Suggesties voor 2005: Herhalen dag 1 1)Aanvullen de behandeling sedimentaire structuren 2)Verschil wave en stroom ripples 2) Lakprofielen inleiden hoe maak je ze etc

Opdrachten 1. Mondelinge presentaties, Dinsdag 09/03/2003 ØForm groups of same size ØChoose one of the Chapters indicated on the sheet ØPrepare oral presentation 2. Choose a spokesperson for your group (or two). These act as line of communication between you and me

Why is this important? ØYou have a problem if you cannot ‘read’ What you learn here is to read sediments and sedimentary rocks ØThe ability to collect geologic information in the field us a basic prerequisite for all geologists/physical geographers. Many if not most jobs you will work in (as geologist/physical geographer) will expose you to the problem of efficient data/information collection.

What is the goals of this exercise? ØYou should learn how to collect geologic information in the field This must be done on a manner that is reproducible for others ØYou should learn how to read/interpret sedimentologic ‘sections’ The ‘interpretation’ refers to the individual features as well as to the overall depositional environment in which these sediments were deposited ØYou should learn to do the job quickly and efficiently

Practicum Sedimentaire Structuren AANPAK Oriëntatie lakprofiel Tekenen structuren Beschrijving texturele eigenschappen sedimentaire structuren

Practicum Sedimentaire Structuren TEKENEN Simpele lijntekening op schaal Belangrijkste karakteristieken sedimentaire structuren hoeken opvallende eigenschappen

Lakprofielen interpretatie Mud with desiccation cracks Root zone Sedimentary structures not generally preserved Dark zones may represent buried soils Interbedded poorly sorted sand and gravel Gravel predominantly with matrix of sand and sandy silt Large scale cross bedded and horizontally bedded gravel; little or no matrix Coarse lag

Hoe werken we met lakprofielen en/of gesteente slabs? 1 bestuderen 2 Tekenen van het profiel gesteente stuk 3 maak een interpretatie van het sedimentaire milieu (depositional environment)

Lakprofielen a) 2-3 tekeningen per college b) Verzamel je tekeningen, lever ze in! c) Tekeningen zijn 20% van het tentamencijfer

1. Afsnijding 2. Toe-sets 3. Convex up of (down)? Practicum Sedimentaire Structuren ORIENTATIE mbv TOP-BOTTOM CRITERIA

ripples

Een partikel in een stroom/windbed Krijgt door de stroom/wind Een opwaartse druk, die het partikel Kan optillen

FLOW REGIME Reynolds number: R= (r.u.d)/h Froude number: F= u / (g.d)½ Lakprofielen interpretatie

FLOW REGIME Maak schatting van Reynolds number en Froude getal INTERPRETATIE Is het afzettingsmilieu fluviatiel, eolisch, marien of getijde Beargumenteer je keuze Lakprofielen interpretatie

INTERPRETATIE Is het afzettingsmilieu fluviatiel, eolisch, marien of getijde? Beargumenteer je keuze

Low sediment-transport rate High sediment- transport rate Angular cross strataTangential cross strata Lakprofielen interpretatie

Practicum Sedimentaire Structuren

Internal structure of a well-developed ripple. Main body is made up of foreset laminae, a single bottom set laminae, and one or few stoss side laminae. Reineck & Singh (1980, p.23) Practicum Sedimentaire Structuren

Sedimentaire structuren Korrelgrootte Grading Grootte cross strata sets Hellingsrichting en hoek Stroomrichting Practicum Sedimentaire Structuren Texturele eigenschappen

Sediment transport under increasing stream velocity. A flume experiment showing the change in sand bed with increasing stream velocity. (a) Sediment transport takes place by sliding and rolling motions of single grains. (b) A rippled forms. Major transport is by bed load and saltation. Ripples migrate faster, they tend to climb over the backs of the dunes. (d) Antidunes migrate upstream, while there is extensive sand-grain movement downstream by suspension and bed load. Almost the entire bed surface is in motion.Press & Siever (1986; p.183)

Celerische beweging

lajilla Planar beds Ripple marks Antidunes