fluvial sediments missing, and the Kashafrud Formation directly starts with coarse-grained marine fan delta deposits. In all cases, a distinct fining-upward indicates a significant deepening trend. In the distal zone, basal conglomerates are thin and commonly marine as indicated by marine fossils. They are vertically replaced by basin plain (dark shales with rare ammonites) and intercalated submarine fan deposits (including coarse upper fan feeder channels, mid-fan leveed channel and inter-channel deposits, and well bedded shale-sandstone outer fan intercalations). Bioturbation is common in turbidite sequences and a deeper marine environment is indicated by rare graphoglyptids of the Nereites ichnofacies. Also in the distal part, a general fining- and thinning-upward trend indicates a deepening. All the observations can be integrated into a rift basin model for the Kashafrud Formation. The basin axis trend was roughly NW-SE and the stratigraphic and sedimentologic data indicate a main sediment input from the southwestern basin margin (Binalud). The northeastern basin margin is inferred below the Koppeh Dagh.

15

The middle-upper Cenomanian of Zilly (Sachsen-Anhalt, northern Germany) with remarks on the Pycnodonte Event

Wilmsen M., Voigt T.

Acta Geologica Polonica

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2006

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Vol. 56, no. 1

17-31

EN

A detailed stratigraphic log of the 28 m thick Cenomanian succession at Zilly (Sachsen-Anhalt) is presented. The succession is composed of 11 m of middle Cenomanian hemi-pelagic marl-limestone alternations ("Planer Limestones") grading into 15 m of upper Cenomanian calcareous pelagites ("Poor rhotomagense Limestones") unconformably overlain by 1,5 m of red-coloured marly clays and limestones ("Rotplaner"). The proof of the interregional marker beds of the Pycnodonte Event at the 11 m level, the Facies Change at 26 m, and the base of the plenus Bed at 26,9 m allow a bio-/chronostratigraphic correlation of these levels with the middle/upper Acanthoceras jukesbrownei Zone (upper middle Cenomanian), the Calycoceras (Proeucalycoceras) guerangeri/Metoicoceras geslinianum Zone transition, and the lower Metoicoceras geslinianumZone, respectively (middle upper Cenomanian).Litho-/microfacies and sequence stratigraphic analyses indicate an overall increase of pelagic influence up to the Facies Change. This retrogradational trend was shortly interrupted by the Pycnodonte Event, the base of which correlates with the late middle Cenomanian sequence boundary SB Ce IV and the succeeding transgressive surface. The Facies Change indicates a significant mid-late Cenomanian sea-level fall (sequence boundary SB Ce V), followed by more shallow water Rotplaner deposition. The Pycnodonte Event is very thick and proximal in character at Zilly. Its monospecific oyster fauna consists of small pycnodonteines assigned to Pycnodonte (Phygraea) vesicularis (LAMARCK) vesiculosa (J. SOWERBY), a secondarily free-lying oyster which lived as a "cup-shaped recliner".The patchy occurrence of the oysters, the sorting and partial damage of valves prior to final burial along with significant supply of terrigenous materials suggest episodically elevated water energy and strong environmental stress during deposition of the Pycnodonte Event. This situation promoted colonization of the sea-floor by, and reproductive success of the inferred eurytopic oyster. The Pycnodonte Event is a classic example of an "onlapping bioevent", the formation of which was controlled by different factors such as sea-level rise, terrigenous influx, environmental stress, and preferential preservation.

16

Latest Campanian to Early Maastrichtian (Cretaceous) nautiloids from the white chalk of Kronsmoor, northern Germany

Wilmsen M., Esser K. J.

Acta Geologica Polonica

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2004

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Vol. 54, no. 4

489-498

EN

A well preserved and stratigraphically tightly constrained nautiloid fauna consisting of two species is described from the uppermost Campanian to Lower Maastrichtian white chalk section of Kronsmoor, northern Germany. Cymatoceras patens (KNER, 1848) occurs rather frequently in the Kronsmoor section; one specimen is from the Upper Campanian Micraster grimmensis/Cardiaster granulosus Zone, one from the upper Belemnella pseudobtusa to lowermost Belemnella obtusa Zone. The bulk of the material (nine specimens) is from the Early Maastrichtian B. obtusa and Belemnella sumensis zones. The species is known from the Upper Campanian to Lower Maastrichtian of northern Germany, The Netherlands, Poland, the Ukraine, and possibly Denmark. Cymatoceras loricatum (SCHLUTER, 1876) occurs in Kronsmoor (four specimens) in an interval comprising the Early Maastrichtian upper B. obtusa to B. sumensis zones.The species was hitherto only recorded from the uppermost Lower and Upper Campanian of Westphalia and Lower Saxony, Germany. Both species appear to be restricted to the Central European Subprovince of the temperate North European Province (Boreal Realm).

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First record of Jurassic (Toarcian - Bajocian) ammonites from the northern Lut Block, east-central Iran

Seyed-Emami K., Fürsich F. T., Wilmsen M., Schairer G., Majidifard M. R.

Acta Geologica Polonica

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2004

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Vol. 54, no. 1

77--94

EN

A very thick and lithologically rather unusual marine sedimentary succession is described from the Kuh-e-Shisui area, northwestern Lut Block (east-central Iran). It contains a low diversity ammonite fauna comprising the families Dactylioceratidae, Hildoceratidae, Graphoceratidae, Hammatoceratidae, and Sonniniidae, which are concetrated in several levels, indicating the Lower-Lower Middle Toarcian, Upper Toarcian, Aalenian, and Lower Bajocian. The ammonite fauna, consisting of 21 taxa, descibed for the first time from the Lut Block, corresponds to that of the Badamu Formation of the Kerman-Ravar region (southern Tabas Block, to the west of the Lut Block), but is far less diverse. An exception is the occurrence of Lower Toarcian Harpoceratinae and Hildoceratinae, which hitherto have not been recorded from east-central Iran. The ammonite fauna is closely related to that of northwestern Europe.

18

Early Cenomanian (Cretaceous) inoceramid bivalves from the Kronsberg Syncline (Hannover area, Lower Saxony, Germany): stratigraphic and taxonomic implications

Wilmsen M., Niebuhr B., Wood C. J.

Acta Geologica Polonica

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2001

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Vol. 51, nr 2

121-136

EN

An Early Cenomanian inoceramid bivalve assemblage collected from material excavated from a temporary exposure in the Kronsberg Syncline east of Hannover (northern Germany) is described. It consists of "Inoceramus" crippsi MANTELL, 1822, "I" hoppenstedtensis TROGER, 1967, Inoceramus virgatus scalprum BOHM, 1914 and I. virgatus virgatus SCHLUTER, 1877, as well as transitional forms between I. virgatus virgatus and I. virgatus scalprum and an apparently undescribed sulcate form. The inoceramid fauna is well preserved and very rich in individuals. Many of the inoceramids occur either as double-valved individuals or with the valves in close association and appear to be cocentrated in distinct layers. Co-occurring ammonites are Mantelliceras dixoni SPATH, Mantelliceras sp., Schloenbachia varians (J. SOWERBY), Hypoturrilities gravesianus (D'ORBIGNY) and Scaphites obliquus J. SOWERBY. Using event stratigraphy, the stratigraphic interval of the collected fauna can be assigned to the lower part of the Lower Cenomanian Mantelliceras dixoni ammonite Zone. It predominantly comprises material from the Inoceramus virgatus acme-event (the Schloenbachia/virgatus event of German event stratigraphy) at the top of the lower subzone (Mantelliceras dixoni & M. saxbii Subzone) of the dixoni Zone, which is known from the Lower Saxony, Cleveland (eastern England) and Anglo-Paris basins, where it invariably occurs in carbonate-rich rocks with low diversity faunas. The lithofacies and geochemistry of the strata are documented and the "Inoceramus" crippsi and Inoceramus virgatus groups are discussed, including the problematic provenance of the type series of Inoceramus virgatus scalprum.

19

Late Cretaceous nautilids from northern Cantabria, Spain

Wilmsen M.

Acta Geologica Polonica

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2000

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Vol. 50, no. 1

29-43

EN

Nautilids do not occur throughout the Upper Cretaceous succesion in northern Cantabria. Alrhough relatively rare, they preferentially occur in condensed transgressive horizons. Nine species belonging to the genera Angulithes MONTFORT 1808, Eutrephoceras HYATT 1894, and Pseudocenoceras SPATH 1927 are recorded. A. westphalicus (SCHLUTER 1872) and E. cf. justum (BLANFORD 1861) are reported for the first time from the Iberian Peninsula. The diagnosis of A. vascogoticus WIEDEMANN 1960 is emended. The Cenomanian was characterized by a relative abundance of nautilids of the genus Angulithes which display a major radiative event, evolving relatively short-lived species. This development was probably related to the "Cenomanian transgression". Compared to co-occuring ammonite faunas, Angulithes inhabited deeper and more distal environments. A possible transitional form, connecting the two genera Angulithes and Deltocymatoceras KUMMEL 1956 (?Turonian, Coniacian - Santonian), is recorded from the Mid-/Late Cenomanian. The Turonian to Campanian succession is dominated by long-ranging nautilids of the genus Eutrephoceras.