Mineralogical and Geochemical Compositions of Sedimentary Rocks in the Gosau Group (Late Cretaceous), Grünbach–Neue Welt Area, Austria

Abstract

Sedimentary rocks of the Gosau Group in the Grünbach–Neue Welt area (Eastern Alps, Austria) were analyzed to determine their mineralogical and geochemical compositions. This study includes the following: (1) the identification of major minerals using X-ray diffraction (XRD), (2) the analysis of major, minor, and trace elements via X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), and (3) the quantification of total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS) using an Elementar Unicube analyzer. Samples were collected from four artificial trenches and one outcrop in Maiersdorf, spanning the Grünbach and Piesting formations deposited during a terrestrial-to-marine transition in the upper Santonian to Campanian (Late Cretaceous). The dominant minerals—quartz, muscovite, illite, and calcite—exhibit relative abundances corresponding with variations in major oxide concentrations. Minor elements show variability but generally follow consistent trends. Trace and rare earth elements display greater variability but similar patterns, with a broader distribution in the Grünbach Formation. Elevated TOC, TN, and TS values are observed near the formation boundary and in the Piesting formation. These results offer the mineralogical and geochemical characterization of the strata, and lay a foundation for further investigations into the paleoenvironmental and basin evolution of the Gosau Group in the region, providing a comparative framework for Gosau basins across the Eastern Alps.

Dataset: Data are contained within the article or Supplementary Materials.

Dataset License: CC-BY-NC 4.0

1. Summary

The Gosau Group is a sedimentary succession deposited from the Late Cretaceous to the Eocene, formed within a series of structurally formed depressions on the northern frontal edge of the Austroalpine [1,2,3,4]. Nowadays, the deposits of Gosau Group are mostly distributed across the Northern Calcareous Alps (NCA) in the Eastern Alps, Austria [3,4,5] (e.g., Figure 1a). The group’s evolution was closely tied to tectonic subsidence driven by the southward subduction of the Penninic Ocean’s oceanic plate beneath the Austroalpine plate, which led to a paleoenvironmental transition from terrestrial to marine settings [2,3,4,5,6,7,8,9,10,11]. It comprises two subgroups, representing a terrestrial-dominated setting with intermittent marginal-shallow marine incursions (Lower Gosau Group; LGS) and a shelf to deep marine setting (Upper Gosau Group; UGS), respectively [3,4]. Therefore, investigating the Gosau Group is crucial for capturing the full scope of Late Cretaceous environmental and tectonic evolution within the Gosau basins, and also deepening our understanding of basin development along subsiding continental margins in the subduction-related setting.

This study examines the upper Santonian to Campanian (Late Cretaceous) deposits of the Gosau Group, situated in the Grünbach–Neue Welt area of eastern Austria, located near the boundary between the NCA and the Vienna Basin (Figure 1a). In this region, the deposits encompass the Grünbach Formation (Fm.) and the Piesting Fm., which record a transition in depositional environments from terrestrial to shallow marine settings [10,11,12,13,14] as well as the stratigraphic shift from the LGS to the UGS (Figure 2). Notably, the boundary between these formations is marked by a conformable contact with transitional features [2,9,10,11,12,13,14], rather than by angular unconformities or erosional surfaces at other Gosau sites (e.g., [15]). Despite its geological significance, the transitional interval remains understudied due to limited outcrop exposure and a lack of an integrated approach. Previous research has largely emphasized paleontological and sedimentological aspects [9,10,11,12,13,14]. Given the continuous sedimentary record in the Grünbach–Neue Welt area, our study aims to acquire mineralogical and geochemical datasets of the Grünbach and lower Piesting fms. for characterizing the strata and, particularly, the transitional interval.

Due to the limited natural exposure conditions of the Grünbach Fm. and Piesting Fm., four artificial trenches were excavated in Maiersdorf, along with the investigation of one nearby outcrop site (Figure 1b); Trench A (47°49′29.07″ N, 16°03′08.88″ E, 15 m in length), Trench B (47°49′33.6″ N, 16°03′03.6″ E, 25.5 m in length), Trench C (47°49′36.00″ N, 16°03′00.07″ E, 70 m in length), Trench D (47°49′30.08″ N, 16°03′10.85″ E, 17 m in length), and the outcrop (47°49′25″ N, 16°03′07″ E). Based on lithological and stratigraphical observations, the profiles of the trenches and outcrops are illustrated in Figure 3. The Grünbach Fm. is primarily composed of claystone and fine- to medium-grained sandstone, interspersed with occasional marl and coal layers. The lower Piesting Fm. consists predominantly of fine- to medium-grained sandstone interbedded with thin claystone and siltstone layers. We collected six samples from Trench A, nine samples from Trench B, twenty-eight samples from Trench C, twenty-three samples from Trench D, and two samples from the outcrop (Figure 3). To determine their mineralogical and geochemical compositions, thirty-four samples were thoroughly selected primarily based on lithological variations, along with twenty-four samples for the Grünbach Fm. and ten samples for the Piesting Fm.

This study analyzes samples from the two formations to assess their mineralogical and geochemical compositions. Mineralogical phases were determined using X-ray diffraction (XRD). Major elements were quantified through X-ray fluorescence spectroscopy (XRF). For minor and trace elements, inductively coupled plasma mass spectrometry (ICP-MS) was employed, enabling the precise quantification of a broad range of elements with high sensitivity. In addition, total organic carbon (TOC), nitrogen (TN), and sulfur (TS) contents were determined using Elementar Unicube analysis. The results offer valuable insights into the mineralogical and geochemical characteristics of the strata, revealing common patterns and distinct variations through the transitional interval. We look forward to these findings laying the groundwork for future investigations into the paleoenvironmental and basin evolution of the Gosau Group in this region and providing a valuable comparative framework for correlating Gosau basins across the Eastern Alps.

2. Data Description

This section presents the results of the mineralogical and geochemical analyses conducted on 34 samples from the Grünbach Fm. and Piesting Fm. of the Gosau Group in the Grünbach–Neue Welt area. The XRD patterns are accompanied by identified mineral phases. Tables of major, minor, and trace elements are organized with each column representing a specific element, while the rows display the weight percentage (wt. %) or parts per million (ppm) data for each sample. The weight percentages of TOC, TN, and TS are grouped for locations.

2.1. Dominant Mineralogical Composition

The XRD patterns of samples from Trenches A, B, C, and D are shown in Figure 4. Across both the Grünbach and Piesting formations, the dominant mineral phases identified include quartz, illite, and muscovite, reflecting a typical siliciclastic composition. Chlorite is also commonly detected. Due to the overlapping diffraction peaks of muscovite and illite, their presence is reported collectively. These clay minerals may reflect the prevailing weathering conditions or diagenetic processes. Calcite is variably present among the samples, with notably higher intensities observed in some intervals in Trench C and D, suggesting occasional carbonate cementation or allochthonous carbonate input [12]. XRD datasets and a list of identified dominant minerals for each sample are provided in Supplementary Material and Table S1.

2.2. Major Element Oxides

The major elements are detected in the form of oxides, which are SiO₂, Al₂O₃, CaO, Fe₂O₃, MgO, K₂O, Na₂O, MnO, and P₂O₅ (

Table 1. Major element oxides of samples from the Grünbach Fm. (GF) and Piesting Fm. (PF). The sample locations are shown in Figure 3. Details of the major oxide contents are available in Table S2.

Location	No.	Fm.	SiO2	Al2O3	CaO	Fe2O3	MgO	K2O	TiO2	Na2O	MnO	P2O5
			wt. %
Outcrop	M-23-1	PF	41.70	2.65	49.72	1.66	0.78	0.43	0.19	0.25	0.07	0.05
	M-23-2	PF	15.50	1.80	71.62	0.90	1.15	0.14	0.03	0.16	0.13	0.02
Trench A	M-A-3	GF	50.97	17.99	7.76	2.58	0.68	4.11	0.94	0.40	0.01	0.03
	M-A-5	GF	55.09	18.34	2.91	8.41	1.65	4.00	0.97	0.60	0.05	0.12
Trench C	M-C-2	GF	52.74	17.60	6.56	5.38	1.89	3.95	0.89	0.57	0.11	0.14
	M-C-3	GF	59.17	7.91	19.83	2.61	1.63	1.53	0.46	0.55	0.18	0.12
	M-C-7	GF	50.99	16.50	5.54	10.05	1.60	3.81	0.81	0.56	0.20	0.21
	M-C-8	GF	62.78	8.96	14.67	3.77	1.42	1.95	0.62	0.65	0.13	0.12
	M-C-9	GF	48.98	16.50	9.22	5.83	1.78	3.72	0.83	0.59	0.11	0.12
	M-C-13	GF	60.12	6.79	22.65	3.42	0.97	1.07	0.31	0.54	0.09	0.09
	M-C-14	GF	59.80	9.27	16.76	3.06	1.49	1.73	0.54	0.53	0.08	0.13
	M-C-15	GF	46.20	18.89	7.97	5.54	2.54	4.34	0.80	0.35	0.23	0.12
	M-C-16	GF	54.65	16.18	7.12	3.36	1.39	3.17	0.82	0.46	0.04	0.12
	M-C-19	GF	45.14	17.44	11.55	5.70	1.74	3.99	0.76	0.45	0.10	0.12
	M-C-22	GF	38.62	13.90	25.97	6.26	1.59	3.27	0.63	0.28	0.13	0.12
	M-C-24	GF	41.72	13.67	23.89	5.94	1.61	3.18	0.66	0.33	0.13	0.13
	M-C-26	GF	42.14	11.07	27.97	5.49	1.62	2.54	0.58	0.39	0.14	0.12
	M-C-28	GF	47.39	12.39	19.15	5.19	1.31	2.98	0.67	0.75	0.09	0.16
Trench D	M-D-2	PF	72.54	10.19	2.82	4.94	1.06	2.14	0.66	0.62	0.11	0.14
	M-D-3	PF	54.70	17.95	2.56	9.69	1.57	4.11	0.95	0.52	0.03	0.13
	M-D-5	PF	64.65	9.59	5.65	8.10	1.01	2.05	0.70	0.55	0.08	0.12
	M-D-7	PF	57.74	12.97	2.94	7.55	0.80	3.04	0.87	0.56	0.02	0.07
	M-D-8	PF	61.91	12.89	1.86	9.02	1.22	2.80	0.81	0.57	0.05	0.12
	M-D-12	PF	66.40	10.39	0.73	13.06	1.03	2.24	0.74	0.66	0.09	0.14
	M-D-13	PF	53.75	17.23	6.23	5.68	1.73	3.95	0.89	0.49	0.06	0.12
	M-D-15	PF	45.46	13.76	31.55	1.88	1.01	0.75	0.27	0.40	0.25	0.11
	M-D-17	GF	65.47	16.74	0.42	5.58	1.64	3.61	1.00	0.63	0.06	0.10
	M-D-19	GF	69.80	9.61	5.08	4.60	1.00	1.98	0.81	0.59	0.09	0.12
	M-D-20	GF	56.85	19.85	0.35	9.06	2.03	4.22	1.00	0.53	0.10	0.11
	M-D-24	GF	58.48	20.20	7.03	7.03	1.83	4.31	1.01	0.64	0.12	0.11
	M-D-25	GF	74.78	9.48	2.81	2.81	0.96	1.86	0.58	0.60	0.05	0.11
	Avg.		54.07	13.18	13.58	5.62	1.41	2.81	0.70	0.51	0.10	0.11

). These elements represent the primary constituents of siliciclastic sedimentary rocks and are present in relatively high concentrations, reflecting the mineralogical composition typical of such deposits.

In the samples from the Grünbach Fm. (Table 1), SiO₂ exhibits the highest concentration, with an average value of 54.38% and a range from 38.62% to 74.78%. Al₂O₃ and CaO are the next most abundant elements, with average concentrations of 14.25% and 11.68%, respectively. Both elements display considerable variability; Al₂O₃ ranges from 6.79% to 20.20%, while CaO ranges between 0.35% and 27.97%. The Fe₂O₃ content has a mean value of 5.32%, with a range of 2.58% to 10.05%. K₂O averages 3.11%, with values between 1.07% and 4.34%. MgO shows a range between 0.68% and 2.54%, with an average concentration of 1.54%. TiO₂ concentrations vary between 0.31% and 1.01%, averaging 0.75%. The concentration of Na₂O is relatively low, ranging from 0.28% to 0.75%. MnO and P₂O₅ exhibit the lowest average concentrations, with mean values of 0.11% and 0.12%, respectively.

The distribution pattern of major elements in the Piesting Fm. samples exhibits similarities to those observed in the Grünbach Fm. (Table 1). SiO₂ is the most abundant element, with concentrations ranging from 15.50% to 72.54% and an average value of 53.44%. CaO shows an average concentration of 17.57%, ranging widely from 0.73% to 71.62%. The average values of Al₂O₃ and Fe₂O₃ contents are 10.94% and 6.25%, respectively. The content of Al₂O₃ varies between 1.80% and 17.95%, and the content of Fe₂O₃ ranges from 0.90% to 13.06%. The average value of K₂O is 2.17%, ranging from 0.14% to 4.11%. The concentrations of MgO and TiO₂ exhibit similar average values of 1.14% and 0.61%, respectively, with MgO ranging from 0.78% to 1.73% and TiO₂ ranging from 0.03% to 0.95%. The content of Na₂O is notably less than that of TiO₂, varying from 0.16% to 0.66%, with an average value of 0.48%. MnO and P₂O₅ are present in trace amounts, with average values below 0.1%.

In summary, the distributions of major oxides in the samples from the Grünbach Fm. and the Piesting Fm. exhibit similar patterns (Table 1), with high abundances of SiO₂, Al₂O₃, and CaO, followed by moderate levels of Fe₂O₃, MgO, and K₂O. TiO₂, Na₂O, MnO, and P₂O₅ are present in relatively lower concentrations. Notably, the samples from the Grünbach Fm. exhibit elevated Al₂O₃ content and reduced CaO levels compared to those from the Piesting Fm., reflecting primary lithology, depositional environment, as well as different levels of clay abundance and carbonate cementation.

2.3. Minor and Trace Elements

Table 2. (a) Minor and trace element data; (b) LREEs and HREEs data of samples from the Grünbach Fm. (GF) and Piesting Fm. (PF). The sample locations are shown in Figure 3. Details of the rare earth element data are available in Table S3.

(a)
Location	Samples No.		Fm.		Minor Elements									Trace Elements
					V		Ni		Sr		Zr	Ba		Sc		Hf		Th	Li	Be		Cr	Co		Cu		Zn		Ga		Ge		Rb	Y	Nb		Cs		Ta		Pb	U
					ppm									ppm
Outcrop	M-23-1		PF		49.4		25.8		320.1		67.2	56.1		2.8		1.6		1.9	2.1	0.1		19.9	1.1		1.6		6.5		0.6		0.1		3.7	0.7	0.8		0.2		0.0		1.3	1.3
	M-23-2		PF		10.2		5.7		239.7		15.1	9.8		0.5		0.3		0.2	15.4	0.3		55.4	6.2		4.9		17.1		3.2		0.3		16.2	8.0	4.2		0.9		0.3		6.7	1.2
Trench A	M-A-3		GF		161.7		16.5		41.3		109.1	300.6		6.7		3.0		4.5	80.2	2.6		101.8	3.8		11.2		23.3		22.5		0.3		99.6	8.1	17.1		7.4		1.2		5.8	2.7
	M-A-5		GF		153.6		74.1		126.6		129.4	512.8		18.9		3.4		10.3	87.9	2.5		113.0	25.3		36.3		74.7		24.0		0.9		220.1	25.6	18.7		19.8		1.3		17.2	2.8
Trench B	M-B-0		GF		230.2		60.4		105.2		120.1	552.4		24.5		3.2		11.6	-	-		163.5	21.2		60.0		82.7		39.1		-		-	18.5	19.1		13.7		1.2		11.5	3.1
	M-B-4		GF		178.5		64.3		73.1		126.9	465.3		21.0		4.0		11.6	-	-		127.1	25.0		60.3		95.9		30.6		-		-	21.4	20.4		9.8		1.4		14.4	3.0
	M-B-5		GF		201.3		85.0		86.3		136.6	428.4		23.4		3.8		12.6	-	-		140.1	36.2		73.6		110.4		31.4		-		-	28.6	22.0		8.6		1.3		14.5	2.6
Trench C	M-C-2		GF		125.9		52.4		120.0		103.6	404.1		13.5		2.7		9.0	77.1	2.0		99.1	15.1		33.9		53.3		21.0		0.5		166.8	17.2	15.6		19.3		1.1		13.6	2.5
	M-C-3		GF		55.2		31.4		169.3		70.5	296.1		14.0		1.9		8.9	43.1	0.9		68.3	7.6		10.6		28.2		10.2		0.4		92.8	30.4	7.7		6.5		0.5		6.4	3.8
	M-C-7		GF		151.6		71.8		84.3		94.4	437.9		11.6		2.6		8.4	58.9	2.3		111.2	22.9		37.3		55.9		21.4		0.9		109.5	15.1	15.8		7.7		1.1		10.0	3.3
	M-C-8		GF		73.2		31.9		125.5		56.4	263.9		6.8		1.5		4.7	38.7	1.1		60.5	8.9		21.3		33.4		11.5		0.4		68.8	9.9	10.8		3.6		0.7		5.3	1.9
	M-C-9		GF		157.7		64.1		207.1		102.1	487.5		15.5		2.6		11.3	73.4	2.1		120.2	19.2		25.7		56.0		21.3		0.6		153.8	21.1	15.5		10.7		1.1		13.7	2.7
	M-C-13		GF		39.1		26.2		170.4		43.9	158.9		4.9		1.1		3.1	22.7	0.7		48.8	6.9		9.8		24.7		6.7		0.4		37.9	9.0	5.4		2.5		0.4		6.0	1.0
	M-C-14		GF		54.1		23.4		116.2		54.4	210.8		3.9		1.4		3.9	29.5	0.9		64.9	5.3		11.6		27.6		9.5		0.3		59.8	7.8	8.0		3.0		0.6		4.9	1.3
	M-C-15		GF		149.1		73.3		258.3		126.7	946.4		36.0		3.3		14.1	95.6	2.4		126.0	23.9		42.1		66.1		28.5		0.8		229.2	34.8	15.8		24.1		1.1		25.6	3.1
	M-C-16		GF		125.4		47.9		159.8		123.7	392.7		9.3		3.0		11.3	142.0	2.0		93.1	12.7		49.7		51.0		20.2		0.4		223.0	18.8	15.2		21.0		1.1		12.4	3.4
	M-C-19		GF		124.3		48.7		105.9		89.7	447.1		9.9		2.5		8.3	60.3	2.2		104.0	14.3		34.5		50.5		22.3		0.6		150.2	14.6	14.2		9.9		1.0		9.8	2.3
	M-C-22		GF		104.1		43.9		151.3		66.8	316.2		6.0		1.8		4.0	45.3	1.8		77.7	17.0		30.2		41.4		17.5		0.6		100.8	8.3	11.1		5.6		0.8		10.1	2.1
	M-C-24		GF		108.5		49.4		211.0		90.5	348.3		9.0		2.4		6.1	52.8	1.8		84.0	15.5		30.1		47.4		18.3		0.6		108.9	11.9	12.4		6.8		0.9		11.1	2.4
	M-C-26		GF		77.0		40.3		206.5		82.5	331.0		5.6		2.1		7.1	43.7	1.3		63.4	12.9		22.3		37.1		13.6		0.6		100.7	11.7	9.4		8.3		0.7		8.8	2.0
	M-C-28		GF		87.5		44.2		214.2		100.5	325.3		14.6		2.7		11.0	50.8	1.8		79.2	13.2		19.2		33.4		17.0		0.6		128.2	20.5	13.5		8.9		1.0		6.3	2.8
Trench D	M-D-2		PF		92.4		34.9		47.2		71.9	237.8		7.1		1.8		5.3	45.9	1.2		68.2	13.1		13.0		30.8		13.0		0.5		61.0	10.4	10.7		2.8		0.7		6.3	1.5
	M-D-3		PF		192.9		31.9		69.4		115.2	489.8		15.9		3.2		6.8	79.5	2.4		121.0	7.0		30.4		81.6		24.0		1.0		141.5	11.4	17.6		12.2		1.2		18.7	3.7
	M-D-5		PF		82.7		43.0		51.7		64.3	261.8		4.8		1.6		3.3	39.3	1.0		60.1	13.4		10.0		27.0		11.8		0.8		62.1	7.7	10.0		2.3		0.7		5.9	1.7
	M-D-7		PF		165.3		27.4		84.8		84.8	395.4		14.9		2.3		7.4	45.2	1.8		99.3	9.9		28.7		33.0		18.6		0.8		103.4	15.6	15.1		5.4		1.0		23.1	2.4
	M-D-8		PF		140.2		53.5		58.6		106.8	339.0		13.1		2.8		7.9	54.9	1.7		92.6	22.7		33.6		57.0		17.1		1.0		83.1	14.1	14.7		4.2		1.0		13.2	2.4
	M-D-12		PF		88.2		38.7		43.2		66.0	288.2		9.7		1.7		5.9	43.8	1.2		62.8	14.3		15.0		32.4		13.3		1.2		65.7	12.0	11.8		2.8		0.8		7.0	1.9
	M-D-13		PF		146.3		36.6		101.7		93.2	334.4		10.1		2.5		7.6	67.6	2.2		101.5	10.2		27.1		49.8		20.5		0.6		121.4	13.1	15.3		9.5		1.1		10.1	2.6
	M-D-15		PF		31.6		15.6		295.5		47.1	91.5		4.5		1.1		2.1	22.4	0.5		26.8	4.2		4.2		16.2		6.0		0.3		29.7	6.9	4.4		1.3		0.3		2.8	1.0
	M-D-17		GF		135.0		44.0		65.1		111.8	380.2		14.1		3.0		7.8	72.8	1.9		99.7	16.6		35.8		50.4		21.4		0.6		114.2	14.5	16.1		8.0		1.2		12.0	2.3
	M-D-19		GF		88.3		31.8		71.4		89.5	277.4		7.8		2.1		5.4	41.4	1.1		68.3	9.2		11.1		35.5		12.5		0.5		67.4	12.3	12.9		2.6		0.9		5.1	1.6
	M-D-20		GF		175.9		64.9		95.8		111.8	653.5		23.7		3.1		13.6	90.6	2.5		125.0	23.5		51.8		71.8		26.8		1.0		190.6	27.7	19.1		10.9		1.3		15.9	3.1
	M-D-24		GF		180.0		58.6		81.9		140.3	536.1		18.3		3.2		8.7	93.0	2.6		126.7	24.4		43.0		65.1		26.8		0.8		127.8	17.4	18.9		7.7		1.3		14.9	3.0
	M-D-25		GF		88.0		24.3		86.9		57.7	269.1		8.5		1.5		5.9	42.3	1.0		59.1	7.2		10.4		36.4		12.4		0.4		64.1	11.5	9.8		2.4		0.7		3.7	1.4
	Avg.				118.4		43.7		130.7		90.3	360.2		12.1		2.4		7.4	56.7	1.6		89.2	14.4		27.7		47.2		18.1		0.6		106.5	15.2	13.2		7.9		0.9		10.4	2.3
(b)
Location		LREEs																						HREEs
				REE		La		Ce		Pr			Nd		Sm		Eu		Pm		ΣLREE			Gd		Tb		Dy		Ho		Er		Tm		Yb		Lu		ΣHREE
		No.
		ppm
Outcrop		M-23-1				7.1		13.8		1.8			7.4		1.5		0.3		0.0		32.0			1.5		0.2		1.3		0.2		0.7		0.1		0.6		0.1		4.7
		M-23-2				0.5		1.1		0.1			0.5		0.1		0.0		0.0		2.3			0.1		0.0		0.1		0.0		0.0		0.0		0.0		0.0		0.3
Trench A		M-A-3				12.5		31.2		3.2			13.2		2.3		0.5		0.0		63.0			2.0		0.3		1.5		0.3		1.0		0.2		1.0		0.1		6.4
		M-A-5				36.4		86.3		9.1			34.5		7.5		1.6		0.0		175.5			6.6		1.0		4.9		0.9		2.6		0.4		2.7		0.4		19.4
Trench B		M-B-0				23.1		49.9		5.8			24.7		5.7		1.2		0.0		110.3			4.9		0.7		3.8		0.8		2.3		0.3		2.3		0.3		15.4
		M-B-4				23.9		49.1		7.1			27.9		6.2		1.3		0.0		115.6			5.8		0.9		4.9		1.0		3.0		0.4		2.9		0.4		19.3
		M-B-5				32.7		60.9		6.9			30.3		7.2		1.5		0.0		139.5			6.5		0.9		5.2		1.1		3.2		0.5		3.1		0.5		20.8
Trench C		M-C-2				25.4		59.0		6.3			24.6		4.8		0.9		0.0		121.1			4.1		0.5		3.0		0.6		1.8		0.3		1.9		0.3		12.4
		M-C-3				34.4		67.1		7.5			30.1		6.3		1.3		0.0		146.8			6.0		0.8		4.7		0.9		2.6		0.4		2.4		0.4		18.1
		M-C-7				20.3		59.8		5.2			21.5		4.5		0.9		0.0		112.3			4.0		0.5		3.0		0.6		1.6		0.2		1.5		0.2		11.7
		M-C-8				16.3		32.7		3.7			14.8		2.9		0.6		0.0		71.1			2.6		0.4		2.0		0.4		1.1		0.2		1.0		0.1		7.7
		M-C-9				32.6		66.2		7.4			29.5		5.7		1.2		0.0		142.5			5.0		0.6		3.6		0.7		2.1		0.3		2.1		0.3		14.7
		M-C-13				10.0		19.5		2.3			10.0		2.0		0.4		0.0		44.1			1.9		0.3		1.6		0.3		0.9		0.1		0.8		0.1		5.9
		M-C-14				14.9		29.6		3.7			13.9		2.8		0.6		0.0		65.5			2.5		0.3		1.9		0.4		1.0		0.1		0.9		0.1		7.3
		M-C-15				50.6		88.1		12.0			48.2		9.6		2.0		0.0		210.4			8.0		1.1		6.0		1.2		3.5		0.5		3.6		0.5		24.4
		M-C-16				29.7		61.8		7.1			28.2		5.5		1.1		0.0		133.4			4.9		0.6		3.4		0.7		1.9		0.3		2.1		0.3		14.1
		M-C-19				26.6		54.6		6.2			26.0		4.6		0.9		0.0		118.9			3.9		0.5		2.8		0.6		1.6		0.2		1.6		0.2		11.4
		M-C-22				19.3		39.6		4.4			17.5		3.1		0.6		0.0		84.7			2.6		0.3		1.8		0.3		1.0		0.1		0.9		0.1		7.3
		M-C-24				23.5		46.8		5.3			21.0		3.9		0.8		0.0		101.3			3.4		0.4		2.4		0.5		1.4		0.2		1.3		0.2		9.8
		M-C-26				32.8		66.3		7.5			29.8		5.7		1.1		0.0		143.2			4.8		0.6		3.4		0.6		1.8		0.3		1.6		0.2		13.3
		M-C-28				24.6		50.7		5.7			22.4		4.7		0.9		0.0		109.1			4.4		0.6		3.4		0.7		2.0		0.3		1.9		0.3		13.5
Trench D		M-D-2				18.0		42.0		4.2			16.9		3.3		0.7		0.0		85.1			2.9		0.4		2.0		0.4		1.1		0.2		1.0		0.1		8.1
		M-D-3				22.6		48.2		5.1			20.7		3.8		0.8		0.0		101.2			3.1		0.4		2.2		0.5		1.6		0.2		1.6		0.2		9.7
		M-D-5				17.5		36.7		4.1			16.6		3.2		0.6		0.0		78.7			2.7		0.4		1.9		0.4		1.0		0.2		0.9		0.1		7.5
		M-D-7				25.2		53.4		5.8			22.8		4.4		0.9		0.0		112.5			3.8		0.5		2.9		0.6		1.7		0.3		1.8		0.3		11.8
		M-D-8				20.4		44.4		5.0			20.2		4.1		0.9		0.0		94.9			3.6		0.5		2.8		0.5		1.5		0.2		1.7		0.2		11.0
		M-D-12				19.3		42.3		4.6			18.7		3.8		0.8		0.0		89.5			3.3		0.4		2.2		0.4		1.2		0.2		1.2		0.2		9.1
		M-D-13				19.4		44.6		4.8			19.3		3.8		0.8		0.0		92.8			3.2		0.4		2.5		0.5		1.4		0.2		1.5		0.2		10.0
		M-D-15				6.9		13.7		1.7			7.0		1.4		0.3		0.0		30.9			1.3		0.2		1.1		0.2		0.6		0.1		0.6		0.1		4.2
		M-D-17				23.3		50.2		5.7			22.8		4.6		0.9		0.0		107.6			3.9		0.5		2.9		0.5		1.6		0.2		1.6		0.2		11.5
		M-D-19				19.5		39.9		4.4			17.8		3.4		0.7		0.0		85.8			3.0		0.4		2.4		0.5		1.4		0.2		1.3		0.2		9.3
		M-D-20				46.6		95.4		10.6			42.4		8.3		1.7		0.0		205.0			7.1		0.9		5.0		1.0		2.8		0.4		2.7		0.4		20.4
		M-D-24				30.2		60.1		6.9			27.7		5.4		1.1		0.0		131.4			4.6		0.6		3.3		0.6		1.9		0.3		2.0		0.3		13.6
		M-D-25				21.9		46.2		5.2			20.3		3.8		0.7		0.0		98.1			3.2		0.4		2.1		0.4		1.2		0.2		1.1		0.2		8.8
		Avg.				23.2		48.6		5.5			22.0		4.4		0.9		0.0		104.6			3.8		0.5		2.9		0.6		1.6		0.2		1.6		0.2		11.6

a provides the concentrations of minor and trace elements analyzed in the samples. In addition, the concentrations of light rare earth elements (LREEs) and heavy rare earth elements (HREEs) are presented separately in Table 2b, offering a more detailed insight into the rare earth element distribution of the two formations. Summary rows are included for the total concentrations of LREEs (ΣLREE) and HREEs (ΣHREE), facilitating comparison between the two formation samples.

Among the minor elements of the Grünbach Fm. (Table 2a), Ba has the highest concentration, averaging 405.9 ppm and ranging from 158.9 to 946.4 ppm. Sr follows with a mean value of 130.5 ppm. V exhibits notable variation, averaging 126.0 ppm. Zr and Ni have mean values of concentrations of 97.4 ppm and 48.9 ppm, respectively. Among the trace elements (Table 2a), Rb has the highest mean concentration at 124.5 ppm. Cr and Li exhibit relatively high average values of 96.9 ppm and 63.9 ppm, respectively. Following them are Zn and Cu, with mean concentrations of 52.2 ppm and 32.2 ppm, respectively. The mean concentrations of Ga, Y, Co, Nb, and Sc range from 10 to 20 ppm, with Ga at 20.3 ppm, Y at 17.4 ppm, Co at 16.2 ppm, Nb at 14.4 ppm, and Sc at 13.7 ppm. Pb and Cs show relatively variable distributions, averaging 10.8 ppm and 9.5 ppm, respectively. Th has a lower mean concentration of 8.5 ppm. U and Hf have similar mean values of 2.5 ppm and 2.6 ppm, while Be, Ta, and Ge average very low values.

In the samples from the Piesting Fm., Ba has the highest average concentration among the minor elements at 250.4 ppm, ranging from 9.8 to 489.8 ppm (Table 2a). Sr follows with a mean of 131.2 ppm. V and Zr have mean values of 99.9 ppm and 73.1 ppm, respectively. Ni has the lowest content among the minor elements, averaging 31.3 ppm. Among the trace elements (Table 2a), Cr has the highest mean concentration at 70.8 ppm, while Rb averages 68.8 ppm. Li and Zn have mean values of 41.6 ppm and 35.1 ppm, respectively. Cu, Ga, Nb, and Co exhibit lower mean concentrations of 16.9 ppm, 12.8 ppm, 10.5 ppm, and 10.2 ppm, respectively. Y, Pb, and Sc follow, averaging 10.0 ppm, 9.5 ppm, and 8.3 ppm, respectively. The mean concentration of Th is slightly higher than that of Cs. For the remaining trace elements, U and Hf have similar mean values of 2.0 ppm and 1.9 ppm, respectively. Be averages 1.2 ppm, while Ta and Ge both have relatively low mean concentrations of 0.7 ppm.

Overall, the Grünbach Fm. and the Piesting Fm. exhibit similar distribution patterns of minor elements, with Ba being significantly abundant. The content of Sr follows, while V, Zr, and Ni are present in relatively lower concentrations. The average concentrations of minor element contents in the Grünbach Fm. are generally higher than those in the Piesting Fm., except Ge and Sr contents. Regarding trace elements, Rb is the most abundant element, followed by Cr, Li, and Zn.

For the samples from the Grünbach Fm., the average total concentration of ΣLREE is 118.2 ppm, with values ranging from 44.1 ppm to 210.4 ppm (Table 2b). In contrast, the mean ΣHREE is 13.2 ppm, ranging from 5.9 ppm to 24.4 ppm. Among the LREEs, Ce exhibits the highest concentration, with a mean value of 54.6 ppm. La and Nd follow with mean values of 26.3 ppm and 25.0 ppm, respectively. Pr and Sm have relatively low mean values of 6.2 ppm and 5.0 ppm, respectively. Eu has a mean value of 1.0 ppm, and no significant concentration of Pm was detected in the samples. In HREEs, Gd and Dy exhibit higher concentrations, with mean values of 4.4 ppm and 3.3 ppm, respectively. The mean concentrations of Er and Yb are notably lower, at 1.9 ppm and 1.8 ppm, respectively. Tb, Ho, Tm, and Lu have significantly low mean values, lower than 1.0 ppm.

In the samples from the Piesting Fm., the ΣLREE averages 72.0 ppm (ranging from 2.3 ppm to 112.5 ppm), which is significantly higher than that of ΣHREE at 7.6 ppm (ranging from 0.3 ppm to 11.8 ppm) (Table 2b). In LREEs, Ce, La, and Nd were the most abundant, with mean values of 34.0 ppm, 15.7 ppm, and 15.0 ppm, respectively. Ce varies from 1.1 ppm to 53.4 ppm, La ranges from 0.5 ppm to 25.2 ppm, and Nd ranges from 0.5 ppm to 22.8 ppm. Pr has an average value of 3.7 ppm, while Sm has a mean value of 2.9 ppm. Eu exhibits a mean value of 0.6 ppm. Pm was not detected in significant concentrations. Among the HREEs, Gd has the highest average concentration at 2.5 ppm. Dy is present at a relatively lower mean value of 1.9 ppm, while both Er and Yb have an average concentration of 1.1 ppm. The distribution patterns of Ho, Tb, Tm, and Lu are low, with mean values less than 0.5 ppm.

Although the REE distribution patterns in the Grünbach and Piesting formations are broadly similar, distinct differences in their concentrations are indicated. The average total REE content in samples from the Grünbach Fm. is significantly higher than that of the Piesting Fm. This is largely due to a wider range and higher variability of REE concentrations in the Grünbach samples, suggesting more heterogeneous sediment sources, differential weathering, or varying depositional conditions. These differences are clearly illustrated in the chondrite-normalized REE distribution patterns shown in Figure 5, where the Grünbach samples exhibit more pronounced enrichment across both light and heavy REEs compared to the relatively subdued patterns observed in the Piesting samples.

2.4. Total Carbon, Nitrogen, and Sulfur

The weight percentages of TOC, TN, and TS for the Grünbach and Piesting samples from the different sampling locations are grouped and presented separately. Each column in

Table 3. Total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS) content data of samples from the Grünbach Fm. and Piesting Fm. The sample locations are shown in Figure 3. Details of major element data are available in Table S4.

Location	Outcrop		Trench A		Trench C
Samples No.	M-23-1	M-23-2	M-A-3	M-A-5	M-C-2	M-C-3	M-C-7	M-C-8	M-C-9	M-C-13	M-C-14
Formation	PF	PF	GF	GF	GF	GF	GF	GF	GF	GF	GF
TOC wt. %	0.08	0.05	2.66	0.37	0.24	0.13	0.28	0.22	0.31	0.15	0.08
TN wt. %	0.01	0.00	0.10	0.06	0.05	0.02	0.04	0.02	0.05	0.01	0.02
TS wt. %	0.02	0.01	0.15	0.04	0.04	0.03	0.02	0.03	0.02	0.07	0.05
Location	Trench C continued							Trench D
Samples No.	M-C-15	M-C-16	M-C-19	M-C-22	M-C-24	M-C-26	M-C-28	M-D-2	M-D-3	M-D-5	M-D-7
Formation	GF	GF	GF	GF	GF	GF	GF	PF	PF	PF	PF
TOC wt. %	0.35	2.10	0.20	0.15	0.21	0.24	0.48	0.21	0.31	0.16	4.68
TN wt. %	0.06	0.10	0.05	0.05	0.05	0.04	0.04	0.03	0.05	0.03	0.13
TS wt. %	0.06	0.05	0.03	0.02	0.02	0.02	0.02	0.02	0.05	0.03	0.30
Location	Trench D continued
Samples No.	M-D-8	M-D-12	M-D-13	M-D-15	M-D-17	M-D-19	M-D-20	M-D-24	M-D-25
Formation	PF	PF	PF	PF	GF	GF	GF	GF	GF
TOC wt. %	2.14	0.30	0.57	0.11	0.42	0.12	0.28	0.31	0.14
TN wt. %	0.08	0.03	0.05	0.01	0.05	0.03	0.06	0.06	0.03
TS wt. %	0.12	0.14	0.04	0.27	0.07	0.05	0.03	0.03	0.02

represents an individual sample, while each row corresponds to the mass fraction of TOC, TN, and TS.

In the Grünbach Fm., the content of TOC ranges from 0.08% to 2.66%, with a mean value of 0.45%. The concentration of TN spans from 0.01% to 0.10%, averaging 0.05%, while the concentration of TS ranges from 0.02% to 0.15%, with an average value of 0.04%.

In the Piesting Fm., the mean values of the TOC, TN and TS are 0.86%, 0.04% and 0.10%, respectively. TOC ranges from 0.05% to 4.68%, TN ranges from 0.00% to 0.13% while TS ranges from 0.01% to 0.30%.

The samples from Grünbach Fm. generally exhibit lower concentrations of TOC, TN, and TS compared to those from the Piesting Fm. Notably, several samples near the formation boundary and from the Piesting Fm. show higher contents than the others, indicating organic matter enrichment likely associated with marine-influenced depositional environments.

3. Methods

Based on lithological characteristics, samples were selected from each distinct unit, prioritizing the best-preserved specimens to ensure representative and reliable measurements for mineralogical and geochemical data. The mineralogical analysis of samples from Trenches A, B, C, and D was conducted at the Department of Geology, University of Vienna in Austria. The geochemical analyses of samples from the Trenches A, C, D, and the outcrop were performed by Suigu Technology Service Company in China, while the minor and trace element analyses of samples from Trench B were carried out at the Department of Lithospheric Research, University of Vienna in Austria.

3.1. Mineralogical Analysis Using XRD

Identifying mineral composition was performed using XRD, a technique associated with changes in the direction of X-ray beams (e.g., [17]). Twenty-one fine-grained samples from Trench A, B, C and D were selected for mineralogical analysis. The samples were ground to a fine powder (less than 300 mesh) and analyzed using whole-rock XRD with a Panalytical X’Pert Pro diffractometer (Malvern Panalytical, Malvern, UK). The instrument operated with CuKα radiation at 40 kV and 40 mA, employing a step size of 0.0167° and a 5 s dwell time per step. Mineral identification and peak matching were performed using MDI Jade 6 software. The XRD pattern dataset is attached in the Supplementary Materials, and their identification is included in Table S1.

3.2. Major Element Analysis Using XRF

Major elements were analyzed using XRF, a non-destructive analytical technique used to determine the elemental compositions of materials [18]. For each analysis, 0.8 g of the sample was mixed with 8.0 g of flux (comprising 67% Li₂B₄O₇ and 33% LiBO₂) to ensure optimal fusion. The mixture was then fused at 1050 °C using a Claisse automatic electric fusion instrument, producing homogeneous beads suitable for precise and reliable XRF measurements. The resulting flat glass discs were analyzed using a Rigaku (Tokyo, Japan) Primus II XRF spectrometer, a fully enclosed X-ray-generating system designed for the rapid and precise quantitative determination of major and minor atomic elements. Loss on ignition (LOI) was calculated by measuring the weight difference of the samples before and after ignition at 1050 °C, providing an estimate of the volatile components present. Details of the major oxide data are available in Table S2.

3.3. Minor and Trace Element Analysis Using ICP-MS

Minor and trace element analysis was performed using ICP-MS [19,20,21]. For the analysis of samples from Trench A, C, D, and the outcrop, a technique that employed inductively coupled plasma to ionize samples for precise elemental quantification was used. Approximately 50 mg of each sample was first heated in a muffle furnace at 650 °C for 6 h to remove organic matter. Subsequently, the samples underwent multiple treatments with 1 mL of high-purity nitric acid and 3 mL of high-purity hydrofluoric acid under high-temperature and high-pressure conditions for 72 h. After digestion, the samples were diluted with deionized water and analyzed using an Agilent 7900 ICP-MS (Santa Clara, CA, USA), a versatile single-quadrupole instrument designed for accurate and reliable trace element analysis. For samples from Trench B, minor and trace element analysis was performed using an iCAP-RQ ICP-MS (e.g., [22]). Around 100 mg of the sample was powdered to a size of less than 80 µm and then mixed with a standard reference material (IFG), a blank sample, and a concentrated supra-pure HCl-HNO₃-HF (3:1:1) mixture in a PicoTrace high-pressure block for two days of melting and then evaporated to concentrate and remove impurities under 180 °C. The sample was then mixed intensively with 3 mL of 6 M HNO₃ twice and immediately evaporated. It was subsequently mixed with 3% HNO₃ for ICP-MS measurement. Analytical accuracy and precision were monitored using certified reference materials, such as BHVO-2 and BCR-2, achieving typical relative uncertainties of better than 5% for most elements. Details of the minor, trace element data and REEs are available in Table S3.

3.4. CNS Analysis

The carbon (C), nitrogen (N), and sulfur (S) contents of the samples were determined using the Elementar Unicube, a high-precision instrument for rapid elemental analysis [23]. Using p-aminobenzenesulfonamide as the standard, the relative error was maintained below 1%. During analysis, the sample was combusted in a furnace at temperatures ranging from 950 to 1200 °C under a pure oxygen flow. The combustion products—CO₂, H₂O, and SO₂—were subjected to a series of purification steps to remove interfering substances. These purified gases were then separated via a gas chromatography column and detected with a thermal conductivity detector. The concentrations were used to calculate the amounts of C, N, and S in the sample. Calibration with standard samples ensured the accuracy of the measurements. Details of the TOC, TN, and TS data are available in Table S4.

4. Conclusions

This study presents mineralogical and geochemical analyses of sedimentary rock samples from the Grünbach and Piesting Fms., contributing to improved characterization of the Gosau Group strata (Late Cretaceous) in the Grünbach–Neue Welt area, Eastern Alps, Austria. The investigations employ XRD, XRF, ICP-MS, and elemental analyses of TOC, TN, and TS to provide a multi-faceted dataset for future geological research. The primary minerals identified include quartz, illite, and muscovite, with sparse chlorite, corresponding to a typical siliciclastic composition and reflecting major oxide abundances and their variations. The variable occurrence of calcite, particularly in specific intervals, corresponds to the variability in CaO, likely indicating episodes of carbonate cementation or allochthonous carbonate input. Minor and trace elements show relatively consistent trends across samples with notable enrichments in Ba and Sr. The concentrations of LREEs exceed those of HREEs, with pronounced enrichments in La and Ce. However, the Grünbach Fm. displays elevated concentrations and broader distributions in minor elements. It also exhibits generally higher REE contents and broader distribution ranges, as shown in chondrite-normalized REE patterns, suggesting more heterogeneous provenance, differential weathering, or varying depositional conditions. TOC, TN, and TS values are low overall but become elevated near the formation boundary and in the Piesting samples, potentially reflecting increased organic matter preservation during marine influence. Despite broad similarities in mineralogical and geochemical compositions between the two formations, notable variations and geochemical differences, particularly in calcite content, REE profiles, and organic indicators, highlight shifts in environmental influences such as episodic marine incursions, terrestrial-to-marine transition, and provenance alteration. These results provide insights into the depositional history and provenance of the strata and form a foundation for reconstructing paleoenvironmental and basin evolution in the region. Moreover, this study establishes a comparative framework for evaluating similar transitions in other Gosau basins throughout the Eastern Alps.