Über Hiatus-Konkretionen (dargestellt an Beispielen aus dem Lias)

Abstract

ZusammenfassungAls Hiatus-Konkretionen werden Kalk-Konkretionen aus dem nord-und sfiddeutsehen Lias (Domerien) beschrieben, welche ein durch Sedimentationsunterbrechungen bedingtes mehrphasiges Waehstum erkennen lassen odor dureh das Zusammenwaehsen versehieden alter, durch Diskontinuitiitsfliichen getrennter Konkretionen entstanden sind.Der Hiatus wird dadurch bewiesen, dab die frtthdiagenetisch im Sediment gebildeten Konkretionen ausgewasehen, korrodiert, angebohrt oder yon Austeru, Serpuliden, Bryozoen oder anderen sessilen Organismen besiedelt wurden. Nach erneuter Einbettung setzt die Konkretionsbildung wieder ein, wobei sich die j~ngeren Toneisensteine um die ~ilteren, die ihnen als Ansatzstellen dienten, herum gebildet haben. AbstraetCalcareous coneretions from the middle Lias (Domerian) of Northern and Southern Germany revealing growth in several phases conditioned by interruptions of sedimentation or by coalescence of concretions of different age are called Hiatus Concretions. The hiatuses are proved by the fact that these concretions, which were formed in the sediment by early diagenetic processes, were washed out and are corroded or bored on the surface and encrusted by oysters, serpulids, bryozoans or other sessile benthonic organisms.After a new beginning of sedimentation the growth of the concretions started again. By this process the younger concretions included the older ones which often were the starting point for a new generation of concretions.In section the aneient surfaces with incrusting shells can be observed. R6sum6Des concr6tions de CaCO, du lias moyen (Dom6rien) de l'Allemagne du Nord et de Sud laissant reconnaitre une croissance en plusieurs phases conditionn6es par des interruptions de la s6dimentation ou qui sont form6es par une fusion des concr6tions separ~es par des surfaces de diseontinnit6 sont appel6es des << concr6tions ~ hiatus >>.Le hiatus est reconnu par le fait que los eoncr6tions form6es dans le s6di-ment pendant la premi6re phase d'une diag6n~se sont erod6es, corrod6es, envahies par des organismes perforants, ou recouvertes en partie par des Hultres, Serpulides, Bryozoaires ou autres animaux sessiles. Apr6s une s6dimentation nouvelle la croissance des concr6tions s'est poursuivie. Les coner6tions nouvelles ont envelopp6es los anciennes qui leur ont servi de noyaux. On pout observer sur les sections des surfaces de discontinuit6 marqu6es par des organismes encrofitants.

Fabric transitions from shell accumulations to reefs: an introduction with Palaeozoic examples

“…4a), this second process is assumed to be the common process in hard-ground formation (Munnecke 1997). A similar process is proposed for the formation of so-called 'hiatus concretions' (Voigt 1968).…”

The Significance of Hiatus Beds in Shallow-Water Mudstones: An Example from the Middle Jurassic of Switzerland

“…In predominantly fine-grained, siliciclastic sediments a break in sedimentation or seafloor erosion may be marked by a horizon of early diagenetic concretions, which have been referred to as ''hiatus concretions'' (Voigt 1968). In addition, certain limestone beds may form in this way (Raiswell 1988), which we suggest can be called ''hiatus beds''.…”

“…Study of individual hiatus concretions and beds (e.g., Voigt 1968;Hallam 1969;Fürsich 1979) has revealed their complex, multiphase history; this includes (1) concretion formation; (2) concretion exhumation, (3) boring and/or encrustation; (4) burial; and (5) precipitation of additional cement. During phases 1 and 5 cracking and precipitation of additional cement may occur (e.g., Kennedy et al 1977;Hesselbo and Palmer 1992).…”

“…In terms of sequence stratigraphy, hiatus concretions and beds are genetically linked to rising or high sealevel (e.g., Van Wagoner et al 1988). They occur at the initiation of transgressions (e.g., Voigt 1968;Fürsich et al 1991). Furthermore, during the time of maximum rate of transgression they form in areas where the sediment input is strongly reduced (''condensed section'' while clastics accumulate nearer to the land (e.g., Loutit et al 1988).…”

Erosional history of the Karkonosze Granite Massif – constraints from adjacent sedimentary basins and thermochronology

“…Which ever the ex act cause, this tec tonic event re sulted in the for ma tion of a se ries of NW-SE trending swells and troughs in Cen tral Po land and E-W trending com pa ra ble struc tures in Ger many, in clud ing the Mid-Pol ish Swell (e.g., Krzywiec, 2006). How the Karkonosze Gran ite Mas sif may have been af fected re mains un known, al though the long-lived Lusatian Fault, which sep arates the base ment block of the West Sudetes from the BCB, was clearly ac tive dur ing this pe riod, ac count ing for brit tle defor ma tion of Cre ta ceous (Cenomanian) rocks (Coubal, 1990;Ulièný et al, 2003;Voigt, 2009). Ex po sures at Mála Skála, where the Lužice Fault Zone makes the north ern bound ary of the BCB, show the ef fects of this ma jor de for ma tion event.…”