Wyniki wyszukiwania - BazTech

1

Aalenian (Jurassic) to Berriasian (Cretaceous) chronostratigraphic zonation and guide ammonites of the Central Andes (Argentina, Chile, Peru)

Parent Horacio

Volumina Jurassica

|

2022

|

Vol. 20

1--46

EN

In the Central Andes there are developed two marine basins with an extensive Jurassic record: the Neuquén (or Central Andean) Basin and the Tarapacá Basin. Their Jurassic and Lower Cretaceous ammonite successions have been studied extensively for more than 150 years, producing detailed chronostratigraphic scales based on ammonite zones and biohorizons. The ammonite faunas include Andean lineages, and cosmopolitan, Tethyan, Caribbean, North American, and Indo-Madagascan elements. This paper presents the results of a revision of the zonation of the interval Aalenian-Berriasian. Before presenting the results, this paper emphasizes the distinction between, and the convenient nomenclature for, biozones, zones, standard zones, and biohorizons. The scissum Hz. (new) is introduced in the lower (-most?) Manflasensis Zone (Aalenian). The Rotundum Subzone (new) with base at the cf.-leptus Hz., is introduced for the upper part of the Rotundum Zone (Bajocian). The Gulisanoi Zone (Bathonian) is standardized by designation of the cf.-aspidoides Hz. (new) as its base. The Chacaymelehuensis Zone (new) with base at the “prahecquense” Hz. (new) is introduced for the Callovian. The Cubanensis Zone (Oxfordian) is introduced to replace nominally, or to rename, the inconveniently named “Passendorferia” Zone. The Tarapacaense Zone (Oxfordian) is standardized by designation of the tarapacaense Hz. (new) as its base. The Tithonian Malarguensis Zone (formerly subzone) is here emended and standardized by designation of the malarguensis Hz. as its base; this zone replaces the unviable Mendozanus Zone. The Zitteli Zone is standardized by designation of the widely recorded perlaevis Hz. as its base. The Fascipartita Subzone (Internispinosum Zone) is standardized by designation of the internispinosum-beta Hz. (new) as its base. The Alternans Zone is standardized by designation of the vetustum Hz. as its base, and the Koeneni Zone (uppermost Tithonian) by designation of the striolatus Hz. as its base.

2

Identification of the Oligocene-Miocene boundary in the Central Iran Basin (Qom Formation) : Calcareous nannofossil evidences

Parandavar Mohammad, Hadavi Fatemeh

Geological Quarterly

|

2019

|

Vol. 63, No. 2

215--229

EN

A diverse Late Oligocene to Early Miocene calcareous nannofossil assemblage was examined from the Qom Formation in the Central Iran Basin, and the Oligocene-Miocene boundary was identified based on the quantitative analysis of the assemblages in 303 smear slides. Eleven well-established calcareous nannofossil bio-events are delineated in the Upper Oligocene through Lower Miocene. The results clearly show that the Highest Occurrence (HO) of Sphenolithus delphix is the closest bio-event to the boundary as traditionally delineated on the lithostratigraphic criteria, and provides a distinct biohorizon below it. The Lowest Occurrence (LO) of the species Discoaster druggii is the oldest Miocene bio-event that is observed shortly after the HO of S. delphix, showing that calcareous nannofossils are well suited for approximating the Oligocene-Miocene boundary in the Qom Formation. The Oligocene-Miocene boundary is placed in the upper part of Sub-member “c1” in all three sections studied here and it is traceable throughout the Central Iran Basin, which makes a potentially reliable marker horizon for sequence stratigraphic and hydrocarbon studies in the area.

3

Waterloo Bay, Larne, Northern Ireland: a potential GSSP for the base of the Jurassic System

Simms M., Jeram A.

Volumina Jurassica

|

2006

|

Vol. 4, no. 1

297-298

EN

Northern Ireland is the type area for two basal Jurassic ammonites, Psiloceras sampsoni (Portlock 1843) and Caloceras intermedium (Portlock 1843). However, with its small and patchy exposures of Triassic and Jurassic strata the region has subsequently been largely overlooked compared with sites in SW England. A foreshore section at Waterloo Bay, Larne, on the east coast of Northern Ireland, exposes an almost uninterrupted succession from the upper part of the Mercia Mudstone Group (Triassic, Norian) through to the Bucklandi Zone of the Lias Group (Jurassic, Sinemurian). Recent study has established that the boundary section here is superior in many respects to that at St. Audrie's Bay, SW Britain, a long-standing candidate GSSP for the base of the Jurassic System. What has the Larne section to offer? 1. Exceptionally thick succession across the Triassic/Jurassic boundary. The boundary succession is significantly thicker, and deposition demonstrably more continuous, at Larne than anywhere else in NW Europe. 2. Potential biohorizon stratotypes for the Planorbis Zone. Clearly definable biohorizons can be recognised for Psiloceras erugatum, Neophyllites imitans, N. antecedens, Psiloceras planorbis/sampsoni and P. plicatulum. This site would make an ideal stratotype for the first three of these, for which currently no surface stratotypes are proposed (Bloos & Page 1998). Ammonites are very common in this section, and preservation by pyrite, or in nodules, is often excellent. 3. Diverse non-ammonite macro- and microfauna, already partly documented. A rich fauna of bivalves, gastropods, echinoids, crinoids, trace-fossils and occasional vertebrates are present at this site. Preliminary stratigraphic distribution of the fossil macrofauna, and of palynomorphs, through correlative strata in the nearby Larne borehole has already been published (Ivimey-Cook 1975; Warrington & Harland 1975). 4. Potential for correlation. Sedimentary cycles, of two orders, are clearly developed here. Combined sequence and cyclostratigraphic analysis indicates that the cycles reflect eustatic fluctuations, and therefore have significant potential for global correlation. A major seismite unit and associated desiccation-cracked bed in the Penarth Group provides an important datum correlated across the UK (Simms 2003).

4

Ammonoidea Toarcian biohorizons in the Basque-Cantabrian Basin (N Spain): a correlation between the Iberian Range and the Mediterranean Province standard scale

Goy A., Martinez G., Ureta S.

Volumina Jurassica

|

2006

|

Vol. 4, no. 1

166-167

EN

In the Basque-Cantabrian Basin several detailed biostratigraphical studies in Toarcian sediments have been carried out, and all the zones and the most subzones from the NW European Province standard scale have been characterized. Recent investigations allow us to complete the reference scale and define 35 successive ammonoidea biohorizons that can be identified in the whole basin with rare exceptions. Biohorizons have been established with similar criteria to those suggested by Page (1995), and when possible, the evolution of a particular taxonomic group has been taken into account. The use of taxa with an important record overlap in the basin has been avoided. • Tenuicostatum Zone (1 – simplex, 2 – mirabile, 3 – crosbeyi, 4 – tenuicostatum, 5 – semicelatum). Successive species of Dactylioceras with reference sections in Camino (1, 2, 3, 5) and San Miguel de Aguayo (4). • Serpentinus Zone (6 – elegantulum, 7 – exaratum, 8 – elegans, 9 – pseudoserpentinus, 10 – douvillei). Species of Harpoceratinae (Eleganticeras, Cleviceras, Harpoceras) and Hildoceratinae (Orthildaites) with reference sections in Tudanca (6, 7, 8, 9) and San Andrés (10). • Bifrons Zone (11 – sublevisoni, 12 – tethysi, 13 – lusitanicum, 14 – apertum, 15 – bifrons, 16 – semipolitum). Successive species of Hildoceras with reference section in San Andrés. • Variabilis Zone (17 – variabilis, 18 – illustris, 19 – phillipsi, 20 – vitiosa). Species of Haugia with reference section in San Andrés. • Thouarsense Zone (21 – “Grammoceras”, 22 – “Essericeras”, 23 – fallaciosum). The presence of discontinuities in numerous sections and the poor and casual record of Grammoceras and Essericeras, challenging the establishment of the lowers biohorizons in this Zone. Their reference sections are Cillamayor (21, 22) and Castillo Pedroso (23). • Dispansum Zone (24 – cappuccinum, 25 – pachu, 26 – gruneri). The firsts two are successive species of Hammatoceras and the third one is a Gruneria species with a extensive record in the basin. All of them have the reference section in Cillamayor. • Pseudoradiosa Zone (27 – levesquei, 28 – munieri, 29 – pseudoradiosa, 30 – tectiforme). Successive species of Dumortieria and Paradumortieria with reference section in Cillamayor. • Aalensis Zone (31 – mactra, 32 – subcompta, 33 – aalensis/fluitans, 34 – falcifer, 35 – buckmani). Successive species of Pleydellia with reference section in San Andrés. This succession of biohorizons has numerous similarities with the one for the Iberian Range and considerable differences with sucessions from regions further south in the Iberian Peninsula. Moreover, the presence of the same taxa as other W. Tethys regions, where detailed biozonations have been made, enable the establishment of a precise correlation between the Basque-Cantabrian Basin and the Mediterranean Province, for some particular intervals and specifically for the base of Tenuicostatum/ Polymorphum Serpentinus/Levisoni, Bifrons, Dispansum/Speciosum and Aalensis zones. The discontinuous records of Collina gemma and Dumortieria meneghinii provide difficulties in correlation between Variabilis/Gradata, and Pseudoradiosa/Meneghinii zones, respectively. The present knowledge on the Basque-Cantabrian Basin doesn’t allow the precise correlation of the base of Thouarense/Bonarelli Zones.