Bollettino SPI Vol. 49 - Issues 1, 2, 3
Issue 1
Published in September 2010
- Jin J. & Paul Copper P. (2010)
Origin and evolution of the early Silurian (Rhuddanian) virgianid pentameride brachiopods – the extinction recovery fauna from Anticosti Island, eastern Canada
pp. 1-11
Discovery of a suite of post-mass extinction virgianid brachiopods from the basal Silurian Becscie Formation of Anticosti Island demonstrates either that the Virgiana lineage originated from Brevilamnulella, or that the two lineages were sister groups. Gradational modifications are observed in a morphoseries from the Hirnantian genus Brevilamnulella, to the early Rhuddanian genus Viridita, and then to the middle-late Rhuddanian genus Virgiana. Four main evolutionary trends were ascertained: 1) adult shell size changed from < 15 mm to about 30 mm in length, and the shell outline from slightly transverse or equidimensional to markedly elongate, with a profile from nearly equibiconvex to strongly ventribiconvex; 2) the ventral umbo changed from low and narrow (1–2 mm above hinge line), with a suberect beak, to high, obtuse, and galeate, with a strongly incurved beak; 3) the shell surface is smooth in Brevilamnulella thebesensis, becoming quasismooth to gently costate in Viridita lenticularis, and then moderately costate in Viridita glomerosa sp. nov. and Virgiana barrandei; 4) the fold and sulcus are absent in Brevilamnulella and also in the early growth stage (up to 5 mm length) of Viridita lenticularis; at later growth stages, a ventral sulcus and a dorsal fold are developed extending to the anterior margin to produce a uniplicate commissure; such a fold and sulcus are present only in the early growth stage of Virgiana barrandei. On the basis of internal structures, it is also suggested that the Clorinda lineage had its origin in Brevilamnulella or Viridita during the late Rhuddanian, and became successful mainly in deeper-water, outer-shelf environments.
- Barrick J., Kleffner M., Gibson M., Peavey F. & Karlsson H. (2010)
The mid-Ludfordian Lau Event and Carbon Isotope Excursion (Ludlow, Silurian) in southern Laurentia – Preliminary Results
pp. 13-33
The mid-Ludfordian Lau Event can be recognized in three areas along the southern margin of Silurian Laurentia in association vwith a major positive carbon isotope excursion (CIE) and an abrupt turnover in conodont faunas: southern Oklahoma, southeastern Missouri, and western Tennessee. Although the major features of the Lau Event and CIE in southern Laurentia are similar to those described from the Baltic region, each site in southern Laurentia displays a different view of the effects associated with the Lau Event and a possible marine flooding episode coincident with the start of the Lau Event. The Lau Event lies at a disconformity between the lower and upper members of the Henryhouse Formation in southern Oklahoma at which the greater part of the CIE is missing. Diverse, but different offshore conodont faunas occur below (Polygnathoides siluricus fauna) and above (Ozarkodina snajdri fauna) the disconformity. In the Moccasin Springs Member of the Bainbridge Formation in southeastern Missouri, the CIE and the Lau Event occupy an offshore condensed section of argillaceous strata in which Pseudooneotodus is the dominant conodont taxon. A less diverse Po. siluricus fauna occurs below the Pseudooneotodus interval and a diverse O. snajdri fauna above it. In western Tennessee, the CIE and Lau Event lie within a grainstone unit assigned to the Bob Member of the Brownsport Formation. The Po. siluricus conodont fauna of the underlying Beech River Member disappears within the base of the Bob Member, but very few conodonts occur in the shallow water facies of the upper Bob and overlying Lobelville Member. No evidence of an associated turnover in the diverse macrofauna of western Tennessee has been recognized. Identification of the Lau Event and the CIE in these areas provides an important line of time effective correlation across southern Laurentia that will allow better placement of poorly time constrained stratigraphic units and faunal assemblages in this region.
- Zhao W., Herten U., Zhu M., Mann U. & Lucke A. (2010)
Carbon isotope stratigraphy across the Silurian-Devonian transition in Zoige (West Qinling), China
pp. 35-45
- Ray D.C. & Butcher A. (2010)
Sequence stratigraphy of the type Wenlock area (Silurian), England
pp. 47-54
The type Wenlock Series is established around the village of Much Wenlock, Shropshire, England, and consists of the Buildwas, Coalbrookdale and Much Wenlock Limestone formations. Based upon new data and a reevaluation of lithological and palaeontological data from the Lower Hill Farm Borehole and outcrops, an assessment of relative sea-level change has been made. Broadly, the type Wenlock consists of two shallow water carbonates separated by terrigenous sediments. Within this framework two major depositional sequences have been recognised, along with six higher-order sequences. These transgressive-regressive sequences have been calibrated against graptolite zonation schemes and are in general agreement with previously published Wenlock eustatic sea-level curves.
- Kiipli T. & Y Kaljo D. (2010)
Silurian sea level variations estimated using SiO2/Al2O3 and K2O/Al2O3 ratios in the Priekule drill core section, Latvia
pp. 55-63
The SiO2/Al2O3 and K2O/ Al2O3 ratios are used as proxies for grain size and sea depth changes in a more than 400 m thick succession of Telychian to Ludfordian shale and marlstone of the Priekule core. Good correlation of the increased SiO2/Al2O3 and K2O/ Al2O3 values in the Priekule section with positive δ13CC excursions recognized worldwide suggests that these sea depth changes correspond to global sea level changes. The curves composed indicate a moderate long-range sea level low stand from the Sheinwoodian to the middle Ludfordian, superimposed with larger sea level falls in the lower Sheinwoodian, upper Homerian and middle Ludfordian. The Telychian and upper Ludfordian are characterized by sea level high stands. Higher sulphur contents over 1% and higher contents of carbonates occur close to the intervals interpreted as sea level low stands.
- Histon C., Hubmann B. & Messner F. (2010)
A preliminary study of the upper Silurian nautiloid cephalopods from the Eggenfeld section (Graz Paleozoic, Austria)
pp. 65-74
The preliminary results of a systematic investigation of the nautiloid faunas from the upper Silurian (Pridoli) Eggenfeld section of the Graz Paleozoic are presented. A faunal list of the seven genera recognized to date, representing the families Oonoceratidae and Lechritrochoceratidae and subfamilies Michelinoceratinae, Kionoceratinae, Leurocycloceratinae is given and selected taxa illustrated. These genera document faunal exchange between the Graz Paleozoic, central Bohemia, the Carnic Alps, Sardinia, France (Montagne Noire), Spain (the Ossa Morena Zone) and Morocco during the late Silurian. The study adds a further contribution to the ongoing systematic description by diverse research groups of Silurian nautiloid cephalopods from the North Gondwana sector within a well defined biostratigraphic framework in order to elaborate their use as a tool for biostratigraphic correlation and paleobiogeographic reconstructions.
- Serventi P., Gnoli M. & Simonetto L. (2010)
Actinocerid cephalopods from the Silurian of the Carnic Alps (Italy)
pp. 75-81
Silurian actinocerid cephalopods from the Italian side of the Carnic Alps are reported on the basis of newly collected material. Three actinocerid taxa, belonging to Armenoceratidae, Huroniidae, and Ormoceratidae families, are described and left in open nomenclature.
- Sherwin L. (2010)
Gondwanan tectonics and European events in the Silurian of Australasia
pp. 83-88
Silurian biostratigraphic events defined in north-west Europe correspond with intervals of marked tectonic activity in Australasia (north-east Gondwana) but the accuracy in correlation is not such that a European biostratigraphic event can be tied to a specific Australasian tectonic event. Problems remain in a strict application of European Silurian zonation schemes in Australasia. In the eastern margin of the Australian plate the earlier part of the Silurian (Llandovery-early Wenlock?) is represented mostly by deep water siliciclastic sediments with few calcareous beds in the Lachlan Fold Belt (LFB) and many of those uncertain as to whether autochthonous or allochthonous. Events of any kind are difficult to recognise within the Llandovery in the eastern part of the LFB in New South Wales because of later structural complications, particularly the imbrication of Late Ordovician and early Silurian fault slices which nonetheless have very similar lithologies. Silurian strata are structurally simpler in the western part of the LFB where the pre-Wenlock is represented by fairly uniform laminate quartzose siltstone in which the late Llandovery guerichi Zone is the youngest recorded. Above the guerichi fauna is an hiatus of uncertain duration but is interpreted as encompassing the lapworthi and murchisoni graptolitic bioevents and the Ireviken, Boge and Valleviken events. Above the hiatus is an horizon with a ludensis-sherrardae fauna. This hiatus is also apparent in the eastern part of the LFB in the Yass and Goulburn districts. The ludensis-sherrardae fauna is overlain with a low angle unconformity by the non graptolitic Derriwong Group. The basal unit of the Derriwong Group is a pebbly sandstone lacking age diagnostic fossils but overlying the sandstone is a felsic volcanic sequence with interbedded limestones which contain a remscheidensis, possibly even crispa Zone conodont fauna. The indicated hiatus thus spans much of the Ludlow and overlaps with the timespan covering the Linde and Lau events. In the eastern part of the LFB there is more or less continuous sedimentation, with notable olistostromes in the Pridoli, corresponding to the hiatus during the Ludlow in the western LFB. Comparisons with Central Victoria show marked similarities in the stratigraphic record for the Llandovery but comparisons with the late Silurian are hindered by a comparatively poor fossil record in Victoria where graptolites are concerned. Silurian graptolite occurrences in Queensland and Tasmania are essentially spot collections and difficult to compare with the more complete sections in New South Wales and Victoria.
Issue 2
Published in June 2010
- Garilli V., Borghi E., Galletti L. & Pollina F. (2010)
First record of the sand dollar Amphiope Agassiz, 1840 (Echinoidea: Astriclypeidae) from the Miocene of Sicily
pp. 89-96
The first Sicilian record of the sand dollar Amphiope is reported on the basis of the occurrence of the species A. bioculata (des Moulins, 1837), recovered from a previously unreported sandy deposit cropping out near Case Genna (western Sicily). The best preserved tests are described and compared with similar congeners. Taphonomic and palaeoecological observations on the A. bioculata-thaphocenoses, and granulometric characterizations indicate that the sand dollar-bearing deposit formed in very shallow, nearshore environments subjected to bottom current. This deposit, if considered as a subunit of the deltaic upper Tortonian-lower Messinian “Molassa” of the Terravecchia Formation, would have a late Miocene age (upper Tortonian). In this case the Mediterranean distribution of A. bioculata, previously known from the Aquitanian to the lower Tortonian, should be extended to the upper part of the latter stage.
- Sassaroli S. & Venturi F. (2010)
Cingolites n.gen., a new lower Toarcian Hildoceratinae (Ammonitina) from the Marchean Apennines (Cingoli, Macerata, Italy)
pp. 97-118
New biostratigraphic data are provided from the Marchean Apennines (Marconessa quarry, near Cingoli, Macerata, Italy) where a lower Jurassic outcrop yielded a remakable Toarcian ammonite assemblage, very rich in early Hildoceratinae (Ammonitina). The site is historically meaningful, because in the past two centuries Italian palaeontologists have figured ammonoid specimens from “Marconessa”. Here, the nodular limestone and grey marl of the Bugarone Formation have recorded a great amount of well preserved Toarcian inner moulds of ammonoids sometimes large sized. From the lower and middle Toarcian layers of the Marconessa quarry sections we collected several ammonite genera, such as Hildaites, Orthildaites, Hildoceras, Harpoceras, Taffertia, Rakusites, Martanites, Praemercaticeras, Mercaticeras, Leukadiella, Frechiella, Phymatoceras, Rarenodia, Praepolyplectus, Polyplectus, Orthodactylites, Mesodactylites, Nodicoeloceras, very rare Dactylioceras and Nejdia, Lytoceras, Calliphylloceras, Phylloceras. We establish herein a new genus Cingolites, to which we ascribe three new species (C. clavatus, C. picenus and C. spiralis) and an already established species (C. stefaninii), which was previously assigned by Merla (1932) to the genus Mercaticeras. To the present-day the genus Cingolites seems to have a Mediterranean Tethys dispersal, mainly in the Apennines, where it occurs with other endemic Hildoceratinae fauna. These ammonite assemblages found in our Apennines sections seem to show a certain amount of provincialism that affected some Hildoceratinae lineages of the lower Toarcian.
- Bernardi M., Petti F.M., Ferretti P. & Avanzini M. (2010)
Asteriacites lumbricalis from the Coste dell’Anglone Lower Jurassic (Sinemurian) dinosaur ichnosite (Valle del Sarca, Trentino)
pp. 119-122
Here we report the first finding of Asteriacites lumbricalis in the Lower Jurassic of the Trento Platform. Palaeoenvironmental indications given by the presence of this trace fossil are added to the stratigraphical and sedimentological data for the Coste dell’Anglone dinosaur ichnosite. We suggest that during the middle-late Sinemurian this geographical sector was occupied by marginal-marine, tidal flat embayments with possible presence of a not to far fresh water source. This would have been necessary to sustain the existence of sedentary populations of dinosaurs recorded in the deposits that directly overlie those preserving the trace fossil described herein.
- Boldrini R., Palombo M.R., Iacumin P. & Melis R.T. (2010)
The Middle Pleistocene fossiliferous sequence of Grotta dei Fiori (Sardinia, Italy): multidisciplinary analysis
pp. 123-134
A multidisciplinary methodological approach (palaeontological, sedimentological and stable isotope analyses) was performed to analyse the fossiliferous sequence exposed in the “Grotta dei Fiori” cave (South Western Sardinia, Italy), where several small mammal remains (Microtus (Tyrrhenicola) henseli, Rhagamys orthodon, “Nesiotites” similis and Prolagus sardus) were discovered together with scanty remains of the endemic canid Cynotherium, and birds. Morphology and morphometry of first lower molars (M1) of Microtus (Tyrrhenicola) henseli from Grotta dei Fiori show that primitive and advanced morphotypes are present in each fossiliferous level. The relative frequency of morphotypes indicates that the population from “Grotta dei Fiori” might be regarded as more advanced than Microtus (Tyrrhenicola) sondaari from Xg3 fissure of Monte Tuttavista (Eastern Sardinia, late Early Pleistocene) and more primitive than the most of ?Middle and Late Pleistocene populations of Microtus (Tyrrhenicola) henseli from Sardinia. All in all, the data thus far provided by sedimentology and geochemistry indicate that the fossiliferous sequence of “Grotta dei Fiori” was deposited under climatic conditions characterized by an alternation of wet and dry periods. Taking into account the evolutionary degree of voles, 13C/12C and 16O/18O ratio and micromorphology of sediments, the hypothesis that the “Grotta dei Fiori” succession would be not older than the marine isotope stage (MIS) 11 cannot be ruled out. The results obtained stress once more the difficulty of a precise chronologic setting for deposits filling caves when no absolute date is available, and highlight the usefulness of a multidisciplinary approach to define environmental context and, perhaps, constrain chronology.
- Dieni I. (2010)
Maastrichtian and Selandian decapod crustaceans from Sardinia
pp. 135-144
Two decapod crustaceans, Protocallianassa cf. faujasi (Desmarest, 1822) and Titanocarcinus cf. subellipticus (Segerberg, 1900), of Maastrichtian and Selandian age respectively, are described from eastern Sardinia. They were found within clasts of a conglomerate (Cuccuru ’e Flores Conglomerate) of middle Lutetian age. This presence in Sardinia of taxa assimilable to species till now known exclusively, and in large number of individuals, in NW Europe allows to confirm faunistic exchanges between the Boreal Sea and Tethys ocean, at least intermittently, during Late Cretaceous and Early Tertiary. The most characteristic foraminifers accompanying the Maastrichtian decapod are figured; they supply evidence of a sedimentary facies no more cropping out in Sardinia.
- Di Bella L. (2010)
Plio-Pleistocene foraminiferal assemblages of the Monte Mario site (Rome, Italy)
pp. 145-161
Tunnel construction at Monte Mario hill (Rome) facilitated detailed study of the Monte Mario historical succession. Qualitative and quantitative analyses were performed on foraminiferal assemblages in order to define new stratigraphical and palaeoecological constraints for this historical site. From a chronostratigraphic point of view, micropalaeontological data assign the basal part of the succession (Monte Vaticano Formation) to the Early Pliocene (Zanclean Stage, upper part of Globorotalia puncticulata Zone) based on the presence of the marker species Globorotalia puncticulata. The presence of Dentoglobigerina altispira altispira, a well-known indicator of the upper Zanclean Stage in the Latium area, confirms the age assignment in agreement with nannoplankton data. The upper part of the Monte Mario Formation is attributed entirely to the Early Pleistocene (Calabrian – Santernian substage) based on the presence of Bulimina etnea. Palaeoecological reconstructions are based on quantitative proxies (percentages of single taxa, inbenthic and oxyphilic species, diversity indices, %P [(P/P+B)%]) that were used to evaluate important palaeoenvironmental and palaeoclimatic conditions. Pliocene deposits (Monte Vaticano Formation) record an upper bathyal environment characterised by warm oligotrophic water and welloxygenated bottom water. Pleistocene sediments (Monte Mario Formation) record highly variable environments controlled by sea level oscillations caused by the combined effects of tectonics and climate change. The deepest environments are recorded in the Pleistocene Farneto silts and represent an upper circalittoral environments that are characterised by cold water with enriched organic matter content and nearly eutrophic conditions. A more oxygenated, shallow-water environment with widespread vegetated cover is recorded from the Grey sands with Arctica islandica Member to the basal part of the Yellow sands with “panchina” Member. More marginal environments developed successively as a result of a shallowing trend. Lagoon/brackish lagoon environments characterised by oligospecific euryhaline foraminiferal assemblages develop to the Yellow sands with silty intercalations Member. The last member, Clays and Cerastoderma-bearing sands, is characterised by the reestablishment of normal marine infralittoral conditions of nutrient input and fresh-water influence. The succession ends with a more confined brackish lagoon environment, which relates to the progradational step of the uppermost portion of the Monte Mario Formation.
- Monaco P. & Cecconi A. (2010)
Taphonomy of the graphoglyptid trace fossil Desmograpton Fuchs 1895 at the sole of Miocene thin-bedded turbidites, Northern Apennines
pp. 163-172
The trace fossil Desmograpton Fuchs 1895 belongs to the biramous meanders group of grapholyptids. It is composed of hypichnial, thin strings and shafts that vary in the spatial arrangement for different ichnospecies. 47 Desmograpton specimens from soles of thin-bedded turbidites in flysch and hemipelagic deposits of Miocene formations (Cervarola, Marnoso-arenacea, Verghereto and Vicchio Marls and associated facies, Northern Apennines) were taphonomically analyzed in order to describe six main aspects: a) system preservation, b) meander preservation, c) axial system, d) string pattern, e) obstacle interference and f) fluting. The pattern of the axial system can be straight, divergent and curved and it seems to be related to the environmental conditions and to the preservation processes. In these deposits obstacles or irregularities in the substrate can be very common and they can strongly influence the string pattern producing local deviations in the burrowing system. The observations on the studied specimens also indicate that the development of Desmograpton immediately precedes the turbiditic event.
Issue 3
Published in December 2010
- Schiavinotto F. (2010)
Neanic stage biometry in Nephrolepidina from the Upper Oligocene of Lonedo (Lugo di Vicenza – Northern Italy)
pp. 173-194
Two populations coming from upper Chattian outcrops near Lonedo (Lugo di Vicenza – Northern Italy), are analysed applying a new method based on the biometric analysis of the first cycles of neanic equatorial chambers, and supplying additional data about parameters and factors that had already demonstrated to be significant. The data evidence that the “Degree of stolonic distalization” (Factor FD5) and the “Shape Index” (Factor SI5), at the 5th annulus show a very slight decrease in time of their mean values, not in accordance with the stratigraphic position of the populations, however not hampering the reliability of their assignment to the same age.
The analysis of the arrangement of the equatorial chambers shows a slight decrease in time of the relative frequency of specimens with neanic equatorial chambers arranged with concentric rings. Eventually, both populations seem to have the same evolutionary degree, with a very good fitting with the previously evidenced overall trend to modify the shape of the equatorial chambers, connected with a gradually more distal position of the radial, intercyclic stolons. On the contrary, a slight increase according to the “Embryonic – Nepionic Acceleration” is detected. Again, both populations can be referred to the same evolutionary stage. The specific, phylogenetic and biostratigraphic definitions could be improved by means of an integration of the embryonic-nepionic-neanic data.
- Manganelli G., Spadini V. & Martin I. (2010)
Rediscovery of an enigmatic Euro-Mediterranean Pliocene nassariid species: Nassarius crassiusculus Bellardi, 1882 (Gastropoda: Nassariidae)
pp. 195-202
Nassarius crassiusculus is an enigmatic Euro-Mediterranean Pliocene nassariid. Since its description, it had not been found until recently, when new material was collected in the Pliocene of Estepona, Spain and Siena, Italy. It is a peculiar species, easily distinguished from all other fossil and modern species of the Euro-Mediterranean area. A remarkable feature is an almost complete absence of sculpture. The only other Euro-Mediterranean Pliocene and Recent nassariids without sculpture are Nassarius bonellii, Nassarius pyrenaicus and the species of Gussonea, Naytiopsis and Plicarcularia. However, Nassarius crassiusculus is unlikely to be related to these species. In fact, absence of sculpture in nassariine nassariids seems a derived state that possibly appeared in different lineages, some of which were already defined in the Early-Middle Miocene.
- Gaudant J., Courme-Rault M.-D., Fornaciari E. & Fourtanier E. (2010)
The Upper Miocene fossil fish locality of Pecetto di Valenza (Piedmont, Italy): a multidisciplinary approach
pp. 203-225
Pecetto di Valenza is the first Upper Miocene fossil fish locality of Piedmont to have been studied and the only one in which fossils are embedded in a diatomitic sediment. Sturani & Sampò (1973) considered that it is Messinian in age. However, as a preliminary examination of the diatom flora from this locality by one of us (EF) suggested a late Tortonian age, it was decided to complete a more thorough micropalaeontological study in order to clarify the stratigraphical question. A comprehensive study of the diatom flora confirmed the preliminary results. Later, the study of the calcareous nannoplankton also concluded a late Tortonian age for the fossiliferous diatomaceous sediment. However, the examination of the planktonic foraminifera supports a Messinian correlation. Such a contradiction is puzzling and is hitherto not understood, even when making reference to a possible reworking. The composition of the fish fauna from Pecetto di Valenza is very similar to that observed in the two other marine Upper Miocene fish faunas of Piedmont, as myctophids predominate in all of them with more than 50% of the total number of specimens, whereas clupeids belonging to the species Alosa elongata comprise about 20% of the fauna. Except for the two species of the genus Lepidopus which, together, reach almost 8%, each one of the other identified taxa is below 5% of the fish fauna. The occurrence of upwellings, which is indicated by the abundance of the diatom Thalassionema nitzchioides in every diatomaceous sample, may have been responsible for the rather significant percentage of Lepidopus in the fish fauna. However, the upwelling environment did not exert any notable influence on the overall composition of the fish fauna from Pecetto di Valenza, relatively to those of the Tortonian of the Tanaro River and of the pre-evaporitic Messinian of Roddi, two localities in which diatoms are missing.
- Conti N., Petronio C. & Salari L. (2010)
The Late Pleistocene Equids from “Tana delle Iene” (Ceglie Messapica, Brindisi, Southern Italy).
pp. 227-236
The Late Pleistocene equids found in the Tana delle Iene site (Ceglie Messapica, Brindisi, Southern Italy) are described. The morphological and dimensional analysis of the dental remains and of the post-cranial skeleton of Equus ferus and Equus hydruntinus has been used to try to understand the biochronological congruity in respect to the other taxa found in the site. Some aspects relative to the functional morphology of the limb bones that furnished paleoenvironmental indications have been investigated. These paleoenvironmental indications agree with data obtained from the entire faunal assemblage of the Tana delle Iene site and from other coeval sites of Apulia.
- Corradini C. & Corriga M.G. (2010)
Silurian and lowermost Devonian conodonts from the Passo Volaia area (Carnic Alps, Italy)
pp. 237-253
Two sections (Rifugio Lambertenghi Fontana – RLF – and Rifugio Lambertenghi Fontana III – RLF III) of the Orthoceras limestones that crop out just South of Passo Volaia in the Carnic Alps yielded a rich and diverse conodont fauna. Twenty-six taxa belonging to eleven genera (Belodella, Coryssognathus, Dapsilodus, Dvorakia, Icriodus, Oulodus, Ozarkodina, Panderodus, Pseudooneotodus, Wurmiella and Zieglerodina) were discriminated. Wurmiella alternata n. sp. is described, and Belodella coarctata, Dvorakia amsdeni and Zieglerodina zellmeri are reported for the first time from the Carnic Alps. The fauna allows recognition of five late Silurian-earliest Lochkovian conodont zones (snajdri, crispa, eosteinhornensis s.l., detortus and woschmidti). The Silurian/Devonian boundary is interpreted to occur in the upper part of the RLF III section.