geosciences Article Edifice of Fluvial Terrace Flights, Stacks and Rows Wolfgang Schirmer Former Department of Geology, Heinrich Heine University Düsseldorf, Wolkenstein 24, D-91320 Ebermannstadt, Germany; [email protected]; Tel.: +49-9194-724772 Received: 31 August 2020; Accepted: 8 December 2020; Published: 15 December 2020 Abstract: The paper presents a review of the architecture and structures of river deposits in valleys. A new terminology for some features is included in this review. It presents principles of the fluvial systems with morphological river terraces and fluments (new term for terrace bodies), different stages of the morphological terraces, the texture—the arrangement—of fluments in the form of terrace flights, terrace stacks and terrace rows, and the (inner) structure of a single flument. The contact between the valley fill and the bedrock is named by the new term “pelma”. Special topics deal with flument overlaps and insight into the deepest valley fill down to the bedrock. A comparison with other terms of the fluvial inventory is annexed. Keywords: river terrace; flument (terrace body); pelma (contact flument/bedrock); terrace flight; terrace row; flument stack; flument overlap; valley underground 1. Introduction This paper highlights frequent as well as rare situations derived from constructing terrace flights, terrace rows and flument stacks. River terrace flights, stacks and rows are well known and described in detail, e.g., [1–20]. In supplement to these papers, the following explanations separate morphological river terraces and fluments as terrace bodies, highlight texture (arrangement) of terrace flights, terrace stacks and terrace rows, and highlight problems of flument overlap and of the study of the deepest valley fill down to the bedrock. It emphasizes the (inner) structure of the fluments as tools for recognizing single flument portions. Fluments and terraces always are indicated by a name and not numbered, as already stressed by Howard [21,22]. As the focus in this text is given to the architecture of the elements of the valley, only sometimes their genesis, e.g., [23–27], and age determination, e.g., [28,29], are mentioned marginally. In the later part of the paper, selected examples besides the general explanations relate to the Upper Main region in south-eastern Germany (Figure1). The selection in Central Europe or sometimes in the Rhine–Main River area gives the results a regional character. In comparison to other visited or studied areas in the world, though, e.g., North America or the Orient [30–32], many common features turned out to fit into the given schemes. Geosciences 2020, 10, 501; doi:10.3390/geosciences10120501 www.mdpi.com/journal/geosciences Geosciences 2020, 10, 501 2 of 22 Geosciences 2020, 10, x FOR PEER REVIEW 2 of 23 Figure 1. Location map of the UpperUpper MainMain areaarea/Bavaria./Bavaria. Inset: Map of Germany. Black rectanglerectangle == location of this map. Violet: Uplift Uplift area area of the the Rhenish Shield. Green Green area: area: Upper Upper Rhine Rhine graben. graben. 2. Materials Materials and and Methods Methods The followingfollowing report report results results from from extended extended and and long long fieldwork fieldwork along riversalong inrivers the Alpine in the foreland, Alpine foreland,the central the upland central and upland the northern and the lowland northern of Central lowland Europe, of Central North Europe, America, North and Mesopotamia. America, and Mesopotamia.The investigation includes: Mapping in scale 1: 5000, 1: 25,000, separation of morphological terraces,The andinvestigation investigation includes: of their Mapping pedological in properties,scale 1: 5000, including 1: 25,000, pedochemical separation properties. of morphological Study of terraces,the vertical and structure, investigation from of thetheir highest pedological fluvial properties, deposits downincluding to the pedochemical very valley properties. underground Study at ofthe the bedrock, vertical is structure, done case from by casethe highest using grain fluvial size deposits separation down of to gravel, the very sand valley and underground fines, chemical at 14 theproperties bedrock, (carbonate, is done case organic by case carbon, using phosphorus, grain size heavy separation metals), of datinggravel, bysandC, and dendrochronology, fines, chemical propertiespollen analysis, (carbonate, and archaeological organic carbon, and phosphorus, historical heavy materials. metals), The dating Main by River 14C, dendrochronology, valley in southern pollenGermany, analysis, to which and the archaeological focus is frequently and givenhistorical here, materials. gave the mostThe completeMain River insight. valley From in southern all these Germany,studies resulted to which the the general focus insights is frequently into the given fluvial here, valley gave edifices the most presented complete in insight. the following. From all these studies resulted the general insights into the fluvial valley edifices presented in the following. 3. Principles of Flument Systems 3.3.1. Principles Flument and of Flument Terrace Systems 3.1. FlumentPenck [and33] triedTerrace to separate the morphological “terrace” from the sedimentological “gravel”, but used the term terrace for both facts. In this way it is often used until today. Boesch [34] points to the Penck [33] tried to separate the morphological “terrace” from the sedimentological “gravel”, but fact that the accumulation body and its topping terrace are mostly not of the same age. Leopold et al. [35] used the term terrace for both facts. In this way it is often used until today. Boesch [34] points to the (p. 460) state that the sedimentary deposit of a terrace “should more properly be referred to as a fill, fact that the accumulation body and its topping terrace are mostly not of the same age. Leopold et al. alluvial fill, or alluvial deposit, in order to differentiate it from the topographic form”. [35] (p. 460) state that the sedimentary deposit of a terrace “should more properly be referred to as a Thus, here a distinction is drawn between the sedimentary body and its morphological surface, fill, alluvial fill, or alluvial deposit, in order to differentiate it from the topographic form”. called terrace. The river deposit is called flument (from Latin flumen = river, stream), a term newly Thus, here a distinction is drawn between the sedimentary body and its morphological surface, introduced [14] (p. 135). As shown in Figure2, the structure of the flument in its best preservation shows: called terrace. The river deposit is called flument (from Latin flumen = river, stream), a term newly basal lag layer, channel deposit, floodplain deposit and floodplain soil. This is a frequent example of introduced [14] (p. 135). As shown in Figure 2, the structure of the flument in its best preservation the flument structure among many other possibilities. The flument is topped morphologically by the shows: basal lag layer, channel deposit, floodplain deposit and floodplain soil. This is a frequent river terrace that is a mere surface feature. example of the flument structure among many other possibilities. The flument is topped morphologically by the river terrace that is a mere surface feature. Geosciences 2020, 10, x FOR PEER REVIEW 3 of 23 GeosciencesGeosciences2020 2020, 10, 10, 501, x FOR PEER REVIEW 33 of of 22 23 Figure 2. Flument structures. A complete flument is composed of all members of the fluviatile series. Figure 2. Flument structures. A complete flument is composed of all members of the fluviatile series. TheFigure skeleton 2. Flument gravel isstructures. marked by A blackcomplete pebbles flument in all is figures composed of this of allpaper. members of the fluviatile series. The skeleton gravel is marked by black pebbles in all figures of this paper. The skeleton gravel is marked by black pebbles in all figures of this paper. In case the flument rests upon the bedrock the contact between the flument and the bedrock is In case the flument rests upon the bedrock the contact between the flument and the bedrock is called Inpelma case (fromthe flument Greek restspélma upon = sole), the a bedrock term introduced the contact recently between [15] the (p. flument 70) (Figure and 3).the The bedrock basal is called pelma (from Greek pélma = sole), a term introduced recently [15] (p. 70) (Figure3). The basal bedrockcalled pelmacontact (from is the Greekground pélma pelma, = sole), and the a term lateral introduced bedrock contact recently is [15]the wall(p. 70) pelma. (Figure Ground 3). The pelma basal bedrock contact is the ground pelma, and the lateral bedrock contact is the wall pelma. Ground pelma hasbedrock a certain contact affinity is the to ground the term pelma, “strath”: and the it lateraldoes not bedrock conform contact to strath is the wallsensu, pelma. Bucher’s Ground original pelma has a certain affinity to the term “strath”: it does not conform to strath sensu, Bucher’s original definitionhas a certain [36]. Theaffinity term to is thediscussed term “strath”: by various it doesredefinitions, not conform e.g., [21,26,37]to strath (seesensu, Chapter Bucher’s 7). original definition [36]. The term is discussed by various redefinitions, e.g., [21,26,37] (see Section7). definition [36]. The term is discussed by various redefinitions, e.g., [21,26,37] (see Chapter 7). Figure 3. Ortho-terrace and pelma: A complete flument is bounded on top by the ortho-terrace as Figure 3. Ortho‐terrace and pelma: A complete flument is bounded on top by the ortho‐terrace as tread, at the basal bedrock contact by the ground pelma, and at the lateral bedrock contact by the wall tread,Figure at the3. Orthobasal ‐bedrockterrace andcontact pelma: by the A groundcomplete pelma, flument and is at bounded the lateral on bedrock top by contactthe ortho by‐ theterrace wall as pelma. (The flument exemplarily is figured as V-flument). pelma.tread, (The at the flument basal bedrock exemplarily contact is figuredby the ground as V‐flument). pelma, and at the lateral bedrock contact by the wall pelma. (The flument exemplarily is figured as V‐flument).