Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: alpheid burrows

Sortuj według:

Ogranicz wyniki do:

Middle Miocene coralgal facies at Maksymivka near Ternopil (Ukraine) : a preliminary account

Radwański A., Górka M., Wysocka A.

Acta Geologica Polonica

2006

Vol. 56, no. 1

89-103

A peculiar coralgal facies is recognized in the Lviv-Ternopil region, Ukraine, from the northern shores of the Middle Miocene (Badenian) Fore-Carpathian Basin. Its complex structure is dominated by algal buildups composed of interfingering red-algal (lithothamnian) colonies and blue-green-algal crusts, associated locally with numerous hermatypic corals (Tarbellastraea reussiana, Porites vindobonarum prima), either isolated, or overlapping each other. The holes amidst, and the crevices in, the buildups are filled with coarse bioclastic sediment (shell-grit), burrowed commonly by crustacean decapods (alpheid shrimps). The alpheid burrows, filled with coarser or finer shell-grit, served frequently as taphonomic traps for crustacean decapods (squat lobsters and crabs) and echinoids.Special attention is paid to the activity of rock-boring bivalves (Jouannetia semicaudata, Lithophaga lithophaga) in coralgal buildups and/or in particular coral colonies, some of which are redeposited, and riddled densely by bivalve borings. Emphasis is given to the environmental significance of alpheid shrimps, the tiered burrows of which are recorded in the Fore-Carpathian Basin for the first time. Crustacean decapods and echinoids are systematically studied. A comparison of the studied coralgal facies with others of the Lviv-Ternopil region, and those from the territory of Poland, indicates their faunistic and biogeographic identity.

Systemy piętrowych nor krewetek-alfeuszy i ich znaczenie środowiskowe w oksfordzie i kimerydzie Gór Świętokrzyskich

Radwańska U., Radwański A.

Volumina Jurassica

2004

Vol. 2, no. 1

113-130

To the activity of alpheid shrimps genus Alpheus Weber, 1795) ascribed are the tiered burrows of a gridlike appearance from Lower Kimmeridgian oolitic shoals and Middle Oxfordian nearshore micritic limestones of the Holy Cross Mountains, Central Poland. The burrow networks are confined to beds of the soft or hard bottom type, the upper parts of which are more or less deeply truncated, to indicate erosional events of storm agitation. At low stand, the open burrows served as traps for solutions derived from the nearby hypersaline lagoons of the sabkha type, to cause precipitation either of dolomite, or of silica gel. At high stand, the open burrows, exemplified by the Małogoszcz section (Lower Kimmeridgian), became taphonomic traps and/or crevice habitats for diverse biota, the echinoderms in particular, to form their graveyards (EchinodermenlagerstŹtten). In these, represented are echinoids (tests, some spine-coated, all either empty, or sediment-filled; broken tests and their fragments, spines) stalkless crinoids (cusps, centrodorsals, radials, brachials, cirrals), stalked crinoids (columnals, pluricolumnals), starfish (marginalia, ambulacral plates), and ophiuroids (vertebrae, arm plates). Eco-taphonomic pathways for particular echinoderms (21 taxa taxonomically recognised) are interpreted since their death to burial in open burrows. Spine-coated echinoids were entrapped alive, others were swept into during successive storms which acted as a lethal agent. The storms, catastrophic for echinoderm communities, have prevailed through a longer timespan, when the alpheid-burrowed shoal evolved from the soft bottom to the hard ground colonized by a successive echinoderm community dominated by stalked crinoids.